Patent Publication Number: US-2022218432-A1

Title: Systems and methods for bifurcated navigation control of a manipulator cart included within a computer-assisted medical system

Description:
RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application No. 62/855,569, filed on May 31, 2019, and entitled “SYSTEMS AND METHODS FOR BIFURCATED NAVIGATION CONTROL OF A MANIPULATOR CART INCLUDED WITHIN A COMPUTER-ASSISTED MEDICAL SYSTEM,” the contents of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND INFORMATION 
     Medical operations, such as various types of surgical and non-surgical procedures, may be performed using computer-assisted medical systems. In some examples, such computer-assisted medical systems may include one or more carts. Example carts include auxiliary carts containing data processing systems, visualization systems, power generators, and so forth. Example carts also include manipulator carts each having one or more arms (e.g., robotic arms) configured for manipulating instruments used to carry out the medical operation, input device carts containing input devices, and the like. For instance, a manipulator cart may be positioned in proximity to a body being operated upon (e.g., a body of a patient, cadaver, training fixture, animal, or the like), and various types of medical operations may be performed on the body by way of the arms of the manipulator cart as directed by a medical practitioner (e.g., a clinician such as a surgeon, etc.) who is located at a control console that may be outside of the operational area. In this way, highly effective medical operations may be performed. 
     In preparation for such computer-assisted medical operations, a manipulator cart is typically navigated by a human operator from an initial location (e.g., a location where the manipulator cart has been kept when not in use and/or where the manipulator cart is draped and otherwise prepared for the operation) to a target location proximate to an operating table upon which the body is located that is to be operated upon. Unfortunately, however, various challenges (e.g., poor visibility afforded to the operator, obstacles on the path, narrow parameters characterizing the target location, target configuration, and/or target orientation of the manipulator cart, etc.) may make it difficult for the operator to effectively navigate the manipulator cart in an efficient manner. 
     SUMMARY 
     Systems and methods for bifurcated navigation control of a manipulator cart included within a computer-assisted medical system are described herein. For instance, one embodiment of such a bifurcated navigation control system is implemented as a computer-assisted medical system comprising a manipulator cart, a memory storing instructions, and a processor communicatively coupled to the memory and the manipulator cart and configured to execute the instructions. For example, the instructions may direct the processor to define a path whereby the manipulator cart is to navigate from an initial location to a target location and to identify a navigation condition associated with a navigation of the manipulator cart along the path from the initial location to the target location. Based on the navigation condition, the processor may define a propulsion limitation for the manipulator cart during the navigation of the manipulator cart along the path, and may direct the manipulator cart to navigate, in a bifurcated navigation control mode, along at least part of the path from the initial location to the target location. In some examples, in the bifurcated navigation control mode, the processor may be configured to execute the instructions to autonomously control a steering of the manipulator cart while allowing operator control of a propulsion of the manipulator cart in accordance with the propulsion limitation. 
     An exemplary embodiment of a bifurcated navigation control method may be performed by a bifurcated navigation control system. For example, the method includes defining a path whereby a manipulator cart included within a computer-assisted medical system is to navigate from an initial location to a target location. The method further includes identifying a navigation condition associated with a navigation of the manipulator cart along the path from the initial location to the target location. Based on the navigation condition, the method defines a propulsion limitation for the manipulator cart during the navigation of the manipulator cart along the path. The method also includes directing the manipulator cart to navigate, in a bifurcated navigation control mode, along at least part of the path from the initial location to the target location. In some examples, in the bifurcated navigation control mode, the bifurcated navigation control system may autonomously control a steering of the manipulator cart while allowing operator control of a propulsion of the manipulator cart in accordance with the propulsion limitation. 
     Yet another exemplary embodiment is implemented by a non-transitory, computer-readable medium storing instructions that, when executed, direct a processor of a computing device to perform operations described herein. For instance, the instructions may direct the processor to define a path whereby a manipulator cart included within a computer-assisted medical system is to navigate from an initial location to a target location, and to identify a navigation condition associated with a navigation of the manipulator cart along the path from the initial location to the target location. Based on the navigation condition, the instructions may further direct the processor to define a propulsion limitation for the manipulator cart during the navigation of the manipulator cart along the path, and to direct the manipulator cart to navigate, in a bifurcated navigation control mode, along at least part of the path from the initial location to the target location. In some examples, in the bifurcated navigation control mode, the instructions may direct the processor to autonomously control a steering of the manipulator cart while allowing operator control of a propulsion of the manipulator cart in accordance with the propulsion limitation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate various embodiments and are a part of the specification. The illustrated embodiments are merely examples and do not limit the scope of the disclosure. Throughout the drawings, identical or similar reference numbers designate identical or similar elements. 
         FIG. 1  illustrates an exemplary bifurcated navigation control system for bifurcated navigation control of a manipulator cart included within a computer-assisted medical system according to principles described herein. 
         FIG. 2  illustrates an exemplary computer-assisted medical system according to principles described herein. 
         FIGS. 3 and 4  illustrate respective exemplary operating rooms within which an exemplary manipulator cart is to be navigated along an exemplary path from an initial location to a target location according to principles described herein. 
         FIGS. 5 and 6  illustrate respective views of the exemplary manipulator cart as the manipulator cart navigates from the initial location and a corresponding initial configuration to the target location and a corresponding target configuration according to principles described herein. 
         FIG. 7  illustrates various exemplary navigation control modes that may be employed as the manipulator cart navigates from the initial location to the target location according to principles described herein. 
         FIG. 8  illustrates exemplary components of a control interface that may be employed during navigation of the manipulator cart from the initial location to the target location according to principles described herein. 
         FIG. 9  illustrates exemplary factors accounted for in the propulsion of the manipulator cart in certain navigation control modes of  FIG. 7  according to principles described herein. 
         FIG. 10  illustrates how exemplary operator-commanded propulsion may be translated into manipulator cart propulsion in accordance with different types of propulsion limitations and with respect to time according to principles described herein. 
         FIGS. 11A-11D  illustrate how exemplary operator-commanded propulsion may be translated into manipulator cart propulsion in accordance with different types of propulsion limitations according to principles described herein. 
         FIG. 12  illustrates how exemplary operator-commanded propulsion may be translated into manipulator cart propulsion in accordance with different types of propulsion limitations imposed in different zones or along different parts of a path according to principles described herein. 
         FIG. 13  illustrates an exemplary method for bifurcated navigation control of a manipulator cart included within a computer-assisted medical system according to principles described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Systems and methods for bifurcated navigation control of a manipulator cart included within a computer-assisted medical system are described herein. For example, in order to facilitate use of a manipulator cart to perform an operation, systems and methods described herein provide bifurcated navigation control modes that automatically assist an operator in navigating a manipulator cart from an initial location (e.g., a storage location) to a target location (e.g., a location at which the manipulator cart is ready for use in performing the operation). Systems and methods described herein also provide bifurcated navigation control modes that automatically assist an operator in navigating a manipulator cart from an initial orientation and/or configuration (e.g. a stowed configuration) to a target orientation and/or configuration (e.g. an orientation and/or a configuration at which the manipulator cart is ready for use in performing the operation). Examples of an operation that may be performed using an implementation of the manipulator carts described herein include medical procedures such as minimally invasive surgical or non-surgical procedures performed by way of an artificial or natural orifice in a body of a live human patient or another suitable body that may be living or non-living, biological or non-biological, natural or artificial, or the like (e.g., including but not limited to a body of an animal, of a cadaver, of a training fixture, etc.). 
     In a bifurcated navigation control mode, a processor autonomously controls a steering of the manipulator cart while allowing operator control of a propulsion of the manipulator cart using a control interface. For example, the operator may direct the manipulator cart forward or backward (e.g., at a speed acceptable to the operator) while the manipulator cart is autonomously steered along an appropriate path. In some examples, the propulsion of the manipulator cart in the bifurcated navigation control mode may be performed by operator control in accordance with a propulsion limitation applied by the system based on one or more navigation conditions associated with the navigation of the manipulator cart along the path. 
     In one implementation, for instance, a bifurcated navigation control system may be implemented by a computer-assisted medical system that includes a manipulator cart, a memory storing instructions, a processor communicatively coupled to the memory and configured to execute the instructions, and any other system components as may serve a particular implementation (examples of which will be described herein). The processor may be configured to execute the instructions to 1) define a path whereby the manipulator cart is to navigate from an initial location to a target location, 2) identify a navigation condition associated with a navigation of the manipulator cart along the path from the initial location to the target location, 3) define (e.g., based on the navigation condition) a propulsion limitation for the manipulator cart during the navigation of the manipulator cart along part of, or the entirety of, the path, and 4) direct the manipulator cart to navigate, in a bifurcated navigation control mode, along at least part of the path from the initial location to the target location. Once the manipulator cart arrives at a target location (and/or a target orientation or a target configuration, as applicable), an operation may be performed. An example target orientation and configuration for the manipulator cart is with the manipulator cart facing a target object with the manipulator arms positioned in a desirable way. An example target configuration for a kinematic structure of the manipulator cart is with one or more joints or links of the kinematic structure at target positions or orientations, or within a range of target positions or orientations, etc., for those joints or links. 
     As mentioned above, in the bifurcated navigation control mode, the processor may be configured to execute the instructions to autonomously control a steering of the manipulator cart while allowing operator control of a propulsion of the manipulator cart. This operator control of the propulsion may be allowed, in some examples, only in accordance with a propulsion limitation during some periods of propulsion, or during the entirety of propulsion. In other words, an operator may be in control of the propulsion while the system imposes a limitation on the propulsion that is based on one or more navigation conditions, given the applicable navigation conditions under those circumstances. 
     As used herein, a “propulsion limitation” may refer to any one or combination of limitations that a navigation control system may impose on the operator-commanded propulsion, which is the operator provided commands related to the propulsion of a manipulator cart other than steering commands. For example, a propulsion limitation may affect the magnitude of velocity (e.g. speed), the magnitude of acceleration, the magnitude of further derivatives of velocity or acceleration, etc. As described herein, a propulsion limitation can be set based on one or more navigation conditions. For example, a propulsion limitation may include an upper (i.e., maximum) speed limit imposed on the manipulator cart (i.e., such that the system does not allow the manipulator cart propulsion to be at a speed higher than the limit, which in some cases may mean that the manipulator cart propulsion is not as high as commanded by an operator-commanded propulsion), a lower (i.e., minimum) speed limit, an upper acceleration limit imposed on the manipulator cart (i.e., such that the system does not allow the manipulator cart propulsion to accelerate at an acceleration rate higher than the limit, which in some cases may mean that the manipulator cart propulsion is not as high as commanded by the operator-commanded propulsion), a lower acceleration limit, or another such limit as may be appropriate given one or more navigation conditions. 
     In some examples, the propulsion limitation may be quantized, such that operator-commanded propulsion meeting one or more first criteria (e.g. in a first propulsion magnitude range) are subject to a first type of propulsion limit (e.g. a first speed limit) and operator-commanded propulsion meeting one or more second criteria (e.g. in a second propulsion magnitude range) are subject to a second propulsion limitation type (e.g. a second speed limit). As a specific example, quantized propulsion limitation may thus quantize a speed commanded by the operator to one of a plurality of speed levels (e.g., a low speed, a medium speed, a high speed, etc.) at which the manipulator cart will actually be propelled as it is navigated. In the same or other examples, a propulsion limitation may be implemented in accordance with a transfer function that relates the operator-commanded propulsion to the manipulator cart propulsion. For example, transfer functions may relate system-implemented manipulator cart speed to operator-commanded speed or velocity, system-implemented magnitude of manipulator cart acceleration to operator-commanded acceleration, etc.). For instance, if navigation conditions dictate that speed or acceleration of a manipulator cart should be lower than commanded by the operator (e.g., while navigating a particular part of a path, while in a particular area or near particular obstacles, etc.), a bifurcated navigation control system may impose a propulsion limitation in accordance with a linear transfer function by directing the speed or acceleration of the manipulator cart to be a particular percentage (e.g., 50%, 75%, etc.) of the speed or acceleration commanded by the operator. The transfer functions can be partially or entirely linear, or partially or entirely nonlinear. 
     It will be understood that limitations on the propulsion of a manipulator cart due to hardware limits (e.g., a maximum torque or speed rating of a motor used for driving the manipulator cart, etc.), or due to design of the manipulator cart (e.g., mass of the cart, size of the wheels, friction in the drive train, etc.) are not referred to herein as propulsion limitations based on navigation conditions because these limitations are not defined during operation based on navigation conditions. Similarly, global control-system-imposed limits on propulsion that are not defined during operation based on navigation conditions (e.g., a maximum speed of the cart to avoid burning out motors, a maximum turning rate to reduce the likelihood of injuries in collisions with people, etc.) are also not referred to herein as propulsion limitations based on navigation conditions. Similarly, features of certain manipulator carts that cause the manipulator cart to indicate a system fault and stop all motion, or to completely shut down, will also be understood to be outside the scope of propulsion limitations based on navigation conditions. Various examples of navigation conditions and corresponding propulsion limitations based on navigation conditions will be described in more detail below. As one example, a propulsion limitation defined based on a navigation condition of a shape of a turn in the path may include a maximum speed limit for the manipulator cart that will reduce or eliminate the likelihood that the manipulator cart will tip while traversing the turn. 
     Aspects of the bifurcated navigation control systems and methods described herein are primarily described with respect to manipulator carts such as might be included within a computer-assisted medical system. It will be understood, however, that principles described herein in relation to manipulator carts (or similar principles) may likewise apply to other types of carts and/or navigable system components. For instance, bifurcated navigation control of carts and system components such as auxiliary systems of a computer-assisted medical system (e.g., auxiliary carts, visualization systems, power generators, etc.), other navigable components of a computer-assisted medical system (e.g., a user control system, etc.), or other suitable navigable components associated with other types of systems (e.g., systems used for non-medical purposes and not described herein, etc.) may be performed using the principles described herein or similar principles. 
     Moreover, while aspects of the bifurcated navigation control systems and methods described herein primarily relate to implementations employing a computer-assisted medical system (e.g., a minimally invasive surgical system), it will be understood that inventive aspects disclosed herein may be embodied and implemented in various ways, including by employing robotic and non-robotic embodiments and implementations. Implementations relating to surgical or other medical systems are merely exemplary and are not to be considered as limiting the scope of the inventive aspects disclosed herein. For example, any reference to surgical instruments, surgical techniques, and/or other such details relating to a surgical context will be understood to be non-limiting as the instruments, systems, and methods described herein may be used for medical treatment or diagnosis, cosmetic improvements, imaging of human or animal anatomy, gathering data from human or animal anatomy, setting up or taking down systems, training medical or non-medical personnel, and so forth (any of which may or may not also involve surgical aspects). In other examples, the instruments, systems, and methods described herein may also be used for procedures performed on, or with, animals, human cadavers, animal cadavers, portions of human or animal anatomy, tissue removed from human or animal anatomies (which may or may not be re-implanted within the human or animal anatomy), non-tissue work pieces, training models, and so forth. In yet other examples, the instruments, systems, and methods described herein may be applied for non-medical purposes including for industrial systems, general robotics, teleoperational systems, and/or sensing or manipulating non-tissue work pieces. 
     Various benefits may be provided by the bifurcated navigation control systems and methods described herein. For example, navigation of a manipulator cart by way of a computer-assisted bifurcated navigation control mode such as those described herein may result in more effective and accurate positioning of the manipulator cart, in a safer manner with less risk of equipment damage, and in a more timely manner than when standard navigation control modes (i.e., navigation control modes in which an operator entirely directs both steering and propulsion of the manipulator cart) are employed. Different types of operations may require different cart placements in relation to the body to be operated upon, and, in certain examples, operators tasked with navigating the manipulator cart may not be intimately involved in certain aspects of the operation such that these operators may not fully understand the ideal target placement (e.g., target location, target orientation, target configuration, etc.) of the manipulator cart. Additionally, because every minute in a typical surgical operating room is costly, it is important that as little time as possible be lost in navigating a manipulator cart to its target location (and/or target orientation or target configuration, as applicable). As a result, conventional navigation of manipulator carts to the target location may suffer from either or both of suboptimal placement (e.g., a non-ideal or inaccurate final placement of the manipulator cart for a given operation type) and inefficient placement (e.g., an ideal or non-ideal placement that takes more time than is necessary to achieve). It is a significant benefit, therefore, that systems and methods described herein facilitate manipulator cart navigation in a manner that results in both optimal and efficient manipulator cart placement. 
     Another exemplary benefit of the systems and methods described herein is that a human operator retains propulsion control of the manipulator cart navigation even as the system autonomously handles the steering control and imposes appropriate propulsion limitations. It may be impractical or otherwise undesirable for the navigation of a manipulator cart to be fully automated such that both steering and propulsion are autonomously controlled. For example, it may be desirable (e.g., for efficiency reasons, safety reasons, etc.) for one or more human operators to always be directly involved in the movement of a large, heavy, valuable piece of equipment such as a manipulator cart. Accordingly, by bifurcating the steering and propulsion control of the manipulator cart, such that the steering is performed autonomously by the system while the propulsion control of the manipulator cart is performed by a human operator with system-imposed propulsion limitations, an effective and efficient navigation and positioning of the manipulator cart may be consistently achieved in a convenient, safe, and cost-effective way that is partially or entirely independent of the operator&#39;s specific knowledge of the ideal cart placement for a given operation type. 
     Certain specific benefits also arise from the propulsion limitations applied by systems and methods described herein to allow for operator control of the propulsion of the manipulator cart in accordance with certain propulsion limitations. For example, an operator may consistently direct propulsion to occur at whatever speed seems most appropriate to the operator, without concern about whether the commanded speed might result in problematic manipulator cart propulsion. This may allow the operator to accelerate the manipulator cart without worrying about commanding the manipulator cart to engage in propulsion (e.g., to move at a speed, to accelerate at a rate, etc.) that could burn out a motor of the manipulator cart. This may also allow the operator to navigate around obstacles without worrying about commanding the manipulator cart to engage in propulsion that would risk tipping the manipulator cart (e.g., if the manipulator cart is turning at too high a speed). In some implementations, this may also allow the operator to direct propulsion at a relatively high speed without worrying that a movable component of the manipulator cart (e.g., a boom, a manipulator arm, etc.) will not be adjusted (e.g., raised, lowered, etc.) in time to avoid hitting an obstacle, and so forth. The propulsion limitations may be used to disallow commanded acceleration, speed, or any other propulsion parameter that is unsafe or otherwise unadvisable. 
     Various embodiments will now be described in more detail with reference to the figures. The systems and methods described herein may provide one or more of the benefits mentioned above as well as various additional and/or alternative benefits that will be made apparent by the description below. 
       FIG. 1  illustrates an exemplary bifurcated navigation control system  100  (“system  100 ”) for bifurcated navigation control of a manipulator cart included within a computer-assisted medical system. As will be described and illustrated in more detail below, a “manipulator cart,” as used herein, may refer to any robotic or other system that includes one or more manipulators (e.g., manipulator arms, etc.) configured to facilitate performance of an operation (e.g., a medical operation such as a surgical procedure, etc.), and that is configured to be independently navigable from one location to another, rather than being mounted, for example, on a physical track. 
     As shown, system  100  may include, without limitation, a storage facility  102  and a processing facility  104  selectively and communicatively coupled to one another. Facilities  102  and  104  may each include or be implemented by hardware and/or software components (e.g., processors, memories, communication interfaces, instructions stored in memory for execution by the processors, etc.). 
     In some examples, facilities  102  and  104  may be integrated into a single device (e.g., a manipulator cart control system, etc.), while, in other examples, facilities  102  and  104  may be distributed between multiple devices and/or multiple locations as may serve a particular implementation. For instance, in one implementation of system  100 , the manipulator cart itself may include one or more built-in processors, data storage devices, sensors, communication interfaces, and so forth for implementing system  100 . In contrast, in other implementations of system  100 , some or all of these components may not be integrated into the manipulator cart itself but, rather, may be implemented on other computing systems as may serve a particular implementation (e.g., edge servers, cloud servers, computing devices integrated with other components of a computer-assisted medical system that includes the manipulator cart, etc.). 
     Storage facility  102  may maintain (e.g., store) executable data used by processing facility  104  to perform any of the functionality described herein. For example, storage facility  102  may store instructions  106  that may be executed by processing facility  104  to perform any of the functionality described herein. Instructions  106  may be implemented by any suitable application, software, code, and/or other executable data instance. Storage facility  102  may also maintain any data received, generated, managed, used, and/or transmitted by processing facility  104 . 
     Processing facility  104  may be configured to perform (e.g., execute instructions  106  stored in storage facility  102  to perform) various processing functions associated with bifurcated navigation control of the manipulator cart. For example, processing facility  104  may define a path whereby the manipulator cart is to navigate from an initial location to a target location. Processing facility  104  may also direct the manipulator cart to identify a navigation condition associated with a navigation of the manipulator cart along the path from the initial location to the target location, and to define, based on the navigation condition, a propulsion limitation for the manipulator cart during the navigation of the manipulator cart along the path. Processing facility  104  may direct the manipulator cart to navigate along at least part of the path from the initial location to the target location in a bifurcated navigation control mode that accounts for the propulsion limitation that was defined. For example, in the bifurcated navigation control mode, processing facility  104  may be configured to autonomously control a steering of the manipulator cart while allowing operator control of a propulsion of the manipulator cart in accordance with the propulsion limitation. 
     To this end, processing facility  104  may autonomously control a steering of the manipulator cart while allowing operator control of a propulsion of the manipulator cart (within limits set by the propulsion limitation) using a control interface. As used herein, controlling the “steering” of a manipulator cart may refer to some or all aspects of navigation control that involve defining the direction in which motion vectors are directed (e.g., which way the wheels of the manipulator cart are pointing, etc.). For example, using a standard automobile as an analogy, the steering control of an automobile may relate to the control of the automobile imposed by way of the steering wheel. In contrast, controlling the “propulsion” of a manipulator cart may refer to some or all aspects of navigation control that involve defining the magnitude and/or sign (e.g., positive or negative) of the motion vectors (e.g., whether and to what degree the wheels of the manipulator cart are turning in either a forward or backward direction). For example, referring again to the automobile analogy, the propulsion control of the automobile may be performed by way of the gas pedal, the brake, and/or the gear shift (e.g., whether the automobile is in a “park” mode, a “drive” mode, a “reverse” mode, etc.). 
     Processing facility  104  may perform the functions described above and other functions described herein in any suitable manner, as will be described in more detail below. Additionally, in an analogous way as described above in relation to the location of the manipulator cart, processing facility  104  may, in certain embodiments involving target orientations and/or target configurations, direct the manipulator cart, in a first bifurcated navigation control mode, from an initial orientation and/or initial configuration to a target orientation and/or target configuration along with guiding the manipulator cart from the initial location to the target location. 
     In some implementations, system  100  (e.g., processing facility  104 ) may be configured to provide bifurcated navigation control of a manipulator cart in real time. As used herein, a function may be said to be performed in real time when the function relates to or is based on dynamic, time-sensitive information and the function is performed while the time-sensitive information remains accurate or otherwise relevant. Due to processing times, communication latency, and other inherent delays in physical systems, certain functions may be considered to be performed in real time when performed immediately and without undue delay, even if performed after small delay (e.g., a delay up to a few seconds or the like). As one example of real-time functionality, processing facility  104  may define a path based on the real-time states of obstacles in between the initial location and the target location, and may update the path as the state of obstacles changes. As another example of real-time functionality, in some embodiments where target orientations and/or configurations exist for the manipulator cart, processing facility  104  may define changes in cart orientation and/or configuration to achieve target orientations and/or configurations based on real-time states of obstacles. 
     System  100  may be used in various contexts with various different types of technologies as may serve a particular implementation. For example, system  100  may be used in a medical context such as in preparation for a computer-assisted medical procedure in which an operation is performed inside of any suitable type of body described herein. In other implementations, system  100  may be used in medical contexts that are not surgical in nature (e.g., diagnostic or exploratory imaging without surgical elements), or that are not for treatment or diagnosis (e.g., training or other procedures where such procedures do not involve treatment). Additionally, in certain implementations, system  100  may be used in non-medical contexts. For instance, system  100  may be useful for navigating other types of large, free-moving objects that may or may not fall under the category of a manipulator cart, as that term is used herein. 
     To illustrate an exemplary context in which system  100  may be implemented and employed, an exemplary computer-assisted medical system that implements system  100  and includes a manipulator cart will now be described. The computer-assisted medical system described below is illustrative and not limiting. It will be understood that bifurcated navigation control systems and methods described herein may operate as part of or in conjunction with the computer-assisted medical system described herein, with other suitable computer-assisted medical systems that may or may not be surgical systems, and/or with other suitable medical and/or non-medical systems as may serve a particular implementation. 
       FIG. 2  illustrates an exemplary computer-assisted medical system  200  (“medical system  200 ”) that may be used to perform surgical and/or non-surgical medical procedures. As shown, medical system  200  may include a manipulator cart  202 , a user control system  204 , and an auxiliary system  206  communicatively coupled one to another. Medical system  200  may be utilized by a medical team to perform a computer-assisted medical procedure or other such operation on a body of a patient  208  or on any other body as may serve a particular implementation. As shown, the medical team may include a first clinician  210 - 1  (such as a surgeon for a surgical procedure), an assistant  210 - 2 , a nurse  210 - 3 , and a second clinician  210 - 4  (such as an anesthesiologist for a surgical procedure), all of whom may be collectively referred to as “team members  210 ,” and each of whom may control, interact with, or otherwise be a user of medical system  200 . Additional, fewer, or alternative team members may be present during a medical procedure as may serve a particular implementation. For example, for some medical procedures, the “clinician  210 - 1 ” may not be a medical doctor. Further, team composition for non-medical procedures would generally be different and would include other combinations of members serving non-medical roles. 
     While  FIG. 2  illustrates an ongoing minimally invasive medical procedure such as a minimally invasive surgical procedure, it will be understood that medical system  200  may also be used to perform open medical procedures or other types of operations that may benefit from the accuracy and convenience of medical system  200 . For example, operations such as exploratory imaging operations, mock medical procedures used for training purposes, and/or other operations may also be performed using medical system  200 . 
     As shown in  FIG. 2 , manipulator cart  202  may include a plurality of manipulator arms  212  (e.g., arms  212 - 1  through  212 - 4 ) to which a plurality of instruments (e.g., surgical instruments, other medical instruments, or other instruments) may be coupled. Each instrument may be implemented by any suitable surgical tool (e.g., a tool having tissue-interaction functions), medical tool, imaging device (e.g., an endoscope), sensing instrument (e.g., a force-sensing instrument), diagnostic instrument, or the like that may be used for a computer-assisted medical procedure such as a surgical procedure on patient  208  (e.g., by being at least partially inserted into patient  208  and manipulated to perform a computer-assisted medical procedure on patient  208 ). While manipulator cart  202  is depicted and described herein as including four manipulator arms  212 , it will be recognized that manipulator cart  202  may include only a single manipulator arm  212  or any other number of manipulator arms as may serve a particular implementation. Additionally, it will be understood that, in some exemplary systems, certain instruments may not be coupled to or controlled by manipulator arms, but rather may be handheld and controlled manually (e.g., by a surgeon, other clinician, or other medical personnel). For instance, certain handheld devices of this type may be used in conjunction with or as an alternative to computer-assisted instrumentation that is coupled to manipulator arms  212  shown in  FIG. 2 . 
     Manipulator arms  212  and/or instruments attached to manipulator arms  212  may include one or more displacement transducers, orientational sensors, and/or positional sensors used to generate raw (i.e., uncorrected) kinematics information. One or more components of medical system  200  may be configured to use the kinematics information to track (e.g., determine positions of) and/or control the instruments. 
     During the medical operation, user control system  204  may be configured to facilitate control by clinician  210 - 1  of manipulator arms  212  and instruments attached to manipulator arms  212 . For a surgical procedure, for example, clinician  210 - 1  may be a surgeon. Clinician  210 - 1  may interact with user control system  204  to remotely move or manipulate manipulator arms  212  and the instruments. To this end, user control system  204  may provide clinician  210 - 1  with imagery (e.g., high-definition 3D imagery) of an operational area associated with patient  208  as captured by an imaging device. In certain examples, user control system  204  may include a stereo viewer having two displays where stereoscopic images of an internal view of the body of patient  208  generated by a stereoscopic imaging device may be viewed by clinician  210 - 1 . Clinician  210 - 1  may utilize the imagery to perform one or more procedures with one or more instruments attached to manipulator arms  212 . 
     To facilitate control of instruments, user control system  204  may include a set of master controls. These master controls may be manipulated by clinician  210 - 1  to control movement of instruments (e.g., by utilizing robotic and/or teleoperation technology). The master controls may be configured to detect a wide variety of hand, wrist, and finger movements by clinician  210 - 1 . In this manner, clinician  210 - 1  may intuitively perform a procedure using one or more instruments. 
     Auxiliary system  206  may include one or more computing devices configured to perform processing operations of medical system  200 . In such configurations, the one or more computing devices included in auxiliary system  206  may control and/or coordinate operations performed by various other components of medical system  200  such as manipulator cart  202  and/or user control system  204 . For example, a computing device included in user control system  204  may transmit instructions to manipulator cart  202  by way of the one or more computing devices included in auxiliary system  206 . As another example, auxiliary system  206  may receive and process image data representative of imagery captured by an imaging device attached to one of manipulator arms  212 . 
     In some examples, auxiliary system  206  may be configured to present visual content to team members  210  who may not have other access to the images provided to clinician  210 - 1  at user control system  204 . To this end, auxiliary system  206  may include a display monitor  214  configured to display one or more user interfaces, one or more images (e.g., 2D images) of the operational area, information associated with patient  208  and/or the medical procedure, and/or any other content as may serve a particular implementation. In some examples, display monitor  214  may display images of an internal view of the operational area together with additional content (e.g., graphical content, contextual information, etc.). Display monitor  214  may be implemented by a touchscreen display with which team members  210  may interact (e.g., by way of touch gestures) to provide user input to medical system  200 , or may be implemented by any other type of display screen as may serve a particular implementation. 
     As will be described in more detail below, system  100  may be implemented within or may operate in conjunction with medical system  200 . For instance, in certain implementations, system  100  may be implemented entirely by manipulator cart  202 , or by sensors and/or computing components implemented by one or more other components of medical system  200 . 
     Manipulator cart  202 , user control system  204 , and auxiliary system  206  may be communicatively coupled one to another in any suitable manner. For example, as shown in  FIG. 2 , manipulator cart  202 , user control system  204 , and auxiliary system  206  may be communicatively coupled by way of control lines  216 , which may represent any wired or wireless communication link as may serve a particular implementation. To this end, manipulator cart  202 , user control system  204 , and auxiliary system  206  may each include one or more wired or wireless communication interfaces, such as one or more local area network interfaces, Wi-Fi network interfaces, cellular interfaces, and so forth. 
     To illustrate a specific environment and scenario in which system  100  may be employed to perform bifurcated navigation control of a manipulator cart such as manipulator cart  202 ,  FIG. 3  shows an exemplary operating room  300  within which manipulator cart  202  is to be navigated toward an operating table  302  along an exemplary path  304  that extends from an initial location  306 —initial to a target location  306 —target. Operating room  300  provides an environment in which, under direction of one or more members of a medical operation team (e.g., team members  210 ), medical system  200  is configured to perform a medical operation on a body located on operating table  302 . 
       FIG. 3  depicts a relatively small operating room  300  with a relatively simple layout. Specifically, as shown, location  306 —initial is located relatively close to location  306 —target within operating room  300 , and there are not shown any obstacles between locations  306 —initial and  306 —target. As a result, path  304  is shown to be relatively straightforward as a path with a single gentle curve. 
     System  100  may define locations  306  (e.g., location  306 —initial and  306 —target), as well as other locations described herein, based on any suitable coordinate system or other formal or informal spatial characterization. For instance, a global coordinate system relative to operating table  302 , a door or center of operating room  300 , a storage location of manipulator cart  202 , or any other suitable origin point may be defined, and locations  306  may be defined and analyzed with respect thereto. 
     As shown, location  306 —initial may be a location that is tucked out of the way in a corner of operating room  300 . For example, this location may be a storage location for manipulator cart  202  when medical system  200  is not in use (e.g., between medical operations, when a non-computer-assisted medical operation is being performed on operating table  302 , etc.). Location  306 —initial may also or alternatively be a preparation location for manipulator cart  202  where manipulator cart  202  may be covered with drapes and/or otherwise be sterilized and prepared to enter a sterile field  308  of operating room  300  in which the operation is to be performed. 
     Location  306 —target may be a location that is relatively proximate to operating table  302 . Specifically, location  306 —target may be positioned where manipulator cart  202  is to be located during performance of the medical operation on the body, therefore making location  306 —target nearer than location  306 —initial to operating table  302 . As depicted in  FIG. 3 , location  306 —target may overlap with operating table  302  from the top view because arms  212  incorporated within manipulator cart  202  may hover over operating table  302  when manipulator cart  202  is in an operative position at operating table  302 . In some examples, location  306 —target may be specifically selected by an operator of manipulator cart  202  (e.g., by selecting a point on a map, by selecting one of a plurality of predetermined locations for manipulator cart  202  that are associated with different operations, etc.). In other examples, however, location  306 —target may be automatically selected by system  100 . For instance, location  306 —target may be automatically selected in a manner that accounts for an operation type that is to be performed, photographic input representative of the room layout, a detected or expected location of cannulas on the body, gestures indicating the location by a person in a vicinity of the target area (e.g., gesturing by a bedside surgical team member), and/or any other criteria as may serve a particular implementation. 
     Other components of medical system  200  are also shown to be located in operating room  300  along with manipulator cart  202 . For example, user control system  204  is shown to be statically located in another corner of operating room  300  in this example (although it will be understood that user control system  204  may, in certain examples, be mobile), and auxiliary system  206  is shown to similarly be moved from an initial location that is away from the target location (e.g. which can be a storage location, a preparation location at the side of operating room  300 , a temporary parking location, etc.) to a target location within sterile field  308  near operating table  302 . It will be understood that other people and objects not explicitly shown may also be present within operating room  300 , although, for purposes of this example, it is understood that there is not any significant obstacle on or near path  304  between locations  306 —initial and  306 —target. 
     In the scenario illustrated in  FIG. 3 , both locations  306 —initial and  306 —target are relatively proximate to one another within operating room  300 . As such, path  304  has a clear beginning and a clear end and is fully contained within operating room  300 . In other examples, however, it will be understood that one or both of the initial and target locations may not be located within the same room as one another, or the initial and/or target locations associated with a path may not yet be explicitly designated while manipulator cart  202  is navigating along the path. For instance, in one example, manipulator cart  202  may be located external to operating room  300  (e.g., in a different operating room, in a storage closet outside operating room  300 , etc.) such that the initial location of manipulator cart  202  is external to room  300  and the target location (in this case, a location within room  300  where manipulator cart  202  will be draped and sterilized) is not designated until manipulator cart  202  enters operating room  300 . Analogously, it will be understood that an initial location and a target location may be swapped so that manipulator cart  202  may be rolled back out of the way of the medical operation location, to a storage location, to another operating room, etc. For instance, after the operation at operating table  302  is complete or if an emergency egress is initiated for manipulator cart  202 , manipulator cart  202  may be configured to navigate back along path  304  in similar (but opposite) manner as described above for navigating forward along path  304 . 
       FIG. 4  shows another exemplary operating room  400  within which manipulator cart  202  is to be navigated toward an operating table  402  via an exemplary path  404  from an initial location  406 —initial to a target location  406 —target near operating table  402  within a sterile field  408 . The scenario illustrated in  FIG. 4  is similar to that shown in  FIG. 3 , and each the of the principles described in relation to  FIG. 3  may similarly apply in the context of  FIG. 4 . However, operating room  400  of  FIG. 4  is shown to be considerably more complex than operating room  300  of  FIG. 3 . For example, a plurality of obstacles  410  (e.g., obstacles  410 - 1  through  410 - 4 ) that must be avoided or otherwise accounted for in the planning of path  404  are located on the ground between locations  406 —initial and  406 —target. Moreover, an obstacle  412  that is shaded in with a different hatch-line pattern than obstacles  410  will be understood to represent an overhead obstacle that also must be accounted for in the defining of path  404 . 
     As described above, system  100  may be configured to define path  404  from location  406 —initial to location  406 —target to thereby allow system  100  to autonomously control the steering of manipulator cart  202  as an operator controls the propulsion (in accordance with any propulsion limitations that may be imposed) in the bifurcated navigation control mode. This path may be defined in any manner as may serve a particular implementation. For example, system  100  may further comprise (e.g. as part of or in addition to facilities  102  and  104 ) at least one sensor such as a visual light image sensor (e.g., a camera, a video capture device, etc.), an infrared image sensor, a depth sensor (e.g., a time-of-flight (“TOF”) sensor, a Light Detection and Ranging (“LIDAR”) sensor, an ultrasonic sensor, a radar sensor, a laser range finder, etc.), or any other sensor configured to detect characteristics of the natural world in a manner that facilitates the defining of a path for manipulator cart  202 . Such sensors may be integrated with manipulator cart  202  itself (e.g., such as by being mounted on arms  212  or a base or other part of manipulator cart  202 ), or may be integrated with other components of medical system  200  or otherwise located in operating room  400  independently from manipulator cart  202  (e.g., mounted on the wall, attached to operating table  402 , etc.). 
     In examples where system  100  includes or is in communication with one or more of these types of sensors, system  100  may perform the defining of path  404  by receiving sensor data from the at least one sensor and defining the path based on the received sensor data. For example, system  100  may receive image data and/or depth data from one or more vantage points and representative of real-time locations of obstacles  410  and/or  412 . Consequently, system  100  may define path  404  in a manner that attempts to avoid or otherwise appropriately handle each of obstacles  410  and/or  412  that the sensors detect. 
     As system  100  plans and defines path  404  whereby manipulator cart  202  is to navigate from location  406 —initial to location  406 —target, system  100  may account for various factors. For example, system  100  may detect an obstacle between location  406 —initial and location  406 —target (e.g., one of obstacles  410  or  412 ), determine a movability status of the obstacle, and account for the movability status of the obstacle in the defining of path  404 . As used herein, a “movability status” associated with an obstacle may refer to characteristics of the obstacle related to how easily the obstacle may be relocated, how much free space is around the obstacle, whether the obstacle is limited in movement by cables connected to the obstacle, how likely the obstacle is to relocate on its own (e.g., whether the obstacle is a person who appears to have awareness of manipulator cart  202  and is likely to move out of the way), and so forth. 
     Accordingly, accounting for a movability status of an easily movable obstacle (e.g., a stool, an observer, etc.) may be done differently than accounting for a movability status of a more permanent or non-movable obstacle (e.g., an anesthesiologist station that is set up near the operating table, etc.). For instance, an easily movable obstacle may be accounted for by routing the path to go through the obstacle and then indicating to the operator that the obstacle should be moved out of the way, while a more permanent or less conveniently-movable obstacle may be accounted for by routing the path around the obstacle to avoid the obstacle altogether. In other examples, certain obstacles may be determined to be likely to move on their own (e.g., a person who crosses over the path but has a clear movement vector indicating that they will not remain on the path for long, etc.) and, at least while the obstacles are not immediately proximate to the manipulator cart, may be treated as a lower priority to avoid or may be ignored by system  100  altogether in the defining of path  404 . Additionally, certain overhead obstacles (e.g., obstacle  412 ) may be accounted for by lowering an operating platform of manipulator cart  202  to a boom and arms  212  are attached. By lowering the operating platform in this way, overhead obstacles may be passed under rather than needing to be routed around. 
     As another exemplary factor for which system  100  may account when defining path  404 , system  100  may, after detecting an obstacle between location  406 —initial and location  406 —target, determine a risk factor, and account for the risk factor in the defining of path  404 . As used herein, a “risk factor” may refer to anything relating to an obstacle, a manipulator cart being navigated, the path being navigated, or any other aspect of the navigation that may be associated with adverse consequences. For example, one risk factor may be that if a speed of the propulsion is too high for a particular curve of the path, the manipulator cart could be at risk of tipping, causing damage to the manipulator cart. As another example, a risk factor associated with a particular obstacle may relate to consequences of the manipulator cart coming into contact with the particular obstacle as the manipulator cart traverses the path, thereby causing potential damage or a sterility breach to the manipulator cart and/or potential damage to the particular obstacle. 
     As such, accounting for a risk factor of an obstacle that is fragile or delicate, valuable or expensive to replace, or that is sterile and intended to remain so, may be done differently than accounting for a risk factor of an obstacle that is less consequential for manipulator cart  202  to come into contact with (e.g., a sterile object that a sterile manipulator arm may brush up against). For example, a delicate, expensive, or sterile obstacle may be accounted for by steering around the obstacle with a relatively wide margin to ensure that manipulator cart  202  does not contact the obstacle even if the obstacle moves or there is a miscalculation in navigating path  404 . In contrast, an object that is not subject to any severe consequence if contacted by manipulator cart  202  (e.g., a stool that would just be bumped out of the way, etc.) may be accounted for by steering around the obstacle with a relatively narrow margin or no margin, thereby assuming the lower risk of negative consequence if minor contact is made. 
     In various examples, system  100  may account for obstacles by steering around the obstacles, requesting that the obstacles by manually moved (e.g., projecting a light of one color on an obstacle to be moved and a light of another color on obstacles that do not need to be moved), lowering the operating platform to pass under the obstacles, raising the operating platform so that arms attached to the boom pass over the obstacles, altering a pose of one or more arms (e.g., spreading or narrowing the spread of the arms, rotating the arms from one side of the cart to the other, lifting or lowering the arms, etc.), or in any other suitable way. Additionally, along with accounting for obstacles, system  100  may further account for other factors that affect the navigation of manipulator cart  202  along path  404 . For example, system  100  may account for the width of manipulator cart  202  in determining a width of path  404  (e.g., including a margin), a turn radius of manipulator cart  202 , which paths people moving about in operating room  400  tend to use to avoid obstacles, whether and how obstacles such as people are moving, how reconfigurable object surfaces are (e.g., distinguishing among solid, monolithic objects, objects with joints or flexible regions that allow bending and shape reconfiguration, objects covered by baggy drapes, etc.), and so forth. 
     In some implementations, system  100  may be configured to define and provide an operator with a plurality of path options, to thereby allow the operator to participate in the defining of path  404  by selecting one of the path options. Specifically, for example, the defining of path  404  by system  100  may include 1) defining a plurality of different paths whereby manipulator cart  202  could navigate from location  406 —initial to location  406 —target, and 2) selecting path  404  from the plurality of different paths and based on input from an operator. Additionally or alternatively, system  100  may request or accept additional operator input to define or revise path  404  in accordance with operator preferences. 
     In some scenarios (e.g., such as the relatively simple scenario illustrated in  FIG. 3 ), it may be possible and desirable for system  100  to define an entire path (or a plurality of options for several entire paths) prior to manipulator cart  202  beginning to navigate along the path. In other examples, however, it may be difficult, impractical, impossible, or undesirable to define path  404  in its entirety at the outset in this way. This may be the case for a variety of reasons. For example, obstacles may be dynamically moving (e.g., some moving out of the way and others getting in the way after manipulator cart  202  has begun navigating). As another example, sensors may provide different characterizations (e.g., more comprehensive characterizations) from different locations along path  404  as different parts of the room become occluded or unoccluded from the vantage point of the sensors as the sensors move. Due to the dynamic and mobile nature of manipulator cart  202 , as well as, in some examples, the dynamic and mobile nature of certain sensors and/or obstacles, system  100  may be configured to update path  404  while manipulator cart  202  is navigating along path  404 , to dynamically provide different path options that may be identified or detected during navigation, or to otherwise dynamically alter path  404  as path  404  is being navigated. 
     System  100  may plan path  404  based on a predefined map of operating room  400  that system  100  accesses and that indicates the layout of operating room  400  (e.g., including wall placement, ceiling height and overhead obstacle height and layout, locations and configurations of permanent obstacles, the location and configuration of operating table  402 , etc.). However, system  100  may also add to this predefined information a more dynamic analysis of temporary or new obstacles, dynamic docking considerations (e.g., detected locations of cannulas, etc.), and so forth. Sensors positioned in a manner that may be at least partially controlled by system  100  may be particularly useful for dynamic path definition. For example, sensors positioned on a boom or on individual arms  212  of manipulator cart  202  may be configured to continuously scan operating room  400  to capture new perspectives as manipulator cart  202  navigates along path  404 . In some examples, system  100  may raise or lower an operating platform, rotate a boom to which arms  212  are attached, reposition a particular link or joint of an arm  212 , or otherwise make adjustments to manipulator cart  202  in order to gather sensor data from different perspectives. In some examples, the predefined map of operating room  400  used by system  100  may have been generated (or may be generated in real time) by system  100  using simultaneous localization and mapping (“SLAM”) techniques or other such techniques to build and update a three-dimensional model of operating room  400 . 
     Even when system  100  has a degree of control over the sensors, it may not be possible in certain examples for system  100  to locate and positively identify location  406 —target until manipulator cart  202  approaches the target location. As such, system  100  may direct, prior to the defining of path  404 , manipulator cart  202  to be moved from a first location from which location  406 —target is undetectable by a sensor of manipulator cart  202  to a second location from which location  406 —target is detectable by the sensor. While manipulator cart  202  is at this second location, system  100  may determine that the sensor detects location  406 —target and, in response to the determining that the sensor detects location  406 —target, may designate the second location to be location  406 —initial (i.e., the location at which path  404  begins). 
       FIG. 4  illustrates a path  404  that may be traversed by manipulator cart  202  by always using forward propulsion (i.e., moving in a forward direction). However, it will be understood that, in certain examples, an implementation of path  404  may be defined to include at least one portion in which manipulator cart  202  uses backward propulsion in order to progress along the path from the initial location to the target location. For example, the turning radius of the manipulator cart  202  may be larger than the radius of the turn needed by the path, and back-and-forth movement of the manipulator cart  202  while turning the manipulator cart  202  may allow the manipulator cart to achieve the sharper turn. As another example, an implementation of a path  404  may have a dead end from which manipulator cart  202  may need to be backed out (i.e., use backwards propulsion to move in a backwards direction) to traverse a new or revised path  404 . In such examples, manipulator cart  202  may indicate to the operator that the operator should commanded propulsion in a reverse direction (e.g., begin pulling backwards rather than pushing forwards) in order to reach the target location. In further examples, a backwards portion of a path  404  may be planned into the path initially when the path is defined. 
     Medical system  200  is only shown to include a single manipulator cart  202  and, as shown by  FIGS. 3 and 4 , this manipulator cart  202  alone is presumed to perform manipulation tasks in connection with the operation being performed at operating tables  302  and  402 . It will be understood, however, that in certain examples, more than one manipulator cart, or a manipulator cart and another equipment component of medical system  200 , may both be navigated to the operating table for use in the operation. For example, medical system  200  may further include an additional equipment component besides manipulator cart  202  and the other equipment components illustrated in  FIGS. 2-4 , such as a second manipulator cart (e.g., a manipulator cart with more than, fewer than, or an equal number of, manipulator arms as manipulator cart  202 ), an equipment component that moves on a track or freely along a floor, an equipment component that moves through the air (e.g., a drone, etc.), or any other equipment component as may serve a particular implementation. In this example, the defining of the path may be performed to account for an additional path whereby the additional equipment component is to navigate from an additional initial location to an additional target location. For instance, path  404  may be defined so as to avoid not only obstacles  410  and  412 , but also to not interfere with (or risk interference from) a path of one or more additional equipment components that may exist in a particular implementation of medical system  200  (not shown in  FIG. 4 ). To this end, the defining of path  404  may account for the additional path based on locations of manipulator cart  202  and the additional equipment component, roles that manipulator cart  202  and the additional equipment component are to have in performing the operation at operating table  402 , and so forth. 
     Along with directing a base of manipulator cart  202  to be navigated along path  404  from location  406 —initial to location  406 —target, system  100  may similarly be configured, in addition or as an alternative to the navigation of the base, to navigate and move other components of manipulator cart  202  in accordance with a predefined or dynamically defined path (e.g., path  404 ). That is, during navigation of manipulator cart  202  toward location  406 —target and/or once the base of manipulator cart  202  has arrived at location  406 —target, system  100  may further direct manipulator cart  202  to be reoriented to a target orientation. Alternatively or in addition, during navigation of manipulator cart  202  toward location  406 —target and/or once the base of manipulator cart  202  has arrived at location  406 —target, system  100  may further direct other movable components of manipulator cart  202  (e.g., an operating platform, a boom, one or more manipulator arms  212 , etc.) to become reoriented, posed, and otherwise reconfigured as part of, in addition to, or as an alternative to the navigation of path  404 . For instance, in certain examples, initial location  406 —initial may be associated with an initial configuration of a movable component of manipulator cart  202 , target location  406 —target may be associated with a target configuration of the movable component of manipulator cart  202 , and the defining of path  404  may further include defining, with respect to path  404 , a configuration plan whereby the movable component of manipulator cart  202  is to transform from the initial configuration to the target configuration. 
     Although  FIGS. 3 and 4  have been described with initial and target locations for the manipulator cart  202 , the technique described can also be applied to transition from an initial orientation to a target orientation of the manipulator cart  202 , and from an initial configuration to a target configuration of the manipulator cart. 
     To illustrate,  FIGS. 5 and 6  show, respectively, a series of side views and a series of top views of manipulator cart  202  as manipulator cart  202  navigates from location  406 —initial and corresponding initial orientation and configuration to location  406 —target and corresponding target orientation and configuration associated with path  404 . Specifically, as shown in  FIG. 5 , a series of snapshots  500  (e.g., snapshots  500 - 1  through  500 - 3 ) depict manipulator cart  202  from a side view at three different points in time as manipulator cart  202  traverses path  404 . Similarly, as shown in  FIG. 6 , a series of snapshots  600  (e.g., snapshots  600 - 2  through  600 - 4 ) depict manipulator cart  202  from a top view at three different points in time that will be understood to overlap with the points in time associated with snapshots  500 . Specifically, snapshot  600 - 2  will be understood to depict a top view of manipulator cart  202  at the same point in time depicted by the side view of snapshot  500 - 2 , and snapshot  600 - 3  will be understood to depict a top view of manipulator cart  202  at the same point in time depicted by the side view of snapshot  500 - 3 . 
     Various movable components of manipulator cart  202  are labeled in each snapshot  500  and  600 . Specifically, manipulator cart  202  is shown to have a base  502  that, when moved across the floor (e.g., driving on wheels or the like that are not explicitly shown), relocates the entire manipulator cart  202 . Manipulator cart  202  is further shown to include an operating platform  504  that may be raised and lowered, and to which is attached a boom  506  that may be extended, retracted, pivoted, and so forth. One or more manipulator arms  212  are attached to boom  506  and may each be laterally translated, spread out, brought in, rotated, and/or manipulated in any other manner as may serve a particular implementation. It will be understood that other movable components not explicitly illustrated herein may also be present on manipulator cart  202  or on other manipulator cart implementations. 
     In some examples, the navigation of base  502  of manipulator cart  202  along path  404  may be planned and performed independently and separately in time from the reconfiguration of other movable components such as operating platform  504 , boom  506 , and/or arms  212 . However, in other examples such as shown in  FIGS. 5 and 6 , a navigation plan and a configuration plan for manipulator cart  202  may be integrated together such that the navigation of base  502  along path  404  may be performed concurrently with the reconfiguration of the other movable components. In some examples, there may be a seamless and/or integrated transition between navigation control of base  502  and configuration control of other movable components. In certain implementations, these types of control may all be treated the same and may be considered to be part of the navigation along path  404 . As such, manipulator cart  202  may not be considered to have completed navigation along path  404  until not only base  502  has arrived at location  406 —target and orientated in a target orientation, but also operating platform  504 , boom  506 , arms  212 , and other movable components of manipulator cart  202  have been properly positioned and configured to allow instruments to be connected to arms  212  and docked with cannulas associated with the body on operating table  402 . In some instances, no further steps for configuring manipulator cart  202  may be necessary before manipulator cart  202  is ready to begin the medical operation. In other instances, further steps for configuring manipulator cart  202  (e.g., further adjustment of arms  212 , adjustment of instruments connected to arms  212 , etc.) may be appropriate before manipulator cart  202  is ready to begin the medical operation. 
     Snapshot  500 - 1  depicts a lateral movement  508  of base  502  along path  404 . Movements such as movement  508  may ultimately result in manipulator cart  202  moving from location  406 —initial to location  406 —target, as described above. In snapshot  500 - 1 , manipulator cart  202  is shown in an initial configuration that may be associated with a relatively small footprint of manipulator cart  202  (e.g., a minimized amount of space that manipulator cart  202  may take up) in which manipulator cart  202  may be configured when not in use (e.g., when being stored, etc.). As shown, in the initial configuration of snapshot  500 - 1 , operating platform  504  may be completely lowered, boom  506  may be completely retracted, and arms  212  may be tucked away and brought in as much as possible. This initial configuration may be useful for navigating certain parts of path  404 . For example, as shown, the initial configuration may allow manipulator cart  202  to pass under overhead obstacle  412  even though, if operating platform  504  were raised somewhat, manipulator cart  202  would not fit under overhead obstacle  412  and obstacle  412  would need to be steered around rather than passed under. Accordingly, path  404  may incorporate and be dependent upon the configuration plan of manipulator cart  202  in the sense that path  404  may be defined to have a requirement that manipulator cart  202  be in a particular configuration (e.g., the initial configuration) when manipulator cart  202  passes under obstacle  412 . Analogously, path  404  may incorporate changes in the orientation of manipulator cart  202  to facilitate moving of the manipulator cart  202  to location  406 —target. 
     In snapshots  500 - 2  (providing a side view) and  600 - 2  (providing a top view), manipulator cart  202  has arrived at operating table  402  and will be understood to be located at location  406 —target such that base  502  has completed all the lateral movements (e.g., movement  508 ) defined for path  404 . At this point in time, it may be desirable for arms  212  to be positioned over operating table  402 , but, if manipulator cart  202  is still in the initial configuration of snapshot  500 - 1 , arms  212  would be too low to the ground and would come into contact with operating table  402  if boom  506  were to be extended. Accordingly, as shown in snapshot  500 - 2 , operating platform  504  may be raised by a movement  510  to lift arms  212  above operating table  402 . 
     Thereafter, snapshots  500 - 3  (providing a side view) and  600 - 3  (providing a top view) illustrate that boom  506  may now be safely extended by a movement  512  until arms  212  are hovering over operating table  402 . For example, boom  506  may be extended until laser crosshairs associated with an arm  212  associated with imaging equipment (e.g., an endoscope) becomes properly aligned with a target cannula that has been inserted into a body (not explicitly shown) on operating table  402 . When this alignment is achieved, arms  212  may each be docked to a respective cannula and instruments may be attached to each arm  212  and inserted into the respective cannula. Once each arm  212  is docked with its respective cannula and any further steps to adjust components of manipulator cart  202  or to set up medical system  200  are complete, the medical operation to be performed by medical system  200  may begin. 
     In certain examples, arms  212  may need to be adjusted (e.g., spread, rotated, reconfigured, etc.) in order to become properly aligned with the cannulas in the manner described above. To illustrate, snapshot  600 - 4  shows how arms  212  may be spread out from one another and rotated in a movement  602  until each arm is properly aligned and ready for docking with a respective cannula so that the medical operation can begin. Once this final movement is complete, manipulator cart  202  may not only be located at location  406 —target, but may also be in the target orientation and/or target configuration associated with the particular medical operation that is to be performed. As such, system  100  may determine and indicate to the operator (e.g., by way of visual, haptic, audible, or any other suitable type of feedback) that the navigation and configuration of manipulator cart  202  is complete. 
     As mentioned above, reconfiguration of one or more movable components of manipulator cart  202  may be performed separate in time from, or may be integrated with, the movement of base  502  along path  404 . For example, in one implementation, the raising of operating platform  504  by movement  510  and the extending of boom  506  by movement  512  may be performed sequentially after movement  508  is complete and base  502  is parked at location  406 —target. In other implementations, however, the raising of operating platform  504  by movement  510  and the extending of boom  506  by movement  512  may be performed concurrently with movement  508  and before base  502  has arrived at location  406 —target. For example, movement  510  may be initiated as soon as obstacle  412  has been cleared (passed under) and movement  512  may be initiated as soon as operating platform  504  has been raised enough that arms  212  will not come into contact with operating table  402  or a body disposed thereon. In this way, additional valuable time in operating room  400  may be conserved as manipulator cart  202  may be in a location (and orientation and/or configuration, as applicable) even sooner to begin the operation. Moreover, as an additional potential way of conserving time, respective instruments could be attached to arms  212  and docked with cannulas while movement  508  of base  502  is still ongoing in certain examples. The parallelizing of various movements associated with the navigation along path  404  in these ways will be described and illustrated in more detail below with respect to  FIGS. 10 and 11 . 
     While implementations have been described above that include both navigation and reconfiguration of movable components of manipulator cart  202 , it will be understood that, in certain implementations, system  100  may only be tasked with navigation or reconfiguration of a manipulator cart, and not both. For instance, certain implementations of system  100  may only be configured to assist operators in steering a manipulator cart to a target location, or only configured to assist operators in steering the manipulator cart to a target location and orientation, and users may direct the configuration of other movable components of the manipulator cart without assistance from system  100  once the base of the manipulator cart is in position. As another example, an implementation of system  100  associated with a manipulator system that is, for example, attached bedside to an operating table or that is configured to be moved along a physical track or the like, may not benefit from navigation assistance of system  100 . Rather, such a manipulator system may benefit only from assistance of system  100  in configuring movable components such as an operating platform, a boom, and/or manipulating arms. 
     System  100  may direct manipulator cart  202  to traverse different portions of path  404  in different navigation control modes. For example, as described above, system  100  may direct manipulator cart  202  to navigate along certain portions of path  404  in a bifurcated navigation control mode in which system  100  autonomously controls a steering of manipulator cart  202  while allowing operator control of a propulsion of manipulator cart  202  (e.g., in accordance with a propulsion limitation defined based on an identified navigation condition in certain examples, and not accounting for such a propulsion limitation in other examples). Along other portions of path  404 , system  100  may instead direct manipulator cart  202  to navigate in a standard navigation control mode in which system  100  allows operator control of both steering and propulsion of manipulator cart  202 . 
     To illustrate,  FIG. 7  shows various exemplary navigation control modes that may be employed as manipulator cart  202  navigates from location  406 —initial (and a corresponding initial orientation and/or a corresponding initial configuration) to location  406 —target (and a corresponding target orientation and/or a corresponding target configuration). Specifically,  FIG. 7  shows representations of a standard navigation control mode  702  and two different bifurcated navigation control modes  704  (bifurcated navigation control modes  704 - 1  and  704 - 2 ). In each navigation control mode representation depicted in  FIG. 7 , an indication is given of who or what commands the steering and the propulsion of manipulator cart  202  by labels indicating “Automated System Command” (i.e., automatically commanded by system  100 ) or “Operator Command” (i.e., commanded by a human operator) being placed, as appropriate, in columns for “Steering” and “Propulsion”. The entity indicated to command the steering determines which direction the manipulator cart will go when moved. The entity (or entities) indicated to command the propulsion determines the movement, speed, and acceleration of the manipulator cart, whether in a forward direction (positive speed), a backward direction (negative speed), or remaining at a standstill (zero speed). 
     As shown, standard navigation control mode  702  is characterized by the operator dynamically commanding both the steering and the propulsion of manipulator cart  202 . In contrast, bifurcated navigation control modes  704 - 1  and  704 - 2  are both characterized by bifurcating the steering and propulsion control in different ways, each allowing operator control of some or all aspects of the propulsion while the steering is controlled by system  100  automatically. It will be understood that other navigation control modes not explicitly shown (e.g., a navigation control mode providing automated system command of the steering and the magnitude of the speed while allowing operator command of whether the manipulator cart moves at a positive (i.e., forward), negative (i.e., backward) or zero speed) may also be employed in certain examples. 
     The differences between bifurcated navigation control modes  704 - 1  and  704 - 2  include the extent to which the system is involved in propulsion control.  FIG. 7  shows that in bifurcated navigation control mode  704 - 1 , the steering of manipulator cart  202  is entirely under automated system command, while the propulsion of manipulator cart  202  is entirely operator commanded. Accordingly, it will be understood that, in bifurcated navigation control mode  704 - 1 , system  100  may be configured to automatically control the steering, and to not impose any propulsion limitations on the propulsion based on navigation conditions. A bifurcated navigation system may or may not implement navigation control mode  704 - 1 . In systems that do implement navigation control mode  704 - 1 , mode  704 - 1  may be the only bifurcated navigation control mode available, or may be one of a plurality of bifurcated navigation control modes available. Where mode  704 - 1  is one of a plurality of bifurcated navigation control modes available, as shown in  FIG. 7 , it may be active in response to being a default control mode when the system enters into bifurcated navigation, to one or more navigation conditions indicating no propulsion limitations are applicable, to the operator indicating that he or she wishes to have full propulsion control without system-imposed limitations, etc. 
     In bifurcated navigation control mode  704 - 2 , the steering of manipulator cart  202  is entirely under automated system command, while the propulsion (e.g., forward or backward speed along path  404 , remaining stopped on path  404 , etc.) is controlled by a human operator with one or more propulsion limitations imposed by system  100 . This is illustrated in  FIG. 7  by the Propulsion column overlapping with both “Automated System Command” and “Operator Command.” As a specific example, the control interface described above in relation to bifurcated navigation control mode  704 - 2  may be configured to detect an operator&#39;s selection of a speed, onto which a system-imposed propulsion limitation is applied; the system and the operator therefore both contribute to the propulsion control. For example, as will be described in more detail below, the operator may control the speed of manipulator cart within system-imposed propulsion limits such as maximum or minimum speed limits, maximum or minimum acceleration limits, etc. In some examples, the operator&#39;s selection of the propulsion may be from a plurality of distinct propulsion settings (e.g. a plurality of discrete speed settings). In other examples, the operator&#39;s selection of the propulsion may be from a continuous spectrum of potential propulsion settings (e.g. an analog input allowing an infinite number of speed settings). Both discrete and continuous propulsion may be based on an input associated with an amount of exertion (e.g., amount and/or direction of force or torque) applied by the operator to command movement of the manipulator cart  202 . 
     Various transitions  706  between navigation control modes  702  and  704  are shown in  FIG. 7  to illustrate that the system may transition between navigation control modes  702  and  704  in any suitable way and for any suitable reason as may serve a particular implementation. For example, certain implementations may support all of the navigation control modes  702 ,  704 - 1 , and  704 - 2  shown in  FIG. 7 , and during operation may transition from mode to mode as the operator or navigation conditions may dictate. As described above, certain implementations may not include bifurcated navigation control mode  704 - 1 , in which case the system may transition between modes  702  and  704 - 2  as appropriate. Further, certain implementations may not include navigation control modes  702  and  704 - 1 . 
     Before system  100  may operate in a navigation control mode (e.g. mode  702 ,  704 - 1 , or  704 - 2 ) where manipulator cart  202  can begin to navigate or move at all, system  100  may monitor for certain criteria being met. For instance, in certain examples, manipulator cart  202  is first determined to be navigable (e.g., based on one or more criteria such as powered on, able to be moved, not have parking feet deployed, have powered drive operational, not have brakes engaged, and so forth). In some implementations, system  100  determines navigability further based on indications of stage of medical procedure (e.g. to not have any arm  212  attached to a cannula or instrument). Once manipulator cart  202  is determined to be navigable, system  100  may check for additional criteria to determine whether any of bifurcated navigation control modes  704  (or a single bifurcated navigation control mode  704 - 1  or  704 - 2  if the system supports only one bifurcated navigation control mode) are to be made available for use. For example, system  100  may determine one or more of: if manipulator cart  202  is in a stowed position (e.g., such as shown above in snapshot  500 - 1  of  FIG. 5 ), if a suitable path from an initial location to a target location (and, as applicable, from an initial orientation or configuration to a target orientation or configuration) can be defined, or the like. 
     In some examples, the entire path (e.g., path  404 ) may be defined before manipulator cart  202  begins to traverse the path. In other examples (as described above), however, the entire path (e.g., path  404 ) may not be defined from the outset before manipulator cart  202  begins to traverse the path (i.e., because the path may be defined and updated dynamically as manipulator cart  202  is moving along the path). If sensors used for pathfinding are blocked, or system  100  determines that no suitable path exists (e.g., because no path actually does exist, because a path cannot be found, because paths that are found are too complex or narrow, etc.), system  100  may determine (and indicate to the operator through visual, audible, haptic, or other suitable cues) that no bifurcated navigation control mode is currently to be made available, and apply the standard navigation control mode. 
     If system  100  determines that a bifurcated navigation control mode  704  is available for use, it may be desirable for manipulator cart  202  to navigate the entirety of path  404  in a single bifurcated navigation control mode (e.g. control mode  704 - 1  or  704 - 2 ), or while switching between bifurcated navigation control modes  704  (e.g., in bifurcated navigation control mode  704 - 1  when navigation conditions do not call for any propulsion limitation, and in bifurcated navigation control mode  704 - 2  when such a propulsion limitation is appropriate in light of the navigation conditions). However, in certain situations, particular conditions or events may cause system  100  to make the bifurcated navigation control modes  704  unavailable during the navigation, such that system  100  switches out of any active bifurcated navigation control mode  704 . For example, system  100  may switch from one of bifurcated navigation control modes  704  to standard navigation control mode  702  in order to allow operator control of both the steering and the propulsion of the manipulator cart in response to pathfinding issues. Once any pathfinding issues are resolved (e.g., once obstacles have been cleared, once the target location is identified or re-acquired, once a valid path can be determined, etc.) and/or once an operator so indicates, system  100  may transition from standard navigation control mode  702  back to an appropriate one of bifurcated navigation control modes  704 . 
     In some examples, system  100  may be configured to exit bifurcated navigation in response to operator input. For example, system  100  may receive, while in one of bifurcated navigation control modes  704 , operator input resisting autonomous steering of the manipulator cart. For example, the operator input may be received at the control interface by the operator exerting a force on the control interface that opposes the steering control that system  100  is performing. In other examples, operator input may not involve physically resisting the system steering control, but instead may involve the pressing of a button or switch, the ceasing of pressing a button or switch, or the selection of another suitable user input mechanism by the operator. In response to any such operator input, system  100  may transition from directing the navigation along the path in the bifurcated navigation control mode  704  to allowing the navigation along the path in standard navigation control mode  702 . System  100  may also indicate to the operator (e.g., using a haptic rumble or any other feedback cue described herein) that the navigation control mode has been changed. 
     In other examples, the switching to standard navigation control mode  702  from the bifurcated navigation control mode  704  may be based on conditions other than explicit user input. For example, system  100  may identify a navigation condition associated with the navigation of manipulator cart  202  along path  404 , and, based on the navigation condition, may transition (and indicate the transition to the operator) from directing the navigation along path  404  in one of bifurcated navigation control modes  704  to allowing the navigation along path  404  in standard navigation control mode  702 . 
     The navigation condition identified may be any of various conditions and/or events that system  100  may detect, and may be the same, similar, or different from navigation conditions discussed below that may be the basis for defining propulsion limitations. For example, one navigation condition that may be determined to initiate a switch from one of bifurcated navigation control modes  704  to standard navigation control mode  702  may be that operating table  402  is detected to have moved from its prior location, thus necessitating a recalculating of location  406 —target and path  404 . Other navigation conditions may include that a battery of manipulator cart  202  is detected to be low or fully exhausted, that manipulator cart  202  or a component thereof is detected to be out of place (e.g., arms  212  splayed too widely) or to not be functioning properly, that manipulator cart  202  has not been fully sterilized (e.g., draped) and is hence not prepared to be placed in the sterile field for the operation, or the like. In still other examples where path  404  is being defined dynamically as manipulator cart  202  is navigating along the path, a navigation condition initiating a return to standard navigation control mode  702  may be that path  404  is detected to become unnavigable, system  100  fails to find the next portion of path  404 , sensor line-of-sight to location  406 —target is lost (e.g., because sensors are blocked, etc.), or the like. In yet another example, detection of general motion of obstacles and other objects within operating room  400  may cause system  100  to decrease a confidence level of a previously-defined path until it is determined that the path must be redefined. For instance, system  100  may measure the amount of entropy in operating room  400 , the level of activity in operating room  400 , or the like, and determine, based on that measurement, whether to proceed in a bifurcated navigation control mode  704  or to require navigation to proceed in standard navigation control mode  702  so that a human operator can determine how best to deal with the complexity. 
     While  FIG. 7  does not explicitly indicate how an operator is to provide operator commands, it will be understood that such commands may be input by way of any control interface as may serve a particular implementation. For instance, in certain implementations or for certain portions of the navigation, a primary control interface may be used such as a handlebar-based control interface integrated into manipulator cart  202 , or one or more other suitable control mechanisms (e.g., a steering wheel, a joystick, a touch screen control panel, a remote control, a throttle, one or more buttons or switches, etc.). In other implementations or for other portions of the navigation, a secondary or auxiliary control interface that is distinct and separate from the primary control interface may be used. For example, a secondary control interface may be employed that is suitable and convenient for use in a bifurcated navigation control mode such as one of bifurcated navigation control modes  704 , but that might not be suitable for use in standard navigation control mode  702  because the secondary control interface is not as well-suited to facilitate operator control of steering of manipulator cart  202 . For instance, exemplary secondary control interfaces may include gesture-based control interfaces, voice-controlled interfaces, manipulator arm-guided interfaces (e.g., in which an operator guides manipulator cart  202  by pulling or pushing on a particular manipulator arm  212 ), separate input devices such as separate joysticks or control pads, or the like. While certain secondary control interfaces may not be well-suited to facilitate operator control of steering, other secondary control interfaces may be configured to facilitate operator control of both the propulsion and the steering of the manipulator cart, but may be auxiliary to the primary control interface by otherwise including fewer features than the primary control interface, by being used from an opposite side of the manipulator cart than the primary control interface, or in other suitable ways. For example, certain such secondary control interfaces may be configured to be used by an operator in a sterile environment (e.g., an operator located in a sterile field on a patient side of the manipulator cart, rather than located in a non-sterile field on the opposite side of the manipulator cart). 
       FIG. 8  illustrates exemplary components of a control interface that may be employed during navigation of manipulator cart  202  from location  406 —initial to location  406 —target. Specifically,  FIG. 8  illustrates a control interface  800  implemented as a handlebar-based primary control interface. As shown, control interface  800  is implemented as a handlebar-based control interface integrated into manipulator cart  202  (i.e., built into manipulator cart  202  such as on the opposite side of manipulator cart  202  from arms  212 ).  FIG. 8  shows various controls that may be included in control interface  800  in a particular implementation. Specifically, control interface  800  is shown to include drive switches  802  (i.e., drive switches  802 - 1  and  802 - 2 ) built into handlebars that allow an operator to conveniently steer and/or direct propulsion of manipulator cart  202 . For example, in standard navigation control mode  702 , one or both of drive switches  802  may be pressed to cause manipulator cart  202  to drive forward, and turns may be directed by the user pulling or pushing the handlebars to one side or the other. The handlebars and drive switches  802  may thus be used to steer and direct propulsion of manipulator cart  202  along a path such as path  404 . 
     Other controls included within control interface  800  may facilitate operator-guided movement of other movable components of manipulator cart  202 . For example, control interface  800  includes a boom position knob  804  that may be pushed forward to extend boom  506  (e.g., such as illustrated by movement  512 ), pulled backwards to retract boom  506 , pushed left or right to pivot boom  506 , or turned clockwise or counterclockwise to rotate arms  212  on boom  506  (e.g., such as illustrated by movement  602 ). As another example, control interface  800  is shown to include a boom height rocker switch  806  that, when pushed forward may raise operating platform  504  (e.g., such as illustrated by movement  510 ), and when pulled backward may lower operating platform  504 . Additionally, as further shown, control interface  800  may include various buttons  808  (e.g., buttons  808 - 1  and  808 - 2 ) used to input an emergency stop command (button  808 - 1 ), to power on and off manipulator cart  202  (button  808 - 2 ), or to perform other operations as may serve a particular implementation. While a few specific input controls are explicitly shown in  FIG. 8  for illustration, it will be understood that more or fewer controls that perform similar or different functionality as described above may be included on other implementations of control interface  800 . 
     Along with the controls described above, control interface  800  is shown to further include a touchscreen  810  used to accept other types of input commands (e.g., based on user selection of touchscreen panels) and to provide output information to the operator. Specifically, touchscreen  810  may provide visual feedback to the operator, while other suitable output mechanisms such as loudspeakers, actuators, LEDs, buzzers, etc., may be used to provide visual and/or other types of feedback (e.g., audible feedback, haptic feedback, etc.). It will be understood that, in certain examples, touchscreen  810  may not include a touch panel, but, rather, may be implemented only as a display monitor capable of outputting information and not accepting operator input. In still other examples, control interface  800  may be implemented exclusively by buttons, knobs, and/or other controls, and may not include any display monitor or touch screen. 
     Various types of feedback may be provided to an operator by way of touchscreen  810  and/or other output mechanisms of control interface  800 . For example, system  100  may provide, to an operator performing operator control of manipulator cart  202  by way of control interface  800 , one or more status indicators. For example, the status indicators may indicate a progression of manipulator cart  202  along path  404 , whether manipulator cart  202  has completed navigating path  404 , details about any propulsion limitation being imposed on the propulsion of manipulator cart  202 , and so forth. The status indicators may take any form as may serve a particular implementation. For example, one status indicator may indicate what percentage of path  404  has been traversed and indicate when manipulator cart  202  arrives at location  406 —target (as well as at a target orientation and/or configuration, if applicable) and/or completes path  404 . As another example, another status indicator may show (e.g., from a top view) a depiction of path  404  (e.g., including locations  406 —initial and  406 —target, obstacles  410  and/or  412 , etc.) so as to indicate a current location of manipulator cart  202  on path  404 . In some examples, after manipulator cart  202  has arrived at location  406 —target and has stopped, the status indicator may continue to indicate that manipulator cart  202  has not completed navigating path  404  until a target orientation has been achieved and/or until each movable component has been properly configured according to the configuration plan. 
     Other types of feedback provided by way of control interface  800  may include a current position of manipulator cart  202  shown on a map of path  404  (e.g., a map indicating turns, obstacles shown in different colors, etc.), an indication that navigation has stopped short, an indication that navigation has been attempted to continue forward after navigation was complete, and/or 2D photographic imagery or 3D model imagery captured by or derived from sensors on manipulator cart  202  (e.g., imagery depicting ports and/or cannulas being approached). Moreover, control interface  800  may provide feedback when system  100  switches between a dynamically-generated path and a full pre-defined path (e.g., when location  406 —target is identified and a path all the way to location  406 —target and/or to a final target configuration is defined), when control switches from one bifurcated navigation control mode to another, or when the navigation control mode switches (e.g., from the standard navigation control mode to a bifurcated navigation control mode, from one bifurcated navigation control mode to another, etc.). As another example, control interface  800  may provide feedback showing regions where manipulator cart  202  may park (e.g., a target location or a range of potential target locations), feedback indicating a range of motion of various movable components of manipulator cart  202 , an indication of when sterile field  408  has been entered by manipulator cart  202 , an indication of which navigation control mode is currently in use, and/or an indication of which direction manipulator cart  202  is moving or is supposed to be moving according to path  404 . With regard to indicating the propulsion limitation, control interface  800  may provide feedback indicative of a current speed of manipulator cart  202 , a top speed of manipulator cart  202  (e.g., if a maximum speed limit for manipulator cart  202  is imposed as a propulsion limitation), a difference between the top speed and the current speed, an indication of the speed gain (e.g., as described below in more detail), and so forth. 
     Haptic or other feedback may also be provided to operators of manipulator cart  202 . For instance, rather that providing visual feedback by way of touchscreen  810 , system  100  may use boom  506 , arms  212 , or another such component of manipulator cart  202  to, for example, point in the direction that manipulator cart  202  is currently steering. It will be understood that certain of the types of feedback described above may be provided in one or more ways other than the ways explicitly described herein (e.g., visually, audibly, haptically, etc.). Additionally, it will be understood that certain types of feedback described above may be provided not only by control interface  800 , but also by other types of control interfaces described herein (e.g., other primary control interfaces, secondary control interfaces, etc.). 
     Regardless of which type of control interface is employed in a particular implementation or along a particular segment of path  404 , propulsion control of manipulator cart  202  may be influenced by both an operator and system  100  whenever navigation proceeds in bifurcated navigation control mode  704 - 2 . To illustrate how this joint effort between the operator and the system may function,  FIG. 9  shows exemplary factors that may be accounted for in the propulsion of manipulator cart  202  in bifurcated navigation control modes  704 . 
     Specifically, as shown, an operator  902  may provide user input indicative of various propulsion characteristics (e.g., speed, acceleration, etc.) selected by operator  902  for manipulator cart  202 . This user input is shown in  FIG. 9  as operator-commanded propulsion  904  and may be provided by operator  902  in any suitable way (e.g., by a magnitude of the exertion operator  902  is delivering to push or pull manipulator cart  202 —such as a magnitude of a force or torque applied by operator  902 , by a degree to which operator  902  is partially or fully engaging a throttling mechanism configured to control the speed of manipulator cart  202 , by a continuous or discrete speed level selected by operator  902 , etc.). System  100  is also shown to account for one or more navigation conditions  906 , which may be detected in various ways and may include various types of conditions that will be described in more detail below. 
     As shown, system  100  may input both operator-commanded propulsion  904  and navigation conditions  906 , and may further manage one or more propulsion limitations  908 . Using propulsion limitations  908 , system  100  may determine how operator-commanded propulsion  904  is to be translated into actual propulsion of manipulator cart  202 , labeled in  FIG. 9  as manipulator cart propulsion  910 . For example, as will be described in more detail below, system  100  may determine that manipulator cart propulsion  910  should be exactly the same as operator-commanded propulsion  904  for certain navigation conditions  906 , and may determine that propulsion limitations  908  should be used to adjust operator-commanded propulsion  904  to a more appropriate or desirable manipulator cart propulsion  910  for other navigation conditions  906 . In either case, system  100  may use one or more propulsion control signals  912  to implement whatever manipulator cart propulsion  910  is deemed to be appropriate (e.g., whether it is exactly what operator  902  commands or a limited version thereof). For example, propulsion control signals  912  may represent voltage or power signals delivered to actuators associated with a drive mechanism of manipulator cart  202 . As another example, propulsion control signals  912  may include data instructions or the like that indicate to an onboard drive controller of manipulator cart how such actuators are to be directed. 
     In  FIG. 9 , manipulator cart propulsion  910  may refer to any suitable propulsion characteristics associated with any type of advancement of manipulator cart  202  along a path (e.g., path  404 ) or in relation to a configuration plan as may serve a particular implementation. For example, manipulator cart propulsion  910  may include movement of base  502  along path  404 , reconfiguration of movable components (e.g., operating platform  504 , boom  506 , arms  212 , etc.) in accordance with a configuration plan, or any other advancement toward a final position and configuration in which manipulator cart  202  will be ready to perform the operation. As such, it will be understood that  FIG. 9  illustrates what has been described herein as system  100  directing manipulator cart  202  to navigate along a part of path  404  in a bifurcated navigation control mode in which system  100  allows operator control of a propulsion of manipulator cart  202  (i.e., operator-commanded propulsion  904 ) in accordance with a propulsion limitation (e.g., one of propulsion limitations  908 ). 
     Operator-commanded propulsion  904  may refer to any operator input as may be provided by an operator  902  and/or as may be accounted for by an implementation of system  100 . For example, in certain implementations or along certain portions of path  404  being navigated, operator-commanded propulsion  904  may provide directional propulsion commands such as forward propulsion commands, backwards propulsion commands, and stop propulsion commands, as well as operator selected speed settings, specific commands to proceed with a configuration plan whereby moveable components of manipulator cart  202  are transformed from an initial configuration to a target configuration, and/or other commands as may serve a particular implementation. As described above, in these examples, manipulator cart propulsion  910  may be said to be controlled in one of bifurcated navigation control modes  704 . Operator-commanded propulsion  904  may be provided by operator  902  in any manner and by way of any control interface as may serve a particular implementation (e.g., including by way of control interface  800 ). 
     As operator  902  provides operator-commanded propulsion  904 , one or more propulsion limitations  908  may influence how operator-commanded propulsion  904  is used to ultimately control manipulator cart propulsion  910 . To illustrate,  FIGS. 10-12  depict various examples of how operator-commanded propulsion  904  may be translated into manipulator cart propulsion  910  in accordance with different types of propulsion limitations  908  that may be used individually or in combination with one another in various implementations or under various navigational circumstances and conditions. Each of these figures will now be described in more detail. 
       FIG. 10  illustrates different ways that exemplary operator-commanded propulsion  904  may be translated into manipulator cart propulsion  910  (e.g., manipulator cart propulsion  910 - 1  or  910 - 2  in different examples) in accordance with different types of propulsion limitations  908 . Specifically,  FIG. 10  includes three graphs: a top graph that is representative of exemplary operator-commanded propulsion  904  and middle and bottom graphs that are each representative of manipulator cart propulsion that may result from different propulsion limitations  908 . Each of the graphs shown in  FIG. 10  represents a propulsion characteristic such as speed or acceleration on the y-axis, where positive values represent propulsion values in a forward direction along path  404  and negative values represent propulsion values in a backward direction along path  404 . Each of the graphs also shows time along the x-axis. 
     As shown, each graph indicates certain reference values that will be understood to be the same values from graph to graph. Specifically, dotted lines labeled as times  1002  (i.e., times  1002 - 1  through  1002 - 4 ) represent the same points in time for each of the graphs, while dashed lines labeled as reference levels  1004  (e.g., reference levels  1004 - 1  and  1004 - 2 ) represent the same propulsion levels (e.g., the same speeds, the same accelerations, etc.) for each of the graphs. 
       FIG. 10  illustrates that operator-commanded propulsion  904  may begin with a zero propulsion command (i.e., no command to move manipulator cart  202 , or a command to stop manipulator cart  202 ) until about time  1002 - 1 . Around time  1002 - 1 , operator-commanded propulsion  904  is shown to move up to about reference level  1004 - 1 , where the operator-commanded propulsion  904  hovers just over or just under this propulsion level until about time  1002 - 2 . At this point, operator-commanded propulsion  904  returns to a level around zero, such that operator-commanded propulsion  904  may be interpreted as another zero propulsion command until about time  1002 - 3 . Then, starting around time  1002 - 3 , operator-commanded propulsion  904  moves down to about reference level  1004 - 2 , where operator-commanded propulsion  904  hovers just over or just under this propulsion level until about time  1002 - 4 , after which operator-commanded propulsion  904  returns to the zero level. 
     System  100  may translate this operator-commanded propulsion  904  into manipulator cart propulsion  910  in various ways based on different propulsion limitations  908 . For example, as illustrated by manipulator cart propulsion  910 - 1  in the middle graph, one exemplary propulsion limitation  908  may impose an upper propulsion limit (e.g., a maximum speed limit, a maximum acceleration limit, etc.) on manipulator cart  202 . System  100  does not modify the operator-commanded propulsion based on this type of propulsion limitation as long as the operator-selected propulsion value (e.g., an operator-selected speed setting, an operator-selected acceleration rate, etc.) satisfies the limit (e.g. remains below a certain level—in this case below reference level  1004 - 1  in the forward direction, or below reference level  1004 - 2  in the backward direction). However, the propulsion value is shown to become saturated at the maximum limit such that operator  902  is not given the ability to direct manipulator cart  202  to accelerate faster or move at any speed above the maximum propulsion limit at reference levels  1004 - 1  and  1004 - 2 . In this example, system  100  achieves this result by modifying operator-commanded propulsion exceeding the propulsion limit to be equal to the propulsion limit. 
     The maximum propulsion limit may be defined, or may be set at any propulsion level (e.g., speed, acceleration rate, etc.) as may serve a particular implementation. For example, system  100  may define the maximum propulsion limit as applicable to the navigation, or define the value of the maximum propulsion limit, or define both the applicability or the value, based on a proximity of manipulator cart  202  to an obstacle to be avoided by manipulator cart  202  during the navigation of manipulator cart  202  along the path (e.g., one of obstacles  410  or  412  during the navigation along path  404 ). As a specific example, system  100  may define the propulsion limitation by determining to apply the maximum propulsion limit or not based on parameter(s) such as the distance of manipulator cart  202  to the obstacle being within a threshold distance; in such an implementation, the value of the maximum propulsion limit may be statically set, or dynamically calculated based on one or more navigation conditions. As another specific example, system  100  may define the propulsion limitation by determining the value of the maximum propulsion limit based the distance of manipulator cart  202  to the obstacle; in such an implementation, the value of the maximum propulsion limit may be lower when the distance of manipulator cart  202  to the obstacle is lower, and higher when the distance of manipulator cart  202  to the obstacle is higher. As a further example, system  100  may define the propulsion limitation by both determining if to apply the maximum propulsion limit, and determining the value of the maximum propulsion limit. As yet another example, system  100  may define the propulsion limitation by determining which operator control interface is to be used (e.g., a primary control interface, a secondary control interface, etc.) to provide propulsion commands. 
     Moreover, the maximum propulsion limit may be defined, or further defined, based on a predetermined deceleration rate of manipulator cart  202 , such that there is sufficient time for manipulator cart  202  to slow to a safe speed, or to a stop, before colliding with the obstacle if necessary. As another example, if manipulator cart  202  comprises one or more movable components (e.g., operating platform  504 , boom  506 , arms  212 , etc.), system  100  may define the maximum propulsion limit based on a proximity of manipulator cart  202  to an obstacle to be avoided by the movable component during the navigation of manipulator cart  202  along the path, an orientation of the movable component with respect to the obstacle, and a movement rate of the movable component. The maximum propulsion limit may thus be selected so as to allow sufficient time for the movable component of manipulator cart  202  to be reconfigured, prior to manipulator cart  202  reaching the obstacle at a current approach trajectory, in order to avoid the obstacle. For example, system  100  may determine that a collision with obstacle  412  may be avoided by lower operating platform  504  to pass under obstacle  412 , as was illustrated above in  FIG. 5 . Similarly, system  100  may also determine that a collision with operating table  402  may be avoided by raising operating platform  402 . Accordingly, the maximum propulsion limit for manipulator cart  202  may be defined in such a way as to give operating platform  504  enough time to be lowered and then to be raised in order to avoid these collisions. In some examples (e.g., when obstacles are in motion or when various other conditions exist), system  100  may dynamically define the maximum propulsion limit based on navigation conditions, and the maximum propulsion limit may therefore be a variable, rather than a fixed, value. 
     As shown in the middle graph, manipulator cart propulsion  910 - 1  generally follows operator-commanded propulsion  904  except when operator-commanded propulsion  904  goes outside of the propulsion levels  1004 - 1  and  1004 - 2  (i.e., except when accelerating or moving faster than the values represented by propulsion levels  1004 ). At these times,  FIG. 10  shows that manipulator cart propulsion  910 - 1  saturates so as to not accelerate at a higher rate, or move at a higher speed, than the propulsion limits set at propulsion levels  1004 - 1  and  1004 - 2 . For example, manipulator cart propulsion  910 - 1  may saturate to limit the acceleration or speed of the base of manipulator cart  202  along path  404 . Additionally or alternatively, manipulator cart  910 - 1  may limit the acceleration or speed of other movable components of manipulator cart  202  such as the boom, the operating platform, or the like. In this way, system  100  allows operator  902  to exert propulsion control on manipulator cart  202  while still ensuring that manipulator cart propulsion  910 - 1  does not exceed an appropriate propulsion level even if so commanded by operator  902 . 
     System  100  may also impose other types of propulsion limitations  908  on the operator-controlled propulsion of manipulator cart  202  (i.e., propulsion limitations other than upper limits). For example, as shown by manipulator cart propulsion  910 - 2  in the bottom graph, another exemplary propulsion limitation  908  may define, act as, or be thought of as, a transfer function or gain control for converting one or more aspects of operator-commanded propulsion  904  (e.g., a commanded speed setting, a commanded acceleration rate, etc.) into a different but corresponding manipulator cart propulsion  910 - 2  (e.g., a reduced percentage such as half of operator-commanded propulsion  904 , a set amount lower than operator-commanded propulsion  904 , etc.). For example, this type of propulsion limitation may include a mapping of input exertion applied to the operator control (e.g., operator-commanded propulsion  904  implemented as how hard a user pushes the operator control) to a speed or an acceleration of manipulator cart  202  (e.g., manipulator cart propulsion  910 ). As another example, this type of propulsion limitation may include a designated speed gain associated with a speed control interface of the manipulator cart, and system  100  direct (e.g., by way of propulsion control signals  912 ) the propulsion of manipulator cart  202  to be performed at a speed determined by an operator-selected speed setting for the speed control interface. 
     As shown in the bottom graph of  FIG. 10 , manipulator cart propulsion  910 - 2  follows the shape of operator-commanded propulsion  904  but does not match the amplitude of operator-commanded propulsion  904 . For example, manipulator cart propulsion  910 - 2  may consistently be directed at a particular percentage (e.g., about 60% in this example) of operator-commanded propulsion  904 . In this example, the manipulator cart propulsion can exceed levels  1004 - 1  and  1004 - 2 , with sufficiently high operator-commanded propulsion  904 . Also, in this example, system  100  modifies operator-commanded propulsion  904  even where operator-commanded propulsion  904  is quite small. In certain implementations, the modification of operator commanded-propulsion  904  are defined such that, for operator-commanded propulsion  904  typically encountered outside of the propulsion levels  1004 - 1  and  1004 - 2 , manipulator cart propulsion  910 - 2  does not exceed these propulsion levels. 
       FIGS. 11A-11D  further illustrate how exemplary operator-commanded propulsion  904  may be translated into manipulator cart propulsion  910  in accordance with different types of propulsion limitations  908 . Specifically, each graph depicted in  FIGS. 11A-11D  depicts exemplary operator-commanded propulsion  904  along the x-axis, and depicts, along the y-axis, a corresponding manipulator cart propulsion  910  that results from one or more propulsion limitations  908  implemented by system  100 . Accordingly, while not explicitly labeled in  FIGS. 11A-11D , it will be understood that each graph is associated with a different propulsion limitation  908  (or a plurality thereof). It will also be understood that positive values (i.e., up and/or to the right) represent propulsion values such as speed or acceleration in the forward direction along path  404 , while negative values (i.e., down and/or to the left) represent these propulsion values in the backward direction along path  404 . Moreover, the dashed lines shown for each of the graphs in  FIGS. 11A-11D  will be understood to correspond to reference levels that are the same for both axes. Thus, for example, an operator-commanded speed at the vertical dashed line would translate to a manipulator cart speed at the horizontal dashed line if propulsion limitation  908  translated operator-commanded speed to manipulator cart speed in a one-to-one manner. 
       FIG. 11A  shows an example where the propulsion limitation  908  limits operator-commanded propulsion  904  using a plurality of discrete propulsion limit levels. For example, as shown, three distinct propulsion levels (e.g., speed levels such as a low-speed level, an intermediate-speed level, and a high-speed level) are available in the forward direction, while two distinct propulsion levels (e.g., speed levels such as a low-speed level and a high-speed level) are available in the backward direction. In this example, each of the discrete propulsion values shown is applied only to operator-commanded propulsion values at or below that discrete propulsion value; thus, a higher operator-commanded propulsion value would encounter a higher propulsion limit level if such is available. Accordingly, as shown, an upper limit for forward speed may be implemented, as well as an upper limit for backward speed. As shown, the upper limit for forward speed is greater than the upper limit for backward speed in this example, although it will be understood that the reverse may be true or both upper speed limits (for forward and backward motion) may be equal in other examples. 
       FIG. 11B  shows an example where the propulsion limitation  908  translates operator-commanded propulsion  904  in a linear manner to a particular propulsion level on a continuum of propulsion levels. As shown, while the translation from operator-commanded propulsion  904  to manipulator cart propulsion  910  is linear, it is not unity. That is, the manipulator cart propulsion that is directed is a certain degree (e.g. about 90%) of any given operator-commanded propulsion. In this example, no upper limit is shown to be implemented. Rather, the propulsion commanded by operator  902  is simply reduced in the actual propulsion of manipulator cart  202 . Another feature illustrated in  FIG. 11B  is that the mapping between operator-commanded propulsion  904  and manipulator cart propulsion  910  is different for the forward direction and the backward direction (i.e., manifested by different slopes in the top-right quadrant and the in the bottom left quadrant). In this way, the propulsion limitation  908  may compel operator  902  to move slowly (e.g., to slow down slightly) in the forward direction, and to move even more slowly (e.g., to slow down even more) in the backward direction. It will be understood that the slope of the lines in either of the quadrants may be any suitable slope, may be the same or different as one another, may change at certain propulsion levels, and so forth as may serve a particular implementation. 
       FIG. 11C  shows another example in which a propulsion limitation  908  translates operator-commanded propulsion  904  in a linear manner to a particular propulsion level on a continuum of propulsion levels. While the example of  FIG. 11C  is similar to the example of  FIG. 11B , the slope is now shown to be equal to 1 for both the forward and backward direction. Accordingly, in this example, the actual manipulator cart propulsion  910  that system  100  directs will be the same as the propulsion  904  that operator  902  commands, regardless of the direction along path  404 . However, in contrast to the example of  FIG. 11B , in this example, there are propulsion limitations (e.g., speed limits, acceleration limits, etc., depending on which characteristic is being represented) beyond which a higher operator-commanded propulsion value will not be translated to a higher manipulator cart propulsion value. These limits may be the same for both the forward and backward directions, or, as shown, in  FIG. 11C , the limit for one direction may be higher than the limit for the other direction (i.e., the limit for the forward direction is shown to be slightly higher than the limit for the backward direction). 
       FIG. 11D  shows another example in which a propulsion limitation  908  translates operator-commanded propulsion  904  to a particular propulsion level on a continuum of propulsion levels. In contrast to the linear nature of the translation in the examples of  FIGS. 11B and 11C , the example of  FIG. 11D  shows that a non-linear translation may be used. As shown, upper limits such as speed limits, acceleration limits, or the like may still be implemented in this example. However, rather than being suddenly reached at particular value, these upper limits may be approached gradually (e.g., asymptotically). In this way, the propulsion control imposed by operator  902  does not saturate in such an abrupt way at a particular speed or acceleration, but, rather, additional increases in the commanded propulsion value have smaller and smaller impacts on the actual propulsion value as the propulsion value gets higher and manipulator cart  202  approaches the upper limit. 
     In some examples, it may be desirable for different propulsion limitations  908  to be used at different portions of path  404  or in different areas or zones of operating room  400 . For instance, different types of propulsion limitations may be employed in different zones, different values for the propulsion limitations such as different speed gains (i.e., slopes in the graphs shown in  FIGS. 11A-11D ) may be used, and so forth. As one example, a relatively high speed gain may be designated for navigation of manipulator cart  202  through a high-speed zone (e.g., a portion of the path where there are no sharp curves, no nearby obstacles, and otherwise minimal risk). As another example, a relatively low speed gain may be designated for navigation of manipulator cart  202  through a low-speed zone (e.g., a portion of the path that has more difficult turns, obstacles on or near the path, and otherwise more significant risk than the high-speed zone). 
     To illustrate,  FIG. 12  shows how exemplary operator-commanded propulsion  904  may be translated into manipulator cart propulsion  910  in accordance with different types of propulsion limitations  908  imposed in different zones or along different parts of path  404 . Specifically, as shown, a plurality of plots  1202  (i.e., plots  1202 - 1  through  1202 - 4 ) that may each be associated with a different zone are shown on a graph similar to the graphs of  FIGS. 11A-11D . 
     Plot  1202 - 1  (the solid line) is drawn with a slope of 1 and without any portion that levels off to represent an upper limit. Accordingly, plot  1202 - 1  may represent the translation that system  100  may perform in a high-speed zone in which there is little or no risk of manipulator cart  202  colliding with an obstacle, taking too sharp of a turn, or the like. As such, plot  1202 - 1  may represent behavior of system  100  when no propulsion limitation  908  is imposed. 
     Plot  1202 - 2  (the dashed line) is drawn with a slope of 1 along most of its length, but eventually levels off, representing an upper limit. Accordingly, plot  1202 - 2  may represent the translation that system  100  may perform in a relatively high-speed zone, but one in which there is an upper limit (e.g., due to a turning radius of manipulator cart  202  or the like). 
     Plot  1202 - 3  (the dash-dotted line) is drawn with a slope less than 1 and also eventually levels off to implement an upper limit. Accordingly, plot  1202 - 3  may represent the translation that system  100  may perform in a relatively low-speed zone where a lower speed gain and an maximum speed limit may both be appropriate (e.g., in order to avoid nearby obstacles, etc.) 
     Plot  1202 - 4  (the dotted line) also may be used for a relatively low-speed zone. In this example, however, the speed gain is shown to not be limited (i.e., such that the slope is 1), but there is an upper propulsion limit that is set at a relatively low value to ensure that operator  902  keeps the propulsion speed of manipulator cart  202  relatively low. 
     Propulsion limitations associated with any of plots  1202  or a variety of other plots that may serve a particular implementation may be implemented in various zones as may be appropriate. As mentioned above, a propulsion value such as a speed setting may be related to an exertion level that operator  902  applies to manipulator cart  202  (e.g., how hard operator  902  attempts to push or pull manipulator cart  202 , how hard operator  902  engages a throttling mechanism for driving manipulator cart  202 , etc.). As such, different propulsion limitations  908  associated with different plots  1202  may each include different mappings of the input exertion to a speed or an acceleration of manipulator cart  202 . In some examples, operator  902  may haptically feel the difference between the different propulsion limitations  908  (e.g., when switching from one zone and one plot  1202  to another) based on how much exertion is required to achieve a desired speed or acceleration. For example, from the perspective of operator  902 , manipulator cart  202  may seem lighter and faster to move when navigating a high-speed zone (e.g., when the propulsion limitation implements plot  1202 - 1  or  1202 - 2 ), and may feel heavier and slower to move when navigating a low-speed zone (e.g., when the propulsion limitation implements plot  1202 - 3 ). 
     Returning to  FIG. 9 , propulsion limitations  908  are shown to be imposed by system  100  based on one or more navigation conditions  906  that may be identified by system  100  in any of the ways described herein. Navigation conditions may be identified and mapped to any of the propulsion limitations described herein in any suitable way. For example, navigation conditions may be tracked by system  100 , may be determined based on sensor data detected or accessed by system  100 , may be indicated by input from another system or from operator input from operator  902 , or may be identified in any other manner as may serve a particular implementation. 
     Navigation conditions  906  may relate to any of various conditions or circumstances associated with manipulator cart  202  or movable components included therein as a path is being navigated and a configuration plan is being carried out. For example, navigation conditions  906  may be relate to the path being navigated (e.g., path  404 ), a configuration plan for the movable components, obstacles along the path (e.g., obstacles  410  or  412 ), the initial and/or target locations of the path (e.g., locations  406 —initial and/or  406 —target), and/or any other aspect of the navigation of manipulator cart  202  along the path. Various non-limiting examples of navigation conditions  906  will now be described. 
     As one example, a navigation condition  906  identified by system  100  may be that manipulator cart  202  is navigating or approaching a turn along the path. The propulsion limitation  908  for such a navigation condition  906  may include a maximum speed limit (e.g., a maximum speed limit lower than a full speed achievable by the propulsion of manipulator cart  202 ) for when manipulator cart  202  is navigating the turn. As another example, a navigation condition  906  identified by system  100  may be that manipulator cart  202  is approaching an obstacle to be avoided by manipulator cart  202  during the navigation of manipulator cart  202  along the path, or is approaching the target location at the end of the path. In these examples, the propulsion limitation  908  may limit the speed as the obstacle or target location is approached. As yet another example, a navigation condition  906  identified by system  100  may be that manipulator cart  202  is navigating along a particular portion of the path (e.g., a portion within an area designated as a low-speed or high-speed zone, a portion within a sterile field, etc.) or is located in a particular area (e.g., an operating room versus a hallway in the hospital, etc.). 
     In certain implementations, manipulator cart propulsion  910  may be performed using battery power provided by a battery of manipulator cart  202 . In such implementations, a navigation condition  906  identified by system  100  may be that manipulator cart propulsion  910  is performed using the battery power and/or that a battery level of the battery is below a predetermined battery level threshold. For example, propulsion limitations  908  limiting the speed or acceleration rate may be imposed in response to these types of navigation conditions if more battery power is consumed by higher speeds and/or acceleration rates than by lower speeds and/or acceleration rates. Similarly, in examples where manipulator cart  202  is connected to other objects by way of cables (e.g., power cables, communication cables, etc.), system  100  may track whether manipulator cart  202  is likely to begin pulling on a cable that is not long enough to allow manipulator cart  202  to navigate any further in a particular direction, and may impose propulsion limitations forcing manipulator cart  202  to slow or stop before any cable is pulled too hard (e.g., so as to come unplugged, undergo damage, or pose a safety risk such as a tripping hazard to people in the vicinity). 
     In some examples, a navigation condition  906  identified by system  100  may comprise an attention measurement indicative of attention paid to the navigation of manipulator cart  202  by a person in a vicinity of manipulator cart  202 . For example, the person may be operator  902  and system  100  may detect (e.g., using gaze tracking techniques or the like) whether operator  902  is paying attention to certain aspects of the navigation (e.g., as opposed to directing his or her attention elsewhere while relying heavily on the ability of the system to automatically steer manipulator cart  202 ). If operator  902  is paying close attention, less significant propulsion limitations  908  may be required than if operator  902  appears to be distracted. As another example, the person may be a person in front of manipulator cart  202  on the path who is identified as a potential obstacle. If the person is detected to be paying attention and to be aware of manipulator cart  202  coming in his or her direction, less significant propulsion limitations may be necessary than if the person is detected to not have an awareness of the approach of manipulator cart  202  (e.g., if the person is detected to have his or her back turned to manipulator cart  202 ). 
     Other navigation conditions  906  that certain implementations of system  100  may identify relate to the overall entropy or chaos in the scene (e.g., in the operating room, etc.). For example, a navigation condition  906  may be that an entropy associated with the path is detected to satisfy a predetermined entropy criterion, and a propulsion limitation  908  such as a maximum speed limit or acceleration limit may be imposed on manipulator cart propulsion  910  until it is determined that the entropy is lower. 
       FIG. 13  illustrates an exemplary method  1300  for bifurcated navigation control of a manipulator cart included within a computer-assisted medical system. While  FIG. 13  illustrates exemplary operations according to one embodiment, other embodiments may omit, add to, reorder, and/or modify any of the operations shown in  FIG. 13 . One or more of the operations shown in  FIG. 13  may be performed by a bifurcated navigation control system such as system  100 , any components included therein, and/or any implementation thereof. 
     In operation  1302 , a bifurcated navigation control system may define a path whereby a manipulator cart included within a computer-assisted medical system is to navigate from an initial location to a target location. Operation  1302  may be performed in any of the ways described herein. 
     In operation  1304 , the bifurcated navigation control system may identify a navigation condition associated with a navigation of the manipulator cart along the path from the initial location to the target location. Operation  1304  may be performed in any of the ways described herein. 
     In operation  1306 , the bifurcated navigation control system may define a propulsion limitation for the manipulator cart during the navigation of the manipulator cart along the path. For example, the bifurcated navigation control system may define the propulsion limitation based on the navigation condition identified in operation  1304 . Operation  1306  may be performed in any of the ways described herein. 
     In operation  1308 , the bifurcated navigation control system may direct the manipulator cart to navigate along at least part of the path from the initial location to the target location. In particular, the bifurcated navigation control system may direct the manipulator cart to navigate in a bifurcated navigation control mode in which the bifurcated navigation control system autonomously controls a steering of the manipulator cart while allowing operator control of a propulsion of the manipulator cart in accordance with the propulsion limitation defined in operation  1306 . Operation  1308  may be performed in any of the ways described herein. 
     In some examples, a non-transitory computer-readable medium storing computer-readable instructions may be provided in accordance with the principles described herein. The instructions, when executed by a processor of a computing device, may direct the processor and/or computing device to perform one or more operations, including one or more of the operations described herein. Such instructions may be stored and/or transmitted using any of a variety of known computer-readable media. 
     A non-transitory computer-readable medium as referred to herein may include any non-transitory storage medium that participates in providing data (e.g., instructions) that may be read and/or executed by a computing device (e.g., by a processor of a computing device). For example, a non-transitory computer-readable medium may include, but is not limited to, any combination of non-volatile storage media and/or volatile storage media. Exemplary non-volatile storage media include, but are not limited to, read-only memory, flash memory, a solid-state drive, a magnetic storage device (e.g. a hard disk, a floppy disk, magnetic tape, etc.), ferroelectric random-access memory (“RAM”), and an optical disc (e.g., a compact disc, a digital video disc, a Blu-ray disc, etc.). Exemplary volatile storage media include, but are not limited to, RAM (e.g., dynamic RAM). 
     In some examples, any of the systems and/or other components described herein may be implemented by a computing device including one or more processors, storage devices, input/output modules, communication interfaces, buses, infrastructures, and so forth. For instance, storage facility  102  of system  100  may be implemented by a storage device of the computing device, and processing facility  104  of system  100  may be implemented by one or more processors of the computing device. In other examples, the systems and/or other components described herein may be implemented by any suitable non-transitory computer-readable medium storing instructions that, when executed, direct a processor of such a computing device to perform methods and operations described herein. 
     In the preceding description, various exemplary embodiments have been described with reference to the accompanying drawings. It will, however, be evident that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the scope of the invention as set forth in the claims that follow. For example, certain features of one embodiment described herein may be combined with or substituted for features of another embodiment described herein. The description and drawings are accordingly to be regarded in an illustrative rather than a restrictive sense.