Patent Publication Number: US-2022227365-A1

Title: Operation of a vehicle using multiple motion constraints

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 16/702,620, filed Dec. 4, 2019 (now allowed), which claims the benefit of U.S. Provisional Application 62/781,566, filed on Dec. 18, 2018, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This description relates generally to operation of vehicles and specifically to operation of a vehicle using multiple motion constraints. 
     BACKGROUND 
     Operation of a vehicle from an initial location to a final destination often requires a user or the vehicle&#39;s decision-making system to select a route through a road network from the initial location to a final destination. The route may involve meeting objectives such as not exceeding a maximum driving time. However, a complex route can require many decisions, making traditional algorithms for route selection impractical. Traditional greedy algorithms are sometimes used to select a route across a directed graph from the initial location to a final destination. However, if a large number of other vehicles on the road use such a greedy algorithm, the selected route may become overloaded and travel may slow to a crawl. In addition, the presence of parked vehicles, construction zones, and pedestrians complicate route selection and operation. 
     SUMMARY 
     Techniques are provided for operation of a vehicle using multiple motion constraints. The techniques include identifying an object using one or more processors of a vehicle. The vehicle has a likelihood of collision with the object that is greater than a threshold. The processors generate motion constraints for operating the vehicle. At least one motion constraint includes a minimum speed of the vehicle greater than zero to avoid a collision of the vehicle with the object. The processors identify one or more motion constraints for operating the vehicle to avoid a collision of the vehicle with the object. The processors operate the vehicle in accordance with the identified motion constraints. 
     These and other aspects, features, and implementations can be expressed as methods, apparatus, systems, components, program products, means or steps for performing a function, and in other ways. 
     These and other aspects, features, and implementations will become apparent from the following descriptions, including the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of an autonomous vehicle (AV) having autonomous capability, in accordance with one or more embodiments. 
         FIG. 2  illustrates an example “cloud” computing environment, in accordance with one or more embodiments. 
         FIG. 3  illustrates a computer system, in accordance with one or more embodiments. 
         FIG. 4  illustrates an example architecture for an AV, in accordance with one or more embodiments. 
         FIG. 5  illustrates an example of inputs and outputs that may be used by a perception module, in accordance with one or more embodiments. 
         FIG. 6  illustrates an example of a LiDAR system, in accordance with one or more embodiments. 
         FIG. 7  illustrates the LiDAR system in operation, in accordance with one or more embodiments. 
         FIG. 8  illustrates the operation of the LiDAR system in additional detail, in accordance with one or more embodiments. 
         FIG. 9  illustrates a block diagram of the relationships between inputs and outputs of a planning module, in accordance with one or more embodiments. 
         FIG. 10  illustrates a directed graph used in path planning, in accordance with one or more embodiments. 
         FIG. 11  illustrates a block diagram of the inputs and outputs of a control module, in accordance with one or more embodiments. 
         FIG. 12  illustrates a block diagram of the inputs, outputs, and components of a controller, in accordance with one or more embodiments. 
         FIG. 13  illustrates a block diagram of an architecture for operation of a vehicle using multiple motion constraints. 
         FIG. 14  illustrates an example of operation of a vehicle using multiple motion constraints. 
         FIG. 15  illustrates a process for operation of a vehicle using multiple motion constraints. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention. 
     In the drawings, specific arrangements or orderings of schematic elements, such as those representing devices, modules, instruction blocks and data elements, are shown for ease of description. However, it should be understood by those skilled in the art that the specific ordering or arrangement of the schematic elements in the drawings is not meant to imply that a particular order or sequence of processing, or separation of processes, is required. Further, the inclusion of a schematic element in a drawing is not meant to imply that such element is required in all embodiments or that the features represented by such element may not be included in or combined with other elements in some embodiments. 
     Further, in the drawings, where connecting elements, such as solid or dashed lines or arrows, are used to illustrate a connection, relationship, or association between or among two or more other schematic elements, the absence of any such connecting elements is not meant to imply that no connection, relationship, or association can exist. In other words, some connections, relationships, or associations between elements are not shown in the drawings so as not to obscure the disclosure. In addition, for ease of illustration, a single connecting element is used to represent multiple connections, relationships or associations between elements. For example, where a connecting element represents a communication of signals, data, or instructions, it should be understood by those skilled in the art that such element represents one or multiple signal paths (e.g., a bus), as may be needed, to affect the communication. 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various described embodiments. However, it will be apparent to one of ordinary skill in the art that the various described embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments. 
     Several features are described hereafter that can each be used independently of one another or with any combination of other features. However, any individual feature may not address any of the problems discussed above or might only address one of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein. Although headings are provided, information related to a particular heading, but not found in the section having that heading, may also be found elsewhere in this description. Embodiments are described herein according to the following outline: 
     1. General Overview 
     2. System Overview 
     3. Autonomous Vehicle Architecture 
     4. Autonomous Vehicle Inputs 
     5. Autonomous Vehicle Planning 
     6. Autonomous Vehicle Control 
     7. Architecture for Operation Using Multiple Motion Constraints 
     8. Example of Operation Using Multiple Motion Constraints 
     9. Process for Operation Using Multiple Motion Constraints 
     General Overview 
     An autonomous vehicle (AV) uses sensors to detect objects and determine distances from objects during operation within an operating environment. The sensors include visual sensors such as cameras and LiDARs. A LiDAR is a remote sensing device that uses a grid of pulsed laser beams to measure a distance from an object to the device. To operate the AV, the visual sensors of the AV are used to receive sensor data representing the operating environment. One or more processors of the AV are used to identify an object located within the operating environment, such as a pedestrian, another vehicle, or a construction zone, etc. The one or more processors are used to determine that the AV is likely to collide with the object, where the likelihood is greater than a threshold. 
     To avoid a collision with the object, the one or more processors are used to generate motion constraints for operating the AV. Each motion constraint is determined to prevent a collision of the AV with the object. At least one motion constraint includes a minimum speed of the AV greater than zero to avoid a collision of the AV with the object. This minimum speed constraint instructs the AV to speed up to avoid a collision, e.g., moving away from a potential collision location. One or more processors of the AV identify one or more motion constraints for operating the AV to avoid a collision of the AV with the object. A motion constraint, such as a maximum speed limit, may be temporarily violated if another motion constraint is deemed more important to prevent collision. A control module of the AV operates the AV in accordance with the identified one or more motion constraints. 
     System Overview 
       FIG. 1  illustrates an example of an autonomous vehicle  100  having autonomous capability. 
     As used herein, the term “autonomous capability” refers to a function, feature, or facility that enables a vehicle to be partially or fully operated without real-time human intervention, including without limitation fully autonomous vehicles, highly autonomous vehicles, and conditionally autonomous vehicles. 
     As used herein, an autonomous vehicle (AV) is a vehicle that possesses autonomous capability. 
     As used herein, “vehicle” includes means of transportation of goods or people. For example, cars, buses, trains, airplanes, drones, trucks, boats, ships, submersibles, dirigibles, etc. A driverless car is an example of a vehicle. 
     As used herein, “trajectory” refers to a path or route to operate an AV from a first spatiotemporal location to second spatiotemporal location. In an embodiment, the first spatiotemporal location is referred to as the initial or starting location and the second spatiotemporal location is referred to as the destination, final location, goal, goal position, or goal location. In some examples, a trajectory is made up of one or more segments (e.g., sections of road) and each segment is made up of one or more blocks (e.g., portions of a lane or intersection). In an embodiment, the spatiotemporal locations correspond to real world locations. For example, the spatiotemporal locations are pick up or drop-off locations to pick up or drop-off persons or goods. 
     As used herein, “sensor(s)” includes one or more hardware components that detect information about the environment surrounding the sensor. Some of the hardware components can include sensing components (e.g., image sensors, biometric sensors), transmitting and/or receiving components (e.g., laser or radio frequency wave transmitters and receivers), electronic components such as analog-to-digital converters, a data storage device (such as a RAM and/or a nonvolatile storage), software or firmware components and data processing components such as an ASIC (application-specific integrated circuit), a microprocessor and/or a microcontroller. 
     As used herein, a “scene description” is a data structure (e.g., list) or data stream that includes one or more classified or labeled objects detected by one or more sensors on the AV vehicle or provided by a source external to the AV. 
     As used herein, a “road” is a physical area that can be traversed by a vehicle, and may correspond to a named thoroughfare (e.g., city street, interstate freeway, etc.) or may correspond to an unnamed thoroughfare (e.g., a driveway in a house or office building, a section of a parking lot, a section of a vacant lot, a dirt path in a rural area, etc.). Because some vehicles (e.g., 4-wheel-drive pickup trucks, sport utility vehicles, etc.) are capable of traversing a variety of physical areas not specifically adapted for vehicle travel, a “road” may be a physical area not formally defined as a thoroughfare by any municipality or other governmental or administrative body. 
     As used herein, a “lane” is a portion of a road that can be traversed by a vehicle and may correspond to most or all of the space between lane markings, or may correspond to only some (e.g., less than 50%) of the space between lane markings. For example, a road having lane markings spaced far apart might accommodate two or more vehicles between the markings, such that one vehicle can pass the other without traversing the lane markings, and thus could be interpreted as having a lane narrower than the space between the lane markings or having two lanes between the lane markings. A lane could also be interpreted in the absence of lane markings. For example, a lane may be defined based on physical features of an environment, e.g., rocks and trees along a thoroughfare in a rural area. 
     “One or more” includes a function being performed by one element, a function being performed by more than one element, e.g., in a distributed fashion, several functions being performed by one element, several functions being performed by several elements, or any combination of the above. 
     It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first contact could be termed a second contact, and, similarly, a second contact could be termed a first contact, without departing from the scope of the various described embodiments. The first contact and the second contact are both contacts, but they are not the same contact. 
     The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “includes,” and/or “including,” when used in this description, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     As used herein, the term “if” is, optionally, construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context. Similarly, the phrase “if it is determined” or “if [a stated condition or event] is detected” is, optionally, construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event],” depending on the context. 
     As used herein, an AV system refers to the AV along with the array of hardware, software, stored data, and data generated in real-time that supports the operation of the AV. In an embodiment, the AV system is incorporated within the AV. In an embodiment, the AV system is spread across several locations. For example, some of the software of the AV system is implemented on a cloud computing environment similar to cloud computing environment  300  described below with respect to  FIG. 3 . 
     In general, this document describes technologies applicable to any vehicles that have one or more autonomous capabilities including fully autonomous vehicles, highly autonomous vehicles, and conditionally autonomous vehicles, such as so-called Level 5, Level 4 and Level 3 vehicles, respectively (see SAE International&#39;s standard J3016: Taxonomy and Definitions for Terms Related to On-Road Motor Vehicle Automated Driving Systems, which is incorporated by reference in its entirety, for more details on the classification of levels of autonomy in vehicles). The technologies described in this document are also applicable to partially autonomous vehicles and driver assisted vehicles, such as so-called Level 2 and Level 1 vehicles (see SAE International&#39;s standard J3016: Taxonomy and Definitions for Terms Related to On-Road Motor Vehicle Automated Driving Systems). In an embodiment, one or more of the Level 1, 2, 3, 4 and 5 vehicle systems may automate certain vehicle operations (e.g., steering, braking, and using maps) under certain operating conditions based on processing of sensor inputs. The technologies described in this document can benefit vehicles in any levels, ranging from fully autonomous vehicles to human-operated vehicles. 
     Referring to  FIG. 1 , an AV system  120  operates the AV  100  along a trajectory  198  through an environment  190  to a destination  199  (sometimes referred to as a final location) while avoiding objects (e.g., natural obstructions  191 , vehicles  193 , pedestrians  192 , cyclists, and other obstacles) and obeying rules of the road (e.g., rules of operation or driving preferences). 
     In an embodiment, the AV system  120  includes devices  101  that are instrumented to receive and act on operational commands from the computer processors  146 . In an embodiment, computing processors  146  are similar to the processor  304  described below in reference to  FIG. 3 . Examples of devices  101  include a steering control  102 , brakes  103 , gears, accelerator pedal or other acceleration control mechanisms, windshield wipers, side-door locks, window controls, and turn-indicators. 
     In an embodiment, the AV system  120  includes sensors  121  for measuring or inferring properties of state or condition of the AV  100 , such as the AV&#39;s position, linear velocity and acceleration, angular velocity and acceleration, and heading (e.g., an orientation of the leading end of AV  100 ). Example of sensors  121  are GNSS, inertial measurement units (IMU) that measure both vehicle linear accelerations and angular rates, wheel speed sensors for measuring or estimating wheel slip ratios, wheel brake pressure or braking torque sensors, engine torque or wheel torque sensors, and steering angle and angular rate sensors. 
     In an embodiment, the sensors  121  also include sensors for sensing or measuring properties of the AV&#39;s environment. For example, monocular or stereo video cameras  122  in the visible light, infrared or thermal (or both) spectra, LiDAR  123 , RADAR, ultrasonic sensors, time-of-flight (TOF) depth sensors, speed sensors, temperature sensors, humidity sensors, and precipitation sensors. 
     In an embodiment, the AV system  120  includes a data storage unit  142  and memory  144  for storing machine instructions associated with computer processors  146  or data collected by sensors  121 . In an embodiment, the data storage unit  142  is similar to the ROM  308  or storage device  310  described below in relation to  FIG. 3 . In an embodiment, memory  144  is similar to the main memory  306  described below. In an embodiment, the data storage unit  142  and memory  144  store historical, real-time, and/or predictive information about the environment  190 . In an embodiment, the stored information includes maps, driving performance, traffic congestion updates or weather conditions. In an embodiment, data relating to the environment  190  is transmitted to the AV  100  via a communications channel from a remotely located database  134 . 
     In an embodiment, the AV system  120  includes communications devices  140  for communicating measured or inferred properties of other vehicles&#39; states and conditions, such as positions, linear and angular velocities, linear and angular accelerations, and linear and angular headings to the AV  100 . These devices include Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communication devices and devices for wireless communications over point-to-point or ad hoc networks or both. In an embodiment, the communications devices  140  communicate across the electromagnetic spectrum (including radio and optical communications) or other media (e.g., air and acoustic media). A combination of Vehicle-to-Vehicle (V2V) Vehicle-to-Infrastructure (V2I) communication (and, in some embodiments, one or more other types of communication) is sometimes referred to as Vehicle-to-Everything (V2X) communication. V2X communication typically conforms to one or more communications standards for communication with, between, and among autonomous vehicles. 
     In an embodiment, the communication devices  140  include communication interfaces. For example, wired, wireless, WiMAX, Wi-Fi, Bluetooth, satellite, cellular, optical, near field, infrared, or radio interfaces. The communication interfaces transmit data from a remotely located database  134  to AV system  120 . In an embodiment, the remotely located database  134  is embedded in a cloud computing environment  200  as described in  FIG. 2 . The communication interfaces  140  transmit data collected from sensors  121  or other data related to the operation of AV  100  to the remotely located database  134 . In an embodiment, communication interfaces  140  transmit information that relates to teleoperations to the AV  100 . In some embodiments, the AV  100  communicates with other remote (e.g., “cloud”) servers  136 . 
     In an embodiment, the remotely located database  134  also stores and transmits digital data (e.g., storing data such as road and street locations). Such data is stored on the memory  144  on the AV  100 , or transmitted to the AV  100  via a communications channel from the remotely located database  134 . 
     In an embodiment, the remotely located database  134  stores and transmits historical information about driving properties (e.g., speed and acceleration profiles) of vehicles that have previously traveled along trajectory  198  at similar times of day. In one implementation, such data may be stored on the memory  144  on the AV  100 , or transmitted to the AV  100  via a communications channel from the remotely located database  134 . 
     Computing devices  146  located on the AV  100  algorithmically generate control actions based on both real-time sensor data and prior information, allowing the AV system  120  to execute its autonomous driving capabilities. 
     In an embodiment, the AV system  120  includes computer peripherals  132  coupled to computing devices  146  for providing information and alerts to, and receiving input from, a user (e.g., an occupant or a remote user) of the AV  100 . In an embodiment, peripherals  132  are similar to the display  312 , input device  314 , and cursor controller  316  discussed below in reference to  FIG. 3 . The coupling is wireless or wired. Any two or more of the interface devices may be integrated into a single device. 
     Example Cloud Computing Environment 
       FIG. 2  illustrates an example “cloud” computing environment. Cloud computing is a model of service delivery for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g. networks, network bandwidth, servers, processing, memory, storage, applications, virtual machines, and services). In typical cloud computing systems, one or more large cloud data centers house the machines used to deliver the services provided by the cloud. Referring now to  FIG. 2 , the cloud computing environment  200  includes cloud data centers  204   a ,  204   b , and  204   c  that are interconnected through the cloud  202 . Data centers  204   a ,  204   b , and  204   c  provide cloud computing services to computer systems  206   a ,  206   b ,  206   c ,  206   d ,  206   e , and  206   f  connected to cloud  202 . 
     The cloud computing environment  200  includes one or more cloud data centers. In general, a cloud data center, for example the cloud data center  204   a  shown in  FIG. 2 , refers to the physical arrangement of servers that make up a cloud, for example the cloud  202  shown in  FIG. 2 , or a particular portion of a cloud. For example, servers are physically arranged in the cloud datacenter into rooms, groups, rows, and racks. A cloud datacenter has one or more zones, which include one or more rooms of servers. Each room has one or more rows of servers, and each row includes one or more racks. Each rack includes one or more individual server nodes. In some implementation, servers in zones, rooms, racks, and/or rows are arranged into groups based on physical infrastructure requirements of the datacenter facility, which include power, energy, thermal, heat, and/or other requirements. In an embodiment, the server nodes are similar to the computer system described in  FIG. 3 . The data center  204   a  has many computing systems distributed through many racks. 
     The cloud  202  includes cloud data centers  204   a ,  204   b , and  204   c  along with the network and networking resources (for example, networking equipment, nodes, routers, switches, and networking cables) that interconnect the cloud data centers  204   a ,  204   b , and  204   c  and help facilitate the computing systems&#39;  206   a - f  access to cloud computing services. In an embodiment, the network represents any combination of one or more local networks, wide area networks, or internetworks coupled using wired or wireless links deployed using terrestrial or satellite connections. Data exchanged over the network, is transferred using any number of network layer protocols, such as Internet Protocol (IP), Multiprotocol Label Switching (MPLS), Asynchronous Transfer Mode (ATM), Frame Relay, etc. Furthermore, in embodiments where the network represents a combination of multiple sub-networks, different network layer protocols are used at each of the underlying sub-networks. In some embodiments, the network represents one or more interconnected internetworks, such as the public Internet. 
     The computing systems  206   a - f  or cloud computing services consumers are connected to the cloud  202  through network links and network adapters. In an embodiment, the computing systems  206   a - f  are implemented as various computing devices, for example servers, desktops, laptops, tablet, smartphones, Internet of Things (IoT) devices, autonomous vehicles (including, cars, drones, shuttles, trains, buses, etc.) and consumer electronics. In an embodiment, the computing systems  206   a - f  are implemented in or as a part of other systems. 
     Computer System 
       FIG. 3  illustrates a computer system  300 . In an implementation, the computer system  300  is a special purpose computing device. The special-purpose computing device is hard-wired to perform the techniques or includes digital electronic devices such as one or more application-specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs) that are persistently programmed to perform the techniques or may include one or more general purpose hardware processors programmed to perform the techniques pursuant to program instructions in firmware, memory, other storage, or a combination. Such special-purpose computing devices may also combine custom hard-wired logic, ASICs, or FPGAs with custom programming to accomplish the techniques. In various embodiments, the special-purpose computing devices are desktop computer systems, portable computer systems, handheld devices, network devices or any other device that incorporates hard-wired and/or program logic to implement the techniques. 
     In an embodiment, the computer system  300  includes a bus  302  or other communication mechanism for communicating information, and a hardware processor  304  coupled with a bus  302  for processing information. The hardware processor  304  is, for example, a general-purpose microprocessor. The computer system  300  also includes a main memory  306 , such as a random-access memory (RAM) or other dynamic storage device, coupled to the bus  302  for storing information and instructions to be executed by processor  304 . In one implementation, the main memory  306  is used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor  304 . Such instructions, when stored in non-transitory storage media accessible to the processor  304 , render the computer system  300  into a special-purpose machine that is customized to perform the operations specified in the instructions. 
     In an embodiment, the computer system  300  further includes a read only memory (ROM)  308  or other static storage device coupled to the bus  302  for storing static information and instructions for the processor  304 . A storage device  310 , such as a magnetic disk, optical disk, solid-state drive, or three-dimensional cross point memory is provided and coupled to the bus  302  for storing information and instructions. 
     In an embodiment, the computer system  300  is coupled via the bus  302  to a display  312 , such as a cathode ray tube (CRT), a liquid crystal display (LCD), plasma display, light emitting diode (LED) display, or an organic light emitting diode (OLED) display for displaying information to a computer user. An input device  314 , including alphanumeric and other keys, is coupled to bus  302  for communicating information and command selections to the processor  304 . Another type of user input device is a cursor controller  316 , such as a mouse, a trackball, a touch-enabled display, or cursor direction keys for communicating direction information and command selections to the processor  304  and for controlling cursor movement on the display  312 . This input device typically has two degrees of freedom in two axes, a first axis (e.g., x-axis) and a second axis (e.g., y-axis), that allows the device to specify positions in a plane. 
     According to one embodiment, the techniques herein are performed by the computer system  300  in response to the processor  304  executing one or more sequences of one or more instructions contained in the main memory  306 . Such instructions are read into the main memory  306  from another storage medium, such as the storage device  310 . Execution of the sequences of instructions contained in the main memory  306  causes the processor  304  to perform the process steps described herein. In alternative embodiments, hard-wired circuitry is used in place of or in combination with software instructions. 
     The term “storage media” as used herein refers to any non-transitory media that store data and/or instructions that cause a machine to operate in a specific fashion. Such storage media includes non-volatile media and/or volatile media. Non-volatile media includes, for example, optical disks, magnetic disks, solid-state drives, or three-dimensional cross point memory, such as the storage device  310 . Volatile media includes dynamic memory, such as the main memory  306 . Common forms of storage media include, for example, a floppy disk, a flexible disk, hard disk, solid-state drive, magnetic tape, or any other magnetic data storage medium, a CD-ROM, any other optical data storage medium, any physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, NV-RAM, or any other memory chip or cartridge. 
     Storage media is distinct from but may be used in conjunction with transmission media. Transmission media participates in transferring information between storage media. For example, transmission media includes coaxial cables, copper wire and fiber optics, including the wires that include the bus  302 . Transmission media can also take the form of acoustic or light waves, such as those generated during radio-wave and infrared data communications. 
     In an embodiment, various forms of media are involved in carrying one or more sequences of one or more instructions to the processor  304  for execution. For example, the instructions are initially carried on a magnetic disk or solid-state drive of a remote computer. The remote computer loads the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to the computer system  300  receives the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector receives the data carried in the infrared signal and appropriate circuitry places the data on the bus  302 . The bus  302  carries the data to the main memory  306 , from which processor  304  retrieves and executes the instructions. The instructions received by the main memory  306  may optionally be stored on the storage device  310  either before or after execution by processor  304 . 
     The computer system  300  also includes a communication interface  318  coupled to the bus  302 . The communication interface  318  provides a two-way data communication coupling to a network link  320  that is connected to a local network  322 . For example, the communication interface  318  is an integrated service digital network (ISDN) card, cable modem, satellite modem, or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, the communication interface  318  is a local area network (LAN) card to provide a data communication connection to a compatible LAN. In some implementations, wireless links are also implemented. In any such implementation, the communication interface  318  sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information. 
     The network link  320  typically provides data communication through one or more networks to other data devices. For example, the network link  320  provides a connection through the local network  322  to a host computer  324  or to a cloud data center or equipment operated by an Internet Service Provider (ISP)  326 . The ISP  326  in turn provides data communication services through the world-wide packet data communication network now commonly referred to as the “Internet”  328 . The local network  322  and Internet  328  both use electrical, electromagnetic, or optical signals that carry digital data streams. The signals through the various networks and the signals on the network link  320  and through the communication interface  318 , which carry the digital data to and from the computer system  300 , are example forms of transmission media. In an embodiment, the network  320  contains the cloud  202  or a part of the cloud  202  described above. 
     The computer system  300  sends messages and receives data, including program code, through the network(s), the network link  320 , and the communication interface  318 . In an embodiment, the computer system  300  receives code for processing. The received code is executed by the processor  304  as it is received, and/or stored in storage device  310 , or other non-volatile storage for later execution. 
     Autonomous Vehicle Architecture 
       FIG. 4  illustrates an example architecture  400  for an autonomous vehicle (e.g., the AV  100  shown in  FIG. 1 ). The architecture  400  includes a perception module  402  (sometimes referred to as a perception circuit), a planning module  404  (sometimes referred to as a planning circuit), a control module  406  (sometimes referred to as a control circuit), a localization module  408  (sometimes referred to as a localization circuit), and a database module  410  (sometimes referred to as a database circuit). Each module plays a role in the operation of the AV  100 . Together, the modules  402 ,  404 ,  406 ,  408 , and  410  may be part of the AV system  120  shown in  FIG. 1 . In some embodiments, any of the modules  402 ,  404 ,  406 ,  408 , and  410  is a combination of computer software (e.g., executable code stored on a computer-readable medium) and computer hardware (e.g., one or more microprocessors, microcontrollers, application-specific integrated circuits [ASICs]), hardware memory devices, other types of integrated circuits, other types of computer hardware, or a combination of any or all of these things). 
     In use, the planning module  404  receives data representing a destination  412  and determines data representing a trajectory  414  (sometimes referred to as a route) that can be traveled by the AV  100  to reach (e.g., arrive at) the destination  412 . In order for the planning module  404  to determine the data representing the trajectory  414 , the planning module  404  receives data from the perception module  402 , the localization module  408 , and the database module  410 . 
     The perception module  402  identifies nearby physical objects using one or more sensors  121 , e.g., as also shown in  FIG. 1 . The objects are classified (e.g., grouped into types such as pedestrian, bicycle, automobile, traffic sign, etc.) and a scene description including the classified objects  416  is provided to the planning module  404 . 
     The planning module  404  also receives data representing the AV position  418  from the localization module  408 . The localization module  408  determines the AV position by using data from the sensors  121  and data from the database module  410  (e.g., a geographic data) to calculate a position. For example, the localization module  408  uses data from a GNSS (Global Operation Satellite System) sensor and geographic data to calculate a longitude and latitude of the AV. In an embodiment, data used by the localization module  408  includes high-precision maps of the roadway geometric properties, maps describing road network connectivity properties, maps describing roadway physical properties (such as traffic speed, traffic volume, the number of vehicular and cyclist traffic lanes, lane width, lane traffic directions, or lane marker types and locations, or combinations of them), and maps describing the spatial locations of road features such as crosswalks, traffic signs or other travel signals of various types. 
     The control module  406  receives the data representing the trajectory  414  and the data representing the AV position  418  and operates the control functions  420   a - c  (e.g., steering, throttling, braking, ignition) of the AV in a manner that will cause the AV  100  to travel the trajectory  414  to the destination  412 . For example, if the trajectory  414  includes a left turn, the control module  406  will operate the control functions  420   a - c  in a manner such that the steering angle of the steering function will cause the AV  100  to turn left and the throttling and braking will cause the AV  100  to pause and wait for passing pedestrians or vehicles before the turn is made. 
     Autonomous Vehicle Inputs 
       FIG. 5  illustrates an example of inputs  502   a - d  (e.g., sensors  121  shown in  FIG. 1 ) and outputs  504   a - d  (e.g., sensor data) that is used by the perception module  402  ( FIG. 4 ). One input  502   a  is a LiDAR (Light Detection and Ranging) system (e.g., LiDAR  123  shown in  FIG. 1 ). LiDAR is a technology that uses light (e.g., bursts of light such as infrared light) to obtain data about physical objects in its line of sight. A LiDAR system produces LiDAR data as output  504   a . For example, LiDAR data is collections of 3D or 2D points (also known as a point clouds) that are used to construct a representation of the environment  190 . 
     Another input  502   b  is a RADAR system. RADAR is a technology that uses radio waves to obtain data about nearby physical objects. RADARs can obtain data about objects not within the line of sight of a LiDAR system. A RADAR system  502   b  produces RADAR data as output  504   b . For example, RADAR data are one or more radio frequency electromagnetic signals that are used to construct a representation of the environment  190 . 
     Another input  502   c  is a camera system. A camera system uses one or more cameras (e.g., digital cameras using a light sensor such as a charge-coupled device [CCD]) to obtain information about nearby physical objects. A camera system produces camera data as output  504   c . Camera data often takes the form of image data (e.g., data in an image data format such as RAW, JPEG, PNG, etc.). In some examples, the camera system has multiple independent cameras, e.g., for the purpose of stereopsis (stereo vision), which enables the camera system to perceive depth. Although the objects perceived by the camera system are described here as “nearby,” this is relative to the AV. In use, the camera system may be configured to “see” objects far, e.g., up to a kilometer or more ahead of the AV. Accordingly, the camera system may have features such as sensors and lenses that are optimized for perceiving objects that are far away. 
     Another input  502   d  is a traffic light detection (TLD) system. A TLD system uses one or more cameras to obtain information about traffic lights, street signs, and other physical objects that provide visual operation information. A TLD system produces TLD data as output  504 d. TLD data often takes the form of image data (e.g., data in an image data format such as RAW, JPEG, PNG, etc.). A TLD system differs from a system incorporating a camera in that a TLD system uses a camera with a wide field of view (e.g., using a wide-angle lens or a fish-eye lens) in order to obtain information about as many physical objects providing visual operation information as possible, so that the AV  100  has access to all relevant operation information provided by these objects. For example, the viewing angle of the TLD system may be about  120  degrees or more. 
     In some embodiments, outputs  504   a - d  are combined using a sensor fusion technique. Thus, either the individual outputs  504   a - d  are provided to other systems of the AV  100  (e.g., provided to a planning module  404  as shown in  FIG. 4 ), or the combined output can be provided to the other systems, either in the form of a single combined output or multiple combined outputs of the same type (e.g., using the same combination technique or combining the same outputs or both) or different types type (e.g., using different respective combination techniques or combining different respective outputs or both). In some embodiments, an early fusion technique is used. An early fusion technique is characterized by combining outputs before one or more data processing steps are applied to the combined output. In some embodiments, a late fusion technique is used. A late fusion technique is characterized by combining outputs after one or more data processing steps are applied to the individual outputs. 
       FIG. 6  illustrates an example of a LiDAR system  602  (e.g., the input  502   a  shown in  FIG. 5 ). The LiDAR system  602  emits light  604   a - c  from a light emitter  606  (e.g., a laser transmitter). Light emitted by a LiDAR system is typically not in the visible spectrum; for example, infrared light is often used. Some of the light  604   b  emitted encounters a physical object  608  (e.g., a vehicle) and reflects back to the LiDAR system  602 . (Light emitted from a LiDAR system typically does not penetrate physical objects, e.g., physical objects in solid form.) The LiDAR system  602  also has one or more light detectors  610 , which detect the reflected light. In an embodiment, one or more data processing systems associated with the LiDAR system generates an image  612  representing the field of view  614  of the LiDAR system. The image  612  includes information that represents the boundaries  616  of a physical object  608 . In this way, the image  612  is used to determine the boundaries  616  of one or more physical objects near an AV. 
       FIG. 7  illustrates the LiDAR system  602  in operation. In the scenario shown in this figure, the AV  100  receives both camera system output  504   c  in the form of an image  702  and LiDAR system output  504   a  in the form of LiDAR data points  704 . In use, the data processing systems of the AV  100  compares the image  702  to the data points  704 . In particular, a physical object  706  identified in the image  702  is also identified among the data points  704 . In this way, the AV  100  perceives the boundaries of the physical object based on the contour and density of the data points  704 . 
       FIG. 8  illustrates the operation of the LiDAR system  602  in additional detail. As described above, the AV  100  detects the boundary of a physical object based on characteristics of the data points detected by the LiDAR system  602 . As shown in  FIG. 8 , a flat object, such as the ground  802 , will reflect light  804   a - d  emitted from a LiDAR system  602  in a consistent manner. Put another way, because the LiDAR system  602  emits light using consistent spacing, the ground  802  will reflect light back to the LiDAR system  602  with the same consistent spacing. As the AV  100  travels over the ground  802 , the LiDAR system  602  will continue to detect light reflected by the next valid ground point  806  if nothing is obstructing the road. However, if an object  808  obstructs the road, light  804   e - f  emitted by the LiDAR system  602  will be reflected from points  810   a - b  in a manner inconsistent with the expected consistent manner. From this information, the AV  100  can determine that the object  808  is present. 
     Path Planning 
       FIG. 9  illustrates a block diagram  900  of the relationships between inputs and outputs of a planning module  404  (e.g., as shown in  FIG. 4 ). In general, the output of a planning module  404  is a route  902  from a start point  904  (e.g., source location or initial location), and an end point  906  (e.g., destination or final location). The route  902  is typically defined by one or more segments. For example, a segment is a distance to be traveled over at least a portion of a street, road, highway, driveway, or other physical area appropriate for automobile travel. In some examples, e.g., if the AV  100  is an off-road capable vehicle such as a four-wheel-drive (4WD) or all-wheel-drive (AWD) car, SUV, pick-up truck, or the like, the route  902  includes “off-road” segments such as unpaved paths or open fields. 
     In addition to the route  902 , a planning module also outputs lane-level route planning data  908 . The lane-level route planning data  908  is used to traverse segments of the route  902  based on conditions of the segment at a particular time. For example, if the route  902  includes a multi-lane highway, the lane-level route planning data  908  includes trajectory planning data  910  that the AV  100  can use to choose a lane among the multiple lanes, e.g., based on whether an exit is approaching, whether one or more of the lanes have other vehicles, or other factors that vary over the course of a few minutes or less. Similarly, in some implementations, the lane-level route planning data  908  includes speed constraints  912  specific to a segment of the route  902 . For example, if the segment includes pedestrians or un-expected traffic, the speed constraints  912  may limit the AV  100  to a travel speed slower than an expected speed, e.g., a speed based on speed limit data for the segment. 
     In an embodiment, the inputs to the planning module  404  includes database data  914  (e.g., from the database module  410  shown in  FIG. 4 ), current location data  916  (e.g., the AV position  418  shown in  FIG. 4 ), destination data  918  (e.g., for the destination  412  shown in  FIG. 4 ), and object data  920  (e.g., the classified objects  416  as perceived by the perception module  402  as shown in  FIG. 4 ). In some embodiments, the database data  914  includes rules used in planning. Rules are specified using a formal language, e.g., using Boolean logic. In any given situation encountered by the AV  100 , at least some of the rules will apply to the situation. A rule applies to a given situation if the rule has conditions that are met based on information available to the AV  100 , e.g., information about the surrounding environment. Rules can have priority. For example, a rule that says, “if the road is a freeway, move to the leftmost lane” can have a lower priority than “if the exit is approaching within a mile, move to the rightmost lane.” 
       FIG. 10  illustrates a directed graph  1000  used in path planning, e.g., by the planning module  404  ( FIG. 4 ). In general, a directed graph  1000  like the one shown in  FIG. 10  is used to determine a path between any start point  1002  and end point  1004 . In real-world terms, the distance separating the start point  1002  and end point  1004  may be relatively large (e.g., in two different metropolitan areas) or may be relatively small (e.g., two intersections abutting a city block or two lanes of a multi-lane road). 
     In an embodiment, the directed graph  1000  has nodes  1006   a - d  representing different locations between the start point  1002  and the end point  1004  that could be occupied by an AV  100 . In some examples, e.g., when the start point  1002  and end point  1004  represent different metropolitan areas, the nodes  1006   a - d  represent segments of roads. In some examples, e.g., when the start point  1002  and the end point  1004  represent different locations on the same road, the nodes  1006   a - d  represent different positions on that road. In this way, the directed graph  1000  includes information at varying levels of granularity. In an embodiment, a directed graph having high granularity is also a subgraph of another directed graph having a larger scale. For example, a directed graph in which the start point  1002  and the end point  1004  are far away (e.g., many miles apart) has most of its information at a low granularity and is based on stored data, but also includes some high granularity information for the portion of the graph that represents physical locations in the field of view of the AV  100 . 
     The nodes  1006   a - d  are distinct from objects  1008   a - b  which cannot overlap with a node. In an embodiment, when granularity is low, the objects  1008   a - b  represent regions that cannot be traversed by automobile, e.g., areas that have no streets or roads. When granularity is high, the objects  1008   a - b  represent physical objects in the field of view of the AV  100 , e.g., other automobiles, pedestrians, or other entities with which the AV  100  cannot share physical space. In an embodiment, some or all of the objects  1008 a-b are static objects (e.g., an object that does not change position such as a street lamp or utility pole) or dynamic objects (e.g., an object that is capable of changing position such as a pedestrian or other car). 
     The nodes  1006   a - d  are connected by edges  1010   a - c . If two nodes  1006   a - b  are connected by an edge  1010   a , it is possible for an AV  100  to travel between one node  1006   a  and the other node  1006   b , e.g., without having to travel to an intermediate node before arriving at the other node  1006   b . (When we refer to an AV  100  traveling between nodes, we mean that the AV  100  travels between the two physical positions represented by the respective nodes.) The edges  1010   a - c  are often bidirectional, in the sense that an AV  100  travels from a first node to a second node, or from the second node to the first node. In an embodiment, edges  1010   a - c  are unidirectional, in the sense that an AV  100  can travel from a first node to a second node, however the AV  100  cannot travel from the second node to the first node. Edges  1010   a - c  are unidirectional when they represent, for example, one-way streets, individual lanes of a street, road, or highway, or other features that can only be traversed in one direction due to legal or physical constraints. 
     In an embodiment, the planning module  404  uses the directed graph  1000  to identify a path  1012  made up of nodes and edges between the start point  1002  and end point  1004 . 
     An edge  1010   a - c  has an associated cost  1014   a - b.  The cost  1014   a - b  is a value that represents the resources that will be expended if the AV  100  chooses that edge. A typical resource is time. For example, if one edge  1010   a  represents a physical distance that is twice that as another edge  1010   b , then the associated cost  1014   a  of the first edge  1010   a  may be twice the associated cost  1014   b  of the second edge  1010   b . Other factors that affect time include expected traffic, number of intersections, speed limit, etc. Another typical resource is fuel economy. Two edges  1010   a - b  may represent the same physical distance, but one edge  1010   a  may require more fuel than another edge  1010   b , e.g., because of road conditions, expected weather, etc. 
     When the planning module  404  identifies a path  1012  between the start point  1002  and end point  1004 , the planning module  404  typically chooses a path optimized for cost, e.g., the path that has the least total cost when the individual costs of the edges are added together. 
     Autonomous Vehicle Control 
       FIG. 11  illustrates a block diagram  1100  of the inputs and outputs of a control module  406  (e.g., as shown in  FIG. 4 ). A control module operates in accordance with a controller  1102  which includes, for example, one or more processors (e.g., one or more computer processors such as microprocessors or microcontrollers or both) similar to processor  304 , short-term and/or long-term data storage (e.g., memory random-access memory or flash memory or both) similar to main memory  306 , ROM  1308 , and storage device  210 , and instructions stored in memory that carry out operations of the controller  1102  when the instructions are executed (e.g., by the one or more processors). 
     In an embodiment, the controller  1102  receives data representing a desired output  1104 . The desired output  1104  typically includes a velocity, e.g., a speed and a heading. The desired output  1104  can be based on, for example, data received from a planning module  404  (e.g., as shown in  FIG. 4 ). In accordance with the desired output  1104 , the controller  1102  produces data usable as a throttle input  1106  and a steering input  1108 . The throttle input  1106  represents the magnitude in which to engage the throttle (e.g., acceleration control) of an AV  100 , e.g., by engaging the steering pedal, or engaging another throttle control, to achieve the desired output  1104 . In some examples, the throttle input  1106  also includes data usable to engage the brake (e.g., deceleration control) of the AV  100 . The steering input  1108  represents a steering angle, e.g., the angle at which the steering control (e.g., steering wheel, steering angle actuator, or other functionality for controlling steering angle) of the AV should be positioned to achieve the desired output  1104 . 
     In an embodiment, the controller  1102  receives feedback that is used in adjusting the inputs provided to the throttle and steering. For example, if the AV  100  encounters a disturbance  1110 , such as a hill, the measured speed  1112  of the AV  100  is lowered below the desired output speed. In an embodiment, any measured output  1114  is provided to the controller  1102  so that the necessary adjustments are performed, e.g., based on the differential  1113  between the measured speed and desired output. The measured output  1114  includes measured position  1116 , measured velocity  1118 , (including speed and heading), measured acceleration  1120 , and other outputs measurable by sensors of the AV  100 . 
     In an embodiment, information about the disturbance  1110  is detected in advance, e.g., by a sensor such as a camera or LiDAR sensor, and provided to a predictive feedback module  1122 . The predictive feedback module  1122  then provides information to the controller  1102  that the controller  1102  can use to adjust accordingly. For example, if the sensors of the AV  100  detect (“see”) a hill, this information can be used by the controller  1102  to prepare to engage the throttle at the appropriate time to avoid significant deceleration. 
       FIG. 12  illustrates a block diagram  1200  of the inputs, outputs, and components of the controller  1102 . The controller  1102  has a speed profiler  1202  which affects the operation of a throttle/brake controller  1204 . For example, the speed profiler  1202  instructs the throttle/brake controller  1204  to engage acceleration or engage deceleration using the throttle/brake  1206  depending on, e.g., feedback received by the controller  1102  and processed by the speed profiler  1202 . 
     The controller  1102  also has a lateral tracking controller  1208  which affects the operation of a steering controller  1210 . For example, the lateral tracking controller  1208  instructs the steering controller  1204  to adjust the position of the steering angle actuator  1212  depending on, e.g., feedback received by the controller  1102  and processed by the lateral tracking controller  1208 . 
     The controller  1102  receives several inputs used to determine how to control the throttle/brake  1206  and steering angle actuator  1212 . A planning module  404  provides information used by the controller  1102 , for example, to choose a heading when the AV  100  begins operation and to determine which road segment to traverse when the AV  100  reaches an intersection. A localization module  408  provides information to the controller  1102  describing the current location of the AV  100 , for example, so that the controller  1102  can determine if the AV  100  is at a location expected based on the manner in which the throttle/brake  1206  and steering angle actuator  1212  are being controlled. In an embodiment, the controller  1102  receives information from other inputs  1214 , e.g., information received from databases, computer networks, etc. 
     Architecture for Operation Using Multiple Motion Constraints 
       FIG. 13  illustrates a block diagram of an operating environment  1304  for an AV  1308  using multiple motion constraints, in accordance with one or more embodiments. The operating environment  1304  includes the AV  1308  and other objects (e.g., pedestrian  1316 ). The operating environment  1304  represents a geographical area, such as a state, a town, a neighborhood, or a road network or segment. The operating environment  1304  may be an example of the operating environment  190  illustrated and described above with reference to  FIG. 1 . A pedestrian  1316 , a vehicle  1320 , and a construction zone  1356  are located within the operating environment  1304 . In other embodiments, the operating environment  1304  includes additional or fewer objects than those described herein. 
     The operating environment  1304  includes objects, which are physical entities external to the AV  1308 . An object can be static or dynamic. A static object can include but is not limited to: a road segment, a traffic signal, a building, a parking space located on a road segment, a highway exit or entrance ramp, multiple lanes of a drivable area of the operating environment  1304  orientated in the same direction, an elevation of the drivable area, a curb located adjacent to the drivable area, a median separating two lanes of the drivable area, and any other object that does not move within the operating environment  1304 . The construction zone  1356  is an example of a static object. A dynamic object can include but is not limited to: another vehicle that is not parked, a pedestrian, a cyclist, and any other object that moves within the operating environment  1304 . The pedestrian  1316  and the vehicle  1320  are examples of dynamic objects. 
     In driving mode, the AV  1308  uses sensor data  1352 , for example, LiDAR data or stereo camera data, to detect and classify or label static objects and dynamic objects in the operating environment  1304 . The classified/labeled objects and their dynamic characteristics if any, for example, positions, velocities, or headings, are used by a planning module  1336  to predict a collision between the AV  1308  and objects within the operating environment  1304 , to generate a safe trajectory through the operating environment  1304 , and to operate the AV  1308  to drive through the operating environment  1304  along the safe trajectory. 
     The planning module  1336  predicts a future trajectory of the vehicle  1320  based on different factors, such as the dynamic characteristics of the vehicle  1320 , a current dynamic state of the vehicle  1320 , and historical dynamic states of the vehicle  1320 . In an embodiment, the planning module  1336  also uses a model of the road infrastructure, including lane connectivity or visual information, such as turn signals to predict the future trajectory of the vehicle  1320 . For example, the planning module  1336  can predict that the vehicle  1320  will move in a straight line at a constant speed or, based on a geometry of the road, the planning module  1336  can predict that the vehicle  1320  will turn, for example, if the road is curved. In one embodiment, the planning module  1336  uses an extended Kalman filter to estimate a trajectory for the vehicle  1320 . The planning module  1336  also estimates a point and time of intersection between the estimated trajectory of the vehicle  1320  and the planned trajectory of AV  1308 . The planning module  1336  determines potential behaviors for the vehicle  1320  and assigns probabilities to each potential behavior to determine a likelihood of collision. In other embodiments, a Kalman filter is not used. 
     In addition to determining the trajectories and the intersection point and time, the planning module  1336  generates multiple motion constraints for operating the AV  1308 . In one embodiment, at least one motion constraint includes a speed profile of the AV  1308 . The speed profile can include a minimum speed, a maximum speed, a minimum acceleration, or a maximum acceleration. For example, a speed profile can include a minimum speed of the AV  1308  greater than zero to avoid a collision of the AV  1308  with the pedestrian  1316 . The planning module  1336  determines that the pedestrian  1316  is about to cross the street at a crossing location l 1  that is a particular distance d 1  from the AV  1308  within t 1  seconds. The current speed of the AV  1308  is v mph. The planning module  1336  generates a minimum speed constraint based on (d 1 /t 1 ) and v, such that the AV  1308  can speed up and safely pass the crossing location l 1  before the pedestrian  1316  crosses the street. 
     In one embodiment, the planning module  1336  generates a motion constraint that includes a maximum speed of the AV  1308  to obey a street speed limit or to avoid a collision of the AV  1308  with the pedestrian  1316 . For example, the street speed limit may be 30 mph. However, the AV  1308  senses that a collision with the pedestrian  1316  can be avoided if the AV  1308  slows down to 20 mph. Therefore the AV  1308  generates a maximum speed constraint that corresponds to the deceleration to 20 mph. In one embodiment, the planning module  1336  generates a motion constraint that includes a minimum speed profile or acceleration of the AV  1308  to avoid a collision of the AV  1308  with the vehicle  1320 . For example, the planning module  1336  determines that the vehicle  1320  is about to cross the street at a crossing location l 2  that is a particular distance d 2  from the AV  1308  within t 2  seconds. The planning module  1336  generates a minimum speed constraint or minimum acceleration constraint based on d 2 , t 2 , and v, such that the AV  1308  can speed up and safely pass the crossing location l 2  before the vehicle  1320  crosses the street. An example of a minimum speed constraint and a maximum speed constraint for the AV  1308  to avoid a collision with other objects crossing the street on which the AV  1308  is operating is illustrated and described in more detail with reference to  FIG. 14 . 
     In one embodiment, the planning module  1336  generates a motion constraint that includes a maximum speed or a minimum deceleration of the AV  1308  to avoid a collision of the AV  1308  with the construction zone  1356 . For example, the planning module  1336  determines that the construction zone  1356  is a particular distance d 3  from the AV  1308 , the current speed of the AV  1308  is v mph, and the AV  1308  is likely to collide with the construction zone in t 3  seconds. The planning module  1336  generates a maximum speed or a minimum deceleration constraint based on d 3 , t 3 , and v, such that the AV  1308  can decelerate and safely stop before a collision. 
     In one embodiment, the planning module  1336  generates a motion constraint that includes a minimum speed of the AV  1308  to avoid blocking an intersection by the AV  1308 . For example, the AV  1308  may be stopped or moving slowly within an intersection. The planning module  1336  determines that a current speed of the vehicle  1320  is v 1 , and the vehicle  1320  is approaching the intersection and is a particular distance d 4  from the intersection. The planning module  1336  further determines that the current speed of the AV  1308  is v and a collision is likely between the AV  1308  and the vehicle  1320  in t 4  seconds. The planning module  1336  generates a minimum speed constraint based on d 4 , t 4 , v 1 , and v, such that the AV  1308  can speed up and safely avoid blocking the intersection before the vehicle  1320  arrives at the intersection. The planning module  1336  will either find a solution that satisfies both (1) a minimum speed constraint to avoid a potential collision with the vehicle  1320  in the intersection and (2) a maximum speed constraint for a potential collision with the construction zone  1308 , or else select a different homotopy including crossing the intersection only after the vehicle  1320  clears the intersection. The different homotopy includes a corresponding maximum speed constraint based on d 4 , t 4 , v 1 , and v. 
     In one embodiment, the planning module  1336  generates a motion constraint that specifies a directional orientation of the AV  1308  to avoid a collision of the AV  1308  with the vehicle  1320 . For example, the planning module  1336  determines that the vehicle  1320  is stopped at a location l 5  on the street that is a particular distance d 5  from the AV  1308 . The planning module  1336  further determines that the current speed of the AV  1308  is v mph and the AV  1308  is likely to collide with the vehicle  1320  in t 5  seconds. Based on the values of l 5 , d 5 , t 5 , and v, the planning module  1336  determines that the AV  1308  will be unable to accelerate or decelerate sufficiently to avoid the collision. The planning module  1336  generates a motion constraint, based on the speed v, the location l 5  of the vehicle  1320 , and the current spatiotemporal location of the AV  1308 . The motion constraint specifies a directional orientation of the AV  1308  to avoid a collision of the AV  1308  with the vehicle  1320 . For example, the motion constraint may specify that the AV  1308  should swerve at an angle of 30° at its present speed to safely avoid the location l 5 . 
     In one embodiment, the planning module  1336  generates motion constraints for the AV  1308  that are not based on navigational safety. For example, the planning module  1336  generates a motion constraint that includes a maximum speed or a maximum acceleration of the AV  1308  associated with a level of passenger comfort measured by passenger sensors located on the AV  1308 . The passenger sensors include specialized sensors to record data such as facial expressions of the passenger, skin conductance, pulse and heart-rate, a temperature of the passenger&#39;s body, pupil dilation, and pressure on the AV seat arm rests. Each type of data can be recorded using a different sensor or a combination of different sensors, for example, heart rate monitors, a sphygmomanometer, a pupilometer, an Infrared thermometer, or a galvanic skin response sensor. The planning module  1336  determines the motion constraint based on, for example, an elevated heart rate or skin conductance level as detected by the passenger sensors indicative of passenger discomfort or stress. As would be understood by one of ordinary skill, one or more physical measurements of one or more passengers may be correlated with a level of discomfort or stress and that may be adjusted for by one or more motion constraints. 
     The planning module  1336  identifies one or more motion constraints  1312  for operating the AV  1308  to avoid a collision of the AV  1308  with the pedestrian  1316 . The one or more motion constraints  1312  identified are a subset of the generated motion constraints. Hence some motion constraints may be temporarily violated in order to operate the AV  1308 , such that a collision is avoided. In one embodiment, the planning module  1336  aggregates the generated motion constraints for operating the AV  1308  into a motion planning graph. Motion planning is a process of disaggregating a desired operation, such as exiting an intersection without a collision, into discrete motions that satisfy motion constraints. 
     The planning module  1336  receives a description of the desired operation for the AV  1308  and uses the generated motion constraints to generate the motion planning graph. The motion planning graph is used to identify the one or more motion constraints  1312  to operate the AV  1308 . The planning module  1336  traverses the motion planning graph to produce speed and turning commands for the throttle and steering of the AV  1308 . In one embodiment, the motion planning graph is overlaid on a configuration space (spatiotemporal location, speed, directional orientation, etc.,) for the AV  1308 . Each configuration for the AV  1308  is associated with a vertex of the motion planning graph. An example motion planning graph is illustrated and described above with reference to  FIG. 10 . From each vertex, the AV  1308  is allowed to move to adjacent vertices as long as the path between them avoids a collision with an object, for example, the pedestrian  1316 . In one embodiment, the planning module  1336  uses the generated motion constraints to generate a minimum-violation motion planning graph. The minimum-violation motion planning graph is used to determine a trajectory and speed for the AV  1308 , such that a number of violations of the motion constraints is minimized. For example, a motion constraint specifying a maximum speed of 60 mph for passenger comfort may be temporarily violated if a minimum speed constraint of 65 mph to avoid a collision is added to the minimum-violation motion planning graph. 
     The planning module  1336  determines a speed, acceleration, or directional orientation for the AV  1308  using the minimum-violation motion planning graph, such that there are a minimum number of violations of the generated motion constraints. In one embodiment, sampling-based motion planning is used to perform model checking for the generated motion constraints based on a ranked hierarchy of motion constraints. The traversing of the minimum-violation motion graph results in a trajectory for the AV  1308  that maximizes a level of safety among several potential trajectories that satisfy the navigational objective. The generated trajectory satisfies the identified one or more motion constraints  1312 . 
     In one embodiment, the generated motion constraints are ranked in a hierarchical order. The motion constraints are ranked in accordance with their relationship to navigational safety. A motion constraint that is based on navigational safety is ranked higher than another motion constraint that is not based on navigational safety. For example, a motion constraint to avoid a collision of the AV  1308  with the pedestrian  1316  is ranked higher than another motion constraint that is based on providing a level of passenger comfort. A minimum speed constraint to avoid a collision of the AV  1308  with the pedestrian  1316  is ranked higher than a maximum speed constraint that is based on a traffic rule. The planning module  1336  may instruct the control module  1340  to temporarily increase the speed of the AV  1308  higher than the speed limit to avoid a collision with a pedestrian  1316 . 
     In one embodiment, the planning module  1336  identifies the one or more motion constraints  1312  by weighting a violation of each motion constraint by a rank of the motion constraint. The planning module  1336  constructs a cost function by assigning a lower weight to lower-ranked motion constraints than to higher-ranked motion constraints. The cost function is based on a weighted aggregate of violations of motion constraints. For example, the cost function may be expressed as Cost=Σi(W i ×V i ), where W i  is the weight assigned to motion constraint i and V i  represents a violation of motion constraint i. The planning module  1336  determines the weighted aggregate of the number of violations of the motion constraints. Once the planning module  1336  has constructed the cost function, the planning module  1336  performs the minimum violation motion planning using the motion graph to generate a trajectory for the AV  1308  that minimizes the cost function. 
     In one embodiment, the planning module  1336  determines that no operation is possible for the AV  1308  without experiencing a collision. For example, the planning module  1336  may determine that operating the AV  1308  in accordance with a first minimum speed constraint to avoid a collision with the pedestrian  1316  violates a second maximum speed constraint to avoid a collision with the vehicle  1320 . For example, the planning module  1336  may determine that the AV  1308  should speed up to greater than 25 mph to avoid a collision with the pedestrian  1316 . However, the planning module also determines that the AV  1308  should slow down to less than 15 mph to avoid a collision with the vehicle  1320 . If it is not possible for the AV  1308  to swerve due to the proximity of other vehicles on the street, the planning module  1336  will instruct the control module  1340  to stop the AV  1308 . 
     In one embodiment, the planning module  1336  determines, using hysteresis data, a speed for operating the AV  1308  based on the identified one or more motion constraints  1312 . Hysteresis data is used to avoid rapid changes in the speed of AV  1308  resulting from the planning module  1336  trying to satisfy different motion constraints. The planning module  1336  may generate a hysteresis loop including curves of speed plotted against motion constraints to determine the speed of AV  1308  based on the past states and current state of AV  1308 . The benefit of the use of the hysteresis data to determine a speed for operating the AV  1308  based on the identified one or more motion constraints  1312  is that the hysteresis data prevents frequent switching of speed. 
     In one embodiment, the control module  1340  operates the AV  1308  in accordance with the identified one or more motion constraints  1312 . The control module  1340  uses the identified motion constraints  1312  from the planning module  1336  to operate the brakes  420   c , steering  420   a , and throttle  420   b  (illustrated and described above with reference to  FIG. 4 ) of the AV  1308 . In one embodiment, the control module  1340  operates the AV  1308  to avoid a collision with the pedestrian  1316  based on a determined distance to the pedestrian  1316  and the identified one or more motion constraints  1312 . The operating of the AV  1308  can include violating a lower-priority motion constraint, for example, a maximum acceleration constraint that is based on providing a level of passenger comfort. In one embodiment, the control module  1340  operates the AV  1308  within a discretized drivable area in accordance with the identified one or more motion constraints  1312  while performing collision checking or probabilistically exploring the drivable area around the pedestrian  1316 . In another embodiment, if the vehicle  1320  is moving, the control module  1340  infers the vehicle  1320 &#39;s intention from its motion, such as giving way or acting aggressively. Based on the identified one or more motion constraints  1312 , the control module  1340  operates the steering control  102 , brakes  103 , gears, or accelerator pedal if a predicted time to collision with the vehicle  1320  falls below a threshold. 
     In one embodiment, the one or more visual sensors  1344  sense a state of the operating environment  1304 , such as the presence and structure of the vehicle  1320 , and transmit the sensor data  1352  and semantic data representing the state to the planning module  1336 . The visual sensors  1344  are communicatively coupled to the planning module  1336  to transmit the sensor data  1352  and semantic data. The visual sensors  1344  include one or more monocular or stereo video cameras in the visible light, infrared or thermal (or both) spectra, LiDAR, RADAR, ultrasonic sensors, time-of-flight (TOF) depth sensors, and may include temperature sensors, humidity sensors, or precipitation sensors. The visual sensors  1344  may be an example of the sensors  122 - 123  illustrated and described above with reference to  FIG. 1 . 
     In one embodiment, the sensor data  1352  includes LiDAR point cloud data or camera images. For example, LiDAR sensors of the AV  1308  are used to illuminate a target, for example, the pedestrian  1316 , with pulsed laser light and measure the reflected pulses. Differences in laser return times and wavelengths can then be used to generate the sensor data  1352  and create a digital 3-D representation (feature) of the pedestrian  1316 . In one embodiment, the LiDAR point cloud data is stored as a multidimensional occupancy grid. The LiDAR point cloud data is pre-processed at the signal level and then processed at a higher level to extract features of the pedestrian  1316 . In some embodiments, a combination two- and three-dimensional grid structure is used and the space in these structures is tessellated into several discrete cells. The structure of the LiDAR point cloud data allows a large amount of raw measurement data to be handled by the perception module  1336 . 
     In one embodiment, illustrated and described in  FIGS. 1 and 3  above, the AV  1308  includes one or more computer processors. The AV  1308  further includes one or more non-transitory storage media storing instructions which, when executed by the one or more computer processors, cause performance of the embodiments disclosed herein. In one embodiment, illustrated and described in  FIGS. 1 and 3  above, the AV  1308  includes one or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of the embodiments disclosed herein. In one embodiment, the AV  1308  performs a method including performing a machine-executed operation involving instructions which, when executed by one or more computing devices, cause performance of the embodiments disclosed herein, wherein the machine-executed operation is at least one of sending said instructions, receiving said instructions, storing said instructions, or executing said instructions. 
     In one alternate embodiment, one or more processors of the AV  1308  are used to store traffic rules for operating the AV  1308 . The visual sensors  1344  of the AV  1308  are used to receive the sensor data  1352  describing the pedestrian  1316 . The one or more processors extract a feature vector from the sensor data  1352 . The feature vector includes at least one feature describing a speed of the pedestrian  1316  relative to the AV  1308 . A machine learning circuit of the AV  1308  is used to identify, based on the feature vector, a speed for operating the AV  1308 . Operating the AV  1308  at the identified speed avoids a collision of the AV  1308  with the pedestrian  1316 . Operating the AV  1308  at the identified speed also minimizes a number of violations of the traffic rules. The control module  1340  of the AV  1308  operates the AV  1308  in accordance with the speed identified by the machine learning circuit. 
     Among the benefits and advantages of the embodiments disclosed herein are that different and complex motion constraints can be addressed by an AV system to prevent collisions with objects. The disclosed embodiments increase navigational safety for the AV as well as for pedestrians and other vehicles. By ranking motion constraints in a hierarchical order in accordance with navigational safety, the AV can select a lower-priority rule to temporarily violate in order to increase vehicular safety. Operating the AV using the disclosed embodiments results in increased passenger and pedestrian safety, lower wear and tear on the AV, reduced travel time, a reduced travel distance, etc. Increased safety for other vehicles on the road network is also achieved. 
     Example of Operation Using Multiple Motion Constraints 
       FIG. 14  illustrates an example of operation of the AV  1308  using multiple motion constraints, in accordance with one or more embodiments. The operating environment  1400 , illustrated in  FIG. 14 , includes the AV  1308  and pedestrians  1408 ,  1412 . In other embodiments, the operating environment  1400  includes additional or fewer objects than those described herein. 
     Referring to  FIGS. 13  and  FIG. 14 , the AV  1308  is traveling along a road  1404 . The AV  1308  determines that the pedestrian  1408  is about to walk across the road  1404  at the spatiotemporal location  1416 . The AV  1308  determines that the AV  1308  has a likelihood of collision with the pedestrian  1408  that is greater than a threshold. The AV  1308  determines the speed and trajectory  1424  of the pedestrian  1408  to generate multiple motion constraints. At least one motion constraint includes a minimum speed of the AV  1308  that is greater than zero to avoid a collision of the AV  1308  with the pedestrian by speeding up to cross the spatiotemporal location  1416  before the pedestrian  1408  can reach the spatiotemporal location  1416 . Another motion constraint may specify that the AV  1308  should slow down below a maximum speed constraint to allow the pedestrian  1408  to pass the spatiotemporal location  1416  before the AV  1308  reaches the spatiotemporal location  1416 . 
     The AV  1308  identifies one or more motion constraints  1312  for operating the AV  1308  to avoid a collision of the AV  1308  with the pedestrian  1408  by incurring a minimum number of violations of the motion constraints. In the example illustrated in  FIG. 14 , the AV  1308  speeds up to cross the spatiotemporal location  1416  before the pedestrian  1408  can reach the spatiotemporal location  1416 . After crossing the spatiotemporal location  1416 , the AV  1308  identifies pedestrian  1412  who is about to run across the road  1404  at the spatiotemporal location  1420 . The AV  1308  determines the speed and trajectory  1428  of the pedestrian  1412  to generate a second set of motion constraints to avoid a collision with the pedestrian  1412 . One motion constraint of the second set of motion constraints specifies a minimum speed for the AV  1308  to travel past the spatiotemporal location  1420  before the pedestrian  1412  reaches the spatiotemporal location  1420 . Another motion constraint specifies a maximum speed for the AV  1308 , such that the pedestrian  1412  crosses the spatiotemporal location  1420  before the AV  1308  reaches the spatiotemporal location  1420 . 
     Based on its current speed and using the hysteresis data to avoid rapid speed switching, the AV  1308  determines that it will be unable to speed up sufficiently to travel past the spatiotemporal location  1420  before the pedestrian  1412  reaches the spatiotemporal location  1420 . The AV  1308  determines that slowing down in accordance with the maximum speed constraint, such that the pedestrian  1412  crosses the spatiotemporal location  1420  before the AV  1308  reaches the spatiotemporal location  1420  violates a smaller number of motion constraints and incurs the least cost. Hence, the AV  1308  slows down, such that the pedestrian  1412  crosses the spatiotemporal location  1420  before the AV  1308  reaches the spatiotemporal location  1420 . 
     Process for Operation Using Multiple Motion Constraints 
       FIG. 15  illustrates a process  1500  for operation of the AV  1308  using multiple motion constraints, in accordance with one or more embodiments. In one embodiment, the process of  FIG. 1500  is performed by the planning module  1336 . Other entities, for example, one or more components of the AV  1308  perform some or all of the steps of the process  1500  in other embodiments. Likewise, embodiments may include different and/or additional steps, or perform the steps in different orders. 
     The AV  1308  identifies  1504 , using one or more processors, a pedestrian  1316 , wherein the AV  1308  has a likelihood of collision with the pedestrian  1316  greater than a threshold. In one embodiment, the AV  1308  determines the likelihood of collision for the AV  1308  with the pedestrian  1316  by predicting a trajectory for the object  1316 . In one embodiment, the AV  1308  predicts that the pedestrian  1316  will move in a straight line at its present speed. In one embodiment, the AV  1308  uses an extended Kalman filter to track the pedestrian  1316  and determine a time for a potential collision. 
     The AV  1308  generates  1508 , using the one or more processors, multiple motion constraints for operating the AV  1308 . At least one motion constraint includes a minimum speed of the AV  1308  that is greater than zero to avoid a collision of the AV  1308  with the pedestrian  1316 . For example, the AV  1308  determines that the pedestrian  1316  is about to cross the street at a crossing location l 1  that is a particular distance d 1  from the AV  1308  in t 1  seconds. The AV  1308  generates a minimum speed constraint based on (d 1 /t 1 ), such that the AV  1308  can speed up and safely pass the crossing location l 1  before the pedestrian  1316  crosses the street. 
     The AV  1308  identifies  1512 , using the one or more processors, one or more motion constraints  1312  for operating the AV  1308  to avoid a collision of the AV  1308  with the pedestrian  1316 . In one embodiment, the AV  1308  aggregates the generated motion constraints for operating the AV  1308  into a motion planning graph. The motion planning graph includes the potential spatiotemporal locations for the AV  1308  as well as the generated motion constraints. The motion planning graph is used to determine a trajectory and speed for the AV  1308  in the presence of the multiple motion constraints, such that the collision is avoided while a number of violations of the motion constraints is minimized. 
     The AV  1308  operates  1516  in accordance with the identified one or more motion constraints  1312 . The operating of the AV  1308  in accordance with the identified one or more motion constraints  1312  can include violating a lower-priority motion constraint, for example, a maximum acceleration constraint that is based on providing a level of passenger comfort. 
     Additional Embodiments 
     In one embodiment, one or more processors of a vehicle store traffic rules for operating the vehicle. One or more sensors of the vehicle receive sensor data describing an object. The one or more processors of the vehicle extract a feature vector from the sensor data. The feature vector includes at least one feature describing a speed of the object relative to the vehicle. A machine learning circuit of the vehicle identifies a speed for operating the vehicle based on the feature vector. Operating the vehicle at the identified speed avoids a collision of the vehicle with the object and minimizes a number of violations of the traffic rules. A control module of the vehicle operates the vehicle in accordance with the speed identified by the machine learning circuit. 
     In the foregoing description, embodiments of the invention have been described with reference to numerous specific details that may vary from implementation to implementation. The description and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the invention, and what is intended by the applicants to be the scope of the invention, is the literal and equivalent scope of the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. Any definitions expressly set forth herein for terms contained in such claims shall govern the meaning of such terms as used in the claims. In addition, when we use the term “further including,” in the foregoing description or following claims, what follows this phrase can be an additional step or entity, or a sub-step/sub-entity of a previously-recited step or entity.