Abstract:
A method for forming a robotic vehicle. The method may involve forming a body and arranging a plurality of movable legs to project from the body for propelling the body over a surface. An actuator may be carried by the body to selectively engage and disengage different ones of the movable legs to cause a motion of the body, and thus the robotic vehicle, to travel over the surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/951,728, entitled “Robotic Rolling Vehicle Apparatus and Method,” filed Dec. 6, 2007 (now U.S. Pat. No. 7,490,681). This application is generally related in subject matter to U.S. Pat. No. 7,165,637, entitled “Robotic All Terrain Surveyor”, to M. Tanielian, issued Jan. 23, 2007, and assigned to The Boeing Company, and also to U.S. Pat. No. 7,434,638, entitled “Robotic All Terrain Surveyor”, to M. Tanielian, issued Oct. 14, 2008, and assigned to The Boeing Company, which is a divisional of U.S. Pat. No. 7,165,637. All of which are hereby incorporated by reference into the present disclosure. 
    
    
     FIELD 
     The present disclosure relates to vehicles, and more particularly to a propulsion system for a robotic vehicle that enables the vehicle to traverse a ground surface. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Interest in robotic vehicles continues to increase. Examples of robotic vehicles are disclosed in U.S. Pat. No. 7,165,637, entitled “Robotic All Terrain Surveyor”, to M. Tanielian, issued Jan. 23, 2007, and U.S. Pat. No. 7,434,638, entitled “Robotic All Terrain Surveyor”, to M. Tanielian, issued Oct. 14, 2008, which is a divisional of U.S. Pat. No. 7,165,637. Both of these references are owned by The Boeing Company, and both are hereby incorporated by reference into the present application. 
     With any form of robotic vehicle, the vehicle&#39;s overall weight and mechanical complexity are factors that designers generally seek to minimize. For example, with the robotic surveyor of U.S. Pat. No. 7,165,637, the device includes a plurality of legs that can be extended to help propel the device in a general rolling motion along a desired course. A plurality of actuators may be included to accomplish this, with one actuator being associated with each leg. Thus, if six legs are used, then a minimum of six actuators may be employed; if twelve legs are used then twelve actuators may be employed and so on. 
     SUMMARY 
     In one aspect the present disclosure relates to a method for forming a robotic vehicle. The method may comprise forming a body and arranging a plurality of movable legs to project from the body for propelling the body over a surface. An actuator may be carried by the body to selectively engage and disengage different ones of the movable legs to cause a motion of the body over the surface, such that the robotic vehicle generally travels over the surface. 
     In another aspect the present disclosure relates to a method for forming a robotic vehicle. The method may comprise forming a body and arranging a plurality of extendable legs on the body. An actuator, moveable in a plurality of non-parallel planes, may be used to selectively extend each of the legs to cause a motion of the body over a surface. 
     In another aspect the present disclosure relates to a method of causing motion of a robotic vehicle. The method may comprise arranging a plurality of movable legs on a body such that the legs are arranged non-parallel to one another. An actuator carried by the body may be used to control movement of the legs. The actuator may be controlled such that specific, desired ones of the legs are moved in a sequence that causes the legs to propel the body over a surface. 
     In still another aspect the present disclosure relates to a method of causing motion of a robotic vehicle. The method may comprise arranging a plurality of extendable and retractable legs on a body such that the legs extend in non-parallel directions. A single actuator may be carried within an interior volume of the body to control extending and retracting movement of the legs. A controller may be used to control a pair of servo motors to cause selective positioning of the actuator. The controller may also control the actuator to cause selective extending and retracting movement of selected ones of the legs to cause the body to travel over a surface. 
     In still another aspect the present disclosure relates to a control system for actuating a plurality of legs arranged around a body of a robotic vehicle. The control system may comprise an actuator and a support platform for supporting the actuator. A gimbal may support the support platform and enable movement of the support platform in a plurality of non-parallel planes into alignment with different ones of the legs. A controller may be used for controlling movement of the gimbal to align the actuator with selected ones of the legs, and to cause movement of the selected ones of the legs when the actuator is aligned therewith, to thus enable the selected ones of the legs to cause a motion of the body over a surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a perspective view of one embodiment of a robotic vehicle of the present disclosure; 
         FIG. 2  is  2 D representation of the vehicle similar to a cross sectional plan view in accordance with section line  2 - 2  in  FIG. 1 , of the interior area of the body of the vehicle of  FIG. 1  showing a gimbal system and the actuator supported on a gimbal system; 
         FIG. 3  is a partial side view of the vehicle in  FIG. 2  taken in accordance with directional line  3 - 3  in  FIG. 2 , and showing a gimbal system and actuator from the side; 
         FIG. 4  is a simplified electrical block diagram illustrating major electrical and electromechanical components of the vehicle of  FIG. 1 ; 
         FIGS. 5A-5D  illustrates a sequence where the actuator is moved into alignment with different ones of the extendable legs so that a general rolling motion can be imparted to the vehicle; 
         FIG. 6  is a flowchart illustrating several operations performed in causing motion of the vehicle of  FIG. 1 ; 
         FIG. 7  is another embodiment of the vehicle in which pivoted legs are used to transmit thrust from the centrally mounted actuator to the ground; and 
         FIGS. 8A and 8B  show perspective views of other embodiments of the vehicle that employ polyhedron shaped bodies 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     Referring to  FIG. 1 , there is shown a robotic vehicle  10  in accordance with one embodiment of the present disclosure. The vehicle  10  in this embodiment includes a spherically shaped body  12  having a plurality of linearly extendable legs  14  supported from, and extending from, the body  12 . The legs  14  are further arranged such that a coaxial center line of each leg  14  extends through the geometric center of the body  12 . The legs  14  may each be constructed as telescoping assemblies where a telescoping end portion  14   1  moves relative to a fixed portion  14   2  that is fixedly supported from the body  12 . 
     Referring to  FIGS. 2 and 3 , the vehicle  10  can be seen to include a volume  16  within the body  12  defined by an interior surface  12   a  of the body  12 . Mounted within the body  12  is two-axis gimbal system  18  having a support platform  20 . Mounted on the support platform  20  is an actuator  22 . In one form the actuator  22  may comprise an electromechanical solenoid actuator having a linearly extendable and retractable rod  24 . In an alternative form the actuator  22  could comprise a linear motion servo motor, a threaded screw drive, air cylinder, or any suitable component able to move an element linearly into contact with an aligned one of the legs  14 . 
     In  FIG. 2 , the gimbal system  18  can be seen to include an X-axis servo motor  26 , which has an output shaft  26   a  connected to the support platform  20  In  FIG. 3 , the gimbal system  18  also can be seen to include a Y-axis servo motor  28  which has its own output shaft  28   a . The servo motors  26  and  28  are supported from a frame element  30  that is pivotally mounted at portions  32  of the frame element  30 , in part by the servo output shaft  26   a , to enable pivoting movement about a first (or “X”) axis  34 , and also about a second (or “Y”) axis  36 . Thus, the gimbal system  18 , and particularly the servo motors  26  and  28 , can be used to position the actuator  22  in a plurality of different non-parallel planes. More particularly, the gimbal system  18  can be used to position the rod  24  of the actuator  22  in longitudinal alignment with the coaxial center line of any one of the extendable legs  14 . 
     When the actuator  22  is actuated by a suitable signal (typically an electrical signal), the rod  24  is extended. The actuator  22  may be designed such that the rod  24  is retracted automatically (for example by an internal spring) when the electrical signal is removed from the actuator  22 . Alternatively, the rod  24  may be retracted via a different electrical signal applied to the actuator  22 , for example a signal of different polarity from that used to extend the rod  24 . Both arrangements are viewed as being within the purview of the present disclosure. The rate of extension and/or retraction of the rod  24  (e.g., centimeters per second) can be tailored through selection of various mechanical properties of the actuator as well as through tailoring of the electrical signal (e.g., magnitude, frequency, duty cycle, etc.) applied to the actuator  22 . 
     With further reference to  FIG. 2 , each extendable leg  14  includes a biasing element  38  that is captured between the internal surface  12   a  of the body  12  and a shoulder  40  of each extendable leg. The biasing element  38  in this example is a coil spring, but it will be appreciated that other forms of biasing elements (e.g., leaf springs) could be substituted for use as well with only minor modifications to the structure of the extendable legs  14 . 
     In  FIGS. 2 and 3 , while the X-axis servo motor  26  is shown supported outside of the body  12 , it will be appreciated that it could just as readily be supported within the body if desired. This could be accomplished by suitable bracing, mounting struts or other like structure disposed within the volume  16  inside the body  12  that enables the gimbal frame element  30  to rotate about the X-axis  34 . 
     Referring briefly to  FIG. 4 , a block diagram of a control scheme for controlling the gimbal system  18  is shown. An electronic controller  42 , for example a programmable controller, a microprocessor or microcontroller, may be used to generate the electrical signals needed to control the X-axis servo motor  26  and the Y-axis servo  28  motor. The controller  42  may also be used to generate the signals needed to extend and retract then rod  24  of the actuator  22 , or alternatively a separate controller (not shown) could be used to perform this task. In one embodiment, the controller  42  provides power to the solenoid actuator  22  by discharging a capacitor bank  45  through a relay  46 . It will be appreciated that, while not shown, suitable amplifiers will typically also be used and controlled by the controller  42  to generate the needed drive signals for the X-axis and Y-axis servo motors  26  and  28 , respectively. A battery  44  may be used to power the controller  42  and to provide the current needed to generate the drive signals for the X-axis and Y-axis servo motors  26  and  28 . Optionally, the controller  42  may be interfaced with a miniature RF receiver or transceiver (not shown) housed within the body  12  to enable an external (i.e., remotely located) control system to control operation of the vehicle  10 . 
     Referring to  FIGS. 5A-5D , operation of the vehicle  10  will be described. For example, if motion in the general direction of arrow  50  is desired, then leg  14   a  will need to be actuated, as this leg presently one of the legs  14  supporting the vehicle  10  on a ground surface  52 . The gimbal system  18  is controlled to align the actuator  22  with the coaxial center line of leg  14   a , as shown in  FIG. 5B . The actuator  22  is then actuated by the controller  42  which causes rod  24  to extend. This extending movement enables the rod  24  to extend portion  14   1  of actuator  14   a , which imparts a rolling motion to the vehicle  10 . The impulse provided by the rapid extension of the actuator rod  24  should be sufficient to cause the body  12  of the vehicle  10  to roll over the immediately adjacent leg (in this example leg  14   b ) along the generally desired path of travel. It will be appreciated that by “generally” desired path of travel, it is meant that the vehicle  10  will have somewhat of a side-to-side travel, or what could be viewed as a general “zig-zag” path of travel, as it moves in a given direction. 
     In  FIG. 5D , the body  12  is now supported by at least legs  14   b  and  14   c , but typically at least one additional leg (not shown in  FIGS. 5A-5B ) will be arranged so that the body  12  is supported by three of the legs  14  when at rest. Continued movement in the general direction of arrow  50  would next require extension of leg  14   b . The actuator  22  would then be repositioned by the controller  42  using the gimbal system  18  to coaxially align the actuator rod  24  with leg  14   b , and the above-described operation of extending and retracting the rod  24  would be repeated. 
     The motion sequence in  FIGS. 5A-5D  produces one type of rolling locomotion, but others are also possible with this type of actuation. For example, if the leg actuator is capable of higher thrust (due to higher velocity motion of the extension rod  24 ), then a hopping type of locomotion can be produced. 
       FIG. 6  illustrates a flowchart  100  illustrating operations for controlling motion of the vehicle  10 . At operation  101 , a high level decision is made by an autonomous planner or human operator as to the desired direction of travel. At operation  102 , the controller  42  determines which leg  14  needs to be actuated to propel the vehicle  10  in the desired direction. At operation  104  the controller  42  generates the needed electrical signals to drive the X-axis servo motor  26  and the Y-axis servo motor  28  so that the actuator  22  is positioned in axial alignment with the leg  14  to be actuated. At operation  106  the controller  42  then generates the required electrical signal to actuate the actuator  22  and extend the rod  24 , thus causing extension of the selected leg  14 . At operation  108 , the controller  42  maintains the selected leg  14  actuated (i.e., maintains the rod  24  extended) for a predetermined time period, which is typically less than 1 second. The body  12  of the vehicle  10  will roll to a new position as the selected leg  14  is fully extended. 
     At operation  110 , after the predetermined time period expires, the controller  42  removes the electrical signal from the actuator  22  to enable the rod  24  of the actuator  22  to be retracted, and thus to enable the extendable portion  14   1  of the selected leg  14  to be retracted by its associated coil spring  38 . At operation  112  the controller  42  determines if further travel of the vehicle  10  is desired and, if not, the sequence of operation terminates. If operation  112  determines that further travel of the vehicle  10  is required, then a loop is made back to operation  102 , and operations  102 - 112  are repeated. Again, it will be appreciated that as different ones of the legs  14  are actuated, the that the vehicle  10  will be propelled in the desired direction (albeit in a somewhat zig-zag fashion). Suitable software or firmware may be included for use with the controller  24  to monitor the position of the body  12  relative to the ground surface  52 , and to determine precisely which leg  14  needs to be actuated next to propel the vehicle  10  in the desired direction. Obviously, any suitable orientation/attitude sensing system may be used in connection with the controller  42  to continuously monitor the orientation of the body  12  relative to the ground surface  52  so that the controller may determine exactly which leg  14  needs to be extended next to effect (or continue) motion of the vehicle  10  in the desired direction. Determination of which legs are in contact can performed by analyzing the state of contact switches that may be attached to the feet of the extension legs. Other options include using sensors that can determine the angular orientation of the vehicle; these types of sensors may include inclinometers (such as the dual-axis inclinometers made by VTI Technologies of Dearborn, Mich.) or inertial measurement units (such as the IMUs made by Cloud Cap Technology, Inc. of Hood River, Ore.). 
       FIG. 7  illustrates an alternate embodiment of the vehicle. In this embodiment (vehicle  11 ), the legs  15  extend from the body by pivoting about hinge  17 , instead of telescoping. Each leg element consists of an internal transfer element  39  rigidly connected to an external extension element  41 , which makes contact with the ground. Each leg  15  is returned or held in the retracted position by a torsional spring  37 . The method of actuation and locomotion is the same as that of the telescopic leg embodiment of the vehicle  10  described above. This pivoting leg modification may prove to be easier to manufacture for some types of vehicles. 
     For the above-described embodiments, it will be appreciated that while the body  12  is shown shaped as a sphere, that the body could just as readily take the shape of a tetrahedron ( FIG. 8A ), icosahedron ( FIG. 8B ), or other form of polyhedron. The precise shape of the body  12  may dictate how many legs can be used on the body. For example, a pyramid (tetrahedron) shaped body  12 ′, as shown in  FIG. 8A , may permit the use of four legs  14 ′ (only three being visible), while an icosahedron shaped body  12 ″ may permit the use of twelve legs  14 ″ (one at each of its twelve vertices). Obviously, the greater the number of legs used, the greater the degree of precision that will be available in causing the vehicle  10  to follow a desired path. Also, depending on the selected body shape, the lengths of the extendable legs  14  may need to be slightly increased or decreased. Generally speaking, the closer the outward shape of the body  12  is to that of a sphere, the lower the amount of leg thrust needed to cause locomotion of the vehicle. 
     The various embodiments of the vehicle  10  enable a single actuator to be used to selectively extend virtually any number of independently extendable legs. By using a single actuator and a gimbal system to position the actuation in the various non-parallel planes needed to align the actuator with different legs, a significant weight savings can be achieved. The overall complexity of the system may also be reduced through the use of only a single actuator. In essence, the greater the number of legs employed with the vehicle, the greater the weight and cost savings is likely to become by using only a single actuator. 
     It will be appreciated that various modifications could be made to the system and method described herein without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.