Robotic arm system and object avoidance methods

Abstract

One variation of a method for controlling a robotic arm includes: moving the robotic arm through a trajectory; at a first time in which the robotic arm occupies a first position along the trajectory, measuring a first capacitance of a first sense circuit comprising a first electrode extending over a first arm segment of the robotic arm; at a second time in which the robotic arm occupies a second position along the trajectory, measuring a second capacitance of the first sense circuit; calculating a first rate of change in capacitance of the first sense circuit based on a difference between the first capacitance and the second capacitance; in response to the first rate of change in capacitance of the first sense circuit exceeding a threshold rate of change, issuing a proximity alarm; and reducing a speed of the robotic arm moving through the trajectory in response to the proximity alarm.

1 . A method for controlling a robotic system, the method comprising:
 when the robotic system occupies a first position along a path at a first time, sensing a first capacitance value of a first sense circuit comprising a first electrode coupled to a first segment of the robotic system;   when the robotic system occupies a second position along the path at a second time succeeding the first time, sensing a second capacitance value of the first sense circuit;   estimating a first speed of the first electrode relative to external mass based on a difference between the first capacitance value and the second capacitance value;   in response to the first speed of the first electrode relative to external mass approximating a speed of the robotic system between the first time and the second time, issuing a proximity alarm for motion toward a static object; and   while the proximity alarm for motion toward a static object is current, reducing a current speed of the robotic system, moving along the path, to less than a maximum speed of the robotic system.   
     
     
         2 . The method of  claim 1 :
 wherein sensing the first capacitance value of the first sense circuit comprises sensing a first resonant frequency of the first sense circuit at the first time;   wherein sensing the second capacitance value of the first sense circuit comprises sensing a second resonant frequency of the second sense circuit at the second time; and   wherein estimating the first speed of the first electrode relative to external mass comprises estimating the first speed of the first electrode relative to external mass based on the difference between the first resonant frequency and the second resonant frequency.   
     
     
         3 . The method of  claim 1 , further comprising:
 at a third time succeeding the second time, sensing a third capacitance value of the first sense circuit;   detecting contact between external mass and the first segment of the robotic system based on the third capacitance value; and   in response to detecting contact between external mass and the first segment of the robotic system, ceasing motion of the robotic system.   
     
     
         4 . The method of  claim 1 , further comprising:
 at approximately a third time:
 sensing a third capacitance value of the first sense circuit, the first electrode arranged proximal a first region of the first segment of the robotic system; and 
 sensing a fourth capacitance value of a second sense circuit comprising a second electrode arranged proximal a second region on the first segment of the robotic system offset from the first region; 
   interpreting the third capacitance value as a first contact on the first region of the robotic system;   interpreting the fourth capacitance value as a second contact on the second region of the robotic system;   interpreting the first contact and the second contact as a manual control gesture to control a first actuatable axis coupled to the first segment of the robotic system; and   unlocking the first actuatable axis in response to the manual control gesture.   
     
     
         5 . The method of  claim 1 , further comprising:
 calculating a first rate of change in capacitance value of the first sense circuit based on a difference between the first capacitance value and the second capacitance value;   sensing a second rate of change in capacitance value of a second sense circuit comprising a second electrode, the second electrode coupled to the first segment of the robotic system adjacent the first electrode and defining a second area less than a first area defined by the first electrode;   wherein issuing the proximity alarm comprises, in response to the first rate of change exceeding a threshold rate of change and in response to the second rate of change falling below the threshold rate of change, issuing the proximity alarm for motion toward a static object within a first proximity range of the robotic system, the first proximity range corresponding to a first sensible range of the first electrode; and   wherein reducing the current speed of the robotic system comprises reducing the current speed of the robotic system to a first proportion of the maximum speed of the robotic system in response to issuance of the first proximity alarm.   
     
     
         6 . The method of  claim 5 , further comprising:
 between the second time and a third time:
 sensing a third rate of change in capacitance value of the first sense circuit; and 
 sensing a fourth rate of change in capacitance value of the second sense circuit; 
   in response to the first rate of change and the second rate of change exceeding the threshold rate of change, issuing a second proximity alarm for motion toward a static object within a second proximity range of the robotic system, the second proximity range corresponding to a second sensible range of the second electrode less than the first sensible range; and   in response to issuance of the second proximity alarm, reducing the current speed of the robotic system to a second proportion of the maximum speed of the robotic system, the second proportion less than the first proportion.   
     
     
         7 . The method of  claim 5 , further comprising, prior to the first time:
 driving the robotic system through a capacitance mapping route;   recording a set of absolute capacitance values of the first sense circuit responsive to the robotic system occupying each waypoint along the capacitance mapping route;   transforming the set of absolute capacitance values into relative capacitance value changes between the waypoints along the capacitance mapping route;   aggregating the relative capacitance value changes into a baseline capacitance map of a physical space occupied by the robotic system; and   calculating the threshold rate of change between the first position and the second position based on the baseline capacitance map and a speed of the robotic system between the first position and the second position.   
     
     
         8 . The method of  claim 1 :
 further comprising driving the robotic system along the path by actuating a first actuatable axis interposed between the first segment and a second segment of the robotic system and actuating a second actuatable axis interposed between the second segment and a base of the robotic system, the robotic system defining a robotic arm, the first segment approximating a first rigid beam extending between the first actuatable axis and the second actuatable axis, and the second segment approximating a second rigid beam extending between the second actuatable axis and the base of the robotic system; and   wherein reducing the current speed of the robotic system comprises setting a reduced maximum speed of rotation of the second actuatable axis while the proximity alarm for motion toward a static object is current.   
     
     
         9 . The method of  claim 1 , further comprising:
 in response to the speed of the first electrode relative to external mass exceeding the speed of the robotic system between the first time and the second time, issuing a proximity alarm for motion of a dynamic object toward the robotic system; and   while the proximity alarm for motion of a dynamic object toward the robotic system is current, ceasing motion of the robotic system.   
     
     
         10 . A method for controlling a robotic system, the method comprising:
 when the robotic system occupies a first position along a path at a first time, sensing a first capacitance value of a first sense circuit comprising a first electrode coupled to a first segment of the robotic system;   when the robotic system occupies a second position along the path at a second time succeeding the first time, sensing a second capacitance value of the first sense circuit;   estimating a speed of the first electrode relative to external mass based on the difference between the first capacitance value and the second capacitance value;   in response to the speed of the first electrode relative to external mass exceeding a speed of the robotic system between the first time and the second time, issuing a proximity alarm for motion of a dynamic object toward the robotic system; and   while the proximity alarm for motion of a dynamic object toward the robotic system is current, reducing a current speed of the robotic system to less than a maximum speed of the robotic system.   
     
     
         11 . The method of  claim 10 , wherein reducing the current speed of the robotic system comprises ceasing motion of the robotic system while the proximity alarm for motion of a dynamic object toward the robotic system is current. 
     
     
         12 . The method of  claim 11 , further comprising:
 in response to the first speed of the first electrode relative to external mass approximating the speed of the robotic system between the first time and the second time, issuing a proximity alarm for motion toward a static object; and   while the proximity alarm for motion toward a static object is current, reducing the current speed of the robotic system, moving along the path, to a fraction of the maximum speed of the robotic system.   
     
     
         13 . The method of  claim 10 :
 further comprising driving the robotic system along the path by actuating a first actuatable axis interposed between the first segment and a second segment of the robotic system and actuating a second actuatable axis interposed between the second segment and a base of the robotic system, the robotic system defining a robotic arm, the first segment approximating a first rigid beam extending between the first actuatable axis and the second actuatable axis, and the second segment approximating a second rigid beam extending between the second actuatable axis and the base of the robotic system; and   wherein reducing the current speed of the robotic system comprises setting a reduced maximum speed of rotation of the second actuatable axis while the proximity alarm for motion of a dynamic object toward the robotic system is current.   
     
     
         14 . The method of  claim 10 :
 wherein sensing the first capacitance value of the first sense circuit comprises sensing a first resonant frequency of the first sense circuit at the first time;   wherein sensing the second capacitance value of the first sense circuit comprises sensing a second resonant frequency of the second sense circuit at the second time; and   wherein estimating the speed of the first electrode relative to external mass comprises estimating the speed of the first electrode relative to external mass based on the difference between the first resonant frequency and the second resonant frequency.   
     
     
         15 . The method of  claim 10 :
 further comprising driving the robotic system along the path by actuating a first actuatable axis interposed between the first segment and a base of the robotic system, the robotic system defining a robotic arm;   wherein reducing the current speed of the robotic system comprises pausing execution of the path while the proximity alarm for motion of a dynamic object toward the robotic system is current;   further comprising:
 at approximately a third time:
 sensing a third capacitance value of the first sense circuit, the first electrode arranged proximal a first region of the first segment of the robotic system; and 
 sensing a fourth capacitance value of a second sense circuit comprising a second electrode arranged proximal a second region on the first segment of the robotic system offset from the first region; 
 
 interpreting the third capacitance value as a first contact on the first region of the robotic system; 
 interpreting the fourth capacitance value as a second contact on the second region of the robotic system; 
 interpreting the first contact and the second contact as a manual control gesture to control a first actuatable axis coupled to the first segment of the robotic system; and 
 unlocking the first actuatable axis in response to the manual control gesture. 
   
     
     
         16 . The method of  claim 15 , further comprising:
 at approximately a fourth time succeeding the third time:
 sensing a fifth capacitance value of the first sense circuit; and 
 sensing a sixth capacitance value of the second sense circuit; 
   detecting release of the first contact from the first region of the robotic system based on the fifth capacitance value;   detecting release of the second contact from the second region of the robotic system based on the sixth capacitance value; and   in response to detecting release of the first contact and the second contact from the robotic system, resuming execution of the path.   
     
     
         17 . The method of  claim 15 , further comprising:
 in response to unlocking the first actuatable axis, recording a second path of the first actuatable axis as the robotic system is manipulated by a user;   at approximately a fourth time succeeding the third time:
 sensing a fifth capacitance value of the first sense circuit; and 
 sensing a sixth capacitance value of the second sense circuit; 
   detecting release of the first contact from the first region of the robotic system based on the fifth capacitance value;   detecting release of the second contact from the second region of the robotic system based on the sixth capacitance value; and   in response to detecting release of the first contact and the second contact from the robotic system, driving the first actuatable axis through the second path.   
     
     
         18 . A method for controlling a robotic system, the method comprising:
 when the robotic system occupies a first position along a path at a first time, sensing a first capacitance value of a first sense circuit comprising a first electrode coupled to a first segment of the robotic system;   when the robotic system occupies a second position along the path at a second time succeeding the first time, sensing a second capacitance value of the first sense circuit;   calculating a first rate of change in capacitance value of the first sense circuit based on a difference between the first capacitance value and the second capacitance value;   calculating a second rate of change in capacitance value of a second sense circuit between the first time and a second time, the second sense circuit comprising a third electrode extending over a second segment of the robotic system;   in response to one of the first rate of change in capacitance and the second rate of change in capacitance exceeding a threshold rate of change, issuing a proximity alarm; and   while the proximity alarm is current, reducing a current speed of the robotic system, moving along the path, to less than a maximum speed of the robotic system.   
     
     
         19 . The method of  claim 18 :
 wherein issuing the proximity alarm comprises,
 in response to the first rate of change exceeding the threshold rate of change and in response to the second rate of change falling below the threshold rate of change, issuing the proximity alarm for motion toward external mass within a first proximity range of the robotic system, the first proximity range corresponding to a first sensible range of the first electrode; and 
 in response to the first rate of change and the second rate of change exceeding the threshold rate of change, issuing a second proximity alarm for motion toward external mass within a second proximity range of the robotic system, the second proximity range corresponding to a second sensible range of the second electrode less than the first sensible range; and 
   wherein reducing the current speed of the robotic system comprises:
 in response to issuance of the first proximity alarm, reducing the current speed of the robotic system to a first proportion of the maximum speed of the robotic system; and 
 in response to issuance of the second proximity alarm, reducing the current speed of the robotic system to a second proportion of the maximum speed of the robotic system, the second proportion less than the first proportion. 
   
     
     
         20 . The method of  claim 18 :
 further comprising driving the robotic system along the path by actuating a first actuatable axis interposed between the first segment and the second segment of the robotic system and actuating a second actuatable axis interposed between the second segment and a base of the robotic system, the robotic system defining a robotic arm, the first segment approximating a first rigid beam extending between the first actuatable axis and the second actuatable axis, and the second segment approximating a second rigid beam extending between the second actuatable axis and the base of the robotic system; and   wherein reducing the current speed of the robotic system comprises setting a reduced maximum speed of rotation of the second actuatable axis while the proximity alarm is current.