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Obstacle avoidance for redundant robots using configuration control

  • US 5,150,026 A
  • Filed: 11/19/1990
  • Issued: 09/22/1992
  • Est. Priority Date: 11/19/1990
  • Status: Expired due to Fees
First Claim
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1. A method of controlling a redundant robot, comprising the steps of:

  • defining end effector coordinates to position an end effector in a workspace by changing joint angles between links connected to the end effector;

    determining spheres of influence having fixed radii surrounding obstacles at known positions in the workspace;

    defining kinematic tasks for collision avoidance corresponding to additional task motion capability available as a result of the redundancy of the robot, said kinematic tasks including(a) continuously determining a first critical point on a link closest to a closest one of said spheres of influence;

    (b) defining a first critical distance related to the distance between the first critical point and the obstacle within said closest sphere of influence;

    (c) forming inequality constraints in which the first critical distance is greater than the radius of said closest sphere of influence; and

    combining said end effector coordinates with said kinematic tasks to form task related configuration variables for control of said redundant robot;

    dynamically modifying said joint angles while operating the robot system to position the end effector in the work space while maintaining said inequality constraints by stopping motion of the first critical point toward said first obstacle when the first critical distance equals the radius of said closest sphere of influence;

    modifying said kinematic tasks to then include(d) continuously determining a second critical point related to a closest point on a link closest to a next closest sphere of influence;

    (e) defining a second critical distance related to the distance between the second critical point and a second obstacle, said second obstacle being in said next closest sphere of influence;

    (f) forming additional inequality constraints in which the second critical distance is greater than the radius of said next closest sphere of influence; and

    dynamically modifying said joint angles while operating the robot system to position the end effector in the work space while continuing to stop motion of said first critical point toward said first obstacle and maintaining said additional inequality constraints by stopping motion of the second critical point toward said second obstacle when the second critical distance equals the radius of said next closest sphere of influence.

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