US 5,430,643 A · Configuration control of seven degree of freedom arms

Abstract

A seven-degree-of-freedom robot arm with a six-degree-of-freedom end effector is controlled by a processor employing a 6-by-7 Jacobian matrix for defining location and orientation of the end effector in terms of the rotation angles of the joints, a 1 (or more)-by-7 Jacobian matrix for defining 1 (or more) user-specified kinematic functions constraining location or movement of selected portions of the arm in terms of the joint angles, the processor combining the two Jacobian matrices to produce an augmented 7 (or more)-by-7 Jacobian matrix, the processor effecting control by computing in accordance with forward kinematics from the augmented 7-by-7 Jacobian matrix and from the seven joint angles of the arm a set of seven desired joint angles for transmittal to the joint servo loops of the arms. One of the kinematic functions constrains the orientation of the elbow plane of the arm. Another one of the kinematic functions minimizing a sum of gravitational torques on the joints. Still another one of the kinematic functions constrains the location of the arm to perform collision avoidance. Generically, one of the kinematic functions minimizes a sum of selected mechanical parameters of at least some of the joints associated with weighting coefficients which may be changed during arm movement. The mechanical parameters may be velocity errors or position errors or gravity torques associated with individual joints.

Claims24

Dependent claims

A method of controlling a robot arm, said robot arm comprising n joints, joint angle sensor means connected to each of said joints, joint servo loop means connected to each of said joints, and two ends comprising a fixed pedestal end and a movable hand end, each of said joints having a joint angle specifying a rotational orientation of said joint, said hand end having m degrees of freedom of movement, wherein m is less than n whereby said robot arm characterized by a degree of redundancy, n-m, said method comprising:

first defining a first m-by-n matrix for defining location and orientation of said hand end in terms of said rotation angles of said joints;
second defining a second r-by-n matrix for defining r user-specified kinematic functions in terms of said joint angles, wherein r is a positive integer exceeding the degree of redundancy of said robot arm;
combining said first and second matrices to produce an augmented m+r-by-n matrix;
and
computing in accordance with forward kinematics from said augmented m+r-by-n matrix and from the joint angles sensed by said joint angle sensor means a set of n desired joint angles and transmitting said set of n desired joint angles to said joint servo loop means to control the robot arm.

2 more elements

first defining a first m-by-n matrix for defining location and orientation of said hand end in terms of said rotation angles of said joints;
second defining a second r-by-n matrix for defining r user-specified kinematic functions in terms of said joint angles, wherein r is a positive integer exceeding the degree of redundancy of said robot arm, and wherein at least one of said kinematic functions minimizes a sum of selected mechanical parameters of at least some of said joints and said selected mechanical parameters include different weighting coefficients for different ones of said joints, said weighting coefficients being able to be changed during movement of said arm;
combining said first and second matrices to produce an augmented m+r-by-n matrix;
and
computing in accordance with forward kinematics from said augmented m+r-by-n matrix and from the joint angles sensed by said joint angle sensor means a set of n desired joint angles and transmitting said set of n desired joint angles to said joint servo loop means to control the robot arm.

2 more elements

first defining a first m-by-n matrix for defining location and orientation of said hand end in terms of said rotation angles of said joints;
second defining a second r-by-n matrix for defining r user-specified kinematic functions in terms of said joint angles, wherein r is a positive integer exceeding the degree of redundancy of said robot arm, and wherein at least one of said kinematic functions corresponds to one of,
i. minimizing a sum of gravitational torques on at least some of said joints,
ii. minimizing a sum of selected mechanical parameters of at least some of said joints, said parameters comprising velocity errors of said joints with respect to desired velocities, and
iii. minimizing a sum of selected mechanical parameters of at least some of said joints, said parameters comprising joint angle errors with respect to desired joint angles;
combining said first and second matrices to produce an augmented m+r-by-n matrix;
and
computing in accordance with forward kinematics from said augmented m+r-by-n matrix and from the joint angles sensed by said joint angle sensor means a set of n desired joint angles and transmitting said set of n desired joint angles to said joint servo loop means to control the robot arm.

5 more elements

Dependencies are inferred from the claim text.

Configuration control of seven degree of freedom arms

Life of this patent

Configuration control of seven degree of freedom arms

Life of this patent

Abstract

Claims24