Velocity method of controlling industrial robot actuators
AssigneeHitachi, Ltd.
InventorsKoichi Sugimoto, Kiyohide Koizumi, Toyohide Hamada, Shinichi Arai
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Abstract
A method of controlling an industrial robot wherein velocities of the actuators for the robot are based on the velocity of a robot hand moving along a predetermined path of travel. When the velocity of any single actuator exceeds its ability, the velocities of the actuators are revised so as to bring the velocities of all the actuators within their abilities, thereby revising the velocity of the robot hand along its path of travel. Calculation of the velocity of each actuator may be carried out based on the position and posture of the robot hand and a Jacobian matrix.
Claims8
A method of controlling an industrial robot for moving a hand of the robot along a predetermined path of travel the method comprising the steps of:
- reading a present displacement of each of a plurality of actuators for moving the hand;
- calculating, at present time, a present position vector p indicating a present position of the hand and present posture unit vectors f, g indicating a present posture of the hand based on the present displacements of the actuators;
- providing a sampling time interval T for controlling the hand;
- providing a projected translational distance d to be covered by the hand during the sampling time interval T;
- providing a target position vector p.sub.f indicating a target position of the hand and target posture unit vectors f.sub.f, g.sub.f indicating target posture of the hand;
- calculating an estimated translational vector .DELTA.p indicating an estimated translational movement of the hand from the present position toward the target position during the sampling time interval T, an estimated rotation unit vector e indicating an axis of rotation of the hand from the present posture toward the target posture and an estimated rotation angle .DELTA..phi. of the hand around the rotation unit vector e from the present posture toward the target posture during the sampling time interval T, by the following relationships;
- ##EQU8## calculating a command velocity of each of the actuators based on the estimated translational vector .DELTA.p, estimated rotation unit vector e and estimated rotation angle .DELTA..phi.;
- calculating a revised command velocity of each of the actuators by reducing the command velocity of each of the actuators by a same rate so that any one of the revised command velocities of the actuators does not exceed a predetermined maximum allowable velocity of a concerned actuator;
- and
- driving each of the actuators with the revised command velocity.
An apparatus for controlling an industrial robot so that a hand provided of the robot moves along a predetermined path of travel, the apparatus comprising:
- means for reading a present displacement of each of a plurality of actuators for moving the hand;
- means for calculating, at present time, a present position vector p indicating a present position of the hand and present posture unit vectors f, g indicating a present posture of the hand based on the present displacements of the actuators;
- means for providing a sampling time interval T for controlling the hand;
- means for providing a projected translational distance d to be covered by the hand during the sampling time interval T;
- means for providing a target position vector p.sub.f indicating a target position of the hand and target posture unit vectors f.sub.f, g.sub.f indicating a target posture of the hand;
- means for calculating an estimated translational vector .DELTA.p indicating an estimated translational movement of the hand from the present position toward the target position during the sampling time interval T, an estimated rotation unit vector e indicating an axis of rotation of the hand from the present posture toward the target posture and an estimated rotation angle .DELTA..phi. of the hand around the rotation unit vector e from the present posture toward the target posture during the sampling time interval T, by the following relationships:
- ##EQU9## means for calculating a command velocity of each of the actuators based on the estimated translational vector .DELTA.p, estimated rotation unit vector e and estimated rotation angle .DELTA..phi.;
- means for calculating a revised command velocity of each of the actuators by reducing the command velocity of each of the actuators by a same rate so that any one of the revised command velocities of the actuators does not exceed a predetermined maximum allowable velocity of a concerned actuator;
- and
- means for driving each of the actuators with the revised command velocity.
Dependencies are inferred from the claim text.