Robot system, robot control device and method for controlling robot

A robot control device comprising:

• a first command generator configured to generate a first joint angular speed command for a robot having a plurality of joint axes including a redundant axis, on the basis of a speed command for a control point of the robot;
• a limit avoidance command generator configured to generate a joint angular speed command A for the robot for avoiding a state in which the robot reaches an operating limit, on the basis of an evaluation function A, while a signal A is being input;
• a posture optimization command generator configured to generate a joint angular speed command B for the robot for optimizing a posture of the robot, on the basis of an evaluation function B, while a signal B is being input;
• a null space matrix calculator configured to calculate a null space matrix of a Jacobian matrix related to the control point;
• a second command generator configured to generate a second joint angular speed command for the robot on the basis of the joint angular speed command A, the joint angular speed command B, and the null space matrix;
• and
• a controller configured to control a servomotor on the basis of a third joint angular speed command that is a sum of the first and second joint angular speed commands.

A method for controlling a robot that has a plurality of joint axes including a redundant axis that are driven by a servomotor, the method comprising:

• generating a first joint angular speed command for the robot on the basis of an input speed command for a control point of the robot;
• generating a joint angular speed command A for the robot for avoiding a state in which the robot reaches an operating limit, on the basis of an evaluation function A, while a signal A is being input;
• generating a joint angular speed command B for the robot for optimizing a posture of the robot, on the basis of an evaluation function B, while a signal B is being input,
• calculating a null space matrix of a Jacobian matrix related to the control point,
• generating a second joint angular speed command for the robot on the basis of the joint angular speed command A, the joint angular speed command B, and the null space matrix, and
• controlling the servomotor on the basis of a third joint angular speed command that is a sum of the first and second joint angular speed commands.