US 7,102,315 B2 · Robot arm control method and control device

Abstract

When either a command value or an actually measured value is appropriately selected as an angular velocity used for the frictional torque calculation, the frictional compensation can be made valid at all times in both the case in which a robot is actively operated according to an angular velocity command and the case in which the robot is passively operated being pushed by an external force. In the case where a motor rotating direction and a collision direction are reverse to each other after a collision has been detected, the control mode is switched from the positional control to the electric current control and a torque, the direction of which is reverse to the direction of the motor rotation is generated by the motor, so that the motor rotating speed can be reduced and the collision energy can be alleviated. After that, when the motor rotating speed is reduced to a value not more than the setting value, the control mode is switched to the compliance control and the distortion caused in a reduction gear is dissolved. On the other hand, in the case where the motor rotating direction and the collision direction are the same, the control mode is directly switched from the positional control to the compliance control without passing through the electric current control. When the robot is operated whole following a collision force, the collision force can be alleviated.

Claims13

Dependent claims

A method of controlling a robot arm comprising:

a step of detecting a rotary angle of a motor to drive the robot arm;
a step of calculating an actually measured angular velocity from the rotary angle;
a step of calculating a command angular velocity from a command value given to the motor;
a step of calculating a frictional torque according to one of the command angular velocity and the actually measured angular velocity, wherein an absolute value of the command angular velocity and an absolute value of the actually measured angular velocity are compared with each other and the angular velocity of a higher absolute value is used for calculating the frictional torque;
and
a step in which a value corresponding to the frictional torque is added to the command value given to the motor when the motor is driven according to the command value.

3 more elements

A method of controlling a robot in a stopping operation conducted after the detection of a collision of the robot driven by a motor, in an axis in which a motor rotary direction and a collision torque direction are reverse to each other, when a control mode is switched from a positional control, in which an electric current command to make an actual position follow a positional command is generated, to an electric current control in which an electric current to generate a torque, the direction of which is reverse to the rotary direction of the motor, by the motor is commanded, a motor rotating speed is decreased, and when the motor rotating speed is decreased to a value not more than a setting value, the control mode is switched to a compliance control in which the robot follows a collision force direction;

and
in an axis in which the motor rotary direction and the collision torque direction are the same, the control mode is switched from the positional control to the compliance control.

A device of controlling a robot comprising:

a collision torque detecting means for detecting an intensity and direction of torque given to a motor, which drives an arm of the robot, by a collision force given to the arm of the robot;
a collision judgment means for judging a collision by comparing the collision torque detecting value with the threshold value of the collision torque which has been set;
a motor rotation detecting means for detecting a rotating speed and a rotating direction of the motor;
a collision direction discriminating means for comparing the collision torque detecting direction with the motor rotary direction;
and
a motor deceleration judging means for confirming a deceleration of the motor by comparing the motor rotating speed with the threshold value which has been set, wherein in an axis in which a motor rotary direction and a collision torque direction are reverse to each other, when a control mode is switched from a positional control, in which an electric current command to make an actual position follow a positional command is generated, to an electric current control in which an electric current to generate a torque, the direction of which is reverse to the rotary direction of the motor, by the motor is commanded, a motor rotating speed is decreased, and when the motor rotating speed is decreased to a value not more than the setting value, the control mode is switched to a compliance control in which the robot follows a collision force direction,
a device of controlling a robot further comprising a control mode switching means for switching from a positional control means to a compliance control means in an axis in which the motor rotary direction and the collision torque direction are the same.

4 more elements

Dependencies are inferred from the claim text.

Robot arm control method and control device

Life of this patent

Robot arm control method and control device

Life of this patent

Abstract

Claims13