Trajectory control device and control method for articulated robot

A trajectory control device for an articulated robot that drives a plurality of joint axes by a motor so that a tool attached to the articulated robot makes a desired motion, the trajectory control device comprising:

• a joint-angle command value calculation unit that calculates and outputs a joint-angle command value θc for each of the joint axes to realize the desired motion of the tool;
• a coupling-torque compensation command value calculation unit that calculates, from the joint-angle command value θc according to a dynamics model, a coupling torque interacting between the joint axes when the motion is made according to the joint-angle command value θc and outputs a coupling-torque compensation command value cc;
• a first dynamic characteristic calculation unit having a high-frequency cutoff characteristic with a cutoff frequency lower than a natural oscillation frequency of the articulated robot, the first dynamic characteristic calculation unit subjecting the joint-angle command value θc to filtering processing, and outputting a processed joint-angle target value θd;
• a joint-angle control unit to which the joint-angle target value θd is input as a target value for the motor;
• a second dynamic characteristic calculation unit having a high-frequency cutoff characteristic with a cutoff frequency lower than or equal to the cutoff frequency of the first dynamic characteristic calculation unit, the second dynamic characteristic calculation unit subjecting at least one of an input to the coupling-torque compensation command value calculation unit and an output from the coupling-torque compensation command value calculation unit to filtering processing, and outputting a processed coupling-torque compensation value cd;
• and
• a motor-current control unit to which a value obtained by adding the coupling-torque compensation value cd to a motor torque command value output from the joint-angle control unit is input as a target value.