Positioning control device of actuator provided with strain wave gearing using H-∞ control

A positioning control device of an actuator provided with a strain wave gearing, in which the actuator provided with a configuration in which rotation of a motor is reduced by the strain wave gearing and transmitted to a load shaft, is driven and controlled, and positioning control for the load shaft is performed, the positioning control device of the actuator provided with the strain wave gearing comprising:

• a full-closed control system for feeding back a position of the load shaft and driving and controlling the motor so that the load shaft is positioned at a target position;
• wherein the full-closed control system has an H∞ compensator designed so that, when a generalized plant that has, as a disturbance input, angular transmission error generated synchronously with relative rotation of constituent components of the strain wave gearing is assumed to be the actuator to be controlled, an H∞ norm of a transfer function from the disturbance input of the generalized plant to an evaluation output becomes a predetermined value or less;
• and
• the H∞ compensator controls a drive current flowing to the motor;
• wherein the full-closed control system feeds back a velocity of the motor to the H∞ compensator in addition to a position of the load shaft;
• and
• wherein a relationship from disturbance inputs w1 to w3 to an evaluation output z is shown by
• z
• =
• [
• W
• 1
• ⁡
• (
• s
• )
• ·
• S
• ⁡
• (
• s
• )
• 0
• 0
• 0
• W
• 2
• ⁡
• (
• s
• )
• ·
• G
• c
• ⁡
• (
• s
• )
• 0
• 0
• 0
• W
• 3
• ⁡
• (
• s
• )
• ·
• G
• l
• ⁡
• (
• s
• )
• ]
• ⁡
• [
• w
• 1
• w
• 2
• w
• 3
• ]
• where, in the generalized plant, w1, w2, and w3 are, respectively, a disturbance input on a load side, a disturbance input on an input side, and a disturbance input representing angular transmission error;
• W1(s), W2(s), W3(s) are frequency weighting transfer fucntions of the disturbance inputs;
• z is an evaluation output;
• S(s) is a sensitivity coefficient;
• Gc(s) is a closed-loop characteristic;
• and GI(s) is a characteristic from angular transmission error to a position of the load shaft;
• and
• the H∞ compensator is designed so that the sensitivity coefficient S(s), the closed-loop characteristic Gc(s), and the characteristic GI(s) from the angular transmission error to the position of the load shaft satisfy, for all frequency bandwidths,
• S(s)<γ/W1(s)
• Gc(s)<γ/W2(s)
• GI(s)<γ/W3(s)
• where γ is a predetermined value set in advance.