Patent ID: 7019482

Claim:
A motion controller for controlling a servomotor to move a movable member to a desired position, comprising: a sliding mode controller for providing a control input to the servomotor wherein the control input includes a linear control input and a nonlinear control input; a state observer for estimating a state of a controlled system which includes the servomotor and the movable member, and for providing an estimated state of the controlled system to the sliding mode controller; and a disturbance observer for providing an estimated disturbance to the sliding mode controller, wherein the nonlinear control input is based on the estimated disturbance, wherein disturbance “d” is defined from an equation of motion for the controlled system as follows: d=Kt·Iq−J{umlaut over (θ)} where Kt is a torque constant, Iq is a q-axis current, J is an inertia moment, θ is an angular position, and {umlaut over (θ)} is the corresponding angular acceleration.