Patent ID: 7777982

Claim:
A disturbance compensation determination apparatus comprising: a disturbance observer (DOB) receiving a control input signal and a servo output signal of a plant, wherein the plant is controlled in accordance with the control input signal, the servo output signal corresponds to the control input signal, the DOB calculates and outputs a current estimated disturbance value, and the current estimated disturbance value is an estimate of disturbance applied to the plant; a disturbance evaluation unit selectively changing a current disturbance compensation (DC) mode, wherein selectively changing the current DC mode comprises evaluating an accumulated estimated disturbance value in accordance with a condition corresponding to the current DC mode, wherein: during a current sample period, the DOB calculates zero or more preceding estimated disturbance values before calculating the current estimated disturbance value; and, the disturbance evaluation unit calculates the accumulated estimated disturbance value by adding the absolute value of the current estimated disturbance value and the respective absolute values of the zero or more preceding estimated disturbance values; and, a switching unit selectively providing the current estimated disturbance value to a control loop of the plant in accordance with the current DC mode as selectively changed by the disturbance evaluation unit.