Disturbance compensation for DC motor mechanism low speed regulation: A feedforward and feedback implementation

The disturbance torque in the DC motor drive of a scan unit was calculated using the known voltage input to the motor and the measured motor speed response. The cogging torque of the motor and the friction in the mechanism can then be estimated from the calculated disturbance torque. The calculated disturbance torque was further utilized to reduce the speed ripples in speed regulation applications. A combined feedforward and feedback configuration was used to reject the disturbance based on both the off-line calculated disturbance and the on-line estimated disturbance. This scheme was successfully implemented in commercial scan devices. Data obtained under real operating conditions demonstrated the effectiveness and robustness of this disturbance compensation scheme.