Measure rotational inertia and friction torque of spindle motors with freewheeling operations

A sensorless method is presented for measuring both the rotational inertia and friction torque of spindle motor through freewheeling operations. In the measurement, only the signals of terminal voltages are detected. For improving the accuracy of the speed data obtained by the sensorless method, the optimal spline method is used to process the discrete speed data. The method proposed can process the measurements quickly, and is easy to be applied in rotational system measurement. The principle of the method is introduced in the paper, and experiment results are used to show the effectiveness of the proposed measurement method.