A nonlinear speed control for a permanent magnet (PM) synchronous motor using a simple disturbance estimation technique is presented. By using a feedback linearization scheme, the nonlinear motor model can be linearized in a controllable canonical form, and the desired speed dynamics can be obtained based on the linearized model. This technique, however, gives an undesirable output performance under the mismatch of the system parameters and load conditions. Recently, an adaptive linearization technique and a sliding mode control technique have been reported. Although a good performance can be obtained, the controller designs become quite complex. To overcome this drawback, the controller parameters will be estimated by using a disturbance observer theory where the disturbance torque and flux linkage are estimated. Since only the two reduced order observers are used for the parameter estimations, the observer designs are considerably simple and the additional load for computation of the controller is negligibly small. Since the nonlinear disturbances caused by the parameter variation can be effectively compensated by using this control scheme, a desired dynamic performance and a zero steady-state error can be obtained. The proposed control scheme is implemented on a PM synchronous moor using the software of DSP TMS320C31 and the effectiveness is verified through the comparative simulations and experiments.
