Robust balanced control of LPMSM servo drive with mass identification and large command change

Robust position control for a linear permanent-magnet (PM) synchronous motor servo drive is presented, considering the constituted component match under unknown mass and large command change. First, a field-weakening forcing current control scheme is developed to yield close current transient tracking response. In the proposed position control scheme, a cascaded two-degrees-of-freedom controller is quantitatively designed, and an internal robust model following controller (RMFC) is arranged to let the prescribed response be preserved under varying plant parameters and operating conditions. Then an identification scheme is devised to obtain a mass estimate from the compensating control signal generated by the RMFC. Finally, in making the large command positioning control, a match between the motor drive constituted components is considered. The amplitudes and/or ramping rate of step and ramp commands are determined according to the identified mass and the ratings of the inverter and motor. In this case, the response time is also predictable. Through applying the proposed simple command shaping control approach, quantitative positioning control performance under unknown mass and efficient capability utilisation of inverter and motor can be achieved, and the instability caused by nonlinearities under excessive saturation can be avoided.