Comparison of Speed Nonlinear Control Strategies for the Synchronous Servomotor

In this paper, several strategies to improve robustness and performances of speed nonlinear control of the synchronous servomotor are proposed and compared. The followed procedure consists in imposing the maximum acceptable motor torque during any speed transient, for any load torque, (the response time becoming then optimum), by means of saturation of the current in the quadrature axis, or by means of a real time speed asymptotic trajectory computation. The latter strategy permits to eliminate the influence of an highly perturbed load torque on the regulated speed. Every controller presented here includes a load torque estimator, and a constraint on the motor currents. Simulations and experimental results are performed in order to confirm theoretical ones.