Search

A new improved robust variable structure controller is presented to provide an accurately prescribed tracking performance for brushless direct drive (BLDD) servo motors (SM) under uncertainties and load variations. A special integral sliding surface suggested for removing the reaching phase problems can define its ideal sliding mode and virtual ideal sliding trajectory from an initial position of SM. The tracking error caused by the nonzero value of the sliding surface is derived. A corresponding continuous control input with the disturbance observer is suggested to track a predetermined virtual ideal sliding trajectory within a prescribed value under all the uncertainties and load variations. The usefulness of the proposed algorithm is demonstrated through the comparative simulations for a BLDD SM under load variations.

A new simple control for the robust position control of a brushless direct drive (BLDD) motor using fuzzy logic controller (FLC) is presented. The integral-proportional (IP) position controller plus fuzzy logic speed controller is employed to obtain the robust BLDD motor system, which is approximately linearized using the field-orientation method for an AC servo. The speed FLC for a BLDD motor has the two rule tables. One is the coarse control rule table for the transient state and another is the fine control rule table for the steady state. The possibility of applying the FLC with simple structure to the AC servo system is investigated in detail. The overall system is controlled by using the microprocessor and the robustness is also obtained without affecting the overall system response. The experimental results show the performance of each control algorithm for the BLDD machine.

A new fault diagnostic algorithm for locating a fault and estimating its magnitude in control systems is proposed for use in the fault tolerant control system. The proposed algorithm is found to be highly effective for control systems with multiple PID controllers, which is demonstrated by a simulation experiment.