Variable structure adaptive control for PM synchronous servo motor drive

A newly designed variable-structure controller for a permanent magnet (PM) synchronous servo motor drive, which is insensitive to uncertainties including parameter variations and external load disturbance, is introduced. To overcome the two main problems with variable-structure control, i.e. the assumption of known uncertainty bounds and chattering phenomena in the control effort, a variable-structure adaptive (VSA) controller is investigated. In the VSA controller a simple adaptive algorithm is utilised to estimate the uncertainty bounds; moreover, the chattering phenomenon is reduced. A variable-structure direct adaptive (VSDA) controller comprising the VSA control algorithm and a direct adaptation law is proposed to further improve the control performance of the variable-structure controller. The position control of a PM synchronous servo motor drive with the variable-structure control strategies is illustrated. Simulated and experimental results show that the developed controllers provide high-performance dynamic characteristics and are robust with regard to plant parameter variations and external load disturbance.