Robust control technique of PM synchronous motor with estimation of parameter and disturbance

Abstract

Permanent magnet (PM) synchronous motors have been gradually replacing DC motors in a wide range of drive applications such as machine tools and industrial robots. The advantage of using a PM synchronous motor is that many drawbacks caused by the brushes and commutators of a DC motor can be eliminated. Furthermore, the PM synchronous motor has the high power density, large torque to inertia ratio, and high efficiency as compared with a DC motor having the same output rating. The PM synchronous motor, however, has the nonlinear characteristics and inherent coupling problem. Therefore, to directly control the developed torque, the field-oriented control is usually employed. With the recent advancements in general purpose microprocessors and digital signal processors (DSPs), the field-oriented control has made the PM synchronous motor drives possible for the high performance applications where traditionally only the DC motor drives were applied. With the high performance field-oriented control system, the torque and flux producing components of the stator current are decoupled so that the independent torque and flux controls are possible as in DC motors. Thus, a high quality control of the stator current vector is essential for the successful implementation of the field-oriented control since the current controller has a direct influence on the drive performance. The current control schemes for a voltage source inverter-fed PM synchronous motor drive can be classified as the hysteresis control, ramp comparison control, synchronous frame proportional-integral (PI) control, and predictive control. Among them, the predictive control is known to give a superior performance. This control scheme, however, requires the informations on the machine parameters and operating conditions with the sufficient accuracy, and cannot give a satisfactory response under the parameter mismatch. To overcome such a limitation, an improved digital current control technique of a PM synchr...