Linear induction drive system completely digital position controlled with minimal hardware investment
This paper presents practical results of a high performance linear induction drive. The cascaded position control of the PWM inverter-fed linear induction motor is based on vector control principles. The complete control algorithm is implemented in a Siemens SAB 80C166 microcontroller. A sampling rate of 10 kHz is determined for the digital current control. The response time of the traction force producing current component control loop amounts to 0.3ms. The sampling period of the speed and position control is fixed to 500us. The disturbing influence of the speed calculated from the measured position by differentiation could be considerable reduced by a speed observer. The implementation of a position reference generator into the software improves the positioning accuracy. The generator calculates online a smooth trajectory from point to point, observing the desirable acceleration and speed. The experimental results show the high performance of the described linear drive system.