IMPLEMENTING FIELD-ORIENTED CONTROL OF AC MOTORS WITH THE TMS320C25 DSP

The field-oriented theory is the base of a special control method for induction motor drives. With this control method, induction motors can successfully replace expensive DC motors. Induction motors require complex control algorithms, because there is no linear relationship between the stator current and either the torque or the flux. This means that it is difficult to control the speed or the torque, because of the transients until the motor reaches its new stationary state. The problem can be solved by controlling the rotor flux since it cannot be measured, only computed. Because of the complexity and nonlinearity of control equations it is useful to implement a part of the control system by a fuzzy logic controller. By using linguistic variables in place of numerical variables, that approach represents a substantive departure from the conventional quantitative techniques of system analysis and control. In the present paper we use fuzzy logic based speed control for field-oriented AC motor.

For implementing the control algorithm we developed a digital signal processor (DSP) based single board controller based on the Texas Instruments (TI(TM)) TMS320C25 DSP. The board contains a configurable digital interface, which can be used to extend the functionality of the board by connecting analog and digital I/O peripherals. It has a flexible memory subsystem with EPROM, SRAM and nonvolatile SRAM support; an RS-232C serial port; a keypad with 6 keys; and four 7 segments LED display. In this paper we present the state-of-the-art of field-oriented control of AC motors, and fuzzy logic controllers. We describe our control system from both software and hardware point of view. The experimental results have been compared by in the case of traditional P1 type speed control, and shows good dynamical behavior.

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