C. Transputer-Based Digital Controller for AC Drives
This work presents two transputer-based controllers for ac drives using space vector modulation (SVM). The first is the EPHSC (Embedded Programmable High Speed Controller) which is a small-scale controller intended for simple, single-motor applications. The second is the GMDSC (Generic Multi-Drive Scalable Controller) which is a fully expandable and scalable controller for use in single-or multidrive applications.
gle- or multidrive applications.
- EPHSC (Embedded Programmable High Speed Controller):
The EPHSC makes use of the INMOS T800 transputer and specialized interfaces (phase current sampling, PWM inverter drive signals generation, shaft encoder signal decoding) to control an ac drive. The internal structure of the EPHSC is shown in Fig. 17.
The interfaces for the ac drive include: a) four independent A/D channels; b) two 16-bit 1/0 ports; c) a PWM inverter control signal generator with a maximum switching frequency of 18 kHz; d) a 16-bit quadrature decoder interface for incremental shaft encoder.
The generation of the PWM signals for the inverter is achieved by using a commercial PWM ASIC.
The inclusion of this ASIC in the controller design relieves the transputer of the time-consuming task of generating the switching signals for the inverter.
- GMDSC (Generic Multi-Drive Scalable Controller):
The GMDSC controller is implemented as a rack of transputer-based cards, with each card consisting of a transputer and a functional subsystem providing I/O function.
The structure of the controller, shown in Fig. 18, consists of seven transputer cells, I/O subsystems and a crossbar switch. A transputer cell consists of a T800 25-MHz transputer, 4 Mbytes of RAM, inter-cell control ports, and a 16-bit memory mapped I/O bus. The controller can be optimally configured for a particular control algorithm to be used for the drive by the master
transputer which configures the crossbar switch to achieve the necessary connections.
The GMDSC can be used to control a single-drive or multidrive system. Multiple drives are readily connected as shown in Fig. 19. The controller automatically determines the interconnection and establishes the necessary communications.