REAL TIME IMPLEMENTATION OF A FUZZY LOGIC CONTROLLER ON FPGA USING VHDL FOR DC MOTOR SPEED CONTROL
Fuzzy logic control (FLC) has met with growing interest in many motor control applications due to its nonlinearity, handling features and independence of plant modelling. The hardware implementation of FLC on FPGA is very important because of the increasing number of fuzzy applications requiring highly parallel and high speed fuzzy processing. Implementation of a FLC and conventional PI controller on an FPGA using VHDL for DC motor speed control is presented in this paper. The proposed scheme is to improve tracking performance and rejection of load disturbances of D.C. motor as compared to the conventional PI control strategy .This paper describes the hardware implementation of two inputs (error and change in error), one output FLC and conventional PI controller using VHDL. Real time implementation of FLC and conventional PI controller is made on Spartan-3A DSP FPGA (XC3SD1800A). It is observed that FLC give better responses than the conventional PI controller for the speed control of dc motor.
Most of the fuzzy logic applications with the physical systems require a real-time operation to interface high speed constraints. The simple and usual way to implement these systems is to realize it as a software program on general purpose computers, these ways cannot be considered as a suitable design solution. Higher density programmable logic device such as Field Programmable Gate Arrays (FPGAs) can be used to integrate large amounts of logic in a single IC. FPGAs are one of the fastest growing parts of the digital integrated circuit market in recent times. Dynamically reconfigurable FPGA systems can adapt to various computational tasks through hardware reuse. FPGA becomes one of the most successful of technologies for developing the systems which require a real time operation. FPGAs are more sufficient than the simple way because they can cover a much wider range of operating conditions. Semi-custom and full-custom Application Specific Integrated Circuit (ASIC) devices are also used for this purpose but FPGA provide additional flexibility: they can be used with tighter time-to-market schedules. FPGA places fixed logic cells on the wafer, and the FPGA designer constructs more complex functions from these cells .In control applications, in order to get better control responses, ,  Controller is implemented in FPGA.FPGA are two dimensional arrays of logic blocks and flip-flops with an electrically programmable interconnection between logic blocks. The interconnections consist of electrically programmable switches which is why FPGA differs from Custom ICs, as Custom IC is programmed using integrated circuit fabrication technology to form metal interconnections between logic blocks. FPGA provides its user a way to configure: The intersection between the logic blocks and the function of each logic block. Logic block of an FPGA can be configured in such a way that it can provide functionality as simple as that of transistor or as complex as that of a microprocessor. It can used to implement different combinations of combinational and sequential logic functions
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