Design of a fuzzy controller mixing analog and digital techniques

Analog circuits are attractive for fuzzy VLSI, as they allow an easy implementation of the arithmetic functions which are needed in a fuzzy controller. Analog circuits are efficient in areas allowing parallelism to be employed. However, they suffer from noise disturbances and interferences. Also, they are susceptible to process variations and mismatching. On the other hand, digital circuits are robust and easy to design and process. However, arithmetic functions (such as multiplication and division) require large digital circuits. To overcome the above-mentioned drawbacks, pulse stream techniques have been proposed. These techniques use digital signals to carry information and control analog circuitry. Among the existing pulse stream techniques, pulse width modulation (PWM) has been selected due to its simplicity. This paper presents the architecture of a fuzzy logic controller using PWM techniques. A prototype circuit is being designed using a standard CMOS process