Sampled-analog implementation of application-specific fuzzy controllers

Sampled-analog circuit techniques are exploited in an application-specific integrated fuzzy controller design. A circuit library comprising a sample-and-hold amplifier, positive and negative ramp amplifiers, an inference cell, adder, and weighted adder amplifiers, and a divider unit was developed for this purpose. Any expert system of piecewise linear input membership functions, conjunctive rules and singleton output classes can be implemented with this library. The library was implemented in a 1.2 /spl mu/m double-metal double-poly CMOS technology. Test results indicate excellent linearity and accuracy in full 5 V rail-to-rail operation in all units. A controller of four inputs, 16 rules, and two outputs fabricated with these library units occupies 1.76 mm/sup 2/ silicon. Test results indicate full functionality. The measured speed, 85 k samples per second, is limited by the unbuffered outputs. Sampling rate can be increased by 50% in those applications where pipelining is permissible.