Fuzzy logic on the MC68HC12 microcontroller: A student design workshop

Fuzzy Logic is a practical alternative for challenging control applications that provides a convenient method for constructing nonlinear controllers via the use of heuristic information from human designers. Such heuristic information is recorded in rules describing how to control the process. Fuzzy Logic emulates the. human decision-making process, and provides a user-friendly formalism for representing and implementing high-performance control at low cost. Until recently, Fuzzy Logic has been used primarily on large-scale computing systems, at least at the level of personal computers. Recent advances, however, make it realistic to implement Fuzzy Logic techniques on small systems based on microcontrollers. Implemented most commonly in control design, Fuzzy Logic-based systems can be found in a rapidly growing number of consumer appliances, from dishwashers to video cameras, as well as in automobile engines and transmissions, and other industrial equipment. Still others are putting Fuzzy Logic to work in pattern recognition, economics, and other areas that involve a high level of uncertainty, complexity, or nonlinearity. Motorola's MC68HC12 microcontroller includes features that promote Fuzzy Logic implementations by incorporating several Fuzzy Logic primitives directly in its instruction set. It includes specific assembly language instructions that implement the Fuzzy Logic operations of trapezoidal membership, rule evaluation, and weighted average defuzzification. Additional instructions that are helpful in Fuzzy Logic applications include min/max instructions and table lookup operations. This set of features makes the MC68HC12 microcontroller uniquely suited to low-level applications that make use of Fuzzy Logic principles. This paper describes a student design workshop conducted in the Electrical and Computer Engineering (ECE) Department at the University of Minnesota Duluth (UMD) in which students implemented microcontroller applications using the principles of Fuzzy Logic as contained in the features of the MC68HC12 microcontroller. This workshop provided students with a unique opportunity to merge their academic understanding of Fuzzy Logic techniques with their ability to design and implement microcontroller systems. The paper describes the MC68HC12 microcontroller features that support Fuzzy Logic, introduces Fuzzy Logic and intelligent control, and details student projects suggested in this design workshop. The goals of these studies are: to illustrate Fuzzy Logic theory, to apply Fuzzy Logic features of the MC68HC12, and to implement applications of fuzzy control.