Craig Jensen

Date of Award

8-1-1995

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical Engineering

Abstract

Internal combustion engines are challenging to model and control. Uncertainties and nonlinearities pose operating problems for classical controllers. Delays inherent to the engine combustion cycle tend to introduce overshoot and oscillations in most control schemes. Most work that has been done in dealing with delays requires the designer to have extensive knowledge of the system to be controlled. Engines are very difficult to model accurately, thereby ruling out most of these techniques. Fuzzy logic is well suited to this problem, since an accurate model is not needed for design, and it is known to be robust to nonlinearities and parameter variations.

The objective of this thesis was to design and implement a fuzzy logic controller to control the speed of a Honda EM3500S portable generator. This new fuzzy controller maintains the robustness of traditional fuzzy logic to nonlinearities and it is also more robust to delays. The control scheme uses dual fuzzy logic control modules in parallel. One of the modules is a traditional fuzzy scheme and the other is a simple two membership fuzzy scheme tuned to reduce oscillations. For optimal performance this second module requires dynamic adjustment of parameters such as input and output gains in response to the system’s current operating condition. The result is a control scheme that offers reduced overshoot and oscillations.

The new control scheme was compared to the classical PID and the traditional fuzzy logic controllers. These comparisons were done via computer simulations and laboratory implementation and testing. A windows based C++ program was developed to realize and test the new controller. The better performance of the new control scheme was illustrated.

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