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Microprocessor-Based Control of Engine Valve Timing

Abstract:

One of the most interesting ways of improving the low-speed performance of spark-ignition engines is the variation of the valve timing in order to reduce mechanical losses. This paper deals with the implementation of valve-timing control by means of a microprocessor-based system which can be used to adapt the inlet and exhaust times to the operating conditions on the engine. The measured variables are manifold pressure, crankshaft speed, and throttle position. Control variables are the opening and closing angles on inlet and exhaust valves. These are acted upon by means of a four-bar mechanism driven by electrical motors. Control angles are determined by the microcomputer from the desired power (throttle position), and the measured engine speed, by means of a stored model. The controller acts directly upon the valve-control mechanism. In this way, an optimal distribution law can be adjusted for every operating condition, resulting in mechanical loss reduction and improvement of engine performance at low speeds. The structure of the microcomputer controller and an outline of the software are presented in this paper for both a premilinary and a final design. A summary of the experimental work carried out is included, together with the main conclusions drawn to date. © 1983 IEEE