Electrohydraullic vehicle load simulation

Karwatzki, J.M. (1973) Electrohydraullic vehicle load simulation. (MPhil thesis), Kingston Polytechnic, .

Abstract

The need for a system which can aocurately simulate various loads encountered under field conditions is discussed. A system is proposed for simulating the loading effects of a vehicle engine working under normal road conditions. It is shown how an equation of motion may be computed to provide control signals to a loading devíce so that the necessary loading equivalents may be met, Comparisons are made between various loading devices, and it is shown that an electrohydraulic system provides the most suitable compromise. The design and development stages of the electro-hydraulic system and a special purpose analogue computer to solve the equation of motion are presented. Comparisons are made between the special purpose analogue computer and a digital computer system for the purposes Of controlling the electrohydraulic loading device. A simplified mathematical model of the electro-hydraulic system is developed and it can be seen that classical control theory is limited in its ability to suggest the most suitable form of control. To overcome this problem an analogue computer simulation of the electrohydraulic system is presented so that various forms of control can be investigated without the possibility of instability arising in the system. For the control procedures suggested, comparisons are made of the system's response to step inputs of throttle. It is shown that a compromise must be reached between a good speed response and the magnitude of topque osoillations which can be tolerated.

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