Simulation of an active spray boom suspension

Abstract

This paper presents a mathematical model of an active inclined link boom suspension. It then demonstrates how the model may be used in the design of a suspension to give a specified response to the rolling motion of the spray vehicle. The response of a boom suspension should be such that it isolates the boom from the high frequency roll of the vehicle as it travels over bumpy ground, while transmitting low frequency roll so that the boom can follow undulating and sloping ground. The model is used to show that a passive suspension can fulfil the high frequency requirement, but that deflection of the tyres of the vehicle, and sinkage of the wheels into the ground, can mean that it fails to meet the low frequency requirement. The model active suspension differs from the conventional passive version, in that the length of the links can be varied automatically. In a design example given, the rate of change of length of one of the links is made to be proportional to the difference between the angles of inclination of the boom and the groud, as measured by proximity transducers mounted on the boom, directed at the ground. The model is used to show that the modification to the suspension can significantly improve its low frequency performance, without losing high frequency isolation, and that this can be done using a negligible amount of power available from the vehicle.