Hydropneumatic semi-active suspension system with continuously variable damping

Abstract

A hydropneumatic semi-active suspension system for an off-road vehicle, that can switch between two discrete damping characteristics as well as two discrete spring characteristics, has been successfully developed and implemented previously. This paper investigates the feasibility of expanding the concept to include four discrete spring characteristics as well as continuously variable damping by controlling two proportional solenoid valves, which can variably restrict flow paths to two accumulators. Spring, damping and response time characteristics are determined experimentally, modelled mathematically and validated with experimental measurements. The model incorporates an iterative solver to determine the flow rate through each valve and the change in the accumulator volumes. The accumulator model uses real gas theory, while also taking compressibility of the oil and heat transfer into account. Damping is calculated by a velocity and solenoid current dependent curve-fit model, parameterised from experimental data.