Component sizing and sensitivity analysis of design parameters of a hydraulic-pneumatic regenerative braking system for heavy duty vehicles

A regenerative hydraulic-pneumatic braking system for trucks or busses must allow recovery of braking energy in both high energy/low power situations, such as long downhill grades, and low energy/high power situations, such as those typical of urban traffic. Proper component sizing must get the best out of both situations. The main contribution of this work is the development of a component sizing strategy that will greatly accelerate the development of designs for a given target. Once components are defined, subsequent studies can be performed under dynamic conditions to refine the design, including improving local and higher-level controls. The design strategy presented is applied to a 12-ton commercial vehicle and its behavior is then simulated using a full nonlinear dynamic numerical model previously validated against a laboratory prototype. The efficiencies pre-dicted by the design method deviate only by 3.1% and 6.7% from the results of the dynamic model for urban and highway traffic, respectively, which is reasonable for the design phase of a hybrid hydraulic-pneumatic pow-ertrain. The component equations and computational strategy can also be used for sizing other hydraulic or pneumatic system architectures.