Uncoupled braking energy recovery system based on proportional relay valve

Abstract

Aiming at the problem that during continuous braking of pure electric commercial vehicles, low air source pressure will lead to slower braking force response speed of drive axle coupling and affect braking energy recovery efficiency, a scheme of uncoupled braking energy recovery system (URBS) based on proportional relay valve was proposed. Firstly, based on the hysteresis characteristics of the proportional relay valve, the feed-forward-single neuron PID control method was adopted to realize the accurate output of braking air pressure. Secondly, taking the battery SOC and vehicle speed as the constraints, the pressure supply mode was determined according to the pressure signal of the air source, and the uncoupled braking energy recovery control strategy was formulated. Finally, a joint simulation platform was built based on AMESim, MATLAB/Simulink and TruckSim, and a single braking condition and cyclic conditions were selected to verify the effect of the braking force coupling and the braking energy recovery of the system. The results show that URBS based on proportional relay valve can achieve rapid response of coupled braking force, with the time of less than 0.1 second to reach 75% of steady-state pressure value. The effective braking energy recovery rates under CHTC-HT（China heary-duty commercial vehicle test cycle for heavy truck) and C-WTVC(China world transient vehicle cycle) conditions are 10.13% and 17.17%, respectively. The proposed URBS scheme can effectively improve the response speed and coupling accuracy of coupled braking force of the drive axle, and can provide reference for the design of pneumatic URBS schemes for pure electric commercial vehicles.

Keywords

• vehicle engineering; uncoupled braking energy recovery system; proportional relay valve; single neuron pid; hysteresis compensation; joint simulation