Research On Integrative Control Of Regenerative Braking And Anti-Lock Braking For Hydraulic Hybrid Vehicle

As a key technology for hybrid vehicles, regenerative braking can reduce fuel consumption efficiently and extend the driving range. The regenerative braking system of the hydraulic hybrid vehicle (HHV) is made up of pump/motor, accumulators, feedback components and control system. It's required to retain the traditional friction brake system for HHV due to the reasons that the energy density of the regenerative braking system is small even if the system owns high power density and strong full charge and full discharge capacity. In addition, the regenerative braking force changed the distribution of braking force on the front and rear wheel, which makes the vehicle unstable when braking. So it's necessary for HHV to have the anti-lock braking system (ABS). However it's a problem for researchers that how to coordinate the regenerative braking system and ABS in order to maximize the recovery braking energy, under the premise of braking safety.Based on characteristics of the regenerative braking system and ECE regulations, this paper develops a composite brake control policy, makes reasonable distribution of front and rear friction brake force and regenerative braking force to ensure braking safety and recovery of braking energy. Considering the effects about regenerative braking and ABS, control strategies for emergency braking on high-friction coefficient road and non-emergency braking on low friction coefficient road are developed. The strategies aim to ensure the stability of vehicle during braking by adjusting the front and rear wheel friction brake force and rear-wheel regenerative braking force to make the slip ratio in the vicinity of optimal slip ratio.Due to the complex non-linear problem of coordinated control for regenerative braking and ABS, models including braking force demand model, distribution of brake force controller model, regenerative braking systems model, vehicle model, wheel model, tire model and ABS model are established in MATLAB/SIMULINK. Simulations are carried out on several situations such as hard or moderate braking on high-friction coefficient road with the wheels unlocked, emergency braking on high friction coefficient road and moderate braking on mid-low friction coefficient road with the wheels locked. Simulation results indicate that the control strategies can guarantee the stability for HHV, and also gets more recovery energy during braking. On the other hand it's verified that the rationality of coordinated control strategy for regenerative braking and ABS.