This study presents the utilization of the hardware-in-the-loop (HIL) approach for regenerative braking (regen) control enhancement efforts for the power split hybrid vehicle architecture. The HIL stand used in this study includes a production brake control module along with the hydraulic brake system, constituted of an accelerator/brake pedal assembly, electric vacuum booster and pump, brake hydraulic circuit and four brake calipers.
This work presents the validation of this HIL simulator with real vehicle data, during mild and heavy braking. Then by using the HIL approach, regen control is enhanced, specifically for two cases. The first case is the jerk in deceleration caused by the brake booster delay, during transitions from regen to friction braking. As an example, the case where the regen is ramped out at a low speed threshold, and the hydraulic braking ramped in, can be considered. During this transition, due to the communication delay and the delay associated with booster dynamics, the regen ramp out and hydraulic braking ramp in are not perfectly synchronized, which can cause a jerk in deceleration.
The second case considered is the jerk in deceleration when the regen torque is ramped out to zero during an ABS event. This causes a sudden loss in deceleration, again causing a jerk. By properly controlling regen torque in these two events, it is shown by real time simulation results that smoother deceleration can be delivered without causing vehicle instability.
