Electric Regenerative Power Assisted Brake Algorithm for a Front and Rear Wheel Drive Parallel Hybrid Electric Commercial Van 2008-01-2606

There is an increasing trend in the worldwide automotive area towards developing hybrid electric vehicles as an intermediate solution to fulfill the new, more stringent pollutant emission level requirements set by governments. Conversion of braking energy into electrical energy stored in the battery through regenerative braking is an important aspect of hybrid electric vehicles that increases their fuel efficiency. This paper presents an electric regenerative power assisted brake algorithm developed to enhance energy efficiency of a front and rear wheel drive parallel hybrid electric commercial vehicle. The commercial vehicle used in this study is a second generation research prototype Ford Transit Parallel Hybrid Electric Van. The existing hydraulic brake system of this van was not altered for reasons of safety and reliability in the case of a problem with regenerative barking. Regenerative braking is an add-on feature and provides brake assist in cooperation with the existing hydraulic brake system by using as much regenerative braking as possible in accordance with the brake regulation limits, brake force proportioning between the rear and front axles, electric motor torque limits and the current battery state of charge when the driver presses the brake pedal. Mimicking of brake pedal to brake force characteristics of the hydraulic brake system through programmed regenerative braking will ensure the presence of the same or similar hydraulic system only braking feel for the driver. If the desired braking force cannot be generated by regenerative braking alone, the driver who is in the braking loop will adjust his pressure on the brake pedal to accommodate the distance through the hydraulic brake system. This proposed system was modeled and simulated in Simulink to demonstrate its successful operation. The simulation results have shown that a significant amount of energy can be recovered and safe and reliable operation of the brake system can be maintained by the proposed regenerative brake assist.