IIT Madras Approaches Towards Improving Braking Performance of EVs

Researchers from the Indian Institute of Technology (IIT) Madras, have developed strategies to improve the braking performance of Electric and Hybrid vehicles. This research could help implement a braking system in Electrified Vehicles (EVs), which can improve the stopping distance and ride comfort in the presence of regenerative braking.

However, such strategies have been developed for lighter road vehicles, there is a lack of approaches through which the braking performance of heavy commercial road vehicles (such as buses and trucks) can be improved through ‘regenerative braking.’

The innovative research was led by Prof. C. S. Shankar Ram, Department of Engineering Design, IIT Madras, and his Ph.D. student Dr. V. S. Kesavan. They explored various procedures to study and incorporate the effect of different dynamic characteristics of ‘friction brake’ and ‘regenerative brake’ on the vehicle’s braking performance. The results of their study have been published in the reputed peer-reviewed Journal Vehicle System Dynamics. 

Pointing up on the need for research in these areas, Prof. C.S. Shankar Ram, Department of Engineering Design, IIT Madras, stated, “Given the increasing adoption of electrified heavy road vehicles, it is imperative to study their dynamic response during on-road operation. Brakes are used to ensure safe operation of vehicles, and this research focuses on the braking of electrified heavy road vehicles.”

According to their developments, two braking systems are being used in electrified vehicles, specifically:

Friction-based Braking System: In conventional fossil fuel-based heavy vehicles, the force that the driver applies on the brake pedal is used to regulate a pneumatic system whose output force is used to stop the vehicle using friction braking. The kinetic energy of the vehicle due to its moving state is converted to heat energy. Thus, a part of the energy obtained from burning the fuel is wasted in the form of heat energy dissipated during friction braking.

Regenerative Braking System: In electric vehicles, an arrangement is made to reduce this energy loss by using another braking system called the ‘Regenerative Braking System.’ In this, when the driver presses the brake foot pedal, a portion of the kinetic energy due to the movement of wheels is converted into electrical energy that gets stored in the battery and is available for use in future driving.

Despite this, the magnitude of regenerative braking is insufficient to stop the vehicle under all conditions since regenerative braking alone cannot typically provide high deceleration. Further, when the battery is fully charged or when vehicle speed falls below a certain level, regenerative braking is unavailable, and the total brake force on driven wheels is applied only through friction braking.

Accordingly, in electrified vehicles both friction and regenerative braking should be used in a co-operative manner to ensure energy conservation and stopping the vehicle within a reasonable distance.

Speaking on the Research, Prof. C. S. Shankar Ram added, “Due to the faster response of regenerative braking, its switch-off can cause momentary perturbations in vehicle’s deceleration and its associated vehicle dynamic parameters until the friction brake system increases its brake pressure to meet the desired brake demand from the driver.”

He further explained, “This situation disturbs the driver’s brake feel momentary due to the difference in the dynamic response characteristics of these two braking systems.”