IIT Madras researchers develop strategies to improve the braking performance of electric and hybrid vehicles


The research was led by Professor CS Shankar Ram, Department of Engineering Design, IIT Madras and his doctoral student, Dr VS Kesavan.

Indian Institute of Technology, Madras Researchers are developing strategies to improve the braking performance of electrified vehicles (electric and hybrid vehicles). This research could help implement a braking system in electrified vehicles, which can improve stopping distance and driving comfort in the presence of regenerative braking.

Although such strategies have been developed for lighter road vehicles, there is a lack of strategies to improve the braking performance of heavy duty road vehicles (such as buses and trucks) through “regenerative braking”. .

The research was led by Professor CS Shankar Ram, Department of Engineering Design, IIT Madras, and his doctoral student, Dr VS Kesavan, who explored various strategies to study and incorporate the effect of different dynamic characteristics of the ‘friction brake. “And” regenerative brake “. ‘on the braking performance of the vehicle. The results of their study were published in the renowned peer-reviewed Journal Vehicle System Dynamics.

Emphasizing the need for research in these areas, Professor CS Shankar Ram, Engineering Design Department, IIT Madras, said: “With the increasing adoption of electrified heavy road vehicles, it is imperative to study their dynamic response during road operation. Brakes are used to ensure safe operation of vehicles, and this research focuses on the braking of electrified heavy road vehicles.

There are two braking systems that are used in electrified vehicles, namely:

Ø “Friction Braking System” – In conventional heavy-duty fossil-fueled road vehicles, the force the driver applies to 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 state of motion is converted into thermal energy. Thus, part of the energy from fuel combustion is wasted in the form of thermal energy dissipated during friction braking.

Ø “Regenerative Braking System” – In electric vehicles, a provision is made to reduce this loss of energy by using another braking system called “Regenerative Braking System”. In this, when the driver presses the brake pedal, part of the kinetic energy due to the movement of the wheels is converted into electrical energy which is stored in the battery and is available for future use.

However, the amplitude of regenerative braking is insufficient to stop the vehicle under all conditions, as regenerative braking on its own generally cannot provide high deceleration. In addition, when the battery is fully charged or when the vehicle speed drops below a certain level, regenerative braking is not available and the full braking force on the drive wheels is only applied by the friction braking.

Therefore, in electrified vehicles, friction braking and regenerative braking should be used cooperatively to ensure energy conservation and stopping the vehicle at a reasonable distance.

Electrified vehicles can get the best of both worlds through the use of such a cooperative braking system. However, a crucial element here is the decision on how the two brake systems should operate to ensure that the vehicle comes to a reasonable distance and smoothly when switching between the two brake systems for good comfort. driving.

Commenting on this research, Professor CS Shankar Ram, Engineering Design Department, IIT Madras, said: “Due to the faster response of regenerative braking, stopping it can cause momentary disturbances in the deceleration of the brake. vehicle and its associated dynamic parameters until the friction brake system increases its brake pressure to meet the driver’s desired braking demand. This situation temporarily disrupts the feel of the driver’s braking due to the difference in the dynamic response characteristics of these two braking systems.

For this study, the team attempted to understand how braking performance is affected when these two braking systems are applied together or sequentially in heavy road vehicles. They further evaluated how braking performance is affected when the regenerative brake is instantly and gradually deactivated. They studied the effects of these strategies on loaded and unloaded heavy road vehicles and considered two types of roads, namely, dry and icy. Various strategies were evaluated through appropriate experiments performed in a Hardware-in-Loop experimental setup equipped with “IPG TruckMaker®”, a commercial vehicle dynamic simulation software.

Cooperative braking (with regenerative braking and friction braking) on ​​dry roads has been found to reduce the vehicle’s stopping distance by 2.1 m (about half the length of a car) compared to conventional braking (friction braking only) for a fully loaded vehicle. In addition, it was found that when the regenerative braking was gradually deactivated, the effect of the different dynamic characteristics of the friction brake and the regenerative brake reduced the percentage of momentary variation of the longitudinal deceleration by 80%, in the pitch movement. 79% suspension travel, 87% suspension travel, and 90% wheel slip rate compared to instant stop.

These provide a better braking feeling for the driver, driving comfort and vehicle stability. Therefore, the strategies developed by this study will ensure that one can achieve good driving comfort while meeting the desired braking demand and are therefore important for the electrified vehicle market.

The research team plans to extend the results of this study to analyze the impact of deactivating regenerative braking during active brake control in safety systems such as the anti-lock braking system and the electronic control system. stability.

Researchers expect the dynamic performance of the vehicle during active brake control to improve due to the smooth dynamic transition between friction braking and regenerative braking, which would help in the proper design of systems. active safety for electrified vehicles.

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