Electric VehicleTransportation Safety & Security

Safety & Security in the Current and Future Mobility

The system which stops the motion of a vehicle by absorbing the energy from rotating or moving system is called as a braking system. In the year 1800’s braking system started to evolve to stop the momentum of vehicle. It was achieved by imparting friction brake system to prevent motion. Braking system has direct correlation with the safety of passengers and driver. Majority of the Automobiles are normally driven by internal combustion engine.  Availability of fuel and advancement in fuel engine technologies through centuries helped IC engine to drive mobility.

All gasoline powered vehicles use frictional and hydraulic braking which serves the purpose of safety. However, 18% to 30% of energy get wasted in the friction process. Nowadays, with the advent of power electronics and advancement in motors, Electric vehicles are becoming a reality. In the electric vehicle, electric motors are used hence braking is possible with electrical braking system which prevents loss of kinetic energy. Electric braking system ensures the safety and maneuverability of a vehicle. In most of Electric vehicles today, it is evolving an effective and economical solution for braking system.

Conventional Frictional Braking

Normally, every conventional vehicle have frictional braking system. In the internal combustion engine vehicle, combustion of fuel provides power to drive the vehicle. At the time of braking operation, kinetic energy gets dissipated in friction between brakes and tires. Sometimes 50% of average of all the effective traction energy get wasted in frictional braking. At present, hydraulic braking system is also used in combination with frictional braking system. Disk braking and Anti-lock braking system gives good stability and accuracy to the vehicle.

Functional block diagram of Frictional Braking System

When the brake pedal is pressed, at that instant lever connected to the brake pedal pushes piston into a narrow cylinder filled with hydraulic brake fluid. When the brake pad touches the brake disc, friction between the two generates the heat. The friction slows down the outer wheel and tire, ultimately the vehicle stops.

Functional Block Diagram of Frictional Braking System

Hybrid braking system (HBS)

In Electric vehicle, braking operation is carried out with a conjunction of Electric braking and mechanical braking system, termed as Hybrid Braking System (HBS). In Hybrid Braking System distribution of braking force between electric and mechanical braking is significantly important. Recent research in HBS, focuses on advanced braking control methodology for distribution of braking forces. It also takes care about various limits of safety and comfort. The challenge in HBS is its complexity increases with Electronic braking and anti-lock braking system (ABS) control.

Functional Block Diagram of Hybrid Braking System

Benefits and  Recent Trends in Hybrid Braking System

Nowadays both braking is controlled by the single pedal in which initial part is for electric braking and the last portion is for mechanical braking. This is decided based on the angle of a brake pedal of the vehicle. In hybrid braking system, electric brake is applied first. After that when vehicle speed has substantially come down that time mechanical brakes are applied. The biggest advantage of hybrid braking system is in case of electric brake failure. Mechanical brakes can be applied which serves as back up for safety. In case of emergency when instant brake is required that time mechanical brakes are applied instantly irrespective of electrical braking. Safety and accuracy of a vehicle to stop immediately is a key feature of hybrid braking system. However, it makes control system somehow complex to design. Skidding of a vehicle is avoided due to such braking strategy.

Fully Electrical Braking System

In fully electrical braking system the responsibility of braking operation is solely taken care by electrical braking system. Internal combustion engines are replaced by electric motors. The selection of electric motors depends on the load requirement, torque-speed characteristics, and vehicle categories. During the braking period, the vehicle is stopped by either applying plugging or regenerative braking operation. Various control algorithm and techniques are available which serves to realize the purpose of fully electrical braking system. If we compare hybrid braking system and fully electrical braking system then one can easily see that the hydraulic assemblies are removed in fully electrical braking system as shown in Functional Block diagram of fully Electrical Braking System.

Functional Block Diagram of Fully Electrical Braking System

Note

The discussion above is about various Baking Systems used in mobility. In which following types of Electric Braking can be used. We will discuss them in separate artificial.

  1. Rheostatic/Dynamic Braking
  2. Plugging
  3. Regenerative Braking

References

  1. The Electrical Machines and Controllers for Electric Vehicles—Part 1: General Specification, Nat. Std. People’s Republic of China GB/T 18488.1-2006, Dec. 1 2006
  2. Ming-Ji Yang, Hong-Lin Jhou, Bin-Yen Ma, and Kuo-Kai Shyu, Member, IEEE, “A Cost Effective Method of Electric Brake with Energy Regeneration for Electric Vehicles”, IEEE Transactions on Industrial Electronics, vol. 56, no. 6, June 2009
  3. S. M. Reza Tousi, S. Omid Golpayegani, Ehsan Sharifian “Anti-Lock Regenerative Braking Torque Control Strategy for Electric Vehicle”, Industrial Technology (ICIT), 2016 IEEE International Conference on, 14-17 March 2016
  4. Guoqing Xu, Kun Xu, Chunhua Zheng, Xinye Zhang, and Taimoor Zahid, “Fully Electrified Regenerative Braking Control for Deep Energy Recovery and Maintaining Safety of Electric Vehicles”, IEEE Transactions on Vehicular Technology, Vol. 65, No. 3, March 2016
  5. Bo Long, Shin Teak Lim, Ji Hyoung Ryu and Kil To Chong January 2014., “Energ Regenerative Braking Control of Electric Vehicles Using Three- Phase Brushless DirectCurrent Motors,” Energies, vol. 7, pp. 99-114,

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