Braking systems are mechanical devices that have been developed with the purpose to slow, stop or prevent motion. They are present on the virtually all moving devices including automobiles and trains. Brakes operate through different mechanisms and some brakes may actually be complex systems that are made of up more than one type of braking device with some automobiles carrying redundant systems. The choice about what kind of brake should be used on answering two questions. The first is about determining the physical energy transfer method that is the best for the application. The second is about determining which actuation method (i.e. mechanical linkages, pneumatic, hydraulic etc.) is the best as each type of brake has optimum performance and value under different conditions [1]. Varying levels of cost and difficulty also enter into calculations about what kind of braking system will actually be used in any given application.
Hydraulic brakes operate using the pressure of the force applied to a flood. The benefit of using a hydraulic braking system is that engineers are able to design very precise braking. One of the most important components of this system is the brake fluid. It must be able to withstand relatively high temperatures because of the heat produced from braking. Although the most common type of brake fluid is glycol-ether based type because of its high boiling point and suitability for anti-lock braking vehicles; however a number of other fluids still exist. These other fluids have lower boiling points and are more inexpensive. Silicon based braking fluids do not absorb water as much; therefore, is more suited for wet braking conditions [2]. The break also consists of a master cylinder that transfers hydraulic pressure to the wheel brake mounts.
The configuration of the hydraulic brake also consists of a brake caliper assembly made of pistons that is made up of either brake pads and rotor, or drum attached to an axle. The former is commonly referred to as brake discs while the latter is commonly referred to as drum brakes. Disc brakes are thought to be better than drum brakes for a number of reasons. They are more efficient at dissipating the heat generated from braking process. They are also more resilient to wearing down. Due to their space, disc brakes are better for wet weather as the force of the spinning disc will throw the water off of the brake where a drum shape will store water on its inside surface. Even though disk brakes are superior, they are usually only used on the front wheels of the car. This is because they are more expensive than drum brakes and the front wheels are the ones that contribute breaking the most [3].
In recent years there has been a move to replace hydraulic components with electro mechanical components [4]. The components of the braking system mentioned above (e.g. the master cylinder, rack and pinioned gear, hydraulic lines, etc.). They are all connected to each other and work to produce the stopping forces; however, they add weight and complexity to the car. Removing these components and allowing a computer to decide how much force to apply to the brakes, relative to the amount of pressure applied by the driver, simplifies the physical breaking system and reduces the weight of the car. This systems work particularly well with energy recovery systems. Electro mechanical components systems slow down the vehicle by converting some of its kinetic energy into another form of energy that is then stored for another purpose. An example of such a system can be found in electric railways where the kinetic energy of the train can be fed back into the system as generated electricity [5]. Regenerative braking strategy are especially appealing for electric vehicles [6]. Concerns with these systems include getting drivers to feel an appropriate amount of sensory feedback from the systems so that they apply the come amount of pressure. These systems have not become mainstream yes as if they are likely to become more popular in the future.
Electromagnetic brakes and eddy current brakes, also known as dynamic braking. Both use electromagnetic force to apply to resistive braking force. They are most commonly used in trains, trams, and increasingly aircraft. These forms of transportation other have several braking system in redundancy to prevent failure, which could be catastrophic. This form of breaking can be both rheostatic and regenerative. Rheostatic brakes dissipate the energy from the braking process as the while energy is regenerative returned to the system. If the brakes on rheostatic systems get too hot, the system will shut down until it cools off, leaving another often friction based system, in its place. It is estimated the regenerative braking can save as much as 25% of the total braking power [7]. The possibilities offered by this system have the potential to revolutionize rail transport, however, electromagnetic compatibility and inner-system issues must first be resolved in its places like the European Union Rail Traffic Management System.
Each type of brake system can be considered as unique system and has it pros and cons. Different breaking systems are not suitable for that kind of vehicle, so professionals analyze which system is better perfectly stable for that kind of vehicle with minimum kinetic energy loose and best breaking results. The type of brake that is used in an automated vehicle depends of the configuration needed to endure the frictional forces, heat, and wear caused by repeated braking. In practical design considerations, designers will substitute, for a lower quality brake in order to cut down on costs. This is the norm in car breaking system which rely on hydraulic frictional braking system that employ disk or drum type brakes. The braking system in trains are more complex than those found in the cars and often made up of multiple braking forms. Electromagnetic systems are especially well suited for electromagnetic trains because they offer greater energy and braking efficiency despite potential compatibility issues among the carriers of countries. As more cars move to electrical power and become more technologically advanced, it is likely that the dynamic braking systems found on electromagnetic will become more popular in these vehicles.
References
[1] C.J.A. and B. G. H. R., Mechanical Design of Machine Elements and Machines, Hoboken, NJ: John Wiley & Sons, 2010
[2] Cdx Automotive, Brakes: Fundamentals of Automotive Technology, Burlington, MA: Jones & Bartlett Learning, 2014
[3] S. Ganguly, H. Tong, G, Dudley and F. Connolly, “Eliminating Drum Brake Squeal by a Damped Iron Drum Assembly,” SAE Technical Paper, pp. 01-0592, 2007.
[4] J. Cheon, “Brake by Wire System Configuration and Functional using front EWB (Electric Wedge Brake) and Rear EMB (Electro-Mechanical Brake) Actuators, “SAE Technical Paper, 2010.
[5] J. Cibulka, “Kinetic Energy Recovery System by means of flywheel energy storage,” Advanced Engineering, vol. 3, no. 1, pp. 864-868, 2009.
[6] J, Guo, J Wang and B. Cao, “Regenerative braking strategy for electric vehicles,” Intelligent Vehicles Symposium IEEE, pp. 864 – 868, 2009.
[7] L. Liudvinavicius and L. P. Lingaitis, “Electrodynamic braking in high-speed rail transport,” Transport, vol. 22, no. 3, pp. 178-186, 2007.
[8] S. Midya and R. Thottappillil, “An overview of electromagnetic compatibility challenges in European Rail Traffic Management System,” Transportation Research Part C: Emerging Technologies, vol. 16, no. 5, pp. 515-534, 2008.
