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Brakes

The University of Jordan Faculty of Engineering and Technology Electrical Engineering Department Electric Drive course. Brakes. Up to down approach . Done by: Amr Aljamal Mou’ath Shakeeb Ayman Atallah Instructor: Prof. Mohammad Zeki Khedher. Why we need brakes ?.

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Brakes

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  1. The University of Jordan Faculty of Engineering and Technology Electrical Engineering Department Electric Drive course Brakes Up to down approach Done by: AmrAljamal Mou’athShakeeb AymanAtallah Instructor: Prof. Mohammad ZekiKhedher

  2. Why we need brakes ? • We need brakes to reduce the speed of moving objects or stop them. • Formula 1 cars are capable of decelerating from 124-mph to a standstill in only 2.9 seconds. What are the brake discs and pads of Formula 1 cars made from?

  3. Over view • Brakes translate a push of a pedal to slowing down your car. • Disc brakes are the part of the brake system that does the actual work of stopping the car.  • The brakes on this race car locked up, causing it to head right into the wall.

  4. The topics • Pascal’s low • Energy transformation: • transforms Kinetic energy into heat using friction brakes • transforms Kinetic energy into electricity using magnetic brakes • Types of brakes • Brake sub-systems (in cars) as a sample • New technologies

  5. Pascal’s low •  ”pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure ratio (initial difference) remains the same.”

  6. Hydraulic press • A multiplication of force can be achieved by the application of fluid pressure according to Pascal’s princible, which for the two pistons implies • P1 = P2 • This allows the lifting of a heavy load with a small force.

  7. Energy transformation • Friction Brake: This brake system converts the kinetic energy of vehicle motion into heat • Magnetic Brake: Capturing kinetic energy generated from braking and converting it to electricity.

  8. Friction brake • Air Brakes. (Pneumatic) • Hydraulic Brakes. (Incompressible) use hydraulic fluid pressure to transmit power.

  9. Friction Brake Action • Brake Pedal is connected to the Master Cylinder. • Each wheel has a Wheel cylinder • (Rear) Or Caliper (Front) • Each wheel has a brake Drum • (Rear) Or Disk (Front) • Each wheel has Shoes • (Rear) Or Pads (Front)

  10. Brake action • When the Brake pedal is pressed, brake fluid travels from Master cylinder to the Caliper or Wheel cylinder, pushing the pistons out. In turn this action pushes the shoes against the drum or the pads against the rotor.

  11. Brake parts • Brake Lining: must be strong enough to absorb the heat and last a long time, yet save the drums and rotors from wearing too quickly. • Brake lining is made of various materials (Asbestos) • Some are bonded or glued to a metal plate. • Some are riveted to a metal plate.

  12. Brake parts • Disk brakes: found on front of most vehicles as well as at rear of four wheel Disk brakes vehicles. • Has a rotor/disk between two pads • Caliper squeezes the pads against the disk when the brakes are applied • Disk brakes work much better then the drum brakes, as they cool better and apply more pressure. • Disk materials Metallic(last longer, but bad for rotor) Semi-metallic Ceramic

  13. Brake parts • Drum Brakes on the rear wheels of the vehicle. • When brakes are applied, the wheel cylinder pushes the brake shoes against the rotating drum.

  14. Parking brakes are part of the rear brakes and are operated mechanically with the help of a leaver and cables.

  15. Dual Brake system • Is a safety feature. If one system fails the other will still work. • Front brakes are on different lines then the rear. • Master cylinder has two compartments for brake fluid. • Bigger for front and smaller for rear.

  16. Dual Brake system

  17. Dual Brake system

  18. regenerative braking is an energy recovery mechanism which slows a vehicle or object down by converting its kinetic energy into another form, which can be either used immediately or stored until needed this can be done by using an electric motor as an electric generator.the energy can be stored : -electrically by  battery or capacitors bank - mechanically via pneumatics, hydraulics

  19. How dose the regenerative brake work -This system use the vehicle's momentum as the mechanical energy that puts the motor into reverse . -Once the motor has been reversed, the electricity generated by the motor is fed back into the batteries, where it can be used to accelerate the car again after it stops.

  20. In this circuit, when the motor is slowing down, Q1 is off and the motor is acting as a generator. The current can flow backwards (because the motor is generating) through Q2 which is turned on. When Q2 turns off, this current is maintained by the inductance, and current will flow up through D2 and back into the battery

  21. Regenerative Braking Controllers •  the brake controller makes the entire regenerative braking process possible. • its monitors the speed of the wheels •  calculate how much torque -- rotational force -- is available to generate electricity to be fed back into the batteries • deciding whether the motor is currently capable of handling the force necessary for stopping the car. If it isn't, the brake controller turns the job over to the friction brakes

  22. advantage of regenerative breaking essential purpose of regenerative braking is to improve the fuel efficiency of a hybrid electric vehicle. According to researchs, modern cars waste more than 80 percent of the energy their engines produce, and about half of that energy goes through the brakes where it takes the form of friction and heat. - For example: The Delhi Metro saved around 90,000 tons of carbon dioxide (CO2) from being released into the atmosphere by regenerating 112,500 megawatt hours of electricity through the use of regenerative braking systems between 2004 and 2007.

  23. Limitations of regenerative breaking • Traditional friction-based braking is used in conjunction with mechanical regenerative braking for the following reasons: • The regenerative braking effect drops off at lower speeds • The friction brake is a necessary back-up in the event of failure of the regenerative brake. • in a two-wheel drive car and regenerative braking power only applies to such wheels because they are the only wheels linked to the drive motor, so in order to provide controlled braking under difficult conditions (such as in wet roads) friction based braking is necessary on the other wheels. • The amount of electrical energy capable of dissipation is limited by either the capacity of the supply system to absorb this energy or on the state of charge of the battery or capacitors.

  24. Limitations of regenerative breaking Cont… • Under emergency braking it is desirable that the braking force exerted be the maximum allowed by the friction between the wheels and the surface without slipping. The maximum force available for acceleration is typically much less than this except in the case of extreme high-performance vehicles. • Therefore, the power required to be dissipated by the braking system under emergency braking conditions may be many times the maximum power which is delivered under acceleration.

  25. New braking system technologies • Anti Brake System (ABS) • Traction Control System (TCS) • Electronic Stability Program (ESP) • Regenerative braking system

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