Brakes

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Brakes
The University of Jordan Faculty of Engineering
and Technology Electrical Engineering
Department Electric Drive course
Up to down approach

• Done by
• Amr Aljamal
• Mouath Shakeeb
• Ayman Atallah
• Instructor
• Prof. Mohammad Zeki Khedher

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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?

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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.

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The topics

• Pascals 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

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Pascals 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.

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Hydraulic press

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

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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.

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Friction brake

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

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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)
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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.

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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.

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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

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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.

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

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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.

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Dual Brake system
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Dual Brake system
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 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

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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.

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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
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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

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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.

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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.

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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.

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New braking system technologies

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