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This resource covers the role of electronics in ABS systems, identifying components, explaining operation, and ABS ECU functions. Detailed information on wheel speed sensors, relays, and actuators is provided.
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Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components
Electronics and Electronic Components Motor Vehicle LevelResource 1 Aims To recognize the role of electronics within an ABS system
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Objectives By the end of the session you will be able to: • Identify Electronic ABS components • Recognize the inputs and outputs of an ABS system • Describe the operation of ABS electrical components.
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 ABS ECU Block Diagram
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Location of Components (Electrical)
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Electronic ABS Components • An ABS system will include the following electronic components • Wheel Speed Sensors • Wiring • Relays • ABS • ECU • Actuators
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Location of ABS Electronic Components
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Wheel Speed Sensors • A wheel speed sensor mounted on each wheel is utilised within an ABS system in order to determine the rotational speed of the vehicles wheels (to determine if a wheel is skidding or de-accelerating), this is then sent to the ABS ECU. • Front wheel speed sensors are mounted onto the steering knuckle. • Rear wheel speed sensors can be mounted to the rear axle carrier or mounted to the suspension arm depending on set up.
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Wheel Speed Sensors
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Wheel Speed Sensor Operation • As the teeth of the sensor rotor pass the iron core, the magnetic lines of force cut through the coil windings • This causes a voltage to be induced into the coil • When the tooth is centered on the iron core the magnetic field does not move and 0v is produced. • As the tooth moves away from the iron core the magnetic field expands causing a negative voltage • The faster the rotor increases the signal increases indicating a high wheel speed which is then sent to the ECU.
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Wheel Speed Sensor Operation • Voltage is induced to the coil when the magnetic field is altered each time the sensor passes the iron core
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 ABS relays • Supplies power to the solenoids in order to prevent wheel lock up but only when the following conditions are met:- • The IGN is on • The self diagnostic check performed by the vehicle on start up was completed OK • If any of these conditions are not met, the ECU will switch the solenoids off.
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Circuit Diagram showing ABS relays
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Relays • The motor relay will switch the voltage to the pump motor • The solenoid relay switches the voltage to the actuator solenoids
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Actuators • The actuators on an ABS system will control the amount of brake pressure that the wheel is subjected to, depending on information received from wheel speed sensors etc. • It controls this via three solenoids:- • Pressure holding • Pressure increase • Pressure Reduction • These solenoids will be discussed further in the next session.
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Actuators
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 ABS ECU • The ECU (Electronic control unit) is the vehicles on board computer that will ensure that all systems are performing correctly. • The ECU will collect data from sensors, battery and brake light switch in order to determine how the ABS system is performing. • If a wheel speed sensor is measuring as de-accelerating (lock up) the ECU will react by sending a signal to the actuators to reduce that pressure at the offending wheel.
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Block Diagram ABS ECU
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Circuit Diagram ECU
Electronics and Electronic Components Motor Vehicle Level 3Resource 1 Summary • Aim: • To recognize the role of electronics within an ABS system • Objectives: • At the end of the session, students should be able to: • Identify Electronic ABS components • Recognize the inputs and outputs of an ABS system • Describe the operation of ABS electrical components.