Fig. 5. Components and other programs in ESC
Hydraulic modulator unit with attached ECU
The hydraulic modulator has input and output solenoid valves for controlling the pressure in the individual wheel brakes. The integrated ECU assumes all electrical and electronic tasks as well as the control functions of the system. The unit is located in the engine compartment between the brake master cylinder and the wheel brake cylinders; so that the hydraulic lines to the brake master cylinder and the wheel brake cylinders can be kept short.
Wheel-speed sensor
The ECU processes the signals from the wheel-speed sensors to compute the speeds of the wheels. Two different operating principles are used: passive (inductive) and active (Hall) speed sensors. Active sensors are becoming more and more widespread. They use a magnetic field for the contactless detection of wheel speed and are capable of recognizing the direction of rotation as well as standstill.
Yaw-rate and lateral acceleration sensor
A yaw-rate sensor records all yawing movements of the vehicle around its vertical axis. Together with the information from an integrated lateral acceleration sensor, the status of the vehicle ("actual state") can be determined and compared with the driver’s wishes.
Steering-angle sensor
The task of the steering-angle sensor is to measure the position of the steering wheel by determining the steering angle. This figure, together with the vehicle speed and desired braking pressure or position of the accelerator, is used to calculate the driving maneuver that the driver wishes to perform (“desired state”).
Communication with engine management
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