Architecture of An Electromechanical Braking System
General architecture of an electromechanical braking (EMB) system in a drive-by-wire car is shown in Fig. 1. The system mainly comprises five types of elements:
- Processors including an Electronic Control Unit (ECU) and other local processors
- Memory (mainly integrated into the ECU)
- Sensors
- Actuators
- Communication network(s).
Once the driver inputs a brake command to the system via a human-machine interface - HMI (e.g. the brake pedal), four independent brake commands are generated by the ECU based on high level brake functions such as anti-lock braking system (ABS) or vehicle stability control (VSC). These command signals are sent to the four electric calipers (e-calipers) via a communication network. As this network might not be able to properly communicate with the e-calipers due to network faults, HMI sensory data are also directly transmitted to each e-caliper via a separate data bus.
In each e-caliper a controller uses the brake command (received from ECU) as a reference input. The controller provides drive control commands for a power control module. This module controls three phase drive currents for the brake actuator which is a permanent magnet DC motor, energised by 42V sources. In addition to tracking its reference brake command, the caliper controller also controls the position and speed of the brake actuator. Thus, two sensors are vitally required to measure the position and speed of the actuator in each e-caliper. Because of the safety critical nature of the application, even missing a limited number of samples of these sensory data should be compensated for.
Read more about this topic: Brake-by-wire
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