Brake-by-wire

In the automotive industry, brake-by-wire technology is the ability to control brakes through electrical means. It can be designed to supplement ordinary service brakes or it can be a standalone brake system.

This technology is widely used on all hybrid and battery electric vehicles, including the Toyota Prius. Brake-by-wire is also common in the form of the Electric Park Brake which is now widely used on mainstream vehicles.

The technology replaces traditional components such as the pumps, hoses, fluids, belts and vacuum servos and master cylinders with electronic sensors and actuators. Drive-by-wire technology in automotive industry replaces the traditional mechanical and hydraulic control systems with electronic control systems using electromechanical actuators and human-machine interfaces such as pedal and steering feel emulators.

Some x-by-wire technologies have been already installed on commercial vehicles such as steer-by-wire, and throttle-by-wire. Brake-by-wire technology has been widely commercialized with the introduction of Battery Electric Vehicles and Hybrid Vehicles. The most widely used application by Toyota in the high volume Prius was preceded by the GM EV1, the Rav4 EV, and other EVs where the technology is required for regenerative braking. Ford, General Motors, and most other manufacturers use the same general design, with the exception of Honda, who designed a notably different design.

Brake-by-wire is used in all common hybrid and electric vehicles produced since 1998 including all Toyota, Ford, and General Motors Electric and hybrid models. The Toyota Synergy Drive and the Rav4 EV use a system where a modified ABS (antilock brake system) actuator is coupled with a special hydraulic brake master cylinder to create a hydraulic system, coupled with the brake control unit (computer). Ford's system is almost identical to the Toyota system, and the General Motors system uses different nomenclature for components while the operation is virtually identical.

The hydraulic force generated by pressing the brake pedal is used only as a sensor input to the computer unless a catastrophic failure occurs including a loss of 12-volt electrical power. The brake actuator has an electric pump that provides the hydraulic pressure for the system, and valves to pressurize each wheel caliper to apply the friction brake when required by the system.

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Wikipedia