Similar to the fly-by-wire technology in aerospace industry, drive-by-wire technology in automotive industry replaces the traditional mechanical and hydraulic systems with mechatronic actuation and control and human-machine interfaces (such as pedals and steering wheels) with emulators. Brake-by-wire in particular, represents the replacement of traditional components such as the pumps, hoses, fluids, belts and brake boosters and master cylinders with electronic sensors and actuators. Some x-by-wire technologies have been already installed on commercial vehicles such as steer-bywire, and throttle-by-wire. Due to its safety-critical nature, the brake-by-wire technology is still under an intensive research and development by some automobile and automotive parts manufacturers worldwide and has not been widely commercialized yet. This paper surveys some recent patents that suggest techniques to solve two challenging problems in brake-by-wire systems. The first problem involves reliable measurement of the drivers brake demand using a multisensor brake pedal mechanism and handling its missing data samples. The second challenge is the measurement or estimation of the clamp force and actuator position/speed in a brake caliper for the purpose of actuator control. After an overview of relevant recent patents, the current development trends as well as suggestions for key future developments are presented.
Keywords: Brake-by-wire, electromechanical brakes, drive-by-wire, nonlinear observer, actuator control, position sensors, speed sensors, force sensors, vehicle stability control
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