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Electro-Mechanical Brake for Front Wheel with Back-up Braking
Abstract:
Electro-Mechanical Brake (EMB) is the brake system that is actuated by electrical energy and has a similar design with the Electric Parking Brake (EPB). It uses motor power and gears to provide the necessary torque and a screw & nut mechanism is used to convert the rotational movement into a translational one. The main difference of EMB compared with EPB is that the functional requirements of components are much higher to provide the necessary performance for service braking such as response time. Such highly responsive and independent brake actuators at each wheel lead to enhanced controllability which should result in not only better basic braking performance, but also improvements in various active braking functions such as integrated chassis control, driver assistance systems, or cooperative regenerative braking. Although the EMB system has the potential for numerous advantages and innovations in braking, it has yet to be successfully introduced in series production mainly due to safety and cost concerns. Recent studies have been made to investigate the functional safety aspects[1] and additional mechanical backup measures[2] in this regard.
Although the EMB is conventionally thought of as a solution for oil-free braking system[3-4], the EMB system introduced in the current paper includes a hydraulic piston to make several functions possible. First, the hydraulic system allows for a mechanical back-up mechanism that leads to increased reliability. Second, the clamping force for braking control can be measured with a pressure sensor. And finally, the dual piston structure proposed in the current paper, which leads to amplification of the force transmission, allows for the design of lower specification and higher cost effective motor and gear components.
This new concept of EMB is termed the hEMB (hybrid EMB) in this paper. This study proposes to use a combined system of front hEMB and rear hydraulic caliper. This type of system has the potential of providing many advanced braking functions without the high cost associated with fully electric four wheel brake by wire systems. Prototypes of hEMB actuators were made and attached in a test vehicle. Results of bench and vehicle tests will be given to show the functionality of the system.