(The) development of robust control logic for electronic wedge brake and adaptation scheme for pad friction-coefficient estimation

Abstract

Siemens VDO, German electronic and mechatronic developer announced an innovative braking device called Electronic Wedge Brake (EWB) several years ago. It uses self-energizing effect using wedges, so it became the most energy-effective braking device among Brake-by-Wire systems which is compatible with existing 12 Volts system. Siemens VDO says that EWB uses only about 10 percent of energy of conventional hydraulic devices. Also, EWB features more fast response characteristic, reducing stopping distance by 15 percent compared to hydraulic ones. But, as EWB uses self-reinforcement effect, it is very sensitive to parametric variance, e.g. friction coefficient variance during braking. Small parametric error is highly amplified through self-energizing effect, degrading system response characteristic. So, it is required to develop robust control techniques. This research is focused on developing such robust control techniques to make system robust to parametric variances, particularly to the pad friction-coefficient error. The pad friction-coefficient is one of the main reasons that make it difficult to control a brake system precisely. Also, the estimation logic will be proposed for the pad friction-coefficient estimation in real time. It will be possible to estimate a brake torque with an estimated pad friction-coefficient. In addition, this research suggests a cost effective control scheme without a complex sensing of clamp force.