Brake Pad Wear Monitor using MOC (Motor on Caliper) EPB ECU

With the spread of new trends such as autonomous driving and vehicle subscription service, drivers may pay less attention to the maintenance of the vehicle. Brake pads being safety critical components, the wear condition of all service brakes is required by regulation to be indicated by either acoustic of optical devices or a means of visually checking the degree of brake lining wear [1]. Current application of the wear indicator in the market uses either sound generating metal strip or wire harness based pad wear sensor. The former is not effective in generating clear alarm to the driver, and the latter is not cost effective, and there is a need for more effective and low cost solution. In this paper, a pad wear monitoring system using MOC(Motor On Caliper) EPB(Electric Parking Brake) ECU is proposed. An MOC EPB is equipped with a motor, geartrain and an ECU. The motor current when applying the parking brake is influenced by the mechanical load at the brake pad side of the system. So, by analyzing the time history of the current it is possible to measure the clearance between brake pad and disc induced by the pad wear. From the measurement of the low load interval along with the mechanical specifications of the geartrain (e.g. lead of the screw), pad wear can be calculated. A sequential procedure for pad wear measurement mode is also proposed. A HILS test bench using production MOC actuator was setup and the measurement accuracy was evaluated across various conditions such as amount of wear, supply voltage, and temperature. The result is shown and a further discussion about practical aspects of the technology is added.