Study of a hall effect brake wear sensor using finite element modelling and analysis

Monitoring of brake wear and warning the driver to replace it at the appropriate time is a critical safety requirement. Recently, basic concept of a new, simple and low-cost Hall-Effect (HE) based angle sensor, which continuously monitors brake wear, by sensing the angle rotated by the Cam Shaft (CS) with-respect-to the Slack Adjuster (SA) in the brake assembly has been presented. The sensor has a spiral shaped moving part. It rotates along with CS, and changes the magnetic field seen by a HE sensor, whose output is directly proportional to angle between CS and SA, for a wide range. A prototype angle sensor has been developed, and test results showed a linear range of 220°, which is sufficient for monitoring brake wear. In the sensor, parameters like positioning of the HE sensor, relative permeability of the materials used, thickness of the moving part, etc. play a crucial role as far as the linearity of output and sensitivity are concerned. Sensor optimisation based on hardware implementation is time consuming, inefficient and less accurate. Hence, a finite element model of the sensor has been developed, and various studies have been conducted to optimise the parameters for best performance of the sensor. This also enables to achieve a linear output without using complex circuitry.