Model-Based Engineering of Magnetic Sensors

A modern car contains about 30 magnetic sensors on average. Their performances depend on the readout circuit imperfections, the magnetic environment, and mechanical assembly tolerances. For angle sensors, this yields a complex physics with magnet tilt and off-axis rotation. Traditionally these effects are studied separately in finite-element-method (FEM) simulators, separated from traditional system and circuit design simulation tools. This creates a simulation gap. A new modeling method for physical modeling of magnetic position sensors is presented. The method is based on spherical harmonic decomposition, and is implemented in Matlab. In this representation, any rigid-body 3-D motion of the magnet and sensor is modeled by matrix operations. Critical physical effects for the sensor accuracy can then be explored directly in system simulation tools such as Matlab, Simulink, Python or even in an integrated circuit simulator. The method maintains FEM accuracy. It represents a paradigm shift in magnetic position sensor design, and brings FEM accuracy to a much wider range of users.