Magnet configuration maximizing the sensitivity and linearity of a magnetic rotation sensor

To facilitate accurate control of the amount of the transmitted light to a micro-display projection TV, the voltage output from a magnetic rotation sensor should vary linearly with aperture motion. Higher sensor sensitivity is also preferred. The sensor in consideration consists of a magnet, an aperture mechanism and a magnetic sensor. Because the magnet attached to the aperture generates magnetic field, which works as the source of the voltage change in the sensor, the sensor performance is most significantly affected by the magnet configuration. Thus, this investigation aims to find the optimal magnet configuration that can maximize the sensitivity and enhance the linearity of the magnetic rotation sensor. Instead of a common cylindrical magnet, two oppositely polarized magnets are considered as a candidate configuration. As a means to find the optimal magnets, the design problem is formulated as a topology optimization problem. When the present formulation is employed and an iterative optimization process is completed, a pair of oppositely polarized crescent shaped-magnets are found. To verify the superior performance of the optimized magnets, a series of numerical simulations are carried out. The physics to explain why the optimized magnets perform better than the nominal is also given.