Study on Design Optimization of a Capacitive Tilt Angle Sensor

This paper presents a design optimization and validation of a two-axis cylindrical capacitive tilt angle sensor. The proposed sensor includes of five electrodes symmetrically arranged surrounding an air-liquid two phases cylindrical tube, forming two pairs of electrodes for roll and pith angle measurement. Cylindrical plastic tube filled partly with dielectric fluid with dielectric constant of 2. The proposed sensor can detect tilt angles in x-axis and y-axis, i.e. roll and pith angles. When the cylindrical plastic tube is rotated, the dielectric fluid covers a portion of the induction electrodes, thereby changing the differential capacitance value of the capacitor corresponding to the tilt angle. By measuring the capacitance change, the tilt angle can be estimated. Performance of the sensor was investigated by Finite element method using Comsol Multiphysics simulation software. Simulation results show the variation in capacitance with respect to the variation of tilt angle. Based on this simulation model, the structure of the electrodes was manipulated for maximizing the sensitivity for roll and pith sensing in an appropriate working range. Experiments were also conducted for validation. The experiment results are well matched with simulated results. The optimized sensor has working range from -70 degrees to +70 degrees with sensitivity of 3 mV/degrees in the roll angle and from -30 degrees to +30 degrees with sensitivity of 17 mV/degrees in the pitch angle.