An integrated high precision absolute angular displacement sensor

Abstract This paper proposed a high precision absolute angular displacement time grating sensor, and was assembled into an integrated encoder. This absolute angle sensor contains two incremental sensors with N 1 and N 2 measurement period, respectively. N 1 and N 2 are mutually prime, and N 1 > N 2 . The induction electrodes of the fine measurement component adopt differential design to minimize the effects of external electromagnetic interference and common mode interference between different sensing units so as to achieve high precision displacement measurement, the phase difference between two incremental sensor is used for absolute positioning. This absolute positioning method reduces the installation requirements and enhances their absolute positioning capability, enhancing adaptability and application prospects. The reflecting ring design simplifies the structure of the encoder and facilitates sensor integration. The induction output signals of different components are cross connected through lead wires to the reflecting ring far away from the measurement component to the first harmonic error during the measurement period. The reading heads adopt a round, uniformly distributed design scheme, and the average effect of the whole circumference closed ring sampling scheme is beneficial for improving measurement accuracy, reduce the influence of edge effects and parasitic capacitance on nonlinear errors within the measurement period and eliminating harmonic errors. A sensor prototype with a diameter of 83 mm was manufactured and assembled into an integrated encoder. Experimental results show that the sensor achieve a precision of 12″ over a full 360° measurement range and a resolution of 0.5″, and it can realize absolute positioning.