Research on the Inherent Nonlinearity Calibration of the Potentiometer of a Miniature Linear Series Elastic Actuator

This paper presents a miniature Linear Series Elastic Actuator (LSEA), in which two low-cost linear potentiometers were adopted to achieve a compact design. To improve the measurement accuracy of the linear potentiometer, a novel Bezier-based Calibration Method (BCM) and its optimization method were proposed to calibrate the inherent nonlinearity of the linear potentiometer. Calibration efficiency of the BCM was investigated numerically by making a comparison with the widely used Polynomial Calibration method (PCM), and the effect of the BCM calibration on the control performance of the LSEA was investigated experimentally by displacement and force control. Results reveal that the BCM exhibits an excellent local calibration ability for the nonlinearity with knee points. Due to the above characteristic, the BCM could produce a better calibration accuracy than the PCM under the same model order and improve the control performance of the LSEA. In addition, the BCM could calibrate the inherent nonlinearity of the potentiometer in a continuous form rather than that of piecewise ones. The continuous calibration form could bring more convenience to practical applications.