Differential Sensing Method for Multidimensional Soft Angle Measurement Using Coiled Conductive Polymer Fiber

Soft robots made from soft materials can adapt to different harsh environments and ensure safety for operators. However, they require efficient sensing methods to feedback their states. This work presents a differential sensing method to measure the angle of a soft system using Coiled Conductive Polymer Fibers (CCPFs). CCPFs, which are economically fabricated and suitable for wide range measurement, can be embedded inside soft materials with high compliance. By modeling the resistance changing regulation of CCPFs, a deferential sensing method based on the resistance changing model is established to eliminate the nonlinearity and drift. A multidimensional angle control system based on the differential sensing method of CCPFs is established to verify the accuracy. The Root Mean Squared Error (RMSE) of the developed method is lower than 3.6% of the measured amplitude in the single dimensional angle testing, and about 4.3% in multidimensional angle testing. The hysteresis of CCPF sensor is reduced from 0.13 to 0.03 by differential sensing method. This work will not only provide a reliable multidimensional angle sensing method for soft robots, but also lay a theoretical foundation for wider application for other types of resistive soft sensors.