An Inverse Capacitance Differential Equation-Based Six-Axis Force/Torque Sensor for the High-Accuracy Decoupling of Complex Multi-Axis Loads

Currently, space-variable, capacitive multi-axis force/torque sensors have limited detection accuracy in the measurement of complex multi-axis loads owing to their inherent nonlinearity and coupling errors in full range. The nonlinearity and coupling of the conventional capacitance differential equation were experimentally verified for a pre-developed space-variable capacitive six-axis force/torque sensing chip. An inverse capacitance differential decoupling equation was practically applied to the chip to suppress the inherent nonlinearity and coupling errors in full range (2.5 N and 12.5 N·mm) under multi-axis loads. The results of complex multi-axis coupled loading tests align with the theoretical analysis. When the inverse decoupling equation is adopted, the maximum nonlinearities of 18.59%FS (Full Scale) and coupling errors of 254.1%FS for the conventional equation can be reduced to 1.05%FS and 10.90%FS, respectively. The efficient decoupling structure combined with the inverse capacitance differential equation can provide critical theoretical guidance for developing high-accuracy capacitive multi-axis force/torque sensors.