Design and fabrication of six axis force/torque sensor using strain gauges

In this paper, a six-axis force/torque sensor is designed and fabricated using strain gauge. The characteristic of minimal mechanical coupling or independent output voltages is very important in designing this type of sensors. For this purpose, an arrangement consisting of 24 strain-gauges is used so that the output voltages of the six Wheatstone bridges corresponding to the loading components are independent of each other. Sensor is subjected to single and combined loads, the output of the Wheatstone bridges is measured and coupling error is calculated. An average of 7.3% of coupling error indicates the independence of the outputs from each other. The calibration process was performed according to the ANSI1979 and the sensor specifications were calculated. The minimum accuracy and maximum nonlinearity error are related to Fx loading and equal to 14.78%Fs and 6.42%Fs respectively and the maximum repeatability error related to the Mz loading is equal to 9.63%Fs. In order to reduce hysteresis losses, loading is applied directly to flexible structure for the Fz. As a result, the accuracy has increased significantly to 3.99%Fs and the errors of nonlinearity and repeatability have decreased to 0.52%Fs and 2.60%Fs.