Design and calibration of a torque sensor based on sectional redundant measurements

This paper presents a torque sensor based on sectional redundant measurements, which can be applied to torque measuring of motor starting, running and stopping. The sensor can withstand an axial force of 1000kg while the interference from the axial load remains low. The maximum range is up to 400Nm. In order to ensure accuracy and rigidity, the entire measuring range is divided into three sections, since the moment of motor starting, motor running and motor stopping, the maximum torque of each stage should be approximately 400Nm, 210Nm, and 60Nm respectively. A wheel shaped elastic body with 8 radial beams on which foil strain gauge and semiconductor strain gauge are adhered and serve as the sensing unit. The combination of foil strain gauge and semiconductor strain gauge forms a redundant measuring system. It was found at lower range, the sensibility of the semiconductor gauge is superior to the foil gauge. But at higher range, the linearity drop of the semiconductor gauge results in lower measuring accuracy compared to the foil gauge. By using semiconductor gauge at lower range and foil gauge at higher range, we are able to achieve fair accuracy and linearity at the whole measuring range.