Analysis and development of the angular twist type torque-meter

The measurement of torque is essentially required for the precise machinery assembly, the improvement of machine performance and the control of power transmission system. The torque sensing part has a qualification such that the torsional stiffness is larger than the bending stiffness for high accuracy extent. Also the deflection of rotational part should be linearly proportional to the input torque and the power loss of coupling should be minimized. Now, the encoder technology is well developed enough to measure even a small twist angle. The type of rotating torque transducer discussed in this paper is the angular twist-type, which utilizes the principle of measuring the angular twist in a gage length proportional to the torque transmitted. This kind of shaft phase of torque-meter should have low stiffness in order to give a high resolution, but the low stiffness can cause a low resonant frequency, which will deteriorate the measuring system. In this paper, the torque-meter using two encoders are designed and manufactured with the rotating stainless steel bar. It is found that the values of axial strain calculated by the equation are in good agreement with the measuring values. Experiments also have been carried out to obtain strain distribution on the sensing plate surface and to investigate the effect of the surrounding conditions. The torque-meter using STS304 bar is designed and manufactured by the proposed equations.