Mid Sweden University

This paper proposes a torque measurement method based on volumetric strain. A model of the measurement system based on the differential pressure monitoring is proposed and theoretically discussed. The error sources are identified and an error propagation model is presented for the proposed torque measurement method. Considering these error sources, a prototype torque sensor is presented as a case study for the method verification. Both the mechanical and readout electronics design are discussed and analyzed. The mechanical sensitivity and maximum stresses are analyzed using Finite Element Method. Whereas, the readout electronics is experimentally verified using an off-the-shelf high performance differential pressure sensor. The results from the conducted analysis show that the presented design of torque sensor can be used to measure torque in the range of ±300 N·m with the resolution of 0.006 % of full scale. The maximum observed stress on the proposed structure is 220 MPa. The experiments conducted on the readout electronics show that the differential pressure sensor is the limiting factor in the design when it comes to the resolution. In conclusion it is summarized that the presented torque sensor can be used in industrial applications requiring both high resolution and wide range. Moreover, the method is fully adaptable to various performance requirements in terms of range and resolution. The future work is also discussed to implement the presented design and characterize it using reference instruments.