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Quartz crystal based sensor head design and analysis for robot torque sensor application

Background: In recent years, with the gradual development of robot human-computer interaction, robots need to meet the precise control of more complex motion. Torque sensors play an important role. The traditional strain gauge sensor uses a metal strain gauge as the sensitive element, which means that the sensor has a slow response, low resolution and can easily be affected by external signal noise. Aiming at these deficiencies of strain gauge sensors, a sensor with cutting quartz square sheet as the sensor head is proposed. Methods: In order to study the application of quartz square sensing head in the sensor, firstly, COMSOL (5.6) simulation modeling is used to obtain the stress relationship between square quartz sheet and circular quartz sheet. Then the calculation formula of the force frequency coefficient of the circular quartz sheet is modified to obtain the calculation formula of the force frequency coefficient of the square quartz sheet, and the feasibility of the formula is verified by practical experiments. Next, the theoretical simulation and experimental research on the buckling limit force of quartz wafer are carried out, and the formula of buckling limit force in the process of quartz wafer installation is modified. Finally, the designed sensitive head is installed on the elastomer structure for verification. The frequency signal is collected by SGS-THOMSON Microelectronics 32 with a sampling rate of 1000Hz. Results: The main performances of the sensor are range 150nm, sensitivity 350Hz / nm, linearity 98.14%, hysteresis 0.51%, repeatability 98.44%, resolution 0.02%. Conclusions: As the sensitive unit of the torque sensor, the designed quartz wafer can obtain high response time and high resolution, solve the problems of low resolution and slow response time of the traditional strain gauge torque sensor, and reduce the use cost of the sensor.