Design Of Quartz Resonant Sensing Unit And Its Application In Torque Sensor

In recent years,with the gradual development of human-computer interaction field of intelligent robot,the motion control of robot is no longer a single and repeated motion,but towards a more complex and accurate direction.Among them,torque sensor plays a vital role,and the performance of torque sensor directly affects the force control performance of the whole robot.So far,the most widely used in the market is still the resistance strain gauge torque sensor.The resistance strain gauge sensor technology is mature,simple and reliable,but it has a series of shortcomings,such as low resolution,slow response time,large signal noise and so on,which can not meet the force control needs of the robot.In order to overcome the shortcomings of traditional strain gauge sensors,meet the force control requirements of robots and reduce the use cost of sensors,a quartz resonant torque sensor is proposed for the first time in this study.The sensor takes AT cut quartz wafer as the sensitive unit,which has the advantages of high resolution,fast response time and natural insensitivity to signal noise.The main research contents of this paper are as follows:First of all,comprehensively analyze the basic principle knowledge of quartz wafer,including quartz wafer cutting,processing technology,piezoelectric effect,resonance principle and force frequency calculation formula of circular wafer,and select the quartz cutting and oscillation circuit of sensitive unit according to the force sensing characteristics and temperature characteristics of quartz crystal.Then,the sensitive unit of quartz wafer is designed,the quartz wafer is modeled by comsol software,the surface stress relationship between square quartz wafer and circular quartz is analyzed,and the calculation formula of force frequency coefficient of circular wafer is modified to obtain the formula suitable for the calculation of force frequency coefficient of square wafer.At the same time,the ultimate failure of quartz wafer is studied by ansys workbench software,according to the design goal of the range and resolution of the torque sensor,the required quartz wafer size is designed.Thirdly,design the pre-processing circuit,in order to ensure that the frequency signal of the sensitive unit can have a stable waveform and amplitude output,and facilitate the subsequent circuit to read the frequency signal,the pre-processing circuit of the sensitive unit is designed so that the final output signal of the sensitive unit is a square wave with an amplitude of 3.3 V and a duty cycle of 50%.Fourth,the elastomer structure of torque sensor is designed to verify the application of the designed sensitive unit,fully consider the frequency variation characteristics of the sensitive unit,design the torque sensor structure,select reasonable materials,and make the sensor obtain high sensitivity through the confirmation of installation position and stress amplification design.At the same time,ansys workbench software is used to optimize the structure to reduce the impact of interference load on the sensor.Finally,torque sensor performance test,the designed sensitive unit is installed in the designed torque sensor structure,and the actual calibration test experiment is carried out on the torque sensor to test the linearity,hysteresis,repeatability and other static parameters of the sensor.Secondly,the dynamic response,resolution and temperature drift of the sensor are tested.The results show that after the designed square quartz wafer is installed in the torque sensor,the linearity of the sensor is 1.06%,the hysteresis is 0.6%,the repeatability is 1.3%,the resolution is 1/5000 of full scale,the response time is 2.67ms,the natural frequency of the sensor is 2600Hz,and the temperature coefficient is 0.006%FS/℃,the stiffness is13.2×10~4N·m/rad,the sensitivity is 603 Hz/N·m.The designed square quartz chip,as the sensitive unit of the torque sensor,can make the torque sensor obtain fast response,high resolution,high sensitivity and high stiffness,solve the problems of low resolution,slow response time and low sensitivity of the traditional strain gauge torque sensor,and reduce the use cost of the torque sensor,which is of great significance to promote the development of human-computer interaction.