Research On MEMS Based Torque Wrench Positioning Technology

It is important to design a torque wrench which can be positioned based on angle measurement to solve the problem of traversal in the operation process.When using angle measuring torque wrenches to tighten bolts in industries such as transportation and machinery,the diagonal method is generally used,which may result in missed tightening,therefore,it is required that torque wrenches can be positioned.This thesis introduces the positioning principle of strapdown inertial navigation into the angular torque wrench.The positioning principle of MEMS sensors was presented,and the positioning algorithm matrices for gyroscopes,accelerometers,and magnetometers were derived,The Dead Reckoning position estimation algorithm was analyzed.By using the attitude and acceleration information obtained from the MPU-9250 module,position calculation is performed to obtain the three-dimensional displacement of the wrench relative to the initial position for positioning.For feasibility verifying,the hardware and software design of a torque wrench with positioning function has completed in this thesis.The hardware design includes the STM32 minimum system,signal acquisition circuit and positioning circuit,etc.with the properties of low power consumption,strong anti-interference ability and design integrity.The software design of the system mainly includes chip initialization,user interface,torque and angle measurement,communication,etc.The positioning calculation software has been designed and implemented.In order to improve the accuracy of positioning calculation,this thesis applies EKF and UKF respectively to the simulation trajectory filtering processing of torque wrenches,The experimental results show that both methods have good results in processing errors and meet the design requirements of torque wrenches.