The Design Of Load Characteristic Calibration System For Spring Torsion Bars

As a key structure in mechanical load simulator,spring torsion bar is always lacking a calibration system to evaluate the effective static and dynamic performance of spring torsion bar,which limits the improvement of loading accuracy of mechanical load simulator to a great extent.Based on this background,a calibration system for the load characteristics of torsion bar is designed in this paper,and the calibration experiments under static and dynamic conditions are analyzed.In this paper,the mechanical properties and modal analysis of torsion bar spring,combined with static and dynamic performance indexes to determine the overall calibration scheme.At the same time,on the basis of the establishment of the spring torsion bar loading mechanism model,according to the design requirements such as Angle limit and installation,the mechanical loading structure was designed,and realized the functions of tight clamping,length adjustment and protection limit of the spring torsion bar in the calibration process.According to the overall architecture of the calibration system,the selection and coordination of the hardware of the upper computer controller,loading system,sensor and data acquisition device were carried out.The data acquisition software system was developed based on Lab Windows/CVI,which realized the real-time acquisition and preservation of Angle and torque signals in the calibration process.As the loading control system is nonlinear coupling system,the mathematical models of servo motor and servo system are established and the parameters are identified,and the effective transfer function of the loading control system is obtained.Combined with PID control algorithm,the Angle loading under static calibration is realized.Meanwhile,in order to improve the control effect,the particle swarm optimization algorithm is used to optimize the control parameters,which improves the accuracy and rapidity of the system loading Angle under static calibration.By static calibration experiment,linearity,sensitivity,hysteresis and repeatability of the spring torsion bar are 2.48%,50.1 m N?m/~?,3.77%and 1.24%respectively.In position control mode,frequency response method and step response method are designed to realize dynamic calibration.Under the frequency response method,frequency loading with Angle amplitude of?2~?is carried out on the torsion bar of spring.By analyzing the amplitude-frequency characteristic curve,it is found that the working frequency band of the torsion bar of spring is 0 Hz-0.8 Hz,and there is no resonance phenomenon.In order to solve the problem of deviation between the input signal and the ideal signal in step response method,the non-standard step signal is studied and analyzed mathematically,and the output response of spring torsion bar under step Angle input from 1~?to 4~?is simulated.The step calibration experiment verifies that the rise time and adjustment time of the response curve of the spring torsion bar are basically consistent with the simulation results.The spring torsion bar can respond quickly to the step Angle signal with good rapidity and stability.The above results show that the calibration system designed in this paper can carry out effective static and dynamic calibration work on the spring torsion bar,and the system meets the design requirements.