WRIST FORCE SENSOR'S DYNAMIC PERFORMANCE CALIBRATION BASED ON NEGATIVE STEP RESPONSE

Negative step response experimental method is used in wrist force sensor＇s dynamic performance calibration. The exciting manner of negative step response method is the same as wrist force sensor＇s load in working. This experimental method needn＇t special experiment equipments. Experiment＇s dynamic repeatability is good. So wrist force sensor＇s dynamic performance is suitable to be calibrated by negative step response method. A new correlation wavelet transfer method is studied. By wavelet transfer method, the signal is decomposed into two dimensional spaces of time-frequency. So the problem of negative step exciting energy concentrating in the low frequency band is solved. Correlation wavelet transfer doesn＇t require that wavelet primary function be orthogonal and needn＇t wavelet reconstruction. So analyzing efficiency is high. An experimental bench is designed and manufactured to load the wrist force sensor orthogonal excitation force/moment. A piezoelectric force sensor is used to setup soft trigger and calculate the value of negative step excitation. A wrist force sensor is calibrated. The pulse response function is calculated after negative step excitation and step response have been transformed to positive step excitation and step response. The pulse response function is transferred to frequency response function. The wrist force sensor＇s dynamic characteristics are identified by the frequency response function.

Numerical simulation and a hybrid method of supersonic turbulent base heating

Detached eddy simulation(DES)model was used to better capture large vortex structure and unsteady flow feature near cone base.Good base heating results were achieved using proper grid and numerical method.The influence of inflow conditions(like Mach number,Reynolds number)and configuration(bluntness ratio of the cone)on base heating was discussed based on numerical computational results.Compared with base heat flux,base pressure can be predicted more accurately by numerical simulation and the time consuming was shorter.A hybrid method combining numerical simulation with experimental correlation was proposed to predict supersonic turbulent base heating.A review of base heating experiment and correlations for slender cone was presented,and a revised correlation was proposed based on the above simulation results.Compared with the experiment data,the maximum error was 24%,agood result for base heating prediction.This proves that the hybrid method using the revised correlation performs well in predicting supersonic turbulent base heating of slender sphere cone and can meet needs of engineering design.