| After the task of CE-3 has been done successfully, Chinese lunar exploration project accesses to the third stage of "Around, Left, Back to the Earth" three steps, namely the sample returns. The vacuum plume occurs as the returner emits from the month surface. Plume hits the surface of spacecraft and the disturbing force/moment affects spacecraft attitude control. The validation tests of full-scale plume and diversion for goddess Chang-e vehicle are taken comprehensively in Beijing Aerospace Institute of Test and Technique. Based on the piezoelectric effect, the plume force/torque measurement system (PFTMS) has been used for the first time in this test. Six dimensional force (SDF) can be measured during the plume experiments. On-line calibration of PFTMS is to ensure the accuracy and reliability of experimental measurement data, which is of momentous significance for improving accuracy of plume force's thermal effect analysis and the spacecraft attitude control.This paper mainly researches on on-line calibration of force/torque measurement system. For the difficulty of online calibration, remote loading and limited space, the PFTMS on-line calibration is in-depth analysis researchedfrom the calibration method, the theoretical analysis and experimental research and so on. The design scheme is put forward, and PFTMS is developed.Firstly, the composition of PFTMS and six dimensional piezoelectric force sensor measurement principles are introduced. Online calibration requirements and difficulties are analyzed based on the analysis of the PFTMS structure. Set up six dimensional force online calibration load model and mechanics model, state in detail theory output of the sensor when six dimensional force calibration.Secondly, this paper is in view of the vertical structure of PFTMS. Calibration system as core with hydraulic pressure source coordinated by standard force sensor is designed. Calibration system can operate remotely, update on line and adjust real-time.Load axial force with using force source in the upper, pull rod in the calibration plan. Lateral force calibration device adopts four force source loader orthogonal layout. The hydraulic cylinder can move in the vertical plane and horizontal plane with guide rail slider mechanism and guide column screw mechanism.Force and torque are calibrated by changing the loading point location. Analysis of hydraulic load pressure, sealing structure design, guarantee the sealing performance of hydraulic system, design of hydraulic control mode, power source stability load requirements.Respectively from the parts size accuracy, system stiffness and load point error, interference caused by the load deviation is analyzed due to the online calibration platform. Using online calibration platform of piezoelectric sensor and the whole test system for static calibration, through comparing with the laboratory calibration, verifying online calibration accuracy and reliability.The results show that the on-line calibration and calibration laboratory its linearity, repeatability are within 1.5%, satisfying the requirement of measurement system technology. Online calibration platform has good loading precision. Online and laboratory calibration slope near linear fitting line is consistent, the components in the better consistency with the laboratory calibration, online calibration system is stable and reliable. Through experimental research on lateral force loading point role of three-way force output. Experiments show that the lateral force loading points have little effect on the 3-axis resultant force, realizing requirements of plume force/torque accurate measurement. |
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