Research On Micro-Newton Thrust Measurement Technology

In recent years,as an upsurge of international research of micro-satellite was set off with the development of space science and technology,people have shown an increasing interest in research on kinds of micro-propellers,such as cold gas thrusters,microresistojet thrusters,electrospray micro-thrusters and micro-pulsed plasma thrusters.Moreover,research on thrust measurement techniques for testing the performance of micro-propellers is gaining in depth.In this thesis,a complete experimental platform of micro-thrust measurement based on the micro-thrust measurement technology has been designed and built independently,which mainly includes four parts: standard weak force generation and calibration device,torsion scale Horizontal twisting device,angular displacement measuring device and thrust compensation device.In the designed micro-negative thrust measurement system,the standard weak force generation and calibration device provides accurate electromagnetic calibration force for the measurement system.The other three parts compose of a closed loop system,in which the position signal of the balance bracket in the horizontal torsion device is fed back to the PID control circuit in the thrust compensation device by the PSD detector in the angular displacement measuring device.And then the movement state of the balance bracket is controlled,so that the electromagnetic generation device generates electromagnetic force to compensate the thrust generated by the micro-thruster.The current is finally measured to calculate the thrust generated by the thruster,thus the thrust measurement work is done there.The combination of C-type magnet and PCB coil for electromagnetic generating device provides a calibration range of 5.2?N~5.78 mN,whose corresponding coil current varies from 0.1 to 100 mA,and linear fit correlation coefficient between force and current is 0.9999.Besides,the output current of the developed PID controller ranges from-107.2mA to 107.8mA,in which the minimum compensation residual generated by the system is ±0.37?N,and the maximum compensation residual is ±0.52?N.Furthermore,the developed micro-thrust measurement system could measure designed in this thesis ranges from 0.05?N~5.78 mN,where the measurement sensitivity and thrust resolution are 57.8?N/mA and 0.05?N,respectively.When the measured thrust is 76.6?N,118.62?N,592.71?N and 1054.20?N,the corresponding relative error is 0.8%,3.18%,3.70% and 4.27%,respectively.The VAT average thrust measurement system,the measurement results are as follows: the average thrust generated at 10 Hz,20Hz,30 Hz,40Hz and 50 Hz is 112.1?N,216.3?N,332.6?N,463.6?N and 574.9?N,respectively.The corresponding impulses bit are 11.21?N?s/c,10.85?N?s/c,11.08?N?s/c,11.59?N?s/c and 11.50?N?s/c,respectively.In addition,this thesis also proposes solutions and research plans to reduce the effects of the change of relative position between coil and magnet and the self-weight change of propeller on measured results,which lays a foundation for the subsequent experimental work.