Study Of Torsion Balance Mirco-thrust Measurement Device

One of the core technologies in the measurement of earth gravitational field is the design and application of Field Emission Electric Propulsion and platform. Both of them provide the technical support for the attitude control and no drag flight of the satellite in space. With the rapid development of space science, there are more and more space task requirements, making greater demands on FEEP. The measuring device of micro-thrust could measure the thrust accurately, not only the pulse impulse, but also the thrust value, reflecting the performance of the thruster. The measurement device plays a crucial role in the research and development of thruster.This article builds upon the study of microgravity laboratory in Chinese Academy of Sciences on torsion balance, researching a device of micro-thrust measurement. The measurement range of torsion balance is from 30μN to 30mN, torsional period of 2.1s, sensitivity of 6μrad/μN·m, resolving ability of 30μN, meeting the demands of the measurement.In order to ensure the torsion balance meeting the technical indicators, the structure of double wires is used to make sure that torsion balance could moving with the way of twisting when acted by the force. In this way, angular displacement could be measured by the sensor so that to decrease the error caused by pendulum. Torsion balance system could measure the thrust from μN to mN range. Two-step calibration methods are showed in the article, weak thrust and angular displacement, calibrating to all the parts of the system. At last, we get the mathematical relationship between thrust and angular displacement, analyzing the relative error with the theoretical value. On the base of many experiments, the effect of property and environment are found, including the single and double wire, effect of vacuum pump, comparison between single censor and differential measurement, magnetic damping system and so on. By analyzing the spectrum, torsional frequency and swing frequency are validated, comparing with the theoretical value, reducing errors. Through the above analysis, physical design and error-control, all the technical indicators of the torsion balance meet the requirements, completing the research task.The results prove that torsion balance measurement system is not only influenced by the vacuum degree, vibration and noise, but also by the processing requirement and assembly accuracy. Finally, according to the experimental results, put forward constructing opinions on the design improvement of torsion balance system and improving the measurement accuracy.