Research On The Thermal Control Technique Of Ground Weak Force Measurement System With Inertial Sensor

Gravitational wave detection is one of the most advanced and important research subjects in the current field of basic science,which is of great significance to the development of astronomy and physics.Space inertial sensor is the core load of gravitational wave detection spacecraft.The ground weak force measurement system of inertial sensor is an important platform for ground testing and evaluation of high precision inertial sensor,which plays an important role in performance testing and optimization design of inertial sensor.The fluctuation of temperature level and temperature difference can affect the detection sensitivity of inertial sensor in many ways.In order to meet the temperature stability requirements of inertial sensor ground weak force measurement system,it is necessary to conduct in-depth research on the thermal control technology of inertial sensor ground weak force measurement systems.Firstly,this thesis briefly describes the thermal environment in which the inertial sensor ground weak force measurement system is located and the structure layout of the ground weak force measurement system,establishes the thermal balance equation of the ground weak force measurement system,analyzes the process of conduction and radiation heat transfer between the components of the weak force measurement system in the vacuum chamber,and calculates the convective heat transfer coefficient between the surface of the passive thermal control structure and the environment in detail.It lays a foundation for thermal design and simulation analysis.Secondly,according to the thermal balance equation and thermal control strategy of the ground weak force measurement system,10 thermal design parameters affecting the temperature stability of the inertial sensor sensitive structure were selected.The Morris screening method based on finite element simulation was used to analyze the local sensitivity of the thermal design parameters,and the sensitivity values of each parameter were obtained.By comparing the sensitivity analysis results of thermal design parameters with the same dimension,it was determined that the thermal design parameters that have a great influence on the temperature stability of the inertial sensor sensitive structure mainly include:the emissivity of the outer surface of the thermal insulation layer,the convective heat transfer coefficient of the inner surface of the thermal insulation layer,the contact thermal resistance between the vacuum chamber and the laboratory floor,and the thermal conductivity of the thermal insulation material.In the process of thermal design,the selection of the above thermal design parameters should be considered emphatically.Then,based on the thermal environment analysis results of the inertial sensor ground weak force measurement system and the local sensitivity analysis results of the thermal design parameters,a thermal design scheme based on the combination of three-stage passive thermal control structure and PID active thermal control algorithm was proposed,and the thermal control measures of each part of the ground weak force measurement system were designed in detail.At the same time,the mathematical model of the controlled object was established,the step response method was used for system identification,the transfer function of the controlled object was obtained,and the Matlab simulation software was used for discrete control simulation analysis to determine the reasonable PID control parameters of the active thermal control system.In order to verify the feasibility and rationality of the internal heat source water-cooled heat dissipation scheme,a water-cooled heat dissipation capability verification test was conducted.The test results show that the water-cooled system can meet the heat dissipation requirements of the internal heat source.The maximum temperature fluctuation value of the simulated internal heat source is 0.108K,which can achieve the temperature control index of the internal heat source temperature fluctuation less than±0.1K.Finally,according to the characteristics of the thermal environment of the ground laboratory,three thermal analysis conditions were defined:high-temperature condition,low-temperature condition and high-temperature without active thermal control condition.The finite element simulation analysis model of the ground weak force measurement system was established by using thermal analysis software,and the temperature field distribution of the ground weak force measurement system under various working conditions is calculated.The thermal simulation results show that the maximum temperature fluctuation value of the electrode housing of the primary torsion balance after transient analysis equilibrium is（1.0-1.6）×10^-5K in both high and low temperature conditions.The temperature curve of the electrode housing of the primary torsion balance is expressed in frequency domain.In the measurement frequency band of 0.1m Hz-1Hz,the temperature stability of the electrode housing of the primary torsion balance is better than 10^-4K/Hz^1/2.The thermal control system can meet the temperature control requirements of ground weak force measurement system of inertial sensor,and the thremal design scheme is reasonable and feasible.