Hardware-in-the-loop Simulation For Electrostatic Accelerometer With A Variable Carrier Amplitude Method

High-precision electrostatic accelerometers have been widely used in the fields of space physical environment research,satellite gravity measurement,space gravitational wave detection and so on,which have the characteristics of small range,high accuracy,and full degree of freedom measurement.The related research of high-precision electrostatic accelerometers has become a frontier subject of space science research,which is of great significance to improve the level of space science in China.Hardware-in-the-Loop（HIL）is a test method that uses a simulator to replace some real mechanical components in a closed-loop control system,and evaluates the control system through experiments.Based on the working principle of the accelerometer,this paper proposes a hardware-in-the-loop simulation testing schemes for the electrostatic accele-rometer on the basis of the variable carrier amplitude,which aims to study the perform-ances of electrostatic accelerometer.Different from the common testing schemes for electrostatic accelerometers,this method has the advantages of low cost,rapid repeatability of experiments and simultaneous long-term testing of six degrees of freedom on-orbit control effects.Based on the principle of accelerometer,this paper introduces the components of the sensitive probe,capacitive position sensor unit,and feedback control unit.According to the output of the front-end circuit in the capacitance position sensing unit,a method of sim-ulating the capacitance difference of a real sensitive probe based on the variation of the carrier amplitude is proposed.The six degrees of freedom is arithmeticized to form a hardware-in-the-loop simulation system with the behavior of the sensitive probe.The capacitance difference information in the hardware-in-the-loop simulation system is the same as the output capacitance difference information of the real sensitive probe.According to the above hardware-in-the-loop simulation theoretical scheme,a single-degree-of-freedom double point simulation model is built to verify its feasibility.And then a single-degree-of-freedom electrostatic accelerometer hardware-in-the-loop simulation platform based on the Red Pitaya hardware platform is established.Among them,the vir-tual probe algorithm is designed in the FPGA that is conducive to parallel computing.The algorithm output is transmitted and uploaded to the host computer in real time through the ARM core through the ethernet interface,and the host computer controls the real-time parameter of the algorithm in the FPGA through the UART.After jointing test with the successfully developed capacitance sensing unit and feedback control unit in the group,combining with the output of the virtual probe algorithm module,the virtual inspection quality is stably controlled near the equilibrium position.In addition,the change in capacitance difference after the input of external acceleration is recorded.Finally,a capacitance variation using this hardware-in-the-loop simulation method can be detected about7×10^-5p Fand acceleration variation can be detected about 8.6×10^-8m s²at the m Hz frequency band,which is limited by the precision of the DAC used here.