Investigation of Charge Control Methods for Disturbances and Parameter Uncertainty in Inertial Sensor Charge Management System

Space inertial sensors are essential for Earth geodesy missions, gravitational wave observations, and fundamental physics experiments in space. A charge management system (CMS) is crucial for charge control in these missions, where the environment is fraught with uncertainties and disturbances. This article presents, for the first time, the application of sliding mode control (SMC) in a CMS to address the parameter uncertainty and variability issues of inertial sensors. First, a physics-based model of the discharging process for a CMS is proposed, characterized by high charging and/discharging rates, based on the geometry of inertial sensors. A disturbance observer-based SMC (DOSMC) approach is then proposed and designed for the CMS, addressing parametric uncertainties and unknown disturbances to maintain the test mass (TM) charge below a specified level and enhance robustness. Simulation results demonstrate that the DOSMC forces the system trajectory to align with the sliding surface, independent of parameters or disturbances. In this way, the DOSMC can effectively mitigate parameter perturbations and external disturbances. The control precision reaches 0.1 mV, outperforming both classical proportional-integral-derivative (PID) controllers and conventional SMC. It provides a robust method for controlling the TM potential of CMSs under parametric uncertainties and unmodelled perturbations, making it applicable to the development of CMSs for various space gravitational missions.