Yunhai Geng

A Novel Approach for Satellite Attitude Reconfigurable Fault-tolerant Control

This paper investigates the reconfiguration fault-tolerant control method of the on-orbit satellite attitude control system with recovered faults. A novel integrated approach is proposed includes a control effectiveness factor and a reconfigurable fault-tolerant controller. A two-stage Kalman filtering algorithm is developed to estimate the size of control effectiveness factor in the closed-loop attitude control system. From the size of control effectiveness factor, a statistical hypothesis tests is developed to replace the fault detection and diagnosis (FDD) frame to diagnose whether there is some fault happened. Then, a reconfiguration fault-tolerant controller is utilized to compensate the primary controller by using the size of control effectiveness factor if some fault has happened. Finally, simulation is carried out and the results indicate the validation and effectiveness of the proposed solution.

Modified super twisting controller for servicing to uncontrolled spacecraft

A relative position and attitude coupled sliding mode controller is proposed by combining the standard super twisting (ST) control and basic linear algorithm for autonomous rendezvous and docking. It is schemed for on-orbit servicing to a tumbling noncooperative target spacecraft subjected to external disturbances. A coupled dynamic model is established including both kinematical and dynamic coupled effect of relative rotation on relative translation, which illustrates the relative movement between the docking port located in target spacecraft and another in service spacecraft. The modified super twisting (MST) control algorithm containing linear compensation items is schemed to manipulate the relative position and attitude synchronously. The correction provides more robustness and convergence velocity for dealing with linearly growing perturbations than the ST control algorithm. Moreover, the stability characteristic of closed-loop system is analyzed by Lyapunov method. Numerical simulations are adopted to verify the analysis with the comparison between MST and ST control algorithms. Simulation results demonstrate that the proposed MST controller is characterized by high precision, strong robustness and fast convergence velocity to attenuate the linearly increasing perturbations.

Integrated fault detection and fault-tolerant based on sliding mode observer

The problem of integrated fault diagnostic and fault-tolerant control for uncertainty linear system is developed. Focusing on the actuator and sensor faults of satellite, we presents a fault diagnosis method based on sliding mode observer. And considering the uncertainties of diagnosis results, we also design a H∞ state-feedback controller to achieve the fault-tolerance by solving a linear matrix inequality (LMI). At last, the simulation for a satellite attitude control system with actuator and sensor faults is carried out and the results validate the effectivity of this algorithm.

An on-orbit calibration system for satellite attitude control

To ensure the long-term on-orbit working precision of attitude sensors, a new approach for the high-precision three-axis stabilized satellite with the typical inertial/stellar measurement mode is presented. This approach employs a real-time on-orbit calibration system to estimate the measurement error of gyro by star sensor. The calibration system is achieved by using a second-order nonlinear filter in a closed-loop satellite attitude control system. Considering the error sources during the attitude measurement, a model of gyros misalignment, scale factor error and drift is constructed to compensate the corresponding errors. Comparing with the attitude control system without on-orbit calibration, this approach provides more attitude measurement information for satellite attitude determination and correction. The computation quantity is small and response time is short. Simulation results indicate that the real-time on-orbit calibration system is extremely effective in improving the attitude pointing accuracy and stabilization

Microspacecraft general cell research

This paper introduces our research that is to conceive and design a micro-platform of spacecraft that we call general cell (GC). The cell is an enabling technology of microspacecraft, and fully adapts to the rapidly developing demands of distributed spacecraft system (DSS). This paper gives detail depictions of characteristics of GC at system level, and a logically hierarchical architecture of DSS is proposed by discussing an improved leader election algorithm briefly. Up to now, a prototype used to demonstrate the cell is preliminarily designed, which comprises information processing unit (IPU) and sensors and actuators units (SAU). IPU, which integrates on-board computer (OBC), attitude control system (ACS), IO subsystem, and telemetry and telecommand subsystem together, is 200 mm times 28 mm times 138 mm, and its dry mass is 640 g. SAU is built with hardware-in-the-loop simulation by dSPACE real-time simulation platform. The two sets of GC have implemented autonomous attitude control and simple formation flying