Geng Yunhai

Fault-tolerant control of linear uncertain systems using H ∞ robust predictive control

Abstract The robust fault-tolerant control problem of linear uncertain systems is studied. It is shown that a solution for this problem can be obtained from a H ∞ robust predictive controller (RMPC) by the method of linear matrix inequality (LMI). This approach has the advantages of both H ∞ control and MPC: the robustness and ability to handle constraints explicitly. The robust closed-loop stability of the linear uncertain system with input and output constraints is proven under an actuator and sensor faults condition. Finally, satisfactory results of simulation experiments verify the validity of this algorithm.

The combined control algorithm for large-angle maneuver of HITSAT-1 small satellite

Abstract The HITSAT-1 is the first small satellite developed by Harbin Institute of Technology (HIT) whose mission objective is to test several pivotal techniques. The large angle maneuver control is one of the pivotal techniques of HITSAT-1 and the instantaneous Eulerian axis control algorithm (IEACA) has been applied. Because of using the reaction wheels and magnetorquer as the control actuators, the combined control algorithm has been adopted during the large-angle maneuver course. The computer simulation based on the MATRIX×6.0 software has finished and the results indicated that the combined control algorithm reduced the reaction wheel speeds obviously, and the IEACA algorithm has the advantages of simplicity and efficiency.

Calibration for star tracker with lens distortion

A new calibration model was proposed in the paper. Compared with traditional measurement models of star tracker containing principal points offset and focal length parameters only, the new model takes lens distortions into account. Lens distortions related mainly indicate radial distortion and tangential distortion. On the basis of the new measurement model, an easy autonomous calibration method, two-step method, based on least-squares method for star trackers is presented. In the first step, principal points, focal length, and attitude angle, were computed with distortion-free model using non-iterative least-square algorithm. In the second step the distortion parameters were estimated and all parameters were optimized by iteratively algorithm. Then synthetic attitude data and star catalog were adopted in the simulation. The results demonstrated that the proposed measurement model was accurate, and the calibration method of star tracker was available.

Staring imaging attitude tracking control of agile small satellite

Attitude tracking control during staring imaging of agile small satellite configured with double-gimbaled control moment gyroscope (DGCMG) is investigated. Firstly, considering the characteristics of agile satellites and the mission requirement of staring imaging, design the actuators configuration. Then, using the orbit information to computer the attitude and attitude angular velocity of staring imaging target relative to the satellite body reference frame, and considering avoidance the singularity of CMG to design control law and steering law. Finally, setup the agile small satellite attitude and orbit control simulation system, the mathematical simulation shows that the solution is simple and effective for staring imaging attitude maneuver control of agile small satellites, and conclude that the minimum angular rate of gimbals of DGCMG is the most important factor to determinate the attitude tracking precision.

Small satellite attitude control based on mechanically-pumped fluid loops

An attitude control system based on mechanically pumped fluid loops is presented in this article, and the controller consisting of “fluid wheels” is investigated. First, the attitude control system is designed based on the principle that fluid of liquid in the closed loops accelerated by mechanical pumps will generate torques on satellite. Then the mathematical model of the controller is built based on the given structure/distribution. Finally, the closed-loop attitude control system with FMC as actuator is set up. The simulation results demonstrate that the design could improve attitude control capacity while decreasing the system volume/mass and complexity.

Spacecraft line-of-sight nonlinear control using two wheels

When an underactuated spacecraft using two wheels has non-zero total angular momentum, it cannot reach an arbitrary stable state unless it meets some constraint conditions. In this paper, with the constraint on pointing direction of the line-of-sight of the spacecraft, we obtain the stable state that the spacecraft can be reached and give a judging criteria. Then, a nonlinear singular controller is presented. This controller can make the line-of-sight move and be stabilized to the desired point, that is, it can minimize the angle between the line-of-sight and the target axis, and satisfy the conservation of system angular momentum as well. This controller is simple in formation, not sensitive to initial conditions of attitude, and can bring the spacecrafts line-of-sight to desired point without any transient oscillations.

Integrated attitude control algorithm and steering law for agile small satellites

This paper investigates the integrated attitude control algorithm and steering law for agile small satellites configured with control moment gyroscope (CMG). Firstly, considering the deterioration over time of the typical pyramid-shaped CMG cluster with 4 single-gimbal CMGs, build the CMG dynamic model. Then, based on the adaptive control theory to design the integrated attitude control algorithm and steering law, and prove the asymptotic stability of the closed-loop system via Lyapunov analysis. Finally, mathematical simulation has validated the solution in a satellite closed-loop attitude control system, and the simulation shows that the solution is simple and effective for attitude maneuver control of agile small satellites.

Problems of Micro-satellite OBC and solving method based on reconfiguration technique

The objective of this work is to solve the problems of On-board Computer (OBC) in Micro-satellite. With the limit of size and weight, and the requirement of multifunction and high-performance, itpsilas almost impossible to design an eligible Micro-satellite OBC by regular methods. To address this issue, this paper researches reconfiguration technique, and proposes one OBC design based on it. The reconfigurable OBC can achieve the multifunction and high processing ability, and there are several measures to ensure the reliability.

STUDYING OF SATELLITE ATTITUDE MANEUVER CONTROL USING REACTION WHEELS

In this research, a brief description is introduced to a small satellite attitude control system. The dynamics and control of the small satellite with flexible appendages were studied for the case of fast multi-axis reorientation using reaction wheels. Two methods are provided to fast reorient the satellite attitude, one is trajectory planning and following, which main idea is planning the maneuver trajectory using optimal theory then following it, another optimal method is named step by step closed, which makes the satellite rotate around simultaneous Euler axis closed to the target direction gradually using the reaction wheels instead of reaction thrusters jet. The methods can ensure the maneuver control process rapidness and stability under the condition of limiting wheels speed and output torque level. The vibration modes can be suppressing when the attitude maneuver is over due to the output torque smoothness using the later method instead of the former. Numerical simulation results are presented to show the theoretical and practical merit of this control approach.