Junquan Li

Design of attitude control systems for cubesat-class nanosatellite

We present a satellite attitude control system design using low-cost hardware and software for a 1U CubeSat. The attitude control system architecture is a crucial subsystemfor any satellite mission since precise pointing is often required to meet mission objectives. The accuracy and precision requirements are even more challenging for small satellites where limited volume, mass, and power are available for the attitude control system hardware. In this proposed embedded attitude control system design for a 1U CubeSat, pointing is obtained through a two-stage approach involving coarse and fine control modes. Fine control is achieved through the use of three reaction wheels or three magnetorquers and one reaction wheel along the pitch axis. Significant design work has been conducted to realize the proposed architecture. In this paper, we present an overview of the embedded attitude control system design; the verification results fromnumerical simulation studies to demonstrate the performance of a CubeSat-class nanosatellite; and a series of air-bearing verification tests on nanosatellite attitude control systemhardware that compares the performance of the proposed nonlinear controller with a proportional-integral-derivative controller.

Fault Tolerant Attitude Synchronization Control during Formation Flying

It is necessary for precise satellite formations to keep each satellite in accurate relative attitude synchronization and to maintain relative angular velocity synchronization. An adaptive fuzzy terminal sliding mode control is proposed for a formation flying tracking system which includes acquisition, tracking, and pointing. The relative attitude of the leader and follower spacecraft under gravity gradient torque and external periodic disturbances is controlled by four reaction wheels. First, a terminal sliding mode controller is used to obtain stable and fast tracking. Then, the adaptive fuzzy logic system is used to approximate and learn the system uncertainty with the online fault and time-varied external disturbances. The system is proved to be stable, and the parameters are proved to be bounded under the control scheme, using a Lyapunov methodology. Finally, simulation results (under actuator faults like wheel failure and wheel degradation) show that the proposed control method has the advantages of...

Nanosatellite attitude air bearing system using variable structure control

This paper details a novel fault tolerant variable structure control law using sliding mode control which can be used to improve fault tolerance in nanosatellite attitude control systems. A locally asymptotically stable adaptive fuzzy first order sliding mode controller is used to solve the local attitude control tracking problem. Simulation results validate the tracking and fault tolerant performance of the proposed controller in the presence of noise and reaction wheel faults. The controller is also tested with embedded attitude control hardware on a spherical air bearing system and compared with a PID controller and 2nd and 3rd order sliding mode controllers. The proposed controller is more tolerant to faults and uses less energy for attitude control, and has a steady-state error of 0.8 degrees while PID accuracy in the same system is 5 degrees.

Nanosatellite air bearing tests of fault-tolerant sliding-mode attitude control with unscented kalman filter

This paper documents the development and testing of a fault tolerant sliding mode attitude control algorithm for a nanosatellite with reaction wheel control actuation.

Real-Time Nonlinear Attitude Control System for Nanosatellite Applications

This paper develops a fault-tolerant attitude controller for next-generation nanosatellites. The proposed fault-tolerant attitude control algorithms in this study are based on first-order and high-order sliding-mode control theories as well as fuzzy logic systems to achieve low cost and real-time autonomy. A locally asymptotically stable adaptive fuzzy first-order sliding-mode controller is chosen as the best solution to the local attitude control tracking problem. This novel fault-tolerant controller is validated by simulation results with reaction wheel Coulomb friction, saturation, noise, dead zones, bias faults, and external disturbances. Simulation and testing results presented in the paper demonstrate that the attitude control system can provide successful pointing and tracking in the presence of system uncertainties for a specified class of reaction wheel failures.

Study for femto satellites using micro Control Moment Gyroscope

Femto-satellites can be used for distributed space missions that can require hundreds to thousands of satellites for real time, distributed, multi-point networks to accomplish remote sensing and science objectives. While suitable sensors are available using micro-electro-mechanical system technology, most femto-satellite designs have no attitude control capability due to the power and size constraints on attitude control actuators. A novel femto-satellite design that uses a micro-electro-mechanical system Control Moment Gyroscope is studied in this paper. We focus on the principal design, modelling, and discussion of the proposed Control Moment Gyroscope while detailing a controllable femto-satellite design that can make use of attitude control for simple sensing missions.

FPGA hardware nonlinear control design for modular CubeSat attitude control system

CubeSat attitude control systems must be compact, fast, and accurate to achieve success in space missions with stringent control requirements. Nonlinear control strategies allow the creation of robust algorithms for orbit and attitude control, but can have higher processing requirements for effective operation. In addition, It is desirable to distribute components of a CubeSat control system across hardware as much as possible to decrease the load on a central computing unit and to make the system more tolerant to point failures. Field Programmable Gate Array technology has become a popular solution to the limited electronic space and demanding processing requirements present in new-generation CubeSat systems. This paper will focus on demonstrating the feasibility and effectiveness of a proposed nonlinear adaptive fuzzy controller implemented on a Field Programmable Gate Array as part of a highly-integrated space hardware system that is under development.

Real Time Fault Tolerant Nonlinear Attitude Control System for Nanosatellite Applications

This paper develops a fault tolerant attitude controller for next generation nanostatellites.