One of the challenges that satellites face is the interaction between control movement and vibration of flexible appendages such as solar arrays and antennas that can negatively affect the performance of the spacecraft. The aim of this thesis is to develop a numerical model of a solar panel structure for KNATTE, a frictionless platform developed by the Onboard Space Systems group at Luleå University of Technology, and develop a control law that reduces the flexible vibration of the solar arrays when attitude control manoeuvres are performed. A set of solar panel structures have been designed and tested, the mathematical model of the multibody system, which consists of KNATTE and two flexible solar panels, has been developed in MATLAB by applying the finite element method. A finite element analysis has been performed in MATLAB to extract the natural frequencies of the system. The model has been numerically verified using a commercial software, and experimentally verified by performing testing on the frictionless vehicle, KNATTE, equipped with the solar panel structures and a number of piezoelectric sensors. Once the model has been verified, a Linear Quadratic Gaussian (LQG) controller has been developed using the results from the finite element model in order to reduce the amplitude of the vibrations of the flexible solar panel structure. The behaviour of the system has been simulated when the spacecraft performs an attitude manoeuvre. The finite element model provides the modal behaviour of the multibody system, obtaining its natural frequencies with low relative error. The LQG controller reduces the amplitude of the vibrations of the flexible solar panel structure.

The effect of flexible panels on a spacecraft during attitude movement may induce problems if not correctly accounted for in the control system for the spacecraft. The aim of this thesis is to find and evaluate, control algorithms that could be suitable for the Kinesthetic Node and Autonomous Table-Top Emulator (KNATTE) with two flexible mock-up solar panels during an attitude movement of 20 degrees. A simulation model of KNATTE was derived in a previous thesis where a Linear– quadratic–Gaussian (LQG) controller was also found, after a literature review the secondary controller was selected to be a Sliding mode control (SMC) and to accurately simulated the environment of KNATTE the continuous control signal would need to be converted to a pulse due to the thrusters on KNATTE either being on or off. The thesis found that the Pulse-width pulse-frequency (PWPF) modulation is necessary for both controllers to have the best performance as the Pulse-width modulation (PWM) is not able to generate a thrust output that gives a desired result. It is also found that the SMC will provide the shortest settling time for the attitude manoeuvre while also displacing the panels the least amount compared to that of the LQG controller.

The design of an attitude control system for a flexible spacecraft using magnetic actuation is considered. The nonlinear, linear, and modal equations of motion are developed for a general flexible body. Magnetic control is shown to be instantaneously underactuated, and is only controllable in the time-varying sense. A PD-like control scheme is proposed to address the attitude control problem for the linear system. Control gain limitations are shown to exist for the purely magnetic control. A hybrid control scheme is also proposed that relaxes these restrictions by adding a minimum control effort from an alternate three-axis actuation system. Floquet and passivity theory are used to obtain gain selection criteria that ensure a stable closed-loop system, which would aid in the design of a hybrid controller for a flexible spacecraft. The ability of the linearized system to predict the stability of the corresponding nonlinear system is also investigated.

The design of an attitude control system for a flexible spacecraft using magnetic actuation is considered. The nonlinear, linear, and modal equations of motion are developed for a general flexible body. Magnetic control is shown to be instantaneously underactuated, and is only controllable in the time-varying sense. A PD-like control scheme is proposed to address the attitude control problem for the linear system. Control gain limitations are shown to exist for the purely magnetic control. A hybrid control scheme is also proposed that relaxes these restrictions by adding a minimum control effort from an alternate three-axis actuation system. Floquet and passivity theory are used to obtain gain selection criteria that ensure a stable closed-loop system, which would aid in the design of a hybrid controller for a flexible spacecraft. The ability of the linearized system to predict the stability of the corresponding nonlinear system is also investigated.