Exponential Attitude Tracking and Vibration Control for 3-D Flexible Spacecraft With Disturbances and Quantized Inputs

This study addresses the problem of attitude tracking and vibration suppression for 3D flexible spacecraft subject to external disturbances and input quantization, which are two critical factors that can significantly degrade control performance in harsh space environments with limited communication capacity. Using Hamilton’s principle, the spacecraft is modeled by coupled ordinary and partial differential equations to accurately characterize its infinite-dimensional dynamics. Nonlinear observers are constructed to exactly estimate unknown boundary disturbances. To deal with the difficulty caused by quantization, a linear time-varying model is introduced to describe hysteretic quantizers, and adaptive laws incorporating exponential functions are developed to estimate resulting unknown terms. Furthermore, a novel disturbance observer-based adaptive quantized control scheme is proposed, which guarantees the boundedness of all closed-loop signals and ensures that both attitude tracking errors and vibrations converge exponentially to zero, whereas existing methods typically achieve only convergence to small residual sets due to quantization effects or disturbances. In particular, the proposed scheme allows the quantizer parameters to be freely adjusted during operation for balancing communication burden and tracking performance. Simulation results show that, compared to traditional PD control, the proposed scheme exhibits faster convergence in attitude tracking and vibration elimination, and achieves higher control accuracy under unknown disturbances and changeable quantizer parameters. Note to Practitioners—This study presents a novel disturbance observer-based quantized control approach to address attitude tracking and vibration control for 3D flexible spacecraft in the presence of external disturbances and input signal quantization. The designed disturbance observers accurately compensate for a large class of disturbances, while the adaptive control scheme allows real-time adjustment of quantizer parameters, offering operational flexibility. By incorporating exponential functions, the controller achieves precise exponential tracking performance and ensures that undesired vibrations are exponentially suppressed to zero. For practical implementation, the proposed scheme is suitable for 3D spacecraft with flexible solar panels and other flexible systems which can be regarded as a rotating Euler-Bernoulli beam in 3D space. Future work will focus on addressing the vibration control problem while tracking time-varying desired attitude signals, with consideration of communication time delays.