Changqing Wang

Bio: Changqing Wang is an academic researcher from Northwestern Polytechnical University. The author has contributed to research in topics: Spacecraft & Sliding mode control. The author has an hindex of 10, co-authored 33 publications receiving 277 citations.

Rotation matrix based finite-time attitude synchronization control for spacecraft with external disturbances.

Abstract: This paper investigates the anti-unwinding finite-time attitude synchronization control problem for Spacecraft formation flying with external disturbances. Two finite-time controllers are designed based on rotation matrix and terminal sliding mode method. By designing a novel sliding mode surface, the first controller is developed when the upper bound of the external disturbances can be exactly known. However, this value is not always available in reality. In addition, the direct use of the upper bound of the external disturbances can result in the chattering problem. For the purpose of overcoming the disadvantage of the first controller, a modified control law is proposed, in which the adaptive law is applied to estimate the unknown value online. Theoretical analysis and numerical simulations are presented to demonstrate the validity of the proposed controllers.

Globally stabilizing saturated attitude control in the presence of bounded unknown disturbances

Abstract: A smooth attitude-stabilizing control law is derived from which known limits on the control authority of the system are rigorously enforced. Unknown disturbance torques, assumed to be of lesser magnitude than the control limits, are included in the formulation. A smooth control signal containing hyperbolic tangent functions that rigorously obeys a known maximum-torque constraint is introduced. The controller can be viewed as a smooth analog of the variable-structure approach, with the degree of sharpness of the control permitted to vary with time according to a set of user-defined parameters. Lyapunov analysis is employed to ensure global stability, and asymptotic convergence of the angular velocity is guaranteed via the Barbalat lemma. Attitude errors, expressed as Euler parameters, are shown via simulation to vanish whenever certain design parameters are selected appropriately, and guidelines for selection of those parameters are provided in depth.

Fractional-Order Fuzzy Sliding Mode Control for the Deployment of Tethered Satellite System Under Input Saturation

Abstract: In this paper, a novel fractional-order fuzzy sliding mode control strategy is developed to realize the deployment of the tethered satellite system (TSS) with input saturation. The considered TSS is modeled as an underactuated system. By decoupling the underactuated system into two subsystems, a fractional-order and a constrained integer-order sliding surfaces are designed for the actuated and unactuated subsystems, respectively. Then, a new hybrid sliding manifold is obtained by coupling the two subsliding surfaces. Adaptive fuzzy algorithm is used to regulate the coupling coefficient in the newly proposed hybrid sliding manifold in order to procure satisfactory performance. Meanwhile, the saturation nonlinearity of control input is also considered. The asymptotic stability of the closed-loop system is demonstrated theoretically. With the existence of fractional order, the presented controller can perform faster and more smooth tether deployment when compared with conventional ones. Finally, the effectiveness and superiority of the proposed control approach are validated by illustrative simulations.