Yanchao Sun

Bio: Yanchao Sun is an academic researcher from Harbin Institute of Technology. The author has contributed to research in topics: Lyapunov function & Adaptive control. The author has an hindex of 7, co-authored 38 publications receiving 193 citations. Previous affiliations of Yanchao Sun include Harbin Engineering University.

Observer-based prescribed performance attitude control for flexible spacecraft with actuator saturation.

Abstract: This paper investigates the prescribed performance attitude control problem for flexible spacecraft subject to external disturbances and actuator constraints. By using a new performance function and an error transformation, the attitude control system is transformed into an error system which will be kept bounded to ensure expected dynamic and steady-state responses. Compared with the commonly used performance function, the modified one has an explicit prespecified terminal time which determines the maximum convergence time of the attitude control system. A modal observer and a disturbance observer are designed to deal with the flexible vibration and disturbances, respectively. Furthermore, when considering actuator saturation, an improved control strategy is developed with an auxiliary system utilized to compensate the saturation. The stability of the closed-loop system is analyzed by Lyapunov theory. Simulation results show the effectiveness and performance of the proposed methods.

Prescribed performance adaptive attitude tracking control for flexible spacecraft with active vibration suppression

Abstract: This paper investigates the high-performance attitude control and active vibration suppression problem for flexible spacecraft in the presence of external disturbances. The active vibration control usually depends on additional sensors and actuators, which will highly increase the difficulty of practical application. In order to reduce the implementation complexity, the piezoelectric sensors are not adopted, but instead a modal observer is introduced to estimate the modal information. Based on the observed modal information and the prescribed performance design process, an adaptive attitude controller is developed, which has the capabilities of rejecting disturbances as well as possessing predetermined transient and steady-state control performance. Similarly, an active controller is constructed to deal with the vibrations induced by attitude motions. It can be proved that by constraining the estimations of the modal variables, the actual modal coordinate will also be constrained with expected attenuation characteristics. The stability of the entire closed-loop system is analyzed by the Lyapunov theory. Simulation results in different cases show the effectiveness and performance of the proposed algorithms.

Distributed coordinated attitude tracking control for spacecraft formation with communication delays.

Abstract: This paper investigates the distributed coordinated attitude tracking control problem for spacecraft formation with time-varying communication delays under the condition that the dynamic leader spacecraft is a neighbor of only a subset of follower spacecrafts. We consider two cases for the leader spacecraft: i) the attitude derivative is constant, and ii) the attitude derivative is time-varying. In the first case, a distributed estimator is proposed for each follower spacecraft by using its neighbors’ information with communication delays. In the second case, to express the dynamic leader’s attitude, an improved distributed observer is developed to estimate the leader’s information. Based on the estimated values, adaptive coordinated attitude tracking control laws are designed to compensate for parametric uncertainties and unknown disturbances. By employing the Lyapunov–Krasovskii functional approach, the attitude tracking errors and estimation errors are proven to converge to zero asymptotically. Numerical simulations are presented to illustrate the effectiveness of theoretical results.

Distributed finite-time configuration containment control for satellite formation:

Abstract: This paper investigates the distributed finite-time configuration containment control problem for satellite formation with multiple leader satellites under directed communication topology. We consider that only a portion of follower satellites can receive leaders’ information and unknown perturbations and model uncertainties exist in the dynamics models of satellites. By defining the relative configuration error functions and selecting suitable nonsingular terminal sliding mode variables, a fully distributed finite-time configuration containment control scheme is proposed using the matrix properties of graph theory. The Lyapunov method is used to demonstrate the finite-time convergence property of the closed-loop systems. Numerical examples and comparisons with other methods are provided to show the effectiveness and the performance of the proposed control strategy.

Distributed finite-time coordinated control for multi-robot systems:

Abstract: In this paper, we study the finite-time coordinated control problems under directed topologies for multi-robot systems with general disturbances. The dynamics model of each robot is described by a ...

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.

Finite-Time $\mathcal{L}_{2}$ Leader–Follower Consensus of Networked Euler–Lagrange Systems With External Disturbances

Abstract: This paper is concerned with finite-time $ {\mathcal {L}_{2}}$ leader–follower consensus of networked Euler–Lagrange systems in the presence of external disturbances. A distributed finite-time $ {\mathcal {L}_{2}}$ control protocol is proposed by using backstepping design such that a group of follower agents modeled by Euler–Lagrange systems can follow a desired leader agent and achieve leader-follower consensus in finite time. Moreover, the finite-time $ {\mathcal {L}_{2}}$ gain is less than or equal to a prescribed value. A simulation example of a network composed of seven two-link manipulators is given to show the effectiveness of the theoretical results.

Robust fixed-time attitude stabilization control of flexible spacecraft with actuator uncertainty

Abstract: A robust fixed-time control framework is presented to stabilize flexible spacecraft’s attitude system with external disturbance, uncertain parameters of inertia, and actuator uncertainty. As a stepping stone, a nonlinear system having faster fixed-time convergence property is preliminarily proposed by introducing a time-varying gain into the conventional fixed-time stability method. This gain improves the convergence rate. Then, a fixed-time observer is proposed to estimate the uncertain torque induced by disturbance, uncertain parameters of inertia, and actuator uncertainty. Fixed-time stability is ensured for the estimation error. Using this estimated knowledge and the full-states’ measurements, a nonsingular terminal sliding controller is finally synthesized. This is achieved via a nonsingular and faster terminal sliding surface with faster convergence rate. The closed-loop attitude stabilization system is proved to be fixed-time stable with the convergence time independent of initial states. The attitude stabilization performance is robust to disturbance and uncertainties in inertia and actuators. Simulation results are also shown to validate the attitude stabilization performance of this control approach.