Weiming Liu

To further improve the safety and reliability of multi-mobile robot systems, this paper investigates the formation control problem with considerations of collision avoidance, communication maintenance and robots’ actuator bias faults. A novel modular formation control scheme, which consists of two modules, is established. In Module I, a formation signal generator is constructed based on graph theory, acting as a virtual multi-agent system through a network of double-integrator dynamic nodes. The outputs of the virtual multi-agent system (i.e., the generator) are designed to asymptotically form the desired formation shape while satisfying some designed specific constraints. Then, in Module II, extended-state observers (ESOs) are firstly employed to estimate and compensate for the actuator bias faults. After embedding the corresponding node within each robot and taking its outputs as formation references, some constrained ESO-based tracking controllers are designed based on back-stepping method. In general, the proposed modular formation control integrates collision avoidance, connectivity maintenance and fault-tolerant functions, while realizing the desired formation shape with bounded convergence of formation errors. Simulations and experiments demonstrate the effectiveness of the proposed modular formation control scheme.

In this paper, the attitude tracking control problem is investigated for flexible spacecraft. A novel feedforward-feedback composite control scheme is proposed based on the combination of a generalized proportional integral observer (GPIO) and the full-order sliding-mode control technique. To estimate the lumped disturbances composed of the flexible appendages’ vibration, external environmental disturbance and model uncertainty, a generalized proportional integral observer is firstly constructed. Then, a two-layer recursive full-order sliding-mode surface is developed, where the inner layer is designed as linear sliding-mode surface and the outer layer is designed as a terminal sliding-mode surface. With the feedforward compensation of the GPIO’s estimates, a continuous unwinding-free composite attitude tracking controller is derived to achieve the finite-time arrival of the full-order sliding-mode surface and further ensure the asymptotic set convergence of the attitude tracking errors. Rigorous set stability analysis of the closed-loop attitude tracking error system is given. Comparative simulations are presented to demonstrate the effectiveness and superiority of the proposed composite control scheme.

The formation control problem for leader–follower wheeled mobile robots (WMRs) is investigated in this article. A formation control strategy is proposed based on the embedded control technique. Different from the conventional design philosophy of designing the formation controller based on the formation tracking errors directly, the proposed strategy decomposes the formation control task into two subtasks. One is the virtual signal generator (i.e., virtual follower) design, and the other is the trajectory tracking controller design. The virtual signal generator is devised to act as a virtual follower such that it “achieves” the desired formation control goal, whose output is taken as the reference trajectory for the follower. To solve the subtask of trajectory tracking controller design, an unconstrained controller and a constrained controller with saturated velocities are designed, respectively. A rigorous stability analysis of the closed-loop system is given under these two kinds of controllers. Comparative simulations and experiments among the unconstrained controller with higher gains/lower gains and the constrained controller are given to illustrate the feasibility and effectiveness of the proposed formation control strategy.

Due to the wind farm 35kV system single-phase grounding fault capacitance current is relatively large, Therefore, the wind farm 35kV system adopts the bus configuration Z-type grounding transformer and the neutral point is grounded by small resistance, Zero sequence protection are used to quickly remove the single phase ground fault.In this paper, the single-phase ground fault of wind power plant collection wire in Eastern Inner Mongoliais is taken as an example. introduces the working principle of zero sequence current transformer,Clarify the setting and matching principles of zero sequence protection,,Comparing the different wiring modes of several cable shielding layers will be cause how Influence on the secondary measurement current of zero-sequence transformer, Analyze the zero sequence protection rejection of the set wire,The cause of the grounding tripping event. Summarizes the cable shield connection mode correctly,And propose rectification measures on site.