ADRC based control for a class of input time delay systems

This paper is concerned with the control design and the theoretical analysis for a class of input time-delay systems with stable, critical stable or unstable poles. In order to overcome the time delay, a novel feed-forward compensation active disturbance rejection control(FFC-ADRC) approach is proposed. It combines advantages of the Smith predictor and the traditional active disturbance rejection control(ADRC). The tracking differentiator(TD) is designed to predict the control signal, which adds an anticipatory control to the control signal and allows a higher observer bandwidth to obtain better disturbance rejection. The modified extended state observer(ESO) is designed to estimate both system states and the total disturbances(internal disturbance, uncertainties and delayed disturbance). Then the Lyapunov theory and the theory of the input-output stability are applied to prove the asymptotic stability of the closed-loop control system. Finally, numerical simulations show the effectiveness and practicality of the proposed design.

Consensus algorithm for multiple quadrotor systems under fixed and switching topologies

The distributed leadless consensus problem for multiple quadrotor systems under fixed and switching topologies is investigated. The objective is to design protocols achieving consensus for networked quadrotors＇ positions and attitudes. Because the model of a quadrotor is a strong high-order nonlinear coupling system, the approach of feedback linearization is employed to transform the model into a group of four linear subsystems among which there is no coupling. Then, a consensus algorithm is proposed which consists of a local feedback controller and interactions from the finite neighbors under fixed undirected topologies. Especially, the problem of choosing the parameters in the consensus algo-rithm is also addressed, enlightened by the results of the robust control theory. Furthermore, it is proved that the proposed algo-rithm also guarantees the consensus under undirected switching topologies. Simulation results show the effectiveness of the pro- posed algorithm.

A parameter optimization approach to robust PI-controller design for systems with interval plants

The purpose of this paper is to develop an analytic way for designing optimal PI-controllers for the interval plant family. Optimality means that the coefficient intervals of the plant stabilized by a PI-controller is maximized. It will be shown that the optimization problem can be formulated in terms of an eigenvalue minimization problem of matrix pairs of the form （H（h0, g0）, H（δ1,k, δ2,k））, where k= 1, 2, 3, 4 and both H（h0, g0） and H（δ1,k,δ2,k） are frequency independent Hurwitz-like matrices. A numerical example is provided to illustrate that optimal controller parameters can be successfully obtained by a two-dimensional search.

Distributed stereoscopic rotating formation control of networks of second-order agents

Distributed stereoscopic rotating formation control of networks of second-order agents is investigated. A distributed control protocol is proposed to enable all agents to form a stereoscopic formation and surround a common axis. Due to the existence of the rotating mode, the desired relative position between every two agents is time-varying, and a Lyapunov-based approach is employed to solve the rotating formation control problem. Finally, simulation results are provided to illustrate the effectiveness of the theoretical results.

Ladder-Type Thienoacenaphthopyrazine-Based Molecules:Synthesis,Properties,and Application to Construct High-Performance Polymer for Organic Solar Cells

We present a new design strategy to synthesize ladder-type thienoacenaphthopyrazine(TAP)-based monomers through two different coupling reactions from starting material 5,6-dibromoacenaphthylene-1,2-dione.By bringing varous electron-deficient groups together(such as five-membered aromatic rings,pyrazine,fluorine,and thiadiazols),this new family of molecules exhibits good stability in ambient conditions and easily tunes the electronic,photophysical and film-forming properties of polymers.The unique molecular shape with its extendedπ-conjugated backbone perpendicular to the polymer chain,offers a remarkable platform for the development of a semiconducting polymer with rare geometry.The planar and enlarged conjugated backbone enables TAP-based copolymers PTAP1 and PTAP2 to exhibit distinguishing solubility properties that are different from small-molecule-based polymers,indicating the advantages of novel ladder-type monomers.Their insolubility in chloroform supports orthogonal solvent processing to fabricate layer-by-layer organic solar cells(LBL-OSCs).Owing to its shorterπ–πstacking distance,higher hole mobility,and more favorable phase separation caused bymultifluorine substitution,polymer PTAP1-based LBL-OSC exhibits the highest efficiency of 17.14%by using Y6-BO as the electron acceptor while the efficiency for the PTAP2-based device is 14.20%.This high efficiency indicates the tremendous potential of these novel building units.

Robust distributed control of robot formations with parameter uncertainty

This paper discusses robot formations in a distributed framework. The most important contribution is the incorporation of robustness into robot formation systems. When robots carry out tasks in a poor environment, the parameters in their models fluctuate around the nominal values, which may destroy the stability of the formation system. By modeling the group of robots as an interconnected system, we aim to develop a set of robust distributed controllers such that the overall system is robust to external disturbance as well as parameter uncertainty. Based on the graph rigidity theory, we also consider the rotation of a formation that plays an important role in real-time applications. Both simulations and real-time experiments are carried out to validate the effectiveness of the proposed framework.