Reduced-Order GPIO Based Dynamic Event-Triggered Tracking Control of a Networked One-DOF Link Manipulator Without Velocity Measurement

In networked robot manipulators that deeply integrate control, communication and computation, the controller design needs to take into consideration the limited or costly system resources and the presence of disturbances/uncertainties. To cope with these requirements, this paper proposes a novel dynamic event-triggered robust tracking control method for a one-degree of freedom (DOF) link manipulator with external disturbance and system uncertainties via a reduced-order generalized proportional-integral observer (GPIO). By only using the sampled-data position signal, a new sampled-data robust output feedback tracking controller is proposed based on a reduced-order GPIO to attenuate the undesirable influence of the external disturbance and the system uncertainties. To save the communication resources, we propose a discrete-time dynamic event-triggering mechanism (DETM), where the estimates and the control signal are transmitted and computed only when the proposed discrete-time DETM is violated. It is shown that with the proposed control method, both tracking control properties and communication properties can be significantly improved. Finally, simulation results are shown to demonstrate the feasibility and efficacy of the proposed control approach.      

Asynchronous Observer Design for Switched Linear Systems: A Tube-Based Approach

This paper proposes a tube-based method for the asynchronous observation problem of discrete-time switched linear systems in the presence of amplitude-bounded disturbances.Sufficient stability conditions of the nominal observer error system under mode-dependent persistent dwell-time(MPDT)switching are first established. Taking the disturbances into account, a novel asynchronous MPDT robust positive invariant(RPI) set and an asynchronous MPDT generalized RPI(GRPI)set are determined for the difference system between the nominal and disturbed observer error systems. Further, the global uniform asymptotical stability of the observer error system is established in the sense of converging to the asynchronous MPDT GRPI set, i.e., the cross section of the tube of the observer error system. Finally, the proposed results are validated on a space robot manipulator example.     

Output feedback control of sensorless photovoltaic systems,with maximum power point tracking

This paper presents an output feedback control of sensorless photovoltaic systems with maximum power point tracking (MPPT). The system consists of a Photovoltaic Generator (PVG) which supplies a DC centrifugal pump, via a DC/DC boost converter. This later being connected to the PVG by a long PV cable. Generally, PV systems are established near the control unit of the converter. The MPPT methods and control laws are based on the PVG voltage and current measurements. However, PV arrays must be located in a site that guarantees good solar radiation. In most cases, such a site is at great distance from the control unit. Thus, on the one hand, the PVG voltage and current measurements become difficult and, on the other hand, the PV cable parameters could significantly effect the MPPT control accuracy if only voltage and current measurements in the cable converter side are used. To overcome these issues, a state estimation for PV systems is considered in this paper. A high gain observer is designed on the basis of a PV system model that accounts for PV cable parameters. It provides estimates of PVG output voltage and current using only current and voltage measurements in the converter side of the cable. A backstepping controller is then synthesized with the view of ensuring the MPPT objective. The output feedback control convergence is formally analyzed and its performances are illustrated by simulation.     

Disturbance observer-based quadrotor attitude tracking control for aggressive maneuvers

In this paper, a disturbance observer-based quadrotor attitude controller for aggressive maneuvering is presented. The controller is made up of the cascade connection between two control-loops: an outer quaternion-based attitude control-loop and an inner disturbance observer-based angular velocity tracking control-loop. The disturbance observer is designed to estimate and compensate for the Coriolis term and the external disturbances. It is shown that, for fast maneuvers, the disturbance observer needs to take into account the motor dynamics. This allows to notably increase the observer bandwidth, leading to significant improvements in the disturbance rejection capabilities. The stability of the resulting closed-loop is analyzed. Also, different simulations and flight tests are carried out to validate the main results, showing an outstanding tracking performance when aggressive attitude maneuvers are being executed, even in the presence of strong disturbances such as suspended payloads.     

有限时间内异构多智能体系统的协同输出调节

针对异构多智能体系统有限时间输出调节问题,本文提出了分布式有限时间状态观测器控制算法和相应的输出反馈控制策略.应用图论、Lyapunov稳定性理论证明了所设计的观测器能够在有限时间内估计出外部系统状态,同时可以保证系统在有限时间内的稳定性,很好的解决了当部分跟随者无法获取外部命令时的有限时间输出调节问题.最后,通过MATLAB数值仿真验证了该协议的有效性和正确性,仿真结果表明系统除了在有限时间内获得更快的收敛速度外,还具有良好的暂态性能.     

线性/非线性切换扩张状态观测器

为了解决非线性扩张状态观测器(NLESO)对大幅度扰动估计能力有限的问题,本文提出一种线性/非线性切换扩张状态观测器.首先分析了非线性扩张状态观测器对大幅度扰动估计能力有限的原因,然后提出在NLESO的非线性区间引入一段线性扩张状态观测器(LESO)弥补NLESO的缺陷,其次从理论上证明了提出的线性/非线性切换扩张状态观测器的收敛性.最后,通过数值仿真验证了提出的线性/非线性切换扩张状态观测器的可行性.     

基于干扰观测器的机械臂改进趋近律的滑模控制

针对机械臂滑模控制中存在抖振的问题以及对外界干扰较为敏感的特性,设计了一种基于干扰观测器的机械臂改进趋近律的滑模控制策略。该策略在指数趋近律中引入饱和函数,提出了一种改进趋近律;根据系统动力学模型,对系统的不确定性和外部干扰采用干扰观测器进行观测;在此基础上设计系统滑模控制律,控制律对未观测的干扰进行补偿。仿真结果表明,控制策略能有效地抑制轨迹跟踪中的抖振问题,较好地克服外界干扰,保证系统的控制性能。     

A sliding mode observer design for uncertain fractional Ito stochastic systems with state delay

This paper addresses the robust observer design problem for uncertain time-delay fractional Ito stochastic systems. A sliding surface is proposed and it is shown that state estimates converge towards it and remain there for the subsequent time. Additionally, by constructing a novel Lyapunov functional, a sufficient condition for the stability of the sliding motion of the estimated states is given in the form of Linear Matrix Inequalities (LMIs). It is demonstrated that the state estimates are stabilizable in probability provided that the LMI is feasible. Moreover, a finite-time sliding mode control law based on the estimated states is proposed. Simulation examples are given to show the validity and effectiveness of the results.     

Almost Disturbance Decoupling for a Class of Nonlinear Systems Subject to Time‐Delays Via Sampled‐Data Output Feedback Control

This paper considers the problem of almost disturbance decoupling (ADD) via sampled‐data output feedback control for a class of uncertain nonlinear systems subject to time‐delays. Based on output feedback domination approach, a sampled‐data output feedback controller is designed to globally stabilize the system under a lower‐triangular linear growth condition. Gronwall‐Bellman‐like inequality and inductive method are introduced to estimate the state growth in the presence of time‐delays, uncertain nonlinearities and unknown disturbances. The proposed controller can attenuate the influence of disturbances on the output to an arbitrary degree in the L₂ gain sense. Finally, simulation results show the effectiveness of the control method.     

Design of Optimal Petri Net Supervisors for Flexible Manufacturing Systems via Weighted Inhibitor Arcs

This paper develops an approach to the design of an optimal Petri net supervisor that enforces liveness to flexible manufacturing systems. The supervisor contains a set of observer places with weighted inhibitor arcs. An observer place with a weighted inhibitor arc is used to forbid a net from yielding an illegal marking by inhibiting the firing of a transition at a marking while ensuring that all legal markings are preserved. A marking reduction technique is presented to decrease the number of considered markings, which can dramatically lower the computational burden of the proposed approach. An integer linear program is presented to simplify the supervisory structure by minimizing the number of observer places. Finally, several examples are used to shed light on the proposed approach which can lead to an optimal supervisor for the net models that cannot be optimally controlled via pure Petri net supervisors.