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Position Control of a Series Elastic Actuator Based on Global Sliding Mode Controller Design

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IEEE/CAA Journal of Automatica Sinica 2019年第3期6卷 850-858页

作者： Wei Yin Lei Sun Meng Wang Jingtai Liu IEEE the Institute of robotics and Automatic Information System Nankai University and also with Tianjin Key Laboratory of Intelligent Robotics

A series elastic actuator(SEA) is a powerful device in the area of human-machine integration, but it still suffers from difficult position control issues. Therefore, in this paper,an efficient approach is proposed to solve this problem. The approach design is divided into two steps: feedback linearization(FL) and global sliding mode(GSM) controller design. The bounded analysis is presented and global asymptotic convergence is analytically proven. Simulation and experiment results illustrate the effectiveness of the proposed scheme.

关键词： Feedback linearization (FL) global sliding mode (GSM) position control series elastic actuator (SEA)

Event-triggered fault-tolerant consensus control with control allocation in leader-following multi-agent systems

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Science China(Technological Sciences) 2021年第4期64卷 879-889页

作者： WANG XingXia LIU ZhongXin CHEN ZengQiang College of Artificial Intelligence Nankai UniversityTianjin 300350China key laboratory of intelligent robotics of tianjin Tianjin 300350China

Event-triggered consensus in leader-following multi-agent systems with actuator fault is considered in this paper, in which the fault investigated can be multiplicative fault and outage fault. An event-triggered mechanism is utilized to relieve the communication burden of the interconnected system. Then, control allocation is proposed to solve actuator fault in the multi-agent systems for the first time. Compared with the existing fault-tolerant methods, the proposed method can guarantee that the consensus errors converge to zero asymptotically without the traditional rank assumption. Meanwhile, the Zeno behavior of the event-triggered system is proved to be avoided. Simulation results are also provided to verify the effectiveness of the proposed method.

关键词： multi-agent systems fault-tolerant control consensus event-triggered mechanism control allocation optimal

Design and analysis of active disturbance rejection control for time-delay systems using frequency-sweeping

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Journal of Systems Engineering and Electronics 2023年第2期34卷 479-491页

作者： WANG Yongshuai CHEN Zengqiang SUN Mingwei SUN Qinglin College of Artificial Intelligence Nankai UniversityTianjin 300350China key laboratory of intelligent robotics of tianjin Tianjin 300350China

For the typical first-order systems with time-delay,this paper explors the control capability of linear active disturbance rejection control(LADRC).Firstly,the critical time-delay of LADRC is analyzed using the frequency-sweeping method and the Routh criterion,and the stable time-delay interval starting from zero is accurately obtained,which reveals the limitations of general LADRC on large *** in view of the large time-delay,an LADRC controller is developed and verified to be effective,along with the robustness ***,numerical simulations show the accuracy of critical time-delay,and demonstrate the effectiveness and robustness of the proposed controller compared with other modified LADRCs.

关键词： active disturbance rejection control frequencysweeping method critical time-delay Routh criterion system with large time-delay

Design and stability analysis of a generalized reduced-order active disturbance rejection controller

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Science China(Technological Sciences) 2022年第2期65卷 361-374页

作者： WANG YongShuai CHEN ZengQiang SUN Ming Wei SUN QingLin College of Artificial Intelligence Nankai UniversityTianjin 300350China key laboratory of intelligent robotics of tianjin Tianjin 300350China

Disturbance and uncertainty rejection is a key objective in control system design, and active disturbance rejection control(ADRC)exactly provides an effective solution to this issue. To this end, this paper presents a generalized active disturbance rejection controller for a class of nonlinear uncertain systems with linear output. To be specific, a generalized reduced-order extended state observer(ESO) is proposed to reduce phase delay and complexity of the system, which can take full advantage of the system output. Also, this method includes the existing results with fewer assumptions, and can be applied to systems with any order measurable states or multiple states, even linear combination states. Furthermore, the stability of this approach is guaranteed and demonstrated through matrix transformation and Lyapunov method, and design examples and numerical simulations are given to show the effectiveness and practicability of the method.

关键词： generalized reduced-order ESO active disturbance rejection control(ADRC) linear combination states stability analysis Gronwall-Bellman inequality

Continuous Robust Control for Series Elastic Actuator With Unknown Payload Parameters and External Disturbances

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IEEE/CAA Journal of Automatica Sinica 2017年第4期4卷 620-627页

作者： Meng Wang Lei Sun Wei Yin Shuai Dong Jingtai Liu Institute of robotics and Automatic Information System Nankai University tianjin key laboratory of intelligent robotics Nankai University IEEE

In this paper, the torque tracking control problem for a class of series elastic actuators(SEAs) in the presence of unknown payload parameters and external disturbances is investigated. The uncertainties/disturbances rejection problem for SEAs is addressed from the view of a continuous nonlinear robust control development. Specifically, based on the analysis of a nonlinear SEA, the generic dynamics of SEA systems is described and a novel nonlinear control framework for SEAs is constructed. Then a RISE(robust integral of the sign of the error)-based second-order filter is introduced to synthesize the control law. Moreover, the control performance is theoretically ensured by Lyapunov analysis. Finally, some experimental results are included to demonstrate the superior performance of the proposed control method, in terms of transient response and robustness.

关键词： Nonlinear robust control torque control series elastic actuator

Reduced-Order Observer-Based Leader-Following Formation Control for Discrete-Time Linear Multi-Agent Systems

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IEEE/CAA Journal of Automatica Sinica 2021年第10期8卷 1715-1723页

作者： Zhongxin Liu Yangbo Li Fuyong Wang Zengqiang Chen College of Artificial Intelligence Nankai UniversityTianjin 300350 tianjin key laboratory of intelligent robotics Nankai UniversityTianjin 300350China

Formation control of discrete-time linear multi-agent systems using directed switching topology is considered in this work via a reduced-order observer, in which a formation control protocol is proposed under the assumption that each directed communication topology has a directed spanning tree. By utilizing the relative outputs of neighboring agents, a reduced-order observer is designed for each following agent. A multi-step control algorithm is established based on the Lyapunov method and the modified discrete-time algebraic Riccati equation. A sufficient condition is given to ensure that the discrete-time linear multi-agent system can achieve the expected leader-following ***, numerical examples are provided so as to demonstrate the effectiveness of the obtained results.

关键词： Discrete-time systems formation control leader-following multi-agent system reduced-order observer

Leader-following consensus of second-order nonlinear multi-agent systems with intermittent position measurements

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Science China(Information Sciences) 2019年第10期62卷 117-132页

作者： Fuyong WANG Zhongxin LIU Zengqiang CHEN College of Artificial Intelligence Nankai University tianjin key laboratory of intelligent robotics Nankai University

This work studies the leader-following consensus problem of second-order nonlinear multi-agent systems with aperiodically intermittent position measurements. Through the filter-based method, a novel intermittent consensus protocol without velocity measurements is designed for each follower exclusively based on the relative position measurements of neighboring agents. Under the common assumption that only relative position measurements between the neighboring agents are intermittently used, some consensus conditions are derived for second-order leader-following multi-agent systems with inherent delayed nonlinear dynamics. Moreover, for multi-agent systems without inherent delayed nonlinear dynamics, some simpler consensus conditions are presented. Finally, some simulation examples are presented to verify and illustrate the theoretical results.

关键词： leader-following consensus second-order multi-agent system delayed nonlinear dynamics distributed filter intermittent measurements

The greedy crowd and smart leaders: a hierarchical strategy selection game with learning protocol

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Science China(Information Sciences) 2021年第3期64卷 193-206页

作者： Linghui GUO Zhongxin LIU Zengqiang CHEN College of Artificial Intelligence Nankai University tianjin key laboratory of intelligent robotics Nankai University

In this paper, a general resource distribution game with a hierarchical structure on the bipartite graph is proposed. In this system, the game is divided into two interacting levels, the agent level and the group level, with negotiations taking place on both levels. Each agent can belong to multiple groups,resulting in a system topology with a bipartite structure. On the agent level, decisions are based on the greedy principle, with the game being a state-based potential game. In contrast, some participants on the group level behave more "smartly" and are more likely to adopt a sophisticated strategy maximizing their personal interest. Strategies on both levels are based on distributed protocols, and the social welfare increases as the system approaches a Nash-equilibrium point. The designed protocols are theoretically analyzed from stability and efficiency. Furthermore, a reinforcement learning algorithm is introduced in the group level, where the smarter players are allowed to refine their strategies in the multi-step decision-making process by learning from historic game outcomes. In theory and according to simulations, agents with the learning behavior improve not only their personal interest but also the efficiency of the systemic resource distribution.

关键词： multi-agent system reinforcement learning game theory complex network bipartite graph

A fast scanning strategy based on trajectory shaping for atomic force microscopy

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Nano Research 2022年第7期15卷 6438-6446页

作者： Yinan Wu Yingao Chang Yongchun Fang Zhi Fan Institute of robotics and Automatic Information System College of Artificial IntelligenceNankai UniversityTianjin 300350China tianjin key laboratory of intelligent robotics Nankai UniversityTianjin 300350China

To improve the scanning speed of an atomic force microscopy(AFM),a smooth scanning pattern is elaborately devised via trajectory shaping in this paper,so as to achieve fast imaging without hardware ***,in the proposed scanning method,the piezoelectric actuator tracks a well-designed smooth periodic signal in x-direction,and simultaneously tracks a step signal in *** advantage of the proposed method is that it does not require additional data reprocessing to construct the morphology of the sample surface,while significantly increasing the scanning bandwidth restricted by the raster scanning ***,to directly utilize the height data collected by scanning to produce the sample morphology,the forward process in the common raster scanning mode is retained in the proposed method,the tracking signal in the forward process is thus set to a ramp function in *** addition,to ensure the continuity and smoothness of the entire tracking signal in x-direction,a segment of a sine curve is uniquely determined as the backward tracking signal by position and acceleration constraints,so as to ensure that the forward and backward curves are continuous and acceleration-continuous at the intersection ***,the frequency spectrum analysis of the designed smooth signal is carried out to exhibit the depressed amplitudes of high-frequency components,which demonstrates that the proposed method is able to reduce the resonance in AFM high-speed scanning,so as to improve the capacity of rapidly generating high-quality ***,convincing comparison experiments are implemented to verify the imaging performance of the designed scanning algorithm.

关键词： atomic force microscopy fast scanning smooth signal trajectory shaping