Peter Xiaoping Liu

Prof. Peter Xiaoping Liu

Department of Systems and Computer Engineering, 1125 Colonel By Drive, Carleton University, Ottawa, ON K1S 5B6, Canada
orcid

Research Focus & Metrics

Academic Career Length

36Years (1991-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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20 June 2017 in IEEE Transactions on Fuzzy Systems
Verified
Journal Article
Closed access
FWFang Wang
Fang Wang
BCBing Chen
Bing Chen
Xiaoping LiuXiaoping Liu
Xiaoping Liu
CLChong Lin
Chong Lin
This paper addresses the finite-time tracking problem of nonlinear pure-feedback systems. Unlike the literature on traditional finite-time stabilization, in this paper the nonlinear system functions, including the bounding functions, are all totally unknown. Fuzzy logic systems are used to model those unknown functions. To present a finite-time control strategy, a criterion of semiglobal practical stability in finite time is first developed. Based on this criterion, a novel adaptive fuzzy control scheme is proposed by a backstepping technique. It is shown that the presented controller can guarantee that the tracking error converges to a small neighborhood of the origin in a finite time, and the other closed-loop signals remain bounded. Finally, two examples are used to test the effectiveness of proposed control strategy.

5 November 2014 in IEEE Transactions on Industrial Electronics
Verified
Journal Article
Closed access
Shichao LiuShichao Liu
Shichao Liu
XWXiaoyu Wang
Xiaoyu Wang
PLPeter Xiaoping Liu
Peter Xiaoping Liu
Low-bandwidth communication channels are used to support the information exchange between a microgrid centralized controller and local controllers in the secondary frequency control of an islanded microgrid. However, the impact of the inherent time delay in these communication channels on the microgrid performance has not been taken into account when the secondary frequency controller is designed. This paper investigates the effect of the communication delays on the secondary frequency control of an islanded microgrid with multiple distributed generators. A small-signal model-based method is introduced for the microgrid to find delay margins below which the microgrid can remain stable. By performing a series of trial studies, the relationships between secondary frequency control gains and delay margins are obtained. A gain scheduling approach is also proposed to compensate the effect of the communication delay on the secondary frequency control. Results from the Canadian urban distribution system have verified that communication delays can adversely affect the microgrid secondary frequency control, and the proposed gain scheduling approach can improve the robustness of the microgrid secondary frequency controller to communication delays.

19 December 2019 in IEEE Transactions on Fuzzy Systems
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Journal Article
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MCMing Chen
Ming Chen
HWHuanqing Wang
Huanqing Wang
Xiaoping LiuXiaoping Liu
Xiaoping Liu
The paper investigates an adaptive practical fixed- time control strategy for the output tracking control of a class of strict feedback nonlinear systems. By utilizing backstepping algo- rithm, finite-time Lyapunov stable theory and fuzzy logic control, a novel adaptive practical fixed-time controller is constructed. Fuzzy logic systems are introduced to approximate the unknown items of the system. Theoretical analysis proves that under the presented control strategy, the closed-loop system is practically fixed-time stable, and the tracking error converges to a small neighborhood of the origin within fixed-time interval, in which the convergence time has no connection with the initial states of the system. In the meantime, all the signals of the closed-loop system are bounded. At last, a numerical example is presented to indicate the feasibility and effectiveness of the proposed method.

29 July 2010 in IEEE Transactions on Industrial Electronics
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Journal Article
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SIShafiqul Islam
Shafiqul Islam
PLPeter Xiaoping Liu
Peter Xiaoping Liu
In the face of large-scale parametric uncertainties, the single-model (SM)-based sliding mode control (SMC) approach demands high gains for the observer, controller, and adaptation to achieve satisfactory tracking performance. The main practical problem of having high-gain-based design is that it amplifies the input and output disturbance as well as excites hidden unmodeled dynamics, causing poor tracking performance. In this paper, a multiple model/control-based SMC technique is proposed to reduce the level of parametric uncertainty to reduce observer-controller gains. To this end, we split uniformly the compact set of unknown parameters into a finite number of smaller compact subsets. Then, we design a candidate SMC corresponding to each of these smaller subsets. The derivative of the Lyapunov function candidate is used as a resetting criterion to identify a candidate model that approximates closely the plant at each instant of time. The key idea is to allow the parameter estimate of conventional adaptive sliding mode control design to be reset into a model that best estimates the plant among a finite set of candidate models. The proposed method is evaluated on a 2-DOF robot manipulator to demonstrate the effectiveness of the theoretical development.

1 March 2011 in Digital Signal Processing
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Journal Article
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FDFeng Ding
Feng Ding
PLPeter Xiaoping Liu
Peter Xiaoping Liu
GLGuangjun Liu
Guangjun Liu

15 January 2021 in IEEE Transactions on Cybernetics
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Journal Article
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HWHuanqing Wang
Huanqing Wang
WBWen Bai
Wen Bai
Xudong ZhaoXudong Zhao
Xudong Zhao
PLPeter Xiaoping Liu
Peter Xiaoping Liu
In this article, finite-time-prescribed performance-based adaptive fuzzy control is considered for a class of strict-feedback systems in the presence of actuator faults and dynamic disturbances. To deal with the difficulties associated with the actuator faults and external disturbance, an adaptive fuzzy fault-tolerant control strategy is introduced. Different from the existing controller design methods, a modified performance function, which is called the finite-time performance function (FTPF), is presented. It is proved that the presented controller can ensure all the signals of the closed-loop system are bounded and the tracking error converges to a predetermined region in finite time. The effectiveness of the presented control scheme is verified through the simulation results.