Policy Iteration Algorithm Based Fault Tolerant Tracking Control: An Implementation on Reconfigurable Manipulators

Li, Yuanchun,Xia, Hongbing,Zhao, Bo The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.4

This paper proposes a novel fault tolerant tracking control (FTTC) scheme for a class of nonlinear systems with actuator failures based on the policy iteration (PI) algorithm and the adaptive fault observer. The estimated actuator failure from an adaptive fault observer is utilized to construct an improved performance index function that reflects the failure, regulation and control simultaneously. With the help of the proper performance index function, the FTTC problem can be transformed into an optimal control problem. The fault tolerant tracking controller is composed of the desired controller and the approximated optimal feedback one. The desired controller is developed to maintain the desired tracking performance at the steady-state, and the approximated optimal feedback controller is designed to stabilize the tracking error dynamics in an optimal manner. By establishing a critic neural network, the PI algorithm is utilized to solve the Hamilton-Jacobi-Bellman equation, and then the approximated optimal feedback controller can be derived. Based on Lyapunov technique, the uniform ultimate boundedness of the closed-loop system is proven. The proposed FTTC scheme is applied to reconfigurable manipulators with two degree of freedoms in order to test the effectiveness via numerical simulation.

Adaptive Dynamic Programming-Based Decentralized Guaranteed Cost Control for Reconfi gurable Manipulators with Uncertain Environments

Yuanchun Li,Weinign Jin,Bing Ma,Bo Dong 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.5

In this paper, a novel decentralized guaranteed cost control method is designed for reconfi gurable manipulators with uncertain environments based on the adaptive dynamic programming (ADP) approach. Each joint module, which is the basic unit for constructing the reconfi gurable manipulators, is regarded as a subsystem with model uncertainties that include the error of frictional modeling and the interconnection dynamic coupling (IDC) eff ect. Then, by employing a robust controller and a neural network (NN) identifi er-based compensation controller, the decentralized guaranteed cost control issue with uncertain environments can be changed into the optimal control issue of reconfi gurable manipulators. Based on ADP algorithm, the critic neural network is introduced to approximate the modifi ed cost function, and then the Hamilton–Jacobi–Bellman equation is addressed by the policy iterative algorithm, thus making the obtention of approximate optimal control policy doable. The stability of the robotic system under the proposed control policy is demonstrated by employing the Lyapunov theory. Finally, the eff ectiveness of the proposed control policy for reconfi gurable manipulators with diff erent confi gurations is verifi ed by simulation experiments.

Policy Iteration Algorithm Based Fault Tolerant Tracking Control

Yuanchun Li,Hongbing Xia,Bo Zhao 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.4

This paper proposes a novel fault tolerant tracking control (FTTC) scheme for a class of nonlinear systems with actuator failures based on the policy iteration (PI) algorithm and the adaptive fault observer. The estimated actuator failure from an adaptive fault observer is utilized to construct an improved performance index function that reflects the failure, regulation and control simultaneously. With the help of the proper performance index function, the FTTC problem can be transformed into an optimal control problem. The fault tolerant tracking controller is composed of the desired controller and the approximated optimal feedback one. The desired controller is developed to maintain the desired tracking performance at the steady-state, and the approximated optimal feedback controller is designed to stabilize the tracking error dynamics in an optimal manner. By establishing a critic neural network, the PI algorithm is utilized to solve the Hamilton-Jacobi-Bellman equation, and then the approximated optimal feedback controller can be derived. Based on Lyapunov technique, the uniform ultimate boundedness of the closed-loop system is proven. The proposed FTTC scheme is applied to reconfigurable manipulators with two degree of freedoms in order to test the effectiveness via numerical simulation.

Microstructural Evolution and Dynamic Recrystallization Behavior of the Homogenized 2195 Al–Li Alloy During Hot Deformation

Rong Fu,Yuanchun Huang,Yu Liu,Hui Li 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.9

The thermal deformation behavior in homogenized 2195 Al–Li alloy was studied at different deformation temperatures(370–520 °C and strain rates (0.001–1 s−1). The flow stress decreases with decreasing strain rate or increasing temperature. The significant decrease in flow stress from 370 to 420 °C is related to the fact that movements of dislocations and (sub)grain boundaries at low temperatures are hindered by the dynamic precipitation of numerous fine secondary phases (mainlyAl2CuLi(T1) phases). Meanwhile, it was found that flow localization regions appear in the microstructure at 370 °C/1 s−1. Besides, DRX and DRV increase with decreasing lnZ (Zener–Hollomon parameter) values, particularly for lnZ values lessthan 26.32 (520 °C/0.1 s−1). The DRX mechanism was discussed for different lnZ based on the variation of misorientationangle and the characteristics of different DRXs. The DDRX is dominant when lnZ ≥ 30.70; CDRX and DDRX dominate at30.70 > lnZ > 26.32; CDRX mainly occurs at lnZ ≤ 26.32; when lnZ value decreases to 21.72, DRX grains with the characteristicsof CDRX and GDRX appear.

Consolidation of Unsaturated Drainage Well Foundation with Smear Effect under Time-Dependent Loading

Yuanchun Huang,Tianyi Li,Xianlei Fu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.3

In real practice, the construction of drainage wells is always accompanied by smear effect, whereas it is scarcely discussed in the field of unsaturated soils. In this case, on the basis of the widely-accepted consolidation theory for unsaturated stratum by Fredlund, this paper studies the equal strain consolidation characteristics of unsaturated foundation with drain wells affected by smear effect under time-varying loading (exponential loading as a case). Firstly, with the consideration of corresponding boundary conditions, the governing equations under the equal strain hypothesis are obtained. Afterwards, decoupling process, constant variation method and Fourier series expansion theory are utilized to get the analytical solutions, which are then verified to be credible by means of the finite difference method. Finally, the consolidation patterns of the drainage well foundation modeling in unsaturated soils are studied against hydraulic coefficients, modeling sizes and loading parameter. It reveals that the smear effect can significantly restrain the consolidation process of the foundation by drain wells, while different parameters will lead to various results.

Torque Sensorless Force/position Decentralized Control for Constrained Reconfigurable Manipulator with Harmonic Drive Transmission

Fan Zhou,Yuanchun Li,Bo Dong 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.5

The difficulty of addressing the decentralized control problem for a torque sensorless constrained reconfigurablemanipulator is associated with decentralized control of the constraint force. This paper studies theforce/position decentralized robust control problem for constrained reconfigurable manipulator system with parameterperturbation and unmodeled dynamics. A joint torque estimation scheme based on the motor-side and link-sideposition measurements along with harmonic drive model is deployed for each joint module. Subsequently, radialbasis function (RBF) neural network is applied to compensate the unmodeled dynamics and unknown terms ofsubsystem, simultaneously. Furthermore, a decentralized force/position robust controller is designed by combiningthe estimated joint torque with the dynamic output feedback control method. The stability of closed-loop system isproved using the Lyapunov theory and linear matrix inequality (LMI) technique. Finally, simulations are performedto verify the advantage of the proposed method.

Model-free Adaptive Dynamic Programming Based Near-optimal Decentralized Tracking Control of Reconfigurable Manipulators

Bo Zhao,Yuanchun Li 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.2

In this paper, a model-free near-optimal decentralized tracking control (DTC) scheme is developed for reconfigurable manipulators via adaptive dynamic programming algorithm. The proposed controller can be divided into two parts, namely local desired controller and local tracking error controller. In order to remove the normboundedness assumption of interconnections, desired states of coupled subsystems are employed to substitute their actual states. Using the local input/output data, the unknown subsystem dynamics of reconfigurable manipulators can be identified by constructing local neural network (NN) identifiers. With the help of the identified dynamics, the local desired control can be derived directly with corresponding desired states. Then, for tracking error subsystems, the local tracking error control is investigated by the approximate improved local cost function via local critic NN and the identified input gain matrix. To overcome the overall error caused by the substitution, identification and critic NN approximation, a robust compensation is added to construct the improved local cost function that reflects the overall error, regulation and control simultaneously. Therefore, the closed-loop tracking system can be guaranteed to be asymptotically stable via Lyapunov stability theorem. Two 2-degree of freedom reconfigurable manipulators with different configurations are employed to demonstrate the effectiveness of the proposed modelfree near-optimal DTC scheme.

A Novel Decentralized Fixed-time Tracking Control for Modular Robot Manipulators: Theoretical and Experimental Verification

Zengpeng Lu,Yuanchun Li,Yan Li 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.9

This paper presents a novel decentralized fixed-time tracking control approach, which realizes the advantages of modular robot manipulators (MRMs) with fixed-time convergence, strong robustness, and high tracking performance. First, to estimate the total uncertainty of MRMs, the fixed-time observer based on the extended state is developed. Then, combined with the disturbance observer, a novel decentralized control method based on a fixedtime control strategy was devised to accomplish global fixed-time convergence of MRMs. And, stability analysis based on Lyapunov is utilized to obtain the fixed-time stability as well as convergence time of MRMs. Finally, numerical analysis and experiment respectively verify the excellent tracking ability of the presented decentralized fixed-time tracking control.

Multiple Faults Detection and Isolation via Decentralized Sliding Mode Observer for Reconfigurable Manipulator

Zhao, Bo,Li, Chenghao,Ma, Tianhao,Li, Yuanchun The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.6

This paper considers a decentralized multiple faults detection and isolation (FDI) scheme for reconfigurable manipulators. Inspired by their modularization property, a global sliding mode (GSM) based stable adaptive fuzzy decentralized controller is investigated for the system in fault free, while for the system suffering from multiple faults (actuator fault and sensor fault), the decentralized sliding mode observer (DSMO) is employed to detect their occurrence. Hereafter, the time and location of faults can be determined by a fault isolation scheme via a bank of DSMOs. Finally, the effectiveness of the proposed schemes in controlling, detecting and isolating faults is illustrated by the simulations of two 3-DOF reconfigurable manipulators with different configurations successfully.

Observer-based Distributed Coordinated Tracking Control for Multiple Simple-pendulum Network Systems with Time-varying Delays

Yu-lian Jiang,Yuanchun Li,Shen-quan Wang 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.6

For networked control systems consisting of multiple simple-pendulums driven by corresponding DCmotors with time-varying communication and input delays, a distributed coordinated controller via observer-basedoutput feedback is designed to solve the tracking problem under both fixed and jointly-connected switching topologies. Firstly, the linearized dynamic model for multiple nonlinear simple-pendulum network systems with DCmotors is presented, and the distributed coordinated tracking problem considering time-varying input delays ismathematically described. Then the distributed observer-based tracking control protocol with time-varying communicationand input delays is proposed, and simultaneously, both the observer gain and feedback gain are designed. Two examples are simulated to demonstrate consensus tracking for three types of states, i.e., swing angles, angularvelocities of multiple simple-pendulums and armature currents of DC motors can be completed utilizing thedeveloped coordinated tracking control with fixed and jointly connected topologies.