Model-free control using time delay estimation and fractional-order nonsingular fast terminal sliding mode for uncertain lower-limb exoskeleton

2018 ◽  
Vol 24 (22) ◽  
pp. 5273-5290 ◽  
Author(s):  
Saim Ahmed ◽  
Haoping Wang ◽  
Yang Tian
Keyword(s):  
Fractional Order ◽  
Lower Limb ◽  
Sliding Mode ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
External Disturbances ◽  
Terminal Sliding Mode ◽  
Robotic Exoskeleton ◽  
Model Free ◽  
Fast Terminal Sliding Mode

A robotic exoskeleton is a nonlinear system, which is subjected to parametric uncertainties and external disturbances. Due to this reason, it is difficult to obtain the exact model of the system, and without knowledge of the system, it cannot be compensated accurately. In this study, time delay estimation (TDE)-based model-free fractional-order nonsingular fast terminal sliding mode control (MFF-TSM) is proposed for the lower-limb robotic exoskeleton in the existence of uncertainties and external disturbance. The main characteristic of the proposed scheme is that it controls the system without relying on the knowledge of exoskeleton dynamics. At first, the fractional-order (FO) with nonsingular fast terminal sliding mode control (NFTSM) is adopted to provide a precise trajectory tracking performance, fast finite-time speed of convergence, singularity-free and chatter-free control inputs. And then, the proposed controller employs TDE, to make the controller model independent, which directly estimates the uncertain exoskeleton dynamics with external disturbances. Later, asymptotical stability analysis of the overall system and finite-time convergence are investigated and ensured using Lyapunov theorem. Finally, the simulation results are conducted to validate the efficacy of the proposed control method.

Joint space tracking control of underwater vehicle-manipulator systems using continuous nonsingular fast terminal sliding mode

2017 ◽  
Vol 232 (4) ◽  
pp. 448-458 ◽  
Author(s):  
Yaoyao Wang ◽  
Bai Chen ◽  
Hongtao Wu
Keyword(s):  
Time Delay ◽  
Tracking Control ◽  
Sliding Mode ◽  
Underwater Vehicle ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Control Performance ◽  
Terminal Sliding Mode ◽  
Model Free ◽  
Fast Terminal Sliding Mode

To ensure satisfactory control performance for the underwater vehicle-manipulator systems, a novel continuous nonsingular fast terminal sliding mode controller is proposed and investigated using time delay estimation in this article. Complex lumped unknown dynamics including the strong nonlinear couplings and external disturbance are properly compensated with time delay estimation, which are mainly based on the time-delayed signals of underwater vehicle-manipulator systems and can provide with a fascinating model-free feature. Afterwards, the satisfactory tracking control performance and good robustness under heavy lumped uncertainties are ensured using the continuous nonsingular fast terminal sliding mode term with a fast terminal sliding mode–type reaching law. Therefore, the proposed controller is easy to use thanks to time delay estimation, and can ensure good control performance owing to continuous nonsingular fast terminal sliding mode. Stability of the closed-loop control system is analyzed using Lyapunov stability theory, and theoretical tracking errors are calculated and presented. Finally, the effectiveness and advantages of the proposed controller are demonstrated through comparative 7-degree-of-freedom pool experiments.

Robust position control of hydraulic manipulators using time delay estimation and nonsingular fast terminal sliding mode

2017 ◽  
Vol 232 (1) ◽  
pp. 50-61 ◽  
Author(s):  
Xichang Liang ◽  
Yi Wan ◽  
Chengrui Zhang ◽  
Yanyun Kou ◽  
Qianqian Xin ◽  
...  
Keyword(s):  
Time Delay ◽  
Position Control ◽  
Sliding Mode ◽  
Time Delay Estimation ◽  
Tracking Performance ◽  
Delay Estimation ◽  
Terminal Sliding Mode ◽  
Model Free ◽  
Fast Terminal Sliding Mode ◽  
Hydraulic Manipulator

A simple and robust tracking controller based on time delay estimation and nonsingular fast terminal sliding mode is proposed for the position control of hydraulic manipulator. The proposed controller does not require the mathematical model of hydraulic manipulator dynamics, which ensures that the method is simple and model free. Two elements, time delay estimation and nonsingular fast terminal sliding mode, are implemented in the proposed controller. Time delay estimation estimates the complex dynamics of the hydraulic manipulator, and nonsingular fast terminal sliding mode is implemented as the nonlinear desired error dynamic to ensure fast convergence and high trajectory tracking accuracy. Experiments are performed to verify the tracking performance of the method on a hydraulic manipulator. The results demonstrate that this method achieves faster and higher precision position tracking performance than a conventional time delay control with linear error dynamics.

scholarly journals Fractional Order Adaptive Fast Super-Twisting Sliding Mode Control for Steer-by-Wire Vehicles with Time-Delay Estimation

Electronics ◽  
2021 ◽  
Vol 10 (19) ◽  
pp. 2424
Author(s):  
Yong Yang ◽  
Yunbing Yan ◽  
Xiaowei Xu
Keyword(s):  
Time Delay ◽  
Sliding Mode Control ◽  
Fractional Order ◽  
Sliding Mode ◽  
Time Delay Estimation ◽  
Lyapunov Theory ◽  
Delay Estimation ◽  
Mode Control ◽  
Model Free ◽  
Steer By Wire

It is difficult to model and determine the parameters of the steer-by-wire (SBW) system accurately, and the perturbation is variable with complex and changeable tire–road conditions. In order to improve the control performance of the vehicle SBW system, an adaptive fast super-twisting sliding mode control (AFST-SMC) scheme with time-delay estimation (TDE) is proposed. The proposed scheme uses TDE to acquire the lumped dynamics in a simple way and establishes a practical model-free structure. Then, a fractional order (FO) sliding mode surface and a fast super-twisting sliding mode control structure were designed on the basic super-twisting sliding mode to ensure fast convergence and high control accuracy. Since the uncertain boundary information of the actual system is unknown, a novel adaptive algorithm is proposed to regulate the control gain based on the control errors. Theoretical analysis concerning system stability is given based on the Lyapunov theory. Finally, the effectiveness of the method is verified through comparative experiments. The results show that the proposed TDE-AFST-FOSMC control scheme has the advantages of model-free, fast response and high accuracy.

Practical continuous fractional-order nonsingular terminal sliding mode control of underwater hydraulic manipulators with valve deadband compensators

2018 ◽  
Vol 232 (4) ◽  
pp. 459-469 ◽  
Author(s):  
Yaoyao Wang ◽  
Bai Chen ◽  
Hongtao Wu
Keyword(s):  
Fractional Order ◽  
Degrees Of Freedom ◽  
Sliding Mode ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Terminal Sliding Mode Control ◽  
Control Performance ◽  
Terminal Sliding Mode ◽  
Hydraulic Manipulators ◽  
Nonsingular Terminal Sliding Mode

For the multi-degrees of freedom control problem of underwater hydraulic manipulators with non-ignorable valve deadband and strong lumped nonlinearities and uncertainties, a practical continuous fractional-order nonsingular terminal sliding mode control design together with a deadband compensator is presented and studied. The presented method contains three parts a time delay estimation utilized to nearly estimate and compensate the extremely complicated system dynamics, a continuous fractional-order nonsingular terminal sliding mode used to ensure high control performance against the strong lumped nonlinearities and uncertainties, and a valve deadband compensator used to compensate for the non-ignorable valve deadband. The proposed method is model-free thanks to the time delay estimation, and can ensure satisfactory control performance thanks to the continuous fractional-order nonsingular terminal sliding mode and deadband compensator. Stability of the closed-loop control system including the deadband compensator is proved rigorously. Finally, practical 2-degrees of freedom experiments are performed, and corresponding results effectively demonstrate the superiorities of the newly presented controller with deadband compensator.

scholarly journals Nonsingular Fast Terminal Sliding Mode Based Model-Free Control: Application to Glycemia Regulation Systems

2019 ◽  
Vol 48 (4) ◽  
pp. 602-617
Author(s):  
Yang Tian ◽  
Haoping Wang ◽  
Qi Wu ◽  
Maiting Hu ◽  
Nicolai Christov
Keyword(s):  
Sliding Mode ◽  
Estimation Error ◽  
Time Delay Estimation ◽  
System Stability ◽  
Terminal Sliding Mode ◽  
Model Free ◽  
Fast Terminal Sliding Mode ◽  
Model Free Control ◽  
Control Application

A new Model-Free Control (MFC) is derived to enhance the control performance of the well-known Nonlinear Integral Backstepping based MFC (NIB-MFC). A Nonsingular Fast Terminal Sliding Mode (NFTSM) component is added to NIB-MFC, which makes possible to compensate the estimation error of the time-delay estimation module of NIB-MFC. The obtained in this way new control structure is called NFTSM-MFC. The system stability with NFTSM-MFC is proved and the application of NFTSM-MFC for glycemia regulation is considered. The performances of NFTSM-MFC are compared with those of the NIB-MFC and the intelligent proportional control for a glucose-insulin model of type 1 diabetes patients under a long term simulation.

scholarly journals A light cable-driven manipulator developed for aerial robots: Structure design and control research

2020 ◽  
Vol 17 (3) ◽  
pp. 172988142092642
Author(s):  
Yaoyao Wang ◽  
Rui Zhang ◽  
Feng Ju ◽  
Jinbo Zhao ◽  
Bai Chen ◽  
...  
Keyword(s):  
Time Delay ◽  
Sliding Mode ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Sliding Mode Controller ◽  
Moving Mass ◽  
Terminal Sliding Mode ◽  
Aerial Robots ◽  
Model Free ◽  
Nonsingular Terminal Sliding Mode

To effectively reduce the mass and simplify the structure of traditional aerial manipulators, we propose novel light cable-driven manipulator for the aerial robots in this article. The drive motors and corresponding reducers are removed from the joints to the base; meanwhile, force and motion are transmitted remotely through cables. Thanks to this design, the moving mass has been greatly reduced. In the meantime, the application of cable-driven technology also brings about extra difficulties for high-precise control of cable-driven manipulators. Hence, we design a nonsingular terminal sliding mode controller using time-delay estimation. The time-delay estimation is applied to obtain lumped system dynamics and found an attractive model-free scheme, while the nonsingular terminal sliding mode controller is utilized to enhance the control performance. Stability is analyzed based on Lyapunov theory. Finally, the designed light cable-driven manipulator and presented time-delay estimation-based nonsingular terminal sliding mode controller are analyzed. Corresponding results show that (1) our proposed cable-driven manipulator has high load to mass ratio of 0.8 if we only consider the moving mass and (2) our proposed time-delay estimation-based nonsingular terminal sliding mode is model-free and can provide higher accuracy than the widely used time-delay estimation-based proportional–derivative (PD) controller.

Model-free robust finite-time force tracking control for piezoelectric actuators using time-delay estimation with adaptive fuzzy compensator

2019 ◽  
Vol 42 (3) ◽  
pp. 351-364
Author(s):  
Shengzheng Kang ◽  
Hongtao Wu ◽  
Xiaolong Yang ◽  
Yao Li ◽  
Yaoyao Wang
Keyword(s):  
Time Delay ◽  
Finite Time ◽  
Sliding Mode ◽  
Piezoelectric Actuators ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Terminal Sliding Mode ◽  
Adaptive Fuzzy ◽  
Model Free ◽  
Force Tracking

A robust and practical force control system is crucial to the sensitive piezo-driven micromanipulation applications. This paper presents a new model-free robust finite-time force tracking controller for piezoelectric actuators (PEAs). The proposed controller composes of three intuitive terms: (1) a time-delay estimation (TDE) term that eliminates the requirement of detailed information about the PEA system, realizing model-free control; (2) a fast integral terminal sliding mode-based desired error dynamics injection term that ensures fast convergence and high tracking precision; (3) a correcting term based on adaptive fuzzy logic system that compensates for TDE errors caused by discontinuous nonlinearities and improves the robustness of the system. Force differential signal used in the controller is estimated online by a force state estimator. Stability of the closed-loop system and finite-time convergence are analyzed in theory. Comparative experiments are carried out on a PEA system with two superposed PEAs. Results show that the proposed control strategy has faster convergence, higher tracking accuracy and stronger robustness compared with the traditional TDE-based force controllers.

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