scholarly journals Model-assisted extended state observer-based computed torque control for trajectory tracking of uncertain robotic manipulator systems

2018 ◽  
Vol 15 (5) ◽  
pp. 172988141880173 ◽  
Author(s):  
Chao Chen ◽  
Chengrui Zhang ◽  
Tianliang Hu ◽  
Hepeng Ni ◽  
WeiChao Luo
Keyword(s):  
Trajectory Tracking ◽  
Robotic Manipulators ◽  
State Observer ◽  
Torque Control ◽  
Extended State Observer ◽  
Effective Control ◽  
Extended State ◽  
Uncertain Dynamics ◽  
Computed Torque Control ◽  
Computed Torque

Computed torque control is an effective control scheme for trajectory tracking of robotic manipulators. However, computed torque control requires precise dynamic models of robotic manipulators and is severely affected by uncertain dynamics. Thus, a new scheme that combines a computed torque control and a novel model-assisted extended state observer is developed for the robust tracking control of robotic manipulators subject to structured and unstructured uncertainties to overcome the disadvantages of computed torque control and exploit its merits. The model-assisted extended state observer is designed to estimate and compensate these uncertain dynamics as a lumped disturbance online, which further improves the disturbance rejection property of a robotic system. Global uniform ultimate boundedness stability with an exponential convergence of a closed-loop system is verified through Lyapunov method. Simulations are performed on a two degree-of-freedom manipulator to verify the effectiveness and superiority of the proposed controller.

scholarly journals Finite-time tracking control for uncertain robotic manipulators using backstepping method and novel extended state observer

2019 ◽  
Vol 16 (3) ◽  
pp. 172988141984465 ◽  
Author(s):  
Chao Chen ◽  
Chengrui Zhang ◽  
Tianliang Hu ◽  
Hepeng Ni ◽  
Qizhi Chen
Keyword(s):  
Trajectory Tracking ◽  
Finite Time ◽  
Tracking Control ◽  
Robotic Manipulators ◽  
State Observer ◽  
Extended State Observer ◽  
Extended State ◽  
Trajectory Tracking Control ◽  
Time Model ◽  
Uncertain Dynamics

This article considers finite-time trajectory tracking control problem for robotic manipulators with parameter uncertainties and external disturbances. A finite-time controller that achieves high precision and strong robustness is proposed without the requirement of the exact dynamic model. First, a novel finite-time model-assisted extended state observer is designed to compensate the system uncertainties with complex and uncertain dynamics. Then, a composite finite-time controller is developed for trajectory tracking control with the help of finite-time model-assisted extended state observer. Compared to the classic extended state observer, it is proved that the estimation error of finite-time model-assisted extended state observer can be stabilized in finite time. Meanwhile, the finite-time convergence of the closed-loop system with the proposed controller can also be proved through Lyapunov’s stability theory. A variable structure term is employed to compensate the estimation errors of finite-time model-assisted extended state observer. The validity of the control scheme is demonstrated by simulations and experiments.

Observer-based finite-time control for trajectory tracking of lower extremity exoskeleton

2021 ◽  
pp. 095965182110337
Author(s):  
Jie Wang ◽  
Jiahao Liu ◽  
Lingling Chen ◽  
Shijie Guo
Keyword(s):  
Lower Extremity ◽  
Trajectory Tracking ◽  
Finite Time ◽  
State Observer ◽  
Lyapunov Theory ◽  
Extended State Observer ◽  
Joint Torque ◽  
Extended State ◽  
Uncertain Dynamics ◽  
Angular Velocities

In this article, an advanced observer-based finite-time trajectory tracking controller is investigated for lower extremity exoskeleton without available joint angular velocities to improve the movement ability of dependent persons, which is robust against uncertain dynamics, human active joint torque and external disturbances. First, the Lagrange principle is applied to analyze the dynamic properties of lower extremity exoskeleton driven by artificial pneumatic muscles, and its swing phase model is established. After that, a novel finite-time extended state observer is proposed to observe the lumped disturbances and unavailable angular velocities of the lower limb exoskeleton simultaneously. Furthermore, a finite-time sliding mode controller of exoskeleton is designed based on the extended state observer, and the finite-time convergence of tracking error is rigorously demonstrated based on the Lyapunov theory. Finally, the control system simulation is established and experimental tests are conducted with a voluntary subject during flexion of wearer’s knee and hip joints, the obtained results demonstrate fast and high-precision tracking performance of the proposed approach.

Event-triggered discrete extended state observer–based model-free controller for quadrotor position and attitude trajectory tracking

2021 ◽  
pp. 095965182110553
Author(s):  
Dingxin He ◽  
Haoping Wang ◽  
Yang Tian ◽  
Konstantin Zimenko
Keyword(s):  
Trajectory Tracking ◽  
Signal Transmission ◽  
State Observer ◽  
Extended State Observer ◽  
Extended State ◽  
Model Free ◽  
Model Free Controller ◽  
Quadrotor System ◽  
Static Threshold ◽  
Event Triggered

In this article, an event-triggered discrete extended state observer–based model-free controller is developed for the position and attitude trajectory tracking of a quadrotor with uncertainties and external disturbances. The referred event-triggered discrete extended state observer–based model-free controller is composed of two event-triggered mechanisms, ultra-local model-based discrete extended state observer and proportional-derivative sub-controller. To reduce system output signal transmission, the event-triggered mechanism of output signal which owns dynamic and static threshold is designed. Based on event-triggered output signals, the discrete extended state observer is constructed to obtain the estimations of state values which are utilized as controller’s variables and to compensate for the lumped disturbances. The proportional-derivative sub-controller is adopted to guarantee the convergence of trajectory tracking error. To decrease control input signal transmission, the event-triggered mechanism of input signal that processes static threshold is constructed. Moreover, the stability analysis of overall quadrotor system with the proposed control strategy is investigated using Lyapunov theorem and the Zeno behavior is avoided. Finally, corresponding control scheme for quadrotor system is structured and the numerical comparative simulation and co-simulation experiment are given to demonstrate the effectiveness and performance of the proposed approach.

Extended State Observer Based Ascent Trajectory Tracking Method

2017 ◽  
Author(s):  
Wenming Nie ◽  
Huifeng Li ◽  
Ran Zhang ◽  
Bo Liu
Keyword(s):  
Trajectory Tracking ◽  
Control Method ◽  
State Observer ◽  
Linearization Method ◽  
Extended State Observer ◽  
Extended State ◽  
External Disturbances ◽  
Modeling Uncertainties ◽  
Trajectory Tracking Controller ◽  
Linearization Errors

The ascent trajectory tracking problem of a launch vehicle is investigated in this paper. To improve the conventional trajectory linearization method which usually omits the linearization errors, the extended state observer (ESO) is employed in this paper to timely estimate the total disturbance which consists of the external disturbances and the modeling uncertainties resulting from linearization error. It is proven that the proposed trajectory tracking controller can guarantee the desired performance despite both external disturbances and the modeling uncertainties. Moreover, compared with the conventional linearization control method, the proposed controller is shown to have much better performance of uncertainty rejection. Finally, the feasibility and performance of this controller are illuminated via simulation studies.

Direct torque control of PMSM using sliding mode backstepping control with extended state observer

2016 ◽  
Vol 24 (4) ◽  
pp. 694-707 ◽  
Author(s):  
Bowen Ning ◽  
Shanmei Cheng ◽  
Yi Qin
Keyword(s):  
Sliding Mode ◽  
Permanent Magnet Synchronous Motor ◽  
Direct Torque Control ◽  
State Observer ◽  
Torque Control ◽  
Extended State Observer ◽  
System Stability ◽  
Extended State ◽  
Recursive Design ◽  
Exponential Reaching Law

Based on the nonlinear characteristics of permanent magnet synchronous motor (PMSM), a nonlinear speed and direct torque control (DTC) using sliding mode backstepping method for PMSM is presented in this paper. The sliding mode speed controller is implemented with exponential reaching law to improve the robustness of the system, and further a step-by-step recursive design for backstepping torque and flux controllers is presented. The system stability with proposed scheme is mathematically proved using Lyapunov stability criteria. At the same time, the load torque is observed with the extended state observer (ESO), and is fed-forward to the controller for rejecting the load disturbance and to mitigate the chattering affect due to the sliding mode controller. Finally, simulation test results are demonstrated to support the effectiveness and feasibility of the proposed strategy.

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