scholarly journals Robust Nonlinear Position Control with Extended State Observer for Single-Rod Electro-Hydrostatic Actuator

Mathematics ◽  
2021 ◽  
Vol 9 (19) ◽  
pp. 2397
Author(s):  
Young Seop Son ◽  
Wonhee Kim
Keyword(s):  
Position Control ◽  
Estimation Error ◽  
External Disturbance ◽  
Input Function ◽  
High Gain ◽  
State Observer ◽  
Extended State Observer ◽  
Position Tracking ◽  
Extended State ◽  
Position Controller

In the existing literature, studies on position controller design using only position feedback, considering the disturbances for single-rod electro-hydrostatic actuators (EHAs), have not been reported. Herein, we propose a robust nonlinear position control with an extended state observer (ESO) for single-rod EHAs. A new EHA model that consists of position, velocity, and acceleration with an internal state variable is developed. Instead of the separated port pressure dynamics, the acceleration dynamics were defined. The external disturbance, model, and input function uncertainties were lumped into a disturbance. An ESO is developed to estimate the disturbance, as well as the position, velocity, and acceleration. In practice, it is difficult to accurately estimate the disturbance because it includes the external disturbance, system dynamics, and input function uncertainty. The poor estimation performance may degrade the position tracking performance, but a high gain cannot be used to suppress the estimation error because of the measurement noise amplification. To resolve this problem, a robust nonlinear position controller is developed via a backstepping procedure. In the controller, a nonlinear gain is implemented to sufficiently suppress position tracking without the use of a high gain. The stability of the closed-loop system is mathematically proven using the input-to-state stability. The proposed method is simple and suitable for real-time control.

scholarly journals Attitude-constrained reorientation control for spacecraft based on extended state observer

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879452 ◽  
Author(s):  
Yu Cheng ◽  
Dong Ye ◽  
Zhaowei Sun
Keyword(s):  
Actuator Saturation ◽  
Estimation Error ◽  
External Disturbance ◽  
Parametric Uncertainty ◽  
State Observer ◽  
Extended State Observer ◽  
Extended State ◽  
Finite Time Stability ◽  
Backstepping Controller ◽  
The Difference

This article investigates the spacecraft attitude reorientation control problem in the presence of attitude constraint, actuator saturation, parametric uncertainty, and external disturbance. First, a nonlinear tracking law based on a strictly convex potential function is proposed to generate the virtual control angular velocity which has only one global minimum. Then, utilizing the auxiliary system governed by the difference between the upper bound of actuator torque and the untreated command torque, a novel backstepping controller is presented, which is able to satisfy the constraint of actuator saturation and guarantee the stability of control system. In addition, an extended state observer with the uniformly ultimately bounded estimation error and finite-time stability is put forward to realize the real-time compensation of the compound disturbance consisting of parametric uncertainty and external disturbance. Therefore, it enhances the robustness and improves the accuracy of the extended state observer–based backstepping controller. Finally, simulation results validate the effectiveness and reliability of the proposed schemes.

Extended state observer-based robust control of an omnidirectional quadrotor with tiltable rotors

2020 ◽  
pp. 014233122096642
Author(s):  
Kaiwen Lu ◽  
Zhong Yang ◽  
Luwei Liao ◽  
Yuhong Jiang ◽  
Changliang Xu ◽  
...  
Keyword(s):  
Attitude Control ◽  
Position Control ◽  
External Disturbance ◽  
State Observer ◽  
Extended State Observer ◽  
Velocity Control ◽  
Control Loop ◽  
Motor Speed ◽  
Extended State ◽  
Attitude Controller

A quadrotor with tiltable rotors is a kind of omnidirectional multirotor aerial vehicle (MAV) that has demonstrated advantages of decoupling control of position from the control of orientation. However, quadrotors with tiltable rotors usually suffer from Coriolis term, modeling error and external disturbance. To this end, the extended state observer (ESO)-based controller is designed to estimate and compensate for the above adverse effects. Especially, the controller involves position and attitude controller in parallel. The attitude controller is made up of cascade control-loops: an outer quaternion-based attitude control-loop and an inner ESO-based Proportional derivative angular velocity control-loop. Similarly, the position controller consists of an outer proportional position control-loop and an inner ESO-based PD velocity control-loop. Besides, a linear control allocation strategy, which allocates the controller outputs to tilting angles and motor speed directly, is proposed to avoid the nonlinear allocation matrix. Extensive simulations and flight tests are carried out to illustrate the effectiveness and robustness of the proposed ESO-based controller.

On Performance Analysis of General Observers for Uncertain Systems

2017 ◽  
Author(s):  
Wenyan Bai ◽  
Chen Sen ◽  
Yi Huang ◽  
Wenchao Xue ◽  
Ping Liu
Keyword(s):  
Disturbance Observer ◽  
Uncertain Systems ◽  
Estimation Error ◽  
High Gain ◽  
State Observer ◽  
Extended State Observer ◽  
Exact Form ◽  
Extended State ◽  
Real State ◽  
General Observer

This paper aims to rigorously study the observer for general uncertain systems. The proposed observer is shown to be the general form of extended state observer (ESO), disturbance observer (DO), generalized extended state observer (GESO) and extended high gain observer (EHGO). The properties of this general observer is discussed by analyzing the estimation error. The paper illustrates that the output of the proposed general observers may not performs as the estimation the real state and uncertainty. We prove that this observer gives the estimations for the group of states and uncertainties whose exact form is given in the paper. Finally, numerical simulations for a typical example validate the theoretical analysis.

Sampled-data extended state observer-based backstepping control of two-link flexible manipulator

2019 ◽  
Vol 41 (13) ◽  
pp. 3581-3599 ◽  
Author(s):  
Umesh Kumar Sahu ◽  
Bidyadhar Subudhi ◽  
Dipti Patra
Keyword(s):  
Control Strategies ◽  
Estimation Error ◽  
Experimental Studies ◽  
State Observer ◽  
Lyapunov Theory ◽  
Extended State Observer ◽  
Flexible Manipulator ◽  
Sampled Data ◽  
Extended State ◽  
Model Uncertainties

Currently, space robots such as planetary robots and flexible-link manipulators (FLMs) are finding specific applications to reduce the cost of launching. However, the structural flexible nature of their arms and joints leads to errors in tip positioning owing to tip deflection. The internal model uncertainties and disturbance are the key challenges in the development of control strategies for tip-tracking of FLMs. To deal with these challenges, we design a tip-tracking controller for a two-link flexible manipulator (TLFM) by developing a sampled-data extended state observer (SD-ESO). It is designed to reconstruct uncertain parameters for accurate tip-tracking control of a TLFM. Finally, a backstepping (BS) controller is designed to attenuate the estimation error and other bounded disturbances. Convergence and stability of the proposed control system are investigated by using Lyapunov theory. The benefits (control performance and robustness) of the proposed SD-ESO-based BS controller are compared with other similar approaches by pursuing both simulation and experimental studies. It is observed from the results obtained that SD-ESO-based BS Controller effectively compensates the deviation in tip-tracking performance of TLFM due to non-minimum phase behavior and model uncertainties with an improved transient response.

scholarly journals Active Disturbance Rejection Station-Keeping Control of Unstable Orbits around Collinear Libration Points

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Min Zhu ◽  
Hamid Reza Karimi ◽  
Hui Zhang ◽  
Qing Gao ◽  
Yong Wang
Keyword(s):  
Disturbance Rejection ◽  
External Disturbance ◽  
State Observer ◽  
Libration Points ◽  
Extended State Observer ◽  
Unstable Periodic Orbits ◽  
Extended State ◽  
Station Keeping ◽  
Tracking Differentiator ◽  
Active Disturbance Rejection

An active disturbance rejection station-keeping control scheme is derived and analyzed for station-keeping missions of spacecraft along a class of unstable periodic orbits near collinear libration points of the Sun-Earth system. It is an error driven, rather than model-based control law, essentially accounting for the independence of model accuracy and linearization. An extended state observer is designed to estimate the states in real time by setting an extended state, that is, the sum of unmodeled dynamic and external disturbance. This total disturbance is compensated by a nonlinear state error feedback controller based on the extended state observer. A nonlinear tracking differentiator is designed to obtain the velocity of the spacecraft since only position signals are available. In addition, the system contradiction between rapid response and overshoot can be effectively solved via arranging the transient process in tracking differentiator. Simulation results illustrate that the proposed method is adequate for station-keeping of unstable Halo orbits in the presence of system uncertainties, initial injection errors, solar radiation pressure, and perturbations of the eccentric nature of the Earth's orbit. It is also shown that the closed-loop control system performance is improved significantly using our method comparing with the general LQR method.

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