Control of Uncertain LTI Systems Based on an Uncertainty and Disturbance Estimator

2004 ◽  
Vol 126 (4) ◽  
pp. 905-910 ◽  
Author(s):  
Qing-Chang Zhong ◽  
David Rees
Keyword(s):  
Time Delay ◽  
Robust Control ◽  
Robust Stability ◽  
Control Strategy ◽  
Time Delay Control ◽  
Delay Control ◽  
Uncertainty And Disturbance Estimator ◽  
Derivatives Of ◽  
Siso Systems ◽  
Disturbance Estimator

This paper proposes a robust control strategy for uncertain LTI systems. The strategy is based on an uncertainty and disturbance estimator (UDE). It brings similar performance as the time-delay control (TDC). The advantages over TDC are: (i) no delay is introduced into the system; (ii) there are no oscillations in the control signal; and (iii) there is no need of measuring the derivatives of the state vector. The robust stability of LTI-SISO systems is analyzed, and simulations are given to show the effectiveness of the UDE-based control with a comparison made with TDC.

Multistability in the Centrifugal Governor System Under a Time-Delay Control Strategy

2019 ◽  
Vol 14 (11) ◽  
Author(s):  
Shuning Deng ◽  
Jinchen Ji ◽  
Shan Yin ◽  
Guilin Wen
Keyword(s):  
Time Delay ◽  
Control Strategy ◽  
Large Amplitude ◽  
Stability Boundary ◽  
Physical Parameters ◽  
Time Delay Control ◽  
Delay Control ◽  
Delayed Feedback Controller ◽  
Trivial Equilibrium ◽  
The Stability

Abstract The centrifugal governor system plays an indispensable role in maintaining the near-constant speed of engines. Although different arrangements have been developed, the governor systems are still applied in many machines for its simple mechanical structure. Therefore, the large-amplitude vibrations of the governor system which can lead to the function failure of the system should be attenuated to guarantee reliable operation. This paper adopts a time-delay control strategy to suppress the undesirable large-amplitude motions in the centrifugal governor system, which can be regarded as the practical application of the delayed feedback controller in this system. The stability region of the trivial equilibrium of the controlled system is determined by investigating the characteristic equation and generic Hopf bifurcations. It is found that the dynamic behavior of multistability can be induced by the Bautin bifurcation, arising on the stability boundary of the trivial equilibrium with a constant delay. More specifically, a coexistence of two desirable stable motions, i.e., an equilibrium or a small-amplitude periodic motion, can be observed in the controlled centrifugal governor system without changing the physical parameters. This is a new feature of the motion control in the centrifugal governor systems, which has not yet been reported in the existing studies. Finally, the results of theoretical analyses are verified by numerical simulations.

Uncertainty and Disturbance Estimator–Based Control for Uncertain LTI-SISO Systems With State Delays

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
R. K. Stobart ◽  
Alon Kuperman ◽  
Qing-Chang Zhong
Keyword(s):  
Control Strategy ◽  
Linear Time ◽  
Single Input Single Output ◽  
Linear Time Invariant ◽  
Single Output ◽  
State Delays ◽  
Uncertainty And Disturbance Estimator ◽  
The Stability ◽  
Siso Systems ◽  
Disturbance Estimator

In this paper, a robust control strategy based on the uncertainty and disturbance estimator (UDE) is proposed for uncertain Linear Time Invariant-Single Input Single Output (LTI-SISO) systems with state delays. The knowledge of the bounds of uncertainties and disturbances is not needed during the design process although it is required for the stability analysis. Both the cases with known and unknown delays are considered. In the case of unknown delays, the terms involving the delays are treated as additional disturbances to the system. The robust stability of the closed-loop system is analyzed in detail, and a stability condition is proposed. Simulations are given to demonstrate the excellent tracking and disturbance rejection capabilities of the UDE-based control strategy.

Robust Control of Robot Manipulators Using Inclusive and Enhanced Time Delay Control

2017 ◽  
Vol 22 (5) ◽  
pp. 2141-2152 ◽  
Author(s):  
Maolin Jin ◽  
Sang Hoon Kang ◽  
Pyung Hun Chang ◽  
Jinoh Lee
Keyword(s):  
Time Delay ◽  
Robust Control ◽  
Robot Manipulators ◽  
Time Delay Control ◽  
Delay Control

Time-delay control of a switchable stiffness system

2015 ◽  
Vol 23 (15) ◽  
pp. 2375-2390 ◽  
Author(s):  
Thai Tran ◽  
Kefu Liu
Keyword(s):  
Time Delay ◽  
Control Strategy ◽  
Control Strategies ◽  
Oscillation Period ◽  
Control Law ◽  
System Delay ◽  
Single Degree Of Freedom ◽  
Time Delay Control ◽  
Single Degree ◽  
Delay Control

This paper focuses on suppression of free vibration of single degree-of-freedom systems that possess time delay. The switchable stiffness (SS) control strategy is reviewed. The implication of time delay is examined. It shows that the system delay can cause malfunction of the direct SS control. To overcome this problem, the two time-delay control strategies are proposed. The first strategy named as half period delay SS control introduces an intentional delay such that the switch action takes place in a half of oscillation period later. The second strategy named as quarter period delay SS control is to add an intentional delay such that the switch action occurs in a quarter of oscillation period later. In this case, the SS control law is inverted. An apparatus consisting of an electromagnetic (EM) spring is developed to validate the proposed strategies. The stiffness models of the system are established. In computer simulation, three cases have been examined. In case A, the system is simplified as linear and the dynamics of the EMs is neglected. In case B, the stiffness models are used and the dynamics of the EMs is neglected. In case C, the stiffness models are used and the dynamics of the EMs is considered. An experimental study is conducted in real time. The results have validated the observations obtained from the computer simulations.

Optimal Time-Delay Control for Multi-Degree-of-Freedom Nonlinear Systems Excited by Harmonic and Wide-Band Noises

2021 ◽  
pp. 2150053
Author(s):  
Rongchun Hu ◽  
Qiangfeng Lü
Keyword(s):  
Time Delay ◽  
Nonlinear Systems ◽  
Control Strategy ◽  
Wide Band ◽  
Stochastic Averaging ◽  
Degree Of Freedom ◽  
Optimal Time ◽  
Time Delay Control ◽  
Strongly Nonlinear ◽  
Delay Control

In this paper, an optimal time-delay control strategy is designed for multi-degree-of-freedom (multi-DOF) strongly nonlinear systems excited by harmonic and wide-band noises. First, by using the generalized harmonic functions, a stochastic averaging method (SAM) is employed for the time-delay controlled strongly nonlinear system under combined harmonic and wide-band noise excitations, by which a set of partially averaged Itô equations are obtained. Then, by solving the dynamical programming equation associated with the partially averaged Itô equations, the optimal control law can be obtained. Finally, by solving the Fokker–Planck–Kolmogorov (FPK) equation, the responses of the optimally time-delay controlled system are predicted. The analytical results are compared with the Monte Carlo simulation to verify the effectiveness and efficiency of the proposed control strategy.

Robust Control of Quadrotors Based on an Uncertainty and Disturbance Estimator

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Ricardo Sanz ◽  
Pedro Garcia ◽  
Qing-Chang Zhong ◽  
Pedro Albertos
Keyword(s):  
Robust Control ◽  
Real Time ◽  
Control Strategy ◽  
Disturbance Rejection ◽  
Reference Model ◽  
Flight Tests ◽  
Real Time Applications ◽  
Uncertainty And Disturbance Estimator ◽  
Noise Amplification ◽  
Disturbance Estimator

In this paper, a robust control strategy is proposed to control the attitude and the altitude of quadrotors, based on an uncertainty and disturbance estimator (UDE). It is shown that the proposed controller can be tuned very easily, achieving the desired performance only by selecting an appropriate reference model and tuning a single parameter to tradeoff disturbance rejection with noise amplification in the control signal. The proposed control strategy is extensively validated in real-time applications with an experimental Quanser platform and also with a quadrotor prototype in real flight tests.

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