Robust l<SUP>∞</SUP> stabilization under datarate constraints

Yumiko Ishido,Kiyotsugu Takaba 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

This paper is concerned with robust stabilization of an uncertain system over a rate-limited digital channel from the view point of input-out put stability. Because of the quantization in the communication channel, it is impossible to apply the traditional small gain theorem to establish robust stability of the feedback system. To over come this difficulty, we in troduce a new notion of small l<SUP>∞</SUP> signal l<SUP>∞</SUP> stability, and derive a sufficient robust stability condition a gainst l<SUP>∞</SUP> gain-bounded uncertainty based on this notion. Furthermore, for the case of a scalar nominal system, a sufficientd a tarate for the existence of a robustly stabilizing encoder-controller pairis explicitly given.

Robust stability analysis of real-time hybrid simulation considering system uncertainty and delay compensation

Pei-Ching Chen,Po-Chang Chen 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.6

Real-time hybrid simulation (RTHS) which combines physical experiment with numerical simulation is an advanced method to investigate dynamic responses of structures subjected to earthquake excitation. The desired displacement computed from the numerical substructure is applied to the experimental substructure by a servo-hydraulic actuator in real time. However, the magnitude decay and phase delay resulted from the dynamics of the servo-hydraulic system affect the accuracy and stability of a RTHS. In this study, a robust stability analysis procedure for a general single-degree-of-freedom structure is proposed which considers the uncertainty of servo-hydraulic system dynamics. For discussion purposes, the experimental substructure is a portion of the entire structure in terms of a ratio of stiffness, mass, and damping, respectively. The dynamics of the servo-hydraulic system is represented by a multiplicative uncertainty model which is based on a nominal system and a weight function. The nominal system can be obtained by conducting system identification prior to the RTHS. A first-order weight function formulation is proposed which needs to cover the worst possible uncertainty envelope over the frequency range of interest. Then, the Nyquist plot of the perturbed system is adopted to determine the robust stability margin of the RTHS. In addition, three common delay compensation methods are applied to the RTHS loop to investigate the effect of delay compensation on the robust stability. Numerical simulation and experimental validation results indicate that the proposed procedure is able to obtain a robust stability margin in terms of mass, damping, and stiffness ratio which provides a simple and conservative approach to assess the stability of a RTHS before it is conducted.

Interactive and Worst-Case Optimized Robust Control for Potential Application to Guaranteeing Roll Stability for Intelligent Heavy Vehicle

Liu Yulong,Ji Xuewu,Yang Kai-ming,He Xiangkun,Nakano Shirou 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.5

Roll stability loss of heavy vehicle is a severe road safety problem and modern intelligent heavy vehicle (IHV) raises new requirement for advanced roll stability control technology. Two novel roll stability control frameworks, namely active steering-active anti-roll (AS-AAR) interactive control and worst-case optimized robust control, which have potential application to guaranteeing roll stability of IHV are proposed and investigated in this paper. The first control framework is implemented based on Nash dynamic game theory in which AS-AAR shared control is investigated as a dynamic difference game so that its two players, namely AS and AAR system, can interact with each other to provide satisfactory control performance. This interactive control scheme can be applied to vehicle automated driving scenario to improve vehicle tracking performance and roll stability. Based on zero-sum game theory, the second worst-case optimized robust control scheme is also developed to guarantee vehicle roll stability. This control method provides a suitable design framework to guarantee roll stability in scenario of vehicle-to-driver handover for IHV in which the steering input from human driver is regarded as uncertain disturbance. Simulation results show that both control frameworks can effectively improve roll stability as well as lateral stability while ensuing satisfied tracking performance.

Research on Oscillation-Free Robust Control for Active Joint Dental Automation

Farzin Piltan,Meysam Esmaeili,Mohammad Ali Tayebi,Mahsa Piltan,Mojtaba Yaghoot,Nasri B. Sulaiman 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.11

Design a robust oscillation-free controller for multi input-multi output (MIMO) nonlinear uncertain dynamical system (sensitive dental joint) is the main objective in this research. In this paper, robust sliding mode controller will be selected as a main control technique and linear controller will be design to improve the stability and robustness to control of dental joint. The proposed approach effectively combines of design methods from switching sliding mode controller, and linear Proportional-Integral-Derivative (PID) control to improve the performance, stability and robustness of the sliding mode controller. Conventional sliding mode controller has two important subparts, switching and equivalent. Switching part (discontinuous part) is very important in uncertain condition but it causes chattering phenomenon. To solve the chattering, the most common method used is linear boundary layer saturation method, but this method lost the stability. To reduce the chattering with respect to stability and robustness; linear controller is added to the switching part of the sliding mode controller. The linear controller is to reduce the role of sliding surface slope and switching (sign) function. This controller improves the stability and robustness, reduces the chattering as well and reduces the level of energy due to the torque performance as well.

BPF-based Grid Voltage Feedforward Control of Grid-connected Converters for Improving Robust Stability

Shude Yang,Xiangqian Tong,Jun Yin,Haiyan Wang,Yaping Deng,Le Liu 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2

Grid voltage feedforward is extensively used for controlling grid-connected converters. However, the conventional voltage feedforward control reduces the stability margins of the converter connected to a high-impedance grid. The effect mechanism of voltage feedforward on the grid-connected converter control under high-inductive conditions of the grid impedance is clearly explained in this study using the equivalent transformations of control block diagrams. Results show that the delay produced by the digital control is the root cause of this effect. An improved voltage feedforward strategy, in which a bandpass filter (BPF) is introduced into the feedforward path, is proposed to strengthen the converter’s robust stability against grid impedance variations. The selection method of the BPF’s bandwidth is also provided considering the tradeoff between the response speed to the grid voltage sag and the system’s robust stability. The converter can work stably over a wide range of the grid impedance through the proposed approach. Simulation and experimental results fully verify the effectiveness of the BPF-based voltage feedforward strategy.

구조물의 랜덤진동 제어를 위한 통합 강인 제어 시스템

이동기 ( Lee Dong-gi ),이우상 ( Lee Woosang ),이규 ( Lee Giu ),허광희 ( Heo Gwanghee ),전준룡 ( Jeon Joonryong ) 한국구조물진단유지관리공학회 2003 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.7 No.1

In this paper, design and analysis of robust feedback control system are presented using the state-space approach. When mathematical models are used to describe real structural system, the differences between the mathematical models and the real structures can cause poor performance of control systems, especially for large-scale structures due to the structural uncertainties. Therefore, when controllers are used to reduce the random vibration caused by rain and wind loads, we cannot expect that control systems achieve satisfactory control result. Hence, it is important that robust feedback control systems must be designed considering system uncertainties. Considering the robust feedback control to carry out the control of uncertain systems, system stability can be guaranteed for structural perturbations occurring by modeling error. In order to explore the system stability with perturbation, the stability of nominal system should be stable. For application, the uncertain systems considering natural frequency and design constraints i.e, structures that have structural perturbations happening by mass and stiffness, are adapted to develop unified controller algorithm, which is optimal and robust. And, to investigate the validity and performance of the algorithm, numerical simulation is illustrated. Numerical result shows that the designed controller can be applied very well to the problem of degradation of control system performance.

Robust stability of spacecraft traffic control system using Lyapunov functions

Gulzhan Uskenbayeva,Mamyrbek Beisenbi,Dana Satybaldina,Vasyl Martsenyuk,Aigul Shaikhanova 제어로봇시스템학회 2016 제어로봇시스템학회 국제학술대회 논문집 Vol.2016 No.10

The article presents a new approach to the construction control systems for objects with uncertain parameters in the form of one-parametric structurally stable maps from catastrophe theory. This method allows synthesizing the highly effective control systems, possessing in the extremely wide area of robust stability. Research of control systems robust stability based on a new approach to A.M Lyapunov’s function construction.

Robust Stability of Two-Degrees-of-Freedom Servosystem with Stricture and Unstructured Uncertainties

Kim, Young-Bok The Korean Society of Mechanical Engineers 2000 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.14 No.11

A two-degrees-of-freedom servosystem for step-type reference signals has been preposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. this paper considers robust stability of the servosystem incorporating an observer against both structured and unstructured uncertainties of the plant. A condition is obtained as a linear matrix inequality, under which the servosystem is robustly stable independently of the gain of the integral compensator. This result implies that we can tune the gain to achieve a desirable transient response of the servpsystem preserving robust stability. An example is presented to demonstrate that under the robust stability condition, the transient response can be improved by increasing the gain of the integral compensator.

외란관측기 제어기의 비선형 자기부상시스템 적용에 관한 연구

조남훈(Nam Hoon Jo) 제어로봇시스템학회 2018 제어·로봇·시스템학회 논문지 Vol.24 No.5

Disturbance observer (DOB) controllers have been widely employed since they have the powerful ability of disturbance attenuation and uncertainty compensation. However, it is difficult to design a nonlinear DOB controller for nonlinear plants. This paper studies the robust stability of nonlinear plants controlled by linear DOB controllers. Using the case study of an electro-magnetic suspension (EMS) system, we studied the effects of nominal model selection on the robust stability of the linear DOB controller. We discuss two effects on robust stability: 1) The high-frequency gain of the nominal model and 2) The pole location of the nominal model.

Design Second Order Vibration Reduction

Meysam Kazeminasab,Zahra Esmaeili,Alireza Salehi,Mahdi Mirshekaran,Farzin Piltan 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.7

Design of a robust controller for multi input-multi output (MIMO) nonlinear uncertain dynamical system can be a challenging work. This paper focuses on the design and analysis of a high performance adaptive baseline sliding mode control for second order nonlinear uncertain system, in presence of uncertainties to reduce the vibration. In this research, sliding mode controller is a robust and stable nonlinear controller which selected to control of robot manipulator. The proposed approach effectively combines of design methods from switching sliding mode controller, adaptive model-free baseline controller and linear Proportional-Derivative (PD) control to improve the performance, stability and robustness of the sliding mode controller. Sliding mode controller has two important subparts, switching and equivalent. Switching part (discontinuous part) is very important in uncertain condition but it causes chattering phenomenon. To solve the chattering, the most common method used is linear boundary layer saturation method, but this method lost the stability. To reduce the chattering with respect to stability and robustness; linear controller is added to the switching part of the sliding mode controller. The linear controller is to reduce the role of sliding surface slope and switching (sign) function. The nonlinearity term of the sliding mode controller is used to eliminate the decoupling and nonlinear term of link’s dynamic parameters. However nonlinearity term of sliding mode controller is very essential to reliability but in uncertain condition or highly nonlinear dynamic systems it can cause some problems. To solve this challenge the baseline controller is used as online tune or adaptive controller. This controller improves the stability and robustness, reduces the chattering as well and reduces the level of energy due to the torque performance as well.