• Journal of Institute of Control, Robotics and Systems
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• v.14 no.8
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• pp.837-841
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• 2008

This paper presents a robust reduced order state observer for a class of Lipschitz nonlinear systems with external disturbance. Sufficient conditions on the existence of the proposed observer are characterized by linear matrix inequalities. It is also shown that the proposed observer design can reduce the effect on the estimation error of external disturbance up to the prescribed level. Finally, a numerical example is provided to verify the proposed design method.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.1-6
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• 1991

This paper is concerned with the design of a robust tracking controller using a state observer on a robotic manipulator under the disturbance. The controller is designed to follow a step or ramp reference input without steady state error in the presence of a disturbance and a system parameter variation. In most cases, since all the state vectors are not measured, unmeasurable state vectors must be estimated or reconstructed. A reduced order observer is proposed to estimate unmeasurable state vectors of the non-linear system. Some problems are caused by the Coulomb friction, the disturbance, and the spring effect of a link between the drive motor and the manipulator arm. The state variables, directly measured and estimated by the reduced order observer, are fed back to the controller. When the robot system exhibits the 'limit cycle, the feedback gains initially obtained by optimal control theory are changed. As a result, the limit cycle is eliminated by the new controller gains,

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1247-1253
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• 2008

A design method of a T-S fuzzy model based reduced order nonlinear unknown input observer(NUIO) is presented. The fuzzy NUIO is designed based on the parallel distributed compensation(PDC) concept. It consists of a number of the linear UIOs, each of which is designed for each local linear model in the T-S fuzzy model of a class of nonlinear systems. The fuzzy NUIO provides not only the state estimates insensitive to the unknown inputs, for example, disturbances and faults etc., but also the estimates of the unknown inputs. Therefore, It can be employed in the state feedback control and disturbance rejection control of a class of nonlinear systems with unknown disturbances. It also applied to the robust residual generation for the fault detection and isolation systems and to the design of fault tolerant control systems. As an example, the NUIO is applied to an inverted pendulum system to show the state and disturbance estimation performance and to illustrate the fuzzy reduced order NUIO design method.

• Journal of the Semiconductor & Display Technology
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• v.23 no.2
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• pp.92-99
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• 2024

As semiconductor processes require several nanometers precision, the importance of motor control is increasing in semiconductor equipment. Due to unpredictable uncertainties such as friction and mechanical vibrations achieving precise position control in semiconductor processes is challenging. The internal model principle-based controller is a control technique that ensures robust steady-state performance by incorporating a model of the reference and disturbance. The disturbance observer-based controller is a prominent robust control technique implemented to cope with various nonlinearities and uncertainties. Provided that the two controllers can be designed to exhibit equivalent performance under certain conditions, this paper demonstrates through experiments that they yield identical results for the case of a BLDC position control problem. The experimental results also indicate that they can offer enhanced robustness compared with the conventional PID controller in the presence of a time-varying disturbance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2353-2363
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• 1994

This paper is concerned with the design of a robust digital controller using reduced-order observer on a robotic manipulator under the disturbance. In most cases of robotic manipulator since all state vectors are not measurable, the unmeasurable state vectors must be estimated or reconstructed. Other problems are caused by the nonlinear element like as nondifferentiable Coulomb friction, disturbance due to the gravitational pull, and the torsional spring effect of a link between the drive motor and the manipulator arm. The controller is based on feeding back the observable variables and the estimated state variables which are generated by the observer, and augmenting the system by additional discrete integrators. The feedback gain parameters are obtained by first applying the optimal control theory and then readjusting the feedback parameters to eliminate the limit cycle by using describing Function for nonlinear hybrid system.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.1034-1039
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• 1992

Time Delay Controller(TDC) is a model following controller which uses input and output values and state variables to estimate additional quantity of dynamics due to external disturbances and/or model parameters variation at some past instant. TDC is very robust against parametric uncertainty whil it is not robust against unmodeled dynamics even showing instability. To solve this problem a stability anlysis is performed and a compensation technique using reduced order observer, Anti-Filtering Compensator(AFC), is proposed for a case in which the high order kinown dynamics is deliberately ignored. If the ignored dynamics causes instability of the TDC control system, AFC is shown to be indispensible fot a stable implementation of TDC.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.270-273
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• 1996

A scheme of observer-based MFAC(Model Following Acceleration Control) system is proposed for the robustness control of DC servo position control systems. The proposed system is composed of LMFC, variable structure feedback controller, and reduced-order state observer. As the servo motor is controlled by the acceleration command, the total servo system becomes the acceleration control system. Simulation results show that the proposed system have robust properties against parameter variations and external disturbances.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.261-264
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• 1995

A scheme of observer-based MFAC(Model Following Acceleration Control) system is proposed for the DC servo position control system. The proposed system is competed of MFAC, feedback controller, and reduced-order state observer. As the servo motor is controlled by the acceleration command, the total servo system becomes the acceleration control system. Simulation results show that the proposed system have robust properties against parameter variations and external disturbances.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.1
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• pp.45-55
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• 1998

In this paper, a robust path tracker and depth controller of Autonomous Underwater Vehicle based on sliding mode control is presented. We have also designed augmented equivalent control inputs by analyzing the sliding mode with the reaching mode. This can enhance the reaching rate, and improve chattering problems, that is, noise caused by the control plane actuator of the vehicle, which is one of the problems that occur when sliding mode control is used. Also to resolve the steady state error generated in the path tracker under current effect, a modified sliding plane is constructed. Also a redesigned sliding plane and control input using transformation matrix is proposed to do easy design of MIMO depth controller. For state variables that cannot be measured directly, reduced order sliding mode control is used to design an observer. The performance of designed path tracker and depth controller is investigated by computer simulation. The results show that the proposed control system has robust performance to parameter variation, modelling error and disturbance.