• 제어로봇시스템학회논문지
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• 제22권6호
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• pp.411-416
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• 2016

This paper presents the design methodology of an unknown input observer for Lipschitz nonlinear systems with unknown inputs in the framework of convex optimization. We use an unknown input observer (UIO) to consider both nonlinearity and disturbance. By deriving a sufficient condition for exponential stability in the linear matrix inequality (LMI) form, existence of a stabilizing observer gain matrix of UIO will be assured by checking whether the quadratic stability margin of the error dynamics is greater than the Lipschitz constant or not. If quadratic stability margin is less than a Lipschitz constant, the coordinate transformation may be used to reduce the Lipschitz constant in the new coordinates. Furthermore, to reduce the maximum singular value of the observer gain matrix elements, an object function to minimize it will be optimally designed by modifying its magnitude so that amplification of sensor measurement noise is minimized via multi-objective optimization algorithm. The performance of UIO is compared to a nonlinear observer (Luenberger-like) with an application to a flexible joint robot system considering a change of load and disturbance. Finally, it is validated via simulations that the estimated angular position and velocity provide true values even in the presence of unknown inputs.

• 조명전기설비학회논문지
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• 제22권2호
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• pp.101-106
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• 2008

본 논문에서는 측정 잡음이 존재하는 선형시스템의 미지 입력 추정에 관하여 기술하였다. 적분관측기를 기초로 한 본 연구의 방법은 미지 입력을 정확히 추정해낼 수 있을 뿐만 아니라 추정 성능도 높일 수 있다. 시뮬레이션 결과와 기존 방법의 비교를 통해 본 연구 방법의 유용성을 입증할 수 있었다.

• 한국항공우주학회지
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• 제38권12호
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• pp.1177-1183
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• 2010

본 논문은 항공기의 신뢰도를 높이기 위한 목적으로, 항공기 조종면에 장착된 구동기에 고장이 발생하여 특정위치에 고정되어 움직이지 않을 때, 다중 미지입력 관측기(UIO, Unknown Input Observer)와 적응기법을 이용하여 고장이 발생한 구동기를 구분하고 해당 조종면의 고정된 위치를 추정하여, 조종력 할당 알고리듬 등의 조종면 고장에 대한 재형상 제어를 위한 입력을 제공하는 방법을 다룬다. 구동기의 개수와 동일한 관측기를 구성하되, 각 구동기의 고장이 반영된 선형모델을 사용함으로써 정상인 경우의 관측기에서 출력된 잔차와 고장이 발생한 경우의 관측기에서 출력된 잔차를 비교하여 고장을 분리하고, 적응기법을 이용하여 1초 내에 고장의 정도를 추정한다. 그러나 2개의 동일 형상의 러더가 존재할 경우, 고장분리가 불가함을 밝힌다.

• International Journal of Control, Automation, and Systems
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• 제6권4호
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• pp.477-487
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• 2008

This paper proposes a new position sensorless drive for brushless DC (BLDC) motors. Typical sensorless control methods such as the scheme with the back-EMF detection method show high performance only at a high speed range because the magnitude of the back-EMF is dependent upon the rotor speed. This paper presents a new solution that estimates the rotor position by using an unknown input observer over a full speed range. In the proposed method, a trapezoidal back-EMF is modelled as an unknown input and the proposed unknown input observer estimating a line-to-line back-EMF in real time makes it possible to detect the rotor position. In particular, this observer has high performance at a low speed range in that the information of a rotor position is calculated independently of the rotor speed without an additional circuit or complicated operation process. Simulations and experiments have been carried out for the verification of the proposed control scheme.

• Smart Structures and Systems
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• 제31권2호
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• pp.131-140
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• 2023

As well-known, the extended Kalman filter (EKF) is a powerful tool for parameter identification with limited measurements. However, traditional EKF is not applicable when the external excitation is unknown. By using least-squares estimation (LSE) for force identification, an EKF with unknown input (EKF-UI) approach was recently proposed by the authors. In this approach, to ensure the influence matrix be of full column rank, the sensors have to be deployed at all the degrees-of-freedom (DOFs) corresponding to the unknown excitation, saying collocated measurements are required. However, it is not easy to guarantee that the sensors can be installed at all these locations. To circumvent this limitation, based on the idea of first-order-holder discretization (FOHD), an improved EKF with unknown input (IEKF-UI) approach is proposed in this study for the simultaneous identification of structural parameters and unknown excitation. By using projection matrix, an improved observation equation is obtained. Few displacement measurements are fused into the observation equation to avoid the so-called low-frequency drift. To avoid the ill-conditioning problem for force identification without collocated measurements, the idea of FOHD is employed. The recursive solution of the structural states and unknown loads is then analytically derived. The effectiveness of the proposed approach is validated via several numerical examples. Results show that the proposed approach is capable of satisfactorily identifying the parameters of linear and nonlinear structures and the unknown excitation applied to them.

• 대한기계학회논문집A
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• 제26권10호
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• pp.2060-2066
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• 2002

The closed-loop state and input observer is a pole-placement type observer and estimates unknown state and input variables simultaneously. Pole-placement type observers may have poor transient performance with respect to ill-conditioning factors such as unknown initial estimates, round-off error, etc. For the robust transient performance, the effects of these ill-conditioning factors must be minimized in designing observers. In this paper, the transient performance of the closed-loop state and input observer is investigated quantitatively by considering the error bounds due to ill-conditioning factors. The performance indices are selected from these error bounds and are related to the observer robustness with respect to the ill -conditioning factors. The closed-loop state and input observer with small performance indices is considered as a well-conditioned observer from the transient perspective.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.476-476
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• 2000

This paper deals with an estimation method far sideslip angle by using an unknown input observation technique in 4WS passenger car systems. Firstly, a 4WS vehicle model with 3DOP is derived under the constant velocity and same tyre's properties. The induced model is transformed into the linear state space model with considering the external disturbance. Secondly, an unknown input observer is introduced and its property which estimating the states of system without any disturbance information is shown. Lastly, the estimated sideslip angle of the 4WS system is verified through numerical simulation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.283-283
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• 2000

In this paper, we deals with a decentralized control scheme with input compensation form for gantry crane systems. By considering the gantry crane's characteristics, the system is decentralized into two subsystems such as the travelling and sway subsystem, and the hoisting subsystem. For decentralizing the system, a simple algorithm is proposed using observability canonical form. The decentralized subsystems include unknown input which coupled with other subsystems and actuator failures. These unknown input and actuator failures are estimated by using PI observation techniques and those estimated values are used to construct an input compensation form. Lastly, the proposed decentralized control scheme far the gantry crane systems is verified by crane simulation.

• 제어로봇시스템학회논문지
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• 제7권4호
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• pp.281-287
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• 2001

In this paper, we deal with a decentralized control scheme with input compensation form for gantry crane systems. By considering the gantry cranes characteristics, the system is decentralized into two subsystems, the travelling and swaying subsystem and the hoisting subsystem. For decentralizing the system, a simple algorithm is proposed using the observability canonical form. The decentralized subsystems include unknown inputs that one coupled with other subsystems and actuator failures. These unknown input and actuator failures are estimated by using PI observation techniques. And those estimated values are used to construct an input compensation form. Finally, the proposed decentralized control scheme for the gantry crane systems is verified by crane simulation.

• 전력전자학회논문지
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• 제11권1호
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• pp.65-71
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• 2006

본 논문에서는 BLDC 전동기 센서리스 드라이브의 성능 향상을 위한 새로운 전동기 제어 기법을 제안한다. 최근 센서리스 제어방법의 주류를 이루고 있는 단자전압을 이용하는 방식들은 전동기를 동기 모드로 운전할 때 과도한 전압이 인가되면, 회전자 위치를 정확하게 검출할 수 없다. 특히 과도상태영역에서의 응답특성이 좋지 않다. 따라서 본 논문에서는 미지 입력인 역기전력을 추가적인 시스템의 상태로 모델링하고, 전체 시스템을 역기전력에 대한 미분방정식 형태 외란 모델을 도입한 확장 상태방정식으로 표현함으로서 얻어지는 상태관측기를 통하여 전동기의 속도 및 회전자 위치를 추정하는 새로운 알고리즘을 제안한다.