• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.2
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• pp.16-24
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• 2010

This paper is proposed a novel fuzzy disturbance observer based on backstepping method for nonlinear systems with unknown disturbance. Using fuzzy logic systems, a fuzzy disturbance observer with the disturbance observation input is introduced for unknown disturbance. To guarantee that the proposed disturbance observer estimates the unknown disturbance, the disturbance observation error dynamic system is employed. Under the framework of the backstepping design, the fuzzy disturbance observer is constructed recursively and an adaptive laws and the disturbance observation input are derived. Numerical examples are given to demonstrate the validity of our proposed disturbance observer for nonlinear systems.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.7
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• pp.615-620
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• 2015

DOB (Disturbance Observer) is an useful control method for estimating the disturbance applied to dynamic systems. Disturbance observer can be used to implement a robust control system to generate a control input for rejecting the disturbance, and it can be also used to estimate the disturbance to obtain information. The system that uses disturbance estimation is investigated for high performance control such as automatic door systems, walking robot and electric power steering system in vehicles. In this paper, a novel disturbance observer which is called disturbance and current observer for estimating load torque in the motor system is proposed. The difference between the DOB for disturbance rejection and DCOB is mathematically verified. Current and angular velocity are required for estimating the load torque of the motor in DOB. However, the DCOB can estimate load torque and current without current sensor. DCOB is designed based on modeling of the motor system. Appropriate Q-filter is selected and the applicability of DCOB is verified by simulation. The estimated disturbance and current of the electric motor can be verified without current sensor, as experiments of the actual motor system.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.199-202
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• 1997

In this paper, a novel disturbance observer is proposed in order to regulate the disturbance in motor systems. The proposed observer does not require the implementation of ideal derivative of the state since the inverse of the nominal model is not used in the design of the observer. The transfer gain from a disturbance to the output of the disturbance observer is one. So, there is no time-delay in the response due to the dynamics of the observer.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.5
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• pp.332-338
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• 2016

In industrial applications, there are disturbances and uncertainties that bring unfavorable effects to achieving the desired performance of a closed-loop system. Not surprisingly, many researchers have developed various techniques to attenuate influence of the disturbance. One intuitive idea is to design a disturbance estimator, called a disturbance observer, and cancel the effects by feedback action. This paper is a survey of disturbance observers and related methods. We categorize existing methods by design approach, applied system, and characterization of disturbance. Several disturbance observers are explained by simple examples. The readers could use this paper to help understand the configurations of representative disturbance observer methods.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.297-303
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• 2015

We propose a disturbance observer(DOB) based feedback linearization control to improve position tracking performance in the presence of disturbance. The proposed method consists of a disturbance observer and a feedback linearization controller. The disturbance observer is designed to estimate the load force disturbance in electro-hydraulic systems. An auxiliary state variable is proposed in order to avoid amplification of the measurement noises in the disturbance observer. Using the estimated disturbance enables the Electro-hydraulic servo systems(EHS) dynamics to be changed into feedback linearization from. In order to compensate for the disturbance and to track the desired position, the feedback linearization based controller is proposed. The proposed method has a simple structure which can easily be implemented in practice. As a result, the proposed method improves the position tracking performance in the presence of disturbance. Its performance is validated via simulations.

• Journal of the Korean Mathematical Society
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• v.50 no.1
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• pp.17-39
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• 2013

The study of nonlinear discrete-time control dynamical systems with disturbance is an important topic in control theory. In this paper, we concentrate our efforts to multiple valued iterative dynamical systems, which model the nonlinear discrete-time control dynamical systems with disturbance. After establishing the validity of such modeling, we study the invariant set theory of the multiple valued iterative dynamical systems, including the controllability/reachablity problems of the maximal invariant sets.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.5
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• pp.402-410
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• 2004

To obtain a good tracking performance in an optical disk drive servo system, it is essential to attenuate periodic disturbances caused by eccentric rotation of the disk. As an effective control scheme for enhancing disturbance attenuation performance, disturbance observers (DOBs) have been successfully applied to the track-following servo system of optical disk drives. In disk drive systems, the improvement of data transfer rate has been achieved mainly by the increase of disk rotational speed, which leads to the increase of the disturbance frequency. Conventional DOBs are no longer effective in disk drive systems with a high-speed rotation mechanism because the performance of conventional DOBs is severely degraded as the disk rotational frequency increases. This paper proposes a new DOB structure for effective rejection of the disturbance in optical disk drives with a very high rotation speed. Asymptotic disturbance rejection is achieved by adopting a band-pass filter in the DOB structure, which is tuned based on the information on the disturbance frequency. In addition, performance sensitivity of the proposed DOB to changes in disk rotational frequency is analyzed. The effectiveness of the proposed DOB is verified through simulations and experiments using a DVD-ROM drive.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.1
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• pp.15-21
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• 2004

This paper deals with asymptotic stabilization problems for linear systems with time-varying input disturbances. In order to eliminate the influence of a disturbance on the system, a disturbance observer is designed and the time-varying disturbance can be rejected using its estimated value. Since the disturbance observer is kind of low-pass filter, it has inevitably estimation errors. To eliminate the inflences on the performance due to these errors, the additional control is designed based on these estimation errors using a well-known min-max control method. It is shown that the asymptotic stability of the closed-loop system is guaranteed. In general, the min-max control method requires the switching of control inputs and the switching magnitude of the control input is determined by the disturbance estimation error bounds. As the error bounds can be made arbitrarily small by choosing the high gain for the disturbance observer, the control method suggested in this paper can reduce the chattering phenomena as small as possible. Therefore, it has superior performance to the existing ones.

• Journal of IKEEE
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• v.21 no.4
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• pp.424-427
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• 2017

Smith predictor can't be applied to the time delay systems that have poles near the origin or a pure integrator or a modeling error, because of occurring the steady state error for the step disturbance. In this paper, a new Smith predictor controller for these systems is designed to eliminate the effects of the disturbance. A disturbance observer to estimate a disturbance is proposed and a new controller is designed using the estimated disturbance. As a result, the new controller can eliminate the effects of the disturbance and modeling error. The simulation results for the steam superheater and the steam pressure systems verify the efficiency of the proposed controller.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.6
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• pp.484-491
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• 2005

Using a disturbance observer is effective in enhancing the performance of dynamic system in presence of disturbances. Although various types of disturbance observers have been proposed to improve sensitivity of systems, there exist poor transient responses due to cross-couplings among disturbance observer loops. In this paper, dual disturbance observer (DOB) is proposed to reduce the effects of the cross-couplings. A different type of loop transfer function is proposed for external disturbance observer. While improving the sensitivity function by adding external DOB, it also provides improved complementary sensitivity function. The proposed dual DOB is applied to a commercial optical disk drive tracking system. It is shown that the dual DOB is an effective method in rejecting the effect of disturbance as well as improving the tracking performance.