• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.5
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• pp.299-307
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• 2003

The local structure of CMAC neural networks (NN) results in better and faster controllers for nonlinear dynamical systems. In this paper, we propose a CMAC NN-based disturbance observer and its corresponding controller for a flexible joint robot. The CMAC NN-based disturbance observer compensates for the parametric uncertainties and the external disturbances throughout the entire mechanical system. Finally, a simulation result is given to demonstrate the effectiveness of proposed design method's robust tracking performance.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.7
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• pp.578-585
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• 2000

This paper presents a robust and systematic bilateral controller design method for a teleoperation of an underwater manipulator. Disturbance observer is used as a local controller of the master and underwater slave manipulator to set up the teleoperation system as a nominal model by compensating coupled nonlinear terms model uncertainties and external disturbances in the water. Using the linearized master/slave model a $H_{\infty}$ optimal control scheme is applied to systematically construct a force reflecting bilateral controller.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.1
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• pp.30-36
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• 2009

Many formation guidance laws have been proposed for VAV formation flight. Since most autonomous formation flight methods require various active communication links between the vehicles to know motion information of other vehicles, damage to the receiver or the transmitter and communication delay are critical problem to achieve a given formation flight mission. Therefore, in this point of view, the method that does not need an inter-vehicle communication is preferred in the autonomous formation flight. In this paper, we first summarize the formation guidance law without an inter-vehicle communication using feedback linearization and sliding mode control proposed in previous study. We also propose the modified formation guidance law with robust disturbance observer, which can provide significantly better performance than previously mentioned guidance law in case that other vehicles maneuver with large accelerations. The robust disturbance observer can estimate uncertainties generated by acceleration of leader vehicle. By eliminating the uncertainties using the estimated uncertainties, VAVs are able to achieve the tight formation flight. The performance of the proposed approach is validated by numerical simulations.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.584-596
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• 2019

This paper presents a Modified Adaptive Complementary Sliding Mode Control (MACSMC) system for the longitudinal motion control of the Fully-Submerged Hydrofoil Craft (FSHC) in the presence of time varying disturbance and uncertain perturbations. The nonlinear disturbance observer is designed with less conservatism that only boundedness of the derivative of the disturbance is required. Then, a complementary sliding mode control system combined with adaptive law is designed to reduce the bound of stabilization error with fast convergence. In particularly, the modified complementary sliding mode surface which contains the estimation of the disturbance can reduce the switching gain and retain the normal performance of the system. Moreover, a hyperbolic tangent function contained in the control law is utilized to attenuate the chattering of the actuator. The global asymptotic stability of the closed-loop system is demonstrated utilizing the Lyapunov stability theory. Ultimately, the simulation results show the effectiveness of the proposed approach.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1500-1503
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• 1996

This paper combines the disturbance accommodating control(DAC) and nonlinear model inversion control for a skid-to-turn(STT) missile. The missile autopilot may be designed to be robust with respect to a variety of uncertainties. We proposes the two step control design method. Nonlinear model inversion control is used as the main design method. Due to the model uncertainties and external disturbances, the exact nonlinear model inversion can not be achieved. DAC is designed to detect, to identify, and to compensate these uncertainties. DAC's disturbance observer is linear. Thus it is easy to implement. It does not cause the convergence problem due to coexistence between the modeling uncertainties and external disturbances. 6 DOF simulation results show that the proposed method may improve the missile tracking performance.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.878-883
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• 1990

There have been many approaches to solve the disturbance rejection problem in the control of LTI systems with state independent disturbances or possibly nonlinear state dependent disturbances. From the view point of each actuator, robot manipulators can be modeled as the second class of systems. With this model, M.Nakao et al. [1] introduced a decentralized control scheme based on interference estimation which is simple in its implementation and robust to the coupled dynamics and parameter variations. This paper systematically generalizes the control scheme to arbitrary finite dimensional LTI systems with disturbances. In doing so, we develop a disturbance observer theory for solving the disturbance rejection problem. We also present a discrete version of the theory with discussion of sampling and time-delay effects.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.5
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• pp.347-353
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• 2003

A nonlinear speed controller for a surface mounted permanent magnet synchronous motor (PMSM) based on a newly developed adaptive backstepping approach is presented To compensate parameter uncertainties and load torque disturbance, a nonlinear adaptive backstepping control law and adaptive law are derived systematically through virtual control input and suitable Lyapunov function. Also, speed observer without using costly speed sensor is presented. Simulation results show that the proposed controller can observe the speed and track the reference speed signal generated by a reference model.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.101-108
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• 2004

An electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and its parameter fluctuations are greater than those of an electrically driven manipulator. So it is relatively difficult to obtain stable control performance. In this report, we applied disturbance estimation and compensation type robust control to all axes in a 3-link electro-hydraulic manipulator. From the results of experiment, it was confirmed that the performance of trajectory tracking and attitude regulating is greatly improved by the disturbance observer, which model is the same for each axis. On the other hand, for the autonomous assembly tasks, it is said that compliance control is one of the most available methods. Therefore we proposed compliance control which is based on the position control by disturbance observer for our manipulator system. To realize more stable contact work, the states in the compliance loop are feedback, where not only displacement but also velocity and acceleration are considered. And we applied this compliance control to Peg-in-Hole insertion task and analyzed mechanical relation between peg and hole. Also we proposed new method of shifting the position of end-effector periodically for the purpose of smooth insertion. As a result of using this method, it is experimentally confirmed that Peg-in-Hole insertion task with a clearance of 0.05［mm］can be achieved.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.1
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• pp.47-53
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• 2004

An electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and its parameter fluctuations are greater than those of an electrically driven manipulator. So it is quite difficult to obtain stable control performance. We have applied a disturbance estimation and compensation type robust control to all the axes in a 6-link electro-hydraulic manipulator. It was confirmed that the performance of trajectory tracking and attitude regulating was greatly improved by the disturbance observer. For autonomous assembly tasks, it is said that compliance control is one of the most popular methods in contact task. We have proposed a compliance control based on the position control by a disturbance observer for our manipulator system. To realize more stable contact work, the states in the compliance loop are feedbacked, where not only displacement but also the velocity and acceleration are considered. We have also applied this compliance control to the Peg-in-Hole insertion task and proposed new methods of (1)rotating of the end-effector periodically in order to reduce the friction force, (2)random searching for the center of a hole and (3)trajectory modification to reduce the impact force. As a result of these new methods, it could be experimentally confirmed that the Peg-in-Hole insertion task with a clearance of 0.007 [mm] could be achieved.

• 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.