• Proceedings of the IEEK Conference
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• 2000.06e
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• pp.39-42
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• 2000

In this paper we design the robust impedance controller of the robot manipulator with time delay. The designed controller considers time delay in the position loop and stabilizes the closed-loop system. The performance of a controller can be easily degraded by external disturbances. To improve the performance when external disturbances exist, we use the disturbance observer to handle the disturbances in the velocity loop and provide robustness to the control system. To show the validity of the designed controller, several experiments are performed for the 5-DOF robot manipulator equipped with the wrist force/torque sensor system.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.604-607
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• 2000

In this paper we design the robust impedance controller of the robot manipulator with time delay. The designed controller considers time delay in the position loop and stabilizes the closed-loop system. The performance of a controller can be easily degraded by external disturbances. To improve the performance when external disturbances exist, we use the disturbance observer to handle the disturbances in the velocity loop and provide robustness to the control system. To show the validity of the designed controller, several experiments are performed for the 5-DOF robot manipulator equipped with the wrist force/torque sensor system.

• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3685-3693
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• 2021

This paper presents a disturbance observer-based robust backstepping load-following control (DO-RBLFC) scheme for modular high-temperature gas-cooled reactors (MHTGRs) in the presence of actuator saturation and disturbances. Based on reactor kinetics and temperature reactivity feedback, the mathematical model of the MHTGR is first established. After that, a DO is constructed to estimate the unknown compound disturbances including model uncertainties, external disturbances, and unmeasured states. Besides, the actuator saturation is compensated by employing an auxiliary function in this paper. With the help of the DO, a robust load-following controller is developed via the backstepping technique to improve the load-following performance of the MHTGR subject to disturbances. At last, simulation and comparison results verify that the proposed DO-RBLFC scheme offers higher load-following accuracy, better disturbances rejection capability, and lower control rod speed than a PID controller, a conventional backstepping controller, and a disturbance observer-based adaptive sliding mode controller.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.10
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• pp.821-828
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• 2021

Quadrotors relatively smaller and lighter than other aircraft have a disadvantage of being sensitive to the external disturbances. In order to solve this disadvantage, many studies have been conducted by various control techniques robust to disturbances. In this paper, CMGs (Control Moment Gyros) introducing relatively large control torque with an identical amount of electric powers are applied to cancel the external disturbances. Two CMGs are considered to control the attitude of quadrotors so that a multi-copter installed with two CMGs and four rotors are introduced for this work. Finally, to verify the control performance of the proposed system by the CMGs, a numerical simulation conducted in the given harsh environment.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.1073-1076
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• 1991

This paper presents a robust model reference adaptive controller for continuous-time single-input single-output linear time-invariant systems which are subjected to output-dependent disturbances as well as bounded external disturbances. In the derived controller form, an additional output error feedback term is included to over-ride the destabilizing effects by the output-dependent disturbances.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.2
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• pp.53-65
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• 2008

This paper proposes the qualitative method for planning the operation of multi-AUVs with environmental disturbances, which is considered to be a very difficult task. In this paper we use an extension collision map as a collision free motion planner. The tool was originally developed for the multiple ground vehicles with no internal/external disturbance. In order to apply the method to a water environment where there are tides and waves, and currents, we analyze the path deviation error of AUVs caused by external disturbances. And we calculate safety margin for the collision avoidance on the extension collision map. Finally, the simulation result proves that the suggested method in this paper make multi-AUVs navigate to the goal point effectively with no collision among them.

• Journal of Astronomy and Space Sciences
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• v.23 no.4
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• pp.405-414
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• 2006

Satellite formation flying has become a critical issue in the aerospace engineering because it is considered as an enabling technology for many space missions. Thus, many nonlinear control theories have been developed for the tracking problem of satellite formation flying, which include full-nonlinear dynamics, external disturbances and parameter uncertainty. In this study, nonlinear adaptive control law is developed using an adaptive backstepping technique to solve the relative position tracking problem of the satellite formation flying in the presence of mass uncertainty and the bounded external disturbance. Simulation studies are included to demonstrate the proposed controller performance. The proposed controller is shown to guarantee the system stability against the external bounded disturbances in the presence of mass uncertainty.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.6
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• pp.39-51
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• 1996

In the turning maneuver of the vehicle, its motion is mainly dependent on the genuine steering characteristics in view of the directional stability for stable turning ability. The under steer vehicle has an ability to maintain its own directonal performance for unknown external disturbances to some extent. From a few years ago, in order to acquire the more enhanced handling performance, some types of four wheel steering vehicle were considered and constructed. And, various rear wheel control logics for external disturbances has not been suggested. For this reason, in this posed rear wheel control logic is based on the yaw rate feed back type and is slightly modified by an yaw rate tuning factor for more stable turning performance. And an external disturbance is defined as a motivation of the additional yaw rate in the center of gravity by an uncertain input. In this study, an external disturbance is applied to the vehicle as a form of the additional yawing moment. Finally, the proposed rear wheel control logic is tested on the multi-body analysis software(ADAMS). J-turn and double lane change test are performed for the validation of the control logic.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.101-111
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• 1993

Many processes such as machining, injection-moulding and metal-forming are usually operated by hydraulic servo-systems. The dynamic characteristics of these systems are complex and highly non-linear and are often subjected to the uncertain external disturbances associated with the processes. Consequently, the conventional approach to the controller design for these systems may not guarantee accurate tracking control performance. An effective neuro-fuzzy controller is proposed to realize an accurate hydraulic servo-system regardless of the uncertainties and the external disturbances. For this purpose, first, we develop a simplified fuzzy logic controller which have multidimensional and unsymmetric membership functions. Secondly, we develop a neural network which consists of the parameters of the fuzzy logic controller. It is show that the neural network has both learning capability and linguistic representation capability. The proposed controller was implemented on a hydraulic servo-system. Feedback error learning architecture is adopted which uses the feedback error directly without passing through the dynamics or inverse transfer function of the hydraulic servo-system to train the neuro-fuzzy controller. A series of simulations was performed for the position-tracking control of the system subjected to external disturbances. The results of simulations show that regardless of inherent non-linearities and disturbances, an accuracy tracking-control performance is obtained using the proposed neuro-fuzzy controller.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.67-69
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• 2007

PMSM (Permanent Magnet Synchronous Motor) current control is a most inner loop of electromechanical driving systems and it plays a foundation role in the hierarchy's control loop of several mechanical machine systems. In this paper, a simple RMRAC control scheme for the PMSM is proposed in the synchronous frame. In the synchronous current model, the input signal is composed of as a calculated voltage by adaptive laws and system disturbances. The gains of feed-forward and feed-back controller are estimated by the proposed e-modification methods respectively, where the disturbances are assumed as filtered current tracking errors. After the estimation of the disturbances from the tracking errors, the corresponding voltage is fed forward to control input to compensate for the disturbances. The proposed method is robust to high frequency disturbances and has a fast dynamic response to time varying reference current trajectory. It also shows a good real-time performance duo to it's simplicity of control structure. Through the simulations considering several cases of external disturbances and experimental results, efficiency of the proposed method is verified