• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.208-208
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• 2000

In realistic control systems, the nonlinear salutation attributes of the control actuator due to physical limitations should be taken into account. This nonlinear saturation of actuators may cause not only deterioration of the control performance but also a large overshoot during start-up and shut-down. As the overshoot increases, the system may become oscillatory unstable. In this paper, the supervisor implementation which guarantees good performance lot saturation operation and prevents reset wind-up is presented. Moreover, the sufficient conditions of the stability for saturated systems using supervisory control with a dynamic controller are provided in the discrete-time domain. A numerical example is illustrated to depict the efficiency of supervisory control for a typical saturated production-distribution system controlled by a discrete-time dynamic controller and to validate basic results by simulation.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.5 s.98
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• pp.169-174
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• 1999

In this paper, the CLQR(Constrained LQR) controller, which considers the actuator saturation in a cross-product term of a given performance index for an automotive active suspension control has been proposed. The effects of actuator saturations have been reflected directly in the states by using the linear relation between the control input and states. The method proposed here is more effective and intuitive compared with the conventional schemes. The CLQR has been applied to designing an automotive active suspension control system to verify its effectiveness and practical aspects.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.4
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• pp.104-109
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• 1997

A robust controller design to corrdinate a robot manipulator under unknown system parameters and bounded disturbance inputs is presented in this paper. Generally, robust controllers require high input torque so that they may face input saturation in actual application due to the power limitation of the actuator. To solve this problem, an improved robust controller with saturated input torque using a fuzzy logic control is proposed. Numerical examples are shown to validate the proposed controller using two degree-of-freedom planar arm.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.2 s.107
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• pp.207-213
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• 2006

In our previous research, we proposed a robust saturation controller which involves both control input saturation and structured real parameter uncertainties. This controller can analytically prescribed the upper and lower bounds of parameter uncertainties, and guarantee the closed-loop robust stability of the system in the presence of actuator's saturation. And the availability and the effectiveness of the proposed robust saturation controller were verified through numerical simulations. In this paper, we verify the robust stability of this controller through experimental tests. Expecially, we show unstable cases of other controllers in comparison with this controller. Experimental tests are carried out in the laboratory using a two-story test structure with a hydraulic-type active mass damper.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.975-980
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• 2004

Positioning system is widely used for many practical applications. This system requires a good controller to achieve high accuracy and fast response with simple and self-adjustable design. In order to satisfy the above requirements, a new practical controller for positioning systems, namely nominal characteristic trajectory following (NCTF) controller with PI compensator, has been proposed. However, the effect of actuator saturation can not be completely compensated for integrator windup when the object parameters vary. This paper presents a method to improve the NCTF controller by overcoming the problem of integrator windup by adopting a fuzzy system. The improvement of the NCTF controller is evaluated through simulation using a rotary positioning system. The simulation result has demonstrated the effectiveness of the compensated NCTF in overcoming the problem of integrator windup.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.21 no.4
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• pp.34-40
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• 2013

Attitude command response type required for enhanced handling qualities of helicopter can be implemented by mechanical automatic flight control system with SAS actuators which have limited authorities. However, the early saturation of SAS actuator hinders the helicopter from following the attitude command for large stick command. Auto-trim controller can delay SAS actuator's saturation by utilizing trim actuators and allows the attitude command response type for larger stick command. This paper describes the control law for limited authority system of helicopter with auto-trim. Limited authority system is applied to BO-105 linear dynamic model and simulation is performed along with handling quality analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.9
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• pp.768-776
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• 2000

A robust high-speed motion controller is proposed. The proposed controller consists of the proximate time optimal servomechai는 (PTOD) for high-speed motion, disturbance observer (DOB) for robustness, friction compensator, and saturation handling element, In the proposed controller, DOB basically provides the chance to apply PTOS to non-double integrator systems by drastically reducing disturbances as well as unwanted signals due to difference between real system and the double integrator model. But, in DOB-based systems, if control input is saturated due to control input PTOS and/or DOB, overall system stability cannot be guaranteed. To solve this problem, ribust stability, when the control input is saturated. Eventually, a simple saturation handling element is inserted to maintain internal stability of overall system. Also, we explain the our two saturation handling methods, Additional Saturation Element (ASE_ and Self Adjusting Saturation (SAS), are the equivalent solutions of the saturation problem to maintain internal stability. The stability and performance of the proposed controller are verified through numerical simulations and experiments using a precision linear motor system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1083-1086
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• 2003

Recently, the study on bearingless motors which integrate both motor and magnetic bearing function in one stator is very active, as many machines have high rotational speed, high precision, smaller size and lighter weight. In this paper, we propose a novel rotary actuator including function of axial bearing using Lorentz force as a preceding research for development of a bearingless motor. As using Lorentz force, this type has some merits such as the linearity of control force, freedom from flux saturation and high efficiency unlike conventional rotary actuators using a reluctance force. This type is cotrolled independently in levitation and rotational directions respectively. It shows by mathematical expression of levitation force and torque in the proposed rotary actuator. And also, the levitation force is generated by magnetic interaction between the magnetic materials and the rotational torque is generated by Lorentz force. Finally. for verification of this proposed system, a prototype is made and some experiments will be performed in the near future.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.69-77
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• 2011

In this paper, an optimal PID sliding mode controller is proposed for the position control of electro-hydrostatic actuator(ERA) systems with system uncertainties and saturation in the motor. An ERA prototype is developed and system modeling and parameter identification are executed. Then, optimal PID and optimal anti-windup PID controller are designed based on identified system model by using optimization toolbox in MA TLAB/Simulink and the performance of the two control systems are compared by experiment. It was found that the optimal anti-windup PID control system has better performance than the optimal anti-windup PID control system.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.4
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• pp.235-242
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• 2005

In this paper, we consider the H$\infty$ tracking control of linear system with a limited actuator capacity. The considered reference is a general time-varying one with bounded magnitude and rate. By adopting a similarity transform and a new sto variable, we convert the original system equation to new one which has a tracking error as a part of the new state variable. First, we obtain a result on the low-gained H$\infty$ tracking control which never permits the actuator saturation. Next, we give a result on scheduled H$\infty$ tracking control which uses the actuator capacity more effectively. All results are in the form of linear matrix inequalities(LMI) which can be easily checked their feasibility. Finally, we give a numerical example to show the validity and usefulness of our results.