• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.11
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• pp.2730-2741
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• 1993

A mathematical model of the seeker scan-loop which is composed of a spin-stabilized gyroscope and its driving signal processors is derived. The derived model has a transmission zero pair on the imaginary axis near to the required bandwidth. The LQG/LTR design methodology is evolved for the derived scan-loop model. To implement the designed LQG/LTR compensator to the actual plant, the compensator order is reduced using the internally balanced realization method. The performances of the LQG/LTR compensator are tested and compared with those of the P-control. Especially, stability-robustnessexperiments for model uncertainties represented in the form of time-delays are performed. It is demonstrated that the LQG/STR compensator is actually very robust to model uncertainties.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1307-1313
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• 1992

The end-point position control of a flexible manipulator is a non-minimum phase system. The PD feedback of the end-point position is not stable in contrast with that of the hub jangle. However, the system can be stabilized conditionally by the feedback of both the hub rate angle and the end-point position. Even in the non-minimum system, the LQG/LTR control law is more systmatic controller design method than the classical control law which uses a root-locus technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.10
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• pp.981-991
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• 1991

LQG/LTR method suggested to improve robustness of LQG have a theoritical constraint that it cannot apply to nonminimum phase plant(NMP). In this paper, we suggest a new LQG/LTR method for NMP which consist of three design steps. The first step is design a additional feed-foward compensator which approximate the given NMP plant to minimum phase(MP) plant and the next step is design a target loop transfer function for approximated MP plant satisfying the design specifications such as robust-performance and robust-stability. The last step is loop transfor recovery(LTR) that the open loop transfer function recovers the terget loop. It was shown by simulation example that the suggested method can solve the NMP constraint in designing LQG/LTR.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.729-735
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• 2012

A LQG/LTR(linear quadratic Gaussian/loop transfer recovery) controller with an integrator is designed to control the electro-hydraulic positioning system. Without considering the nonlinearity in the dead-zone, computer simulations are performed and show good performances and tracking abilities with the feedback controller based on the linear system model. However, the performance of the closed loop hydraulic positioning system shows big steady-state error in real system because of the dead-zone. In this paper, the feedback controller with a nonlinear compensator is introduced to overcome the dead-zone phenomenon in hydraulic systems. The inverse dead-zone as a nonlinear compensator is used to cancel out the dead-zone phenomenon. Experimental tests are performed to verify the performance of the controller.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.614-619
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• 2012

A LQG/LTR(Linear Quadratic Gaussian/Loop Transfer Recovery) controller with an integrator is designed to control the electro-hydraulic positioning system. Without considering the nonlinearity in the dead-zone, computer simulations are performed and show good performances and tracking abilities with the feedback controller based on the linear system model. However, the performance of the closed loop hydraulic positioning system shows big steady-state error in real system because of the dead-zone. In this paper, the feedback controller with a nonlinear compensator is introduced to overcome the dead-zone phenomenon in hydraulic systems. The inverse dead-zone as a nonlinear compensator is used to cancel out the dead-zone phenomenon. Experimental tests are performed to verify the performance of the controller.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.3
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• pp.57-64
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• 2015

In this paper, a model reference adaptive control (MRAC) scheme is applied for the precise and robust motion control of a pneumatic system with load variation. The reference model for MRAC is designed systematically using linear quadratic Gaussian control with loop transfer recovery (LQG/LTR). The sigmoid function of inverse velocity is used to compensate for the nonlinear friction force between the sliding parts. The experimental results show that MRAC effectively overcame the limit of the PID controller when there was unknown disturbance, including abrupt load variation and model uncertainty in the pneumatic control system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.93-101
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• 2016

This study presents a simple genetic algorithm to systematically design a PID controller for a hydraulic positioning system operated by a proportional solenoid valve. The inverse dead-zone compensator with nonlinear characteristics is used to cancel out the dead-zone phenomenon in the hydraulic system. The object function considering overshoot, settling time, and control input is adopted to search for optimal PID gains. The designed PID controller is compared with the LQG/LTR controller to check the performance of the hydraulic positioning system in the time and frequency domains. The experimental results show that the hydraulic servo system with the proposed PID controller responds effectively to the various types of reference input.