• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.563-568
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• 2010

Turbopump-gas generator open-loop coupled tests are performed during the development of a 30tonf-LOx/Kerosene rocket engine. In the turbopump-gas generator open-loop tests, the propellants to gas generator are supplied from the outlets of turbopump, while the gas exhausted from the gas generator is vented out to the atmosphere, instead of being used to turbine driving. This paper presents the objectives, procedure, and results of the open-loop coupled test, in addition to a schematic representation of the test apparatus and the operating conditions for the test facility system and control system. The results of turbopump-gas generator open-loop coupled test confirm chill-down procedure, startup characteristics, nominal operability and smooth shutdown of the open-loop coupled Test Plant in test conditions simulating engine system operation environment.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.1065-1072
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• 2008

A HDD adopts a sensorless brushless DC (BLDC) motor as a spindle motor. Because there is no direct sensor measuring rotor position. open loop commutations with inductive sensing are used to increase the rotor speed up to a certain speed where the zero crossings of the back electromotive force (EMF) voltage are measurable. Therefore, successful open loop commutations are necessary for the stable start-up control of the spindle motors. In this paper, the time scale and the number of the open loop commutations are employed for design parameters to guarantee robustness to torque constant variation and initial rotor position. The design results are verified by experiments on a very low current start-up of the spindle motor with various environment. The experimental results show that the design results can decrease the start-up failure rate considerably.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.5-12
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• 2008

This paper presents the features of an impact angle constrained open-loop optimal trajectory which is given by a function of initial conditions and optimal guidance gains. Using missile motion described by linearized kinematic equations and a proper form of performance index, an inverse optimal problem is suggested to investigate the gains related to the performance index. The flight trajectory and time-to-go can be shaped in terms of the optimal guidance gains. The results are evaluated by 3-DOF simulation.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.403-408
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• 2001

In order to control hydration heat in mass concrete, pipe cooling method has been widely used. However, open pipe cooling system cannot be applied to the mass concrete structures when cooling water supply is difficult. To control hydration heat of high strength mass foundation, closed loop pipe cooling system was developed to solve the cooling water supply. This paper reports the performance result of hydration heat control with closed loop pipe cooling system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.10
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• pp.1796-1803
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• 2006

This Paper describes a systematic method for designing the $H_{\infty}$ controller for the inverted pendulum which is a nonlinear and single-input double-outputs system. In particular, the open-loop system is conbined with a pre-filter to shape the open-loop transfer function for the sensitivity function ind the complementary sensitivity function to be kept the desirable frequency characteristics. Consequently, the loop shaping technique of the open-loop transfer function reduces the impacts of the model uncertainties, measurement noises and exogenous disterbances on the dynamic characteristics of the inverted pendulum. The results of simulation and experiment show the efficiency of the proposed control method comparing with conventional PID control method.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.163-167
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• 2000

This paper presents the digital control of single-phase power factor correction(PFC) converter which has the variable gain according to the condition of inner control loop error. Generally the gain of inner current control loop in single-stage PFC converter has a constant magnitude. This has a bad influence on the power factor because current loop doesn't operate smoothly in the condition that input voltage is low In particular a digital controller has more time delay than an analog controller and degrades This drops the phase margin of the total digital PFC system,. It causes the problem that the gain of current control loop isn't increased enough. In addition the oscillation happens in the peak value of the input voltage open loop PFC system gain changes according to ac input voltage. These aspects make the design of the digital PFC controller difficult The digital PFC controller presented in this paper has a variable gain of current control loop according to input voltage. The 1kW converter was used to verify the efficiency of the digital PFC controller.

• Journal of Power Electronics
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• v.10 no.5
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• pp.468-476
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• 2010

This paper proposes and develops a new direct voltage control (DVC) approach. This method is designed to be applied in various applications for AC drives fed with a three-phase voltage source inverter (VSI) working with a constant switching time interval as in the standard direct torque control (DTC) scheme. Based on a very strong min(max) criterion dedicated to selecting the inverter voltage vector, the developed DVC scheme allows the generation of accurate voltage forms of waves. The DVC algorithm is implemented on a dSPACE DS1104 controller board and then compared with the space vector pulse width modulation technique (SVPWM) in an open loop AC drive circuit. To demonstrate the efficiency of the developed algorithm in real time and in closed loop AC drive applications, a scalar control scheme for induction motors is successfully implemented and experimentally studied. Practical results prove the excellent performance of the proposed control approach.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.4
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• pp.383-392
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• 2012

This paper reports the active vibration control of plates using a positive position feedback(PPF) controller with moment pair actuators. The equations of motion of the plates under a force and moment pairs are derived and the equations of PPF controllers are formulated. The numerical active control system is then achieved. The effect of the parameters - gain and damping ratio - of the PPF controllers on the open loop transfer function was investigated mainly in terms of the system stability. Increasing the gain of the PPF controller tuned at a mode, the magnitude of the open loop transfer function is increased at all frequencies without changing the phase behavior. The increase of the damping ratio of the PPF controller leads to decrease the magnitude of the open loop transfer function and to modify its phase characteristics, ie, system stability. Based on the behavior of the gain and the damping ratio of the controller, PPF controller for reduction of the plate vibration can be achieved. Two PPF controllers are designed with their connection in parallel to control the two modes simultaneously. Each PPF controller is tuned at the $1^{st}$ and $2^{nd}$ modes, respectively. Their parameters were determined to remain the system to be stable based on the results of the parametric study. A significant reduction in vibration at the tuned modes can be obtained.

• Proceedings of the KIEE Conference
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• summer
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• pp.117-119
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• 2004

An optimal flight motion simulator path generation method is proposed for hardware in the loop simulation of high maneuverable missile. The proposed method consists of open loop and closed loop path calculation algorithm based on the energy optimal control strategies. The optimal angle command is able to protect the simulator from high acceleration shock at initial control phase.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.605-614
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• 1995

In the automatic transmission using planetary gear there exists nonlinearities due to the finite difference between gear ratios, which yield torque hole during shift and influence on the ride quality and life of clutch. Based on the reaction carrier and converter turbine speed sliding functions are defined. Nonlinear closed-loop control laws are derived using them. Computer simulation shows that the closed loop design is better than the open loop design and semi-closed loop design.