• Journal of Institute of Control, Robotics and Systems
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• v.17 no.10
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• pp.967-982
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• 2011

This paper presents a FTNCS (Fault-Tolerant Networked Control System) that can tolerate control surface failure and packet delay/loss in an UAV (Unmanned Aerial Vehicle). The proposed method utilizes the benefits of self-diagnosis by smart actuators along with the control allocation technique. A smart actuator is an intelligent actuation system combined with microprocessors to perform self-diagnosis and bi-directional communications. In the event of failure, the smart actuator provides the system supervisor with a set of actuator condition data. The system supervisor then compensate for the effect of faulty actuators by re-allocating redundant control surfaces based on the provided actuator condition data. In addition to the compensation of faulty actuators, the proposed FTNCS also includes an efficient algorithm to deal with network induced delay/packet loss. The proposed algorithm is based on a Lagrange polynomial interpolation method without any mathematical model of the system. Computer simulations with an UAV show that the proposed FTNCS can achieve a fast and accurate tracking performance even in the presence of actuator faults and network induced delays.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1514-1519
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• 2001

This paper is concerned with design, manufacturing and performance test of LIPCA ( Lightweight Piezo- composite Curved Actuator) using a top carbon fiber composite layer with near -zero CTE(coefficient of thermal expansion), a middle PZT ceramic wafer and a bottom glass/epoxy layer with high CTE. The main point of this design is to replace the heavy metal layers of THUNDER by thigh tweight fiber reinforced plastic layers without losing capabilities to generate high force and large displacement. It is possible to save weight up to about 30% if we replace the metallic backing material by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a graphite/epoxy prepreg were simply stacked and cured at an elevated temperature (177 $^{circ}C$ after following an autoclave bagging process. It was found that the manufactured composite laminate device had a sufficient curvature after detached from a flat mold. The analysis method of the cure curvature of LIPCA using the classical lamination theory is presented. The predicted curvatures are fairly in agreement with the experimental ones. In order to investigate the merits of LIPCA, a performance test of both LIPCA and THUNDE$^{TM}$ were conducted under the same boundary conditions. From the experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDERT$^{TM}$.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1109-1114
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• 2007

This paper presents the road simulator control technology for reproducing the road input signal to implement the real road data. The simulator consists of the hydraulic pump, servo valve, hydraulic actuator and its control equipment. The QFT is utilized to control the simulator effectively. The control system illustrates a tracking performance of the closed-loop controller with low order transfer function G(s) and pre-filter F(s) for a parametric uncertain model. A force controller is designed to communicate the control signal between simulator and digital controller. The efficacy of the QFT force controller is verified through the numerical simulation, in which combined dynamics and actuation of the hydraulic servo system are tested. The simulation results show that the proposed control technique works well under uncertain hydraulic plant system. The conventional software (Labview) is used to make up for the real controller in the real-time basis, and the experimental works show that the proposed algorithm works well for a single road simulator.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.214-221
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• 2007

This paper presents a myoelectric hand prosthesis(MHP) with two degree of freedom(2-DOF), which consists of a mechanical hand, a surface myoelectric sensor(SMES) for measuring myoelectric signal, a control system and a charging battery. The actuation for the 2-DOF hand functions such as grasping and wrist rotation was performed by two DC-motors, and controlled by myoelectric signal measured from the residual forearm muscle. The grip force of the MHP was automatically changed by a mechanical automatic speed reducer mounted on the hand. The skin interface of SMES was composed of the electrodes using the SUS440 metal in order to endure a wet condition due to the sweat. The sensor was embedded with a amplifier and a filter circuit for rejecting the offset voltage caused by power line noises. The control system was composed of the grip force sensor, the slip sensor, and the two controllers. The two controllers were made of a RISC-type microprocessor, and its software was executed on a real-time kernel. The control system used Force Sensing Resistors, FSR, as slip pick-ups at the fingertip of a thumb and the grip force information was obtained from a strain-gauge on the lever of the MHP. The experimental results were showed that the proposed control system is feasible for the MHP.

• Journal of Aerospace System Engineering
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• v.10 no.1
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• pp.51-58
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• 2016

In this paper, we present some results on No-failure accelerated life test of aerial vehicle for reliability demonstration. The design of general accelerated life test consists of the three phases: 1) Estimating normal life test time of a single product from Weibull distribution model; 2) Determining the acceleration factor (AF) by utilizing the relation between the life of mechanical components and the applied torque; 3) Calculating the accelerated life test time, which comes from dividing the estimated normal life test time into AF. Then, we applied the calculated life test time to the real reliability test of the flap actuating system, while considering the requirement specification for mechanical components and operating environment of the actuation system. Real experimental processes and results are presented to validate the theory.

• Nuclear Engineering and Technology
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• v.45 no.6
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• pp.795-802
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• 2013

For the improvement of APR1400 Diverse Protection System (DPS) design, the Advanced DPS (ADPS) has recently been developed to enhance the fault tolerance capability of the system. Major fault masking features of the ADPS compared with the APR1400 DPS are the changes to the channel configuration and reactor trip actuation equipment. To minimize the fault occurrences within the ADPS, and to mitigate the consequences of common-cause failures (CCF) within the safety I&C systems, several fault avoidance design features have been applied in the ADPS. The fault avoidance design features include the changes to the system software classification, communication methods, equipment platform, MMI equipment, etc. In addition, the fault detection, location, containment, and recovery processes have been incorporated in the ADPS design. Therefore, it is expected that the ADPS can provide an enhanced fault tolerance capability against the possible faults within the system and its input/output equipment, and the CCF of safety systems.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.3
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• pp.191-201
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• 1997

Accurate positioning of a throttle valve is required to implement the traction control system(TCS) which improves acceleration performance in slippery roads. In this research, position control system is developed for the main throttle actuator(MTA) system which uses one throttle actuation for small volume and DC servo motor for fast response. In order to drive DC motor, PWM signal generator and PWM amplifier were built and interfaced to the motor and controller. Digital PID control law is used as basic control algorithm. In order to prevent overshoot and improve accuracy, velocity profiles are generated and implemented whenever the targer throttle angle is given from the TCS controller. Thanks to velocity profiles, the control performance was very good and only one set of PID gains was used to cover the entire operating range. Also, the resolution of position is about 0.4$^{\circ}C$, which is better than that of stepping motor also used as throttle actuator in some products. The response time of the developed system is also fast enough to implement the engine control based TCS algorithm.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.617-624
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• 1997

Over 100 experiments have been conducted at the University of Maryland to evaluate the performance of a water mist fire suppression system for protection of an interstitial space below a raised subfloor. Experiments are conducted as part of an ongoing research effort to compare the fire suppression capabilities of various water mist system designs in a raised subfloor space. Water mist system design parameters considered in the investigation include means of actuation, concentration of water mist required for extinguishment of fires, and delivery mechanisms of water mist within close proximity to the fire. Delivery of the required concentration of water mist within close proximity to the fire is a principal factor governing the adequacy of water mist systems. Two sets of experiments have been conducted to document the performance of water mist system designs. One set is involved in documenting the concentration of water mist as a function of position within the space. The second set of experiments is concerned with the ability of water mist system designs to control fires in the space. One result of the research is the assessment of the ability of a water mist system to control fires at particular locations as a function of water mist density at that location.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.6 no.2
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• pp.55-62
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• 2012

In this paper we propose a control system to preserve the interior angle between back section and upper leg section to be larger than 90 degrees using a single limit switch. To design the control system we analyze the kinematics of actuation mechanisms for the back section and the upper leg section, and find out an optimal solution for the controller design. Using a prototype control system we perform experiments to test the controller performance, and show that the interior angle between the back section and the upper leg section is always preserved larger than 90 degree. From the experimental results, we show the proposed control system is feasible to keep the body posture stability.

• International Journal of Control, Automation, and Systems
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• v.5 no.1
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• pp.24-34
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• 2007

Closed-loop active twist control of integral helicopter rotor blades is investigated in this paper for reducing hub vibration induced in forward flight. A four-bladed fully articulated integral twist-actuated rotor system has been designed and tested successfully in wind tunnel in open-loop actuation. The integral twist deformation of the blades is generated using active fiber composite actuators embedded in the composite blade construction. An analytical framework is developed to examine integrally twisted helicopter blades and their aeroelastic behavior during different flight conditions. This aeroelastic model stems from a three-dimensional electroelastic beam formulation with geometrical-exactness, and is coupled with finite-state dynamic inflow aerodynamics. A system identification methodology that assumes a linear periodic system is adopted to estimate the harmonic transfer function of the rotor system. A vibration minimizing controller is designed based on this result, which implements a classical disturbance rejection algorithm with some modifications. Using the established analytical framework, the closed-loop controller is numerically simulated and the hub vibratory load reduction capability is demonstrated.