• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.65-74
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• 1994

Backcap is an electric remote control system for the operation of directional flow control valves. This paper presents a new type of basckcap system which is characterized by its simple construction. The backcap is essentially a hydraulic cylinder of which the piston is connected to a spool of hydraulic valve and controlled by input current. An inherent feedback is imposed on its mechanism so that no artificial noe is needed. Characteristics of the backcap is verified by stability analysis, transient motion and steady state positioning for step inputs. Design parameter analyses have been executer by some analytical approaches and computer simulations, which lead to their optimal valves. These results contributed to an effective new backcap system and its design strategy.

• Journal of the Korean Society for Precision Engineering
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• v.3 no.1
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• pp.29-39
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• 1986

An adaptive controller which is robust to the unknown load disturbance is developed for electro-hydraulic speed control systems. Since the load disturbance degrades the performance of the controller such as a steady state error and rise time in the conventional control system, appropriate adjustment of the controller is necessary in order to obtain the desired performances. The adaptation mechanism was designed to tune the feedforward gain, based upon minimization of ITAE (integral of time-multiplied absolute error) performance. The unknown load distrubance was identified by using an analog computer from the relationship between the velocity of the hydraulic motor and the load pressure. To evaluate the performance of the controller a series of simulations and experiments were conducted for various load conditions. Both results show that the proposed adaptive controller shows abetter performance than the conventional controller in terms of the steady state error and rise time.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.5
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• pp.108-115
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• 2014

In this study, experimental approaching method was applied under and single-cylinder engine to research the performance of direct needle-driven piezo injector (DPI) for CR direct-injection. As key-point factor of this DPI that relies on direct-acting operating of injector needle, unlike conventional hydraulic-servo, its nozzle needle can be directly driven by piezo actuator. Thus, effect of direct-acting injection of DPI on diesel combustion and emission characteristics was investigated under common-rail single-cylinder direct-injection engine, equipped with three different driving mechanism, including indirect-acting solenoid, piezo and DPI system. As main results, it found that a direct-acting piezo injector has higher of IMEP. And it has higher heat release rate during premixed combustion and mixing controlled combustion phase due to its higher heat release, even though nitrogen oxide (NOx) formations were increased slightly.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.366-372
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• 2000

In a power plant, it is generally accepted that a turbine governor system is necessary to control amount of steam supply toward the turbine system. There are many kinds of trouble at this governor system, which is recognized one of the most sensitive systems in the power plant. Especially we have experienced the internal leakage of motorization oil of servo valve. In the study, we investigated the mechanism of an internal leakage such as erosion by foreign materials and corrosion by chemical reaction between chloric healed oil and motorization oil. A precautionary measures is also performed to help the field service engineers.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.105-111
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• 2003

The three-axis road simulator is the test equipment which can simulate the standardized road conditions for the durability evaluation of automotive components such as suspensions. The road load data are collected and acquired from a vehicle test, and then these data are used to simulate road load conditions by the road simulator which consists of hydraulic actuators, link mechanism and servo controller. The link mechanism must be designed in consideration of the dynamic effect and interference during three axes motions in order to generate accurate motions. In this paper, the structural and kinematic analysis of the link mechanism is performed, and these results can be used for developing the three-axis road simulator. The three-axis road simulator provides considerable savings in cost, development time, and testing risk during developing automotive components.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.111-116
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• 2019

With the recent acceleration of industrial technologies and active research, wearable robot technologies have been applied to various fields. To study the utility of wearable robots, basic research on kinetic mechanisms of the human body, bio-signal analysis, and system control are essential. In this study, we investigated the basic structure of a wearable system and the operating principles of a driving mechanism. The control system and supporting structure, which comprise the driving mechanism, were designed and manufactured. Motion and load analyses were performed simultaneously for the design of the kinematic drive, and the driving mechanism was constructed by analyzing walking motion. The operating conditions of the cylinder were verified by stride via driving experiments. Further, the accuracy and responsiveness of the system were confirmed by comparison with actual motion, and the system safety was validated by applying loads.

• Journal of Biosystems Engineering
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• v.34 no.5
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• pp.315-324
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• 2009

Various types of vibration are transmitted to operators of agricultural tractors while working in the field. Most harmful vibration to human body is ride vibrations with low frequency ranging from 1 to 10 Hz, caused by rough terrain. These ride vibration has vertical and rotational components. This study was conducted to develop an active seat suspension system with two degrees of freedoms, enabling effectively reduce vibrations in vertical and pitch motions. Therefore, a mechanism for the active seat suspension was developed, and an electro-hydraulic servo system and a controller to drive the active seat suspension system were also developed in this study. A simulation model was developed to evaluate how the active seat suspension system effectively reduce the vibrations transmitted to the base of seat. Active seat suspension was optimized to enhance the performance using the developed simulation model. The performance of the seat suspension system was evaluated according to the test codes described in EEC78/764 in order to investigate the feasibility of application to agricultural tractors. The result showed that the developed active seat suspension system could reduce the magnitude of vertical vibration up to 80% for the input vibrations according to the test codes described in EEC78/764. The system could reduce the rotational displacement of ${\pm}\;2.5$ degrees up to 50% for the pitch vibration on the average in the frequency range of 1 to 2 Hz.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.2
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• pp.357-364
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• 2001

This study deals with the effect on non-martensitic layer on the fatigue strength in carburized gear. The test gears are carburized, then treated by the combination of chemical polishing and electro-polishing. Carburization treatment is used widely on parts of power transmission system like surface hardened layer to improve fatigue strength. Carburized gears are observed using a scanning electron microscope(SEM) to determine the characteristics of crack initiation mechanism in the surface layer. The constant street amplitude fatigue test is performed by using and electro-hydraulic servo-controlled pulsating tester. The S-N curves are obtained and illustrated. The effect of non-martensitic layer on the fatigue strength is clarified.

• Journal of the Korean Arthroscopy Society
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• v.8 no.1
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• pp.37-44
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• 2004

Purpose: To evaluate the optimal number of additional half hitches for achieving an optimal knot-holding capacity (KHC) of Lockable sliding knots. Methods: Four configurations of arthroscopic knots (Duncan loop, Field knot, Giant knot, and SMC knot) were tested for their knot-holding capacity. For each knot configuration, 6 sequential knots were made including the initial sliding knot and additional 5 knots by incrementing one half hitches at a time. Each added half-hitch were in reversing half-hitches with alternate posts (RHAPs) fashion. For each sequential knot configuration, 12 knots were made by No. 2 braided sutures. On the servo-hydraulic material testing system (Instron 8511, MTS, Minneapolis, MN), cyclic loading, load to clinical failure (3-mm displacement), load to ultimate failure, and mode of failure were measured. Results: Most of the initial loop without additional half-hitch showed dynamic failure with cyclic loading. The mean displacement after the end of cyclic loading decreased with each additional half-hitches. SMC and Giant knot reached plateau to 0.1 mm or less displacement after one additional half-hitch, shereas Field and Duncan loop needed 3 additional half-hitches. The SMC and Duncan knots needed 1 additional half-hitch to reach greater than 80N at clinical failure, whefeas the other 2 knots needed2 additional half-hitches. For the load exceeding 100N for clinical failure, the SMC knot required 3 additional half-hitches and the other three knots needed 4 additional half-hitches. As the number of additional half-hitches incremented, the mode of failure switched from pure loop failure (slippage) to material failure (breakage). Duncan loop showed poor loop security in that even with 5 additional half-hitches, some failed by slippage (17%). On the other hand, after 3 additional half-hitches, the 3 other knots showed greater than 75% of failure by material breakage mode (SMC and Field 92%, Giant 75%). Conclusion: Even with its own locking mechanism, lockable sliding knot alone does not withstand the initial dynamic cyclic load. For all tested variables, SMC knot requires a minimum of 2 additional half-hitches. Duncan knot may need more than 3 additional half-hitches for optimal security. All knots showed a mear plateau in knot security with 3 or more additional half-hitches.