• Tribology and Lubricants
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• v.12 no.2
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• pp.55-64
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• 1996

Frictional characteristics with the change of loading method and normal stiffness at dry sliding surfaces were experimentally and theoretically evaluated in this study. For the study, a ball-on-disk typed test rig was built and implemented, which allowed a proper selection of loading mechanism and normal stiffness of the test rig. Loading method were varied from dead weight to pneumatic cylinder and spring loading, and the normal stiffness was varied by a spring of different stiffness. Test results showed that frictional characteristics at various loading methods were different even though the operating variables were the same. Discrepancy in the frictional characteristics, such as coefficient of friction and fluctuation in the normal load, were explained by the change in dynamic parameters of the test rigs. Results also showed that coefficient of friction, which defines as a ratio of frictional force divided a normal load, could be differently evaluated in the calculation when fluctuation in the normal load was significant.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.10
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• pp.41-50
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• 1998

In this study, to investigate a characteristics of slip ratio control of H.C.U for ABS, half car model tester were developed and a new H.C.U. was compactly designed comparing to the commercical H.C.U. for ABS. In half car model tester, variable inertia wheel has been used to load the car weights and braking forces according to the road surface conditions which were realized by pneumatic cylinder. And solenoid valves using P.W.M. (Pulse Width Modulation) method were installed in the new H.C.U The slip ratio characteristics of tire had been measured using half car model tester and the results were used in the control simulation for a new H.C.U.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.146-154
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• 1997

Solenoid-folw control type ABS is used with a 'dump and reapply' pressure control arrangement instead of using 2/2 (normal open/close) solenoid valves in convensional systems(sol. -sol. control type), a flow control valve is used which replaces the (no) inlet valve. The flow control valve controls fluid flow providing a nearly constant reapply rate( .theta. ) after the dump plase of ABS operation. In this study, to investigate a characteristics of brake pressure by PWM control, test rig was consisted of ABS hydraulic modulator, digital controller, pneumatic power supply and brake master cylinder. For comparison with experi- mental results, system modelling and computer simulation were performed. As a result, experiment results showed fairly agreement with the simulation. Also, it is shown that the pressure gradient (tan .theta. ) is affected by pressure, frequency, duty ratio and expressed with an exponential funtion.

• 대한공업교육학회지
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• v.31 no.1
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• pp.211-225
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• 2006

Gabion can be used for the purpose of preventing overflow of river and side loss of road. However the manufacturing process of the gabion is manually controlled especially to the joining process at the terminal part of gabion with small diameter wire. In this paper automatic feeding guide system was designed and fabricated to make automation. The fabricated system was tested in the factory level. Pneumatic system was considered as the main idea of the feeding system. 3/2-way and 5/2-way manual control valve, eight double-acting cylinders were used. The system took 46.48 seconds during a cycle. Additional environmental noise and vibration were not detected when the machine operated at the working area. Based on the theoretical simulation and actual test the fabricated system was well controlled. The system was applied to the patent in 2006.

• Journal of the Society of Disaster Information
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• v.17 no.1
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• pp.112-119
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• 2021

Purpose: This study is based on the detailed inspection data for the last 6 years of fire-fighting high ladder vehicles, fire-fighting inflected ladder vehicles, fire-fighting chemical vehicles and fire-fighting pump vehicles used in front-line fire departments. The purpose is to contribute to the technological development of fire-fighting vehicles by grasping the implementation status of each city and province, the rate of defects, and the occurrence of defects by year. Method: The implementation status by city and province, defect incidence rate, and defect occurrences by year were analyzed. Result: From 2012 to 2017, when the average of 230 or more overhaul vehicles was requested, the results of each city/province show slight fluctuations, but the number of defects gradually decreased due to the old fire-fighting vehicle replacement project and the response of fire vehicle manufacturers. Conclusion: In the case of fire-fighting ladders, the incidence rate of defects was found to be in the order of elevator device, electric device, ladder device, and pneumatic supply device. And in the case of the fire fighting ladder, it was confirmed that the incidence of defects appeared in the order of the refractive ladder, hydraulic cylinder, hydraulic oil, and pneumatic supply device. In the case of fire-fighting chemical vehicles, it was confirmed that defects occurred in the powder fire extinguishing device, fire pump, vacuum pump, and pneumatic supply device.

• Journal of the Korean GEO-environmental Society
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• v.22 no.12
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• pp.41-50
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• 2021

This study investigated the changes in engineering characteristics of sand-tire chip mixtures during repetitive loading. To quantify the changes in the maximum shear modulus according to the tire chip content in the mixtures and the particle size ratio between sand particle and tire chip, the samples were prepared with tire chip content of TC = 0, 10, 20, 40, 60, and 100%, and the particle size ratios SR were also set to be SR = 0.44, 1.27, 1.87, and 4.00. The stress of the prepared sample was applied through a pneumatic cylinder. The experiment was conducted in the order of static loading (= 50 kPa), cyclic loading (= 50-150 kPa), static loading (= 400 kPa) and unloading. The stress applied to tested mixtures was controlled by a pressure panel and a pneumatic valve by using an air compressor. The shear wave velocity was measured during static and cyclic loadings by installing bender elements at the upper and lower caps of the mold. The results demonstrated that the change in maximum shear modulus of all tested materials with varying SR during repetitive loading is the most significant when TC ~ 40%. In addition, the mixture with smaller SR at a given TC shows greater increase in maximum shear modulus during repetitive loading.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.5 no.1
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• pp.79-85
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• 2011

In this paper, we proposed a design of upper-limb rehabilitation device with power-assist function for stroke survivals. The designed upper-limb rehabilitation device has three degrees of freedom； it is possible to perform flexion and extension motions of wrist, index finger and the other fingers except the thumb independently. The power-assist for wrist motion is performed by a pneumatic double-acting cylinder, but the fingers are actuated by electrical linear actuators to assist motions. A prototype upper-limb rehabilitation device and its controller were implemented. The position controller showed 0.8 mm errors in the steady-state. Experimental results showed that the proposed upper-limb rehabilitation device with power-assist function is feasible.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.9
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• pp.723-730
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• 2016

This paper presents a cable-driven hydraulic actuator named Cable Rod Hydraulic Actuator (CRHA). The cable actuating system is attractive for designing a compact joint in robotic applications since it can be installed remotely from the joint. Recently, cable rods have been used in pneumatic area for inertia reduction. However, designing cable rods in hydraulics is challenging because it is difficult to achieve flexibility and endurance simultaneously under high pressure conditions. In this paper, the cable rod, which consists of a cable and jacket, is proposed to meet both requirements. To design the CRHA, we determined the design parameters, such as cylinder size, and selected the cable rod's material by friction and leakage test. Finally, comparisons experiments about step and frequency responses with conventional hydraulic actuators were performed to assess feasibility for robotic joints, and the results show that the proposed system has good bandwidth and fast response as robotic joints.

• Tribology and Lubricants
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• v.39 no.2
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• pp.76-80
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• 2023

This paper describes an experimental investigation of the effect of cooling flow rate on gas foil thrust bearing (GFTB) performance. In a newly developed GFTB test rig, a non-contact type pneumatic cylinder provides static loads to the test GFTB and a high-speed motor rotates a thrust runner up to the maximum speed of 80 krpm. Force sensor, torque arm connected to another force sensor, and thermocouples measures the applied static load, drag torque, and bearing temperature, respectively, for cooling flow rates of 0, 25, and 50 LPM at static loads of 50, 100, and 150 N. The test GFTB with the outer radius of 31.5 mm has six top foils supported on bump foil structures. During the series of tests, the transient responses of the bearing drag torque and bearing temperature are recorded until the bearing temperature converges with time for each cooling flow rate and static load. The test data show that the converged temperature decreases with increasing cooling flow rate and increases with increasing static load. The drag torque and friction coefficient decrease with increasing cooling flow rate, which may be attributed to the decrease in viscosity and lubricant (air) temperature. These test results suggest that an increase in cooling flow rate improves GFTB performance.

• Journal of Biosystems Engineering
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• v.35 no.1
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• pp.37-45
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• 2010

Since SRC (Short-term Rotation Coppice) such as poplar and willow can be harvested in three years, they are known to be a potential forest biomass as fuel for a power plant. The production system including transplanting and harvesting is, however, necessary to be mechanized because such a biomass should be handled in a massive volumetric size. A pull-type stem-cutting transplanter was developed in the research as the first step to realize the production of SRC. A needle-like transplanting device pushes a stem-cutting into the prepared soil bed by a pneumatic cylinder, and another device firms soil around a stem-cutting transplanted. Since this is an intermittent operation, it was necessary to develop a zero horizontal velocity mechanism which enabled only the transplanting needle part to continue a zero horizontal movement relative to the ground during the transplanting operation even when the tractor kept moving forward. The 2-row transplanter can transplant stem-cuttings at the rate of 6.5 seconds per row without missing a single attempt. The planting depth and distance were well maintained and controlled. Their CVs were between 2.1~3.4% and 0.87~1.7% for the depth and the distance, respectively. Although, the transplanted stem-cuttings tended to lean outward from the back-view and forward from the side view, they were planted within the range of $3^{\circ}$ from the upright position.