• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.457-458
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• 2006

A method for obtaining smooth, jerk bounded feed rate profile in high speed machining has been developed. This study proposes a NURBS interpolator based on adaptive feed rate control with a well developed look ahead algorithm which takes into account the machining dynamics as well. Limitation of jerk and proportional torque rate result in smoothened loads on the machine which effectively reduces excitation of the resonant frequencies of the machine. It is found that the values of the feed rate of the down stream sharp corner have profound effect on the feed rate of the upstream sharp corners. By using a windowing scheme the feed rate profile obtained after look ahead method is re-interpolated to reduce the jerk related problems. This is compared with the adaptive NURBS interpolator to show the effectiveness of the proposed method. Simulation results indicate that the consideration of 'ripple effect' is important in avoiding jerk and thereby increasing the machining accuracy.

• 한국운동역학회지
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• 제16권2호
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• pp.1-8
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• 2006

The purpose of this study was to evaluate normalized jerk according to shoes, slope, and velocity during walking. Eleven different test subjects used three different types of shoes (running shoes, mountain climbing boots, and elevated forefoot walking shoes) at various walking speeds(1.19, 1.25, 1.33, 1.56, 1.78, 1.9, 2, 2.11, 2.33m/sec) and gradients(0, 3, 6, 10 degrees) on a treadmill. Since there were concerns about using the elevated forefoot shoes on an incline, these shoes were not used on a gradient. Motion Analysis (Motion Analysis Corp. Santa Rosa, CA USA) was conducted with four Falcon high speed digital motion capture cameras. Utilizing the maximum smoothness theory, it was hypothesized that there would be differences in jerk according to shoe type, velocity, and slope. Furthermore, it was assumed that running shoes would have the lowest values for normalized jerk because subjects were most accustomed to wearing these shoes. The results demonstrated that elevated forefoot walking shoes had lowest value for normalized jerk at heel. In contrast, elevated forefoot walking shoes had greater normalized jerk at the center of mass at most walking speeds. For most gradients and walking speeds, hiking boots had smaller medio-lateral directional normalized jerk at ankle than running shoes. These results alluded to an inverse ratio for jerk at the heel and at the COM for all types of shoes. Furthermore, as velocity increased, medio-lateral jerk was reduced for all gradients in both hiking boots and running shoes. Due to the fragility of the ankle joint, elevated forefoot walking shoes could be recommended for walking on flat surfaces because they minimize instability at the heel. Although the elevated forefoot walking shoes have the highest levels of jerk at the COM, the structure of the pelvis and spine allows for greater compensatory movement than the ankle. This movement at the COM might even have a beneficial effect of activating the muscles in the back and abdomen more than other shoes. On inclines hiking boots would be recommended over running shoes because hiking boots demonstrated more medio-lateral stability on a gradient than running shoes. These results also demonstrate the usefulness of normalized jerk theory in analyzing the relationship between the body and shoes, walking velocity, and movement up a slope.

• 한국운동역학회지
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• 제19권4호
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• pp.739-748
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• 2009

본 연구의 목적은 2008년 베이징올림픽 남자 역도 금메달리스트인 사재혁선수를 대상으로 최대의 노력으로 경기력을 수행하고 있는 실제 경기상황에서 동일한 중량으로 Jerk동작의 1차시기 실패 후 2차시기 성공을 운동학적으로 분석하여 실패의 원인을 구명하여 사재혁 선수의 Jerk기술 향상과 경기력을 극대화시키고 현장에서 선수들을 지도하는데 필요한 기초자료를 제공하는데 있었다. 본 연구를 수행한 결과 다음과 같은 결론을 얻었다. 성공 동작이 실패동작에 비하여 1국면에서는 짧은 시간을, 3국면과 4국면에서는 다소 긴 수행시간을 보였다. 바벨의 수직변화는 큰 차이를 보이지는 않았으나, 무릎에서는 E4에서 실패 시 낮은 수직 위치를 나타냈다. 바벨의 수직속도는 4국면에서 무릎의 수직속도는 3국면과 4국면에서 성공과 실패동작 간에 큰 차이를 보였다. 3국면의 실패동작에서 성공동작에 비하여 빠른 신체무게중심의 하방속도가 나타났다. E3순간의 실패동작에서 성공동작에 비하여 더 굴곡된 무릎각도가 나타났다.

• 한국운동역학회지
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• 제16권1호
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• pp.1-10
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• 2006

The purpose of this study was to identify critical parameters of a putting performance using jerk cost function. Jerk is the time rate of change of acceleration and it has been suggested that a skilled performance is characterized by decreased jerk magnitude. Four elite golfers($handicap{\leq}2$) and 4 novice golfers participated in this study for the comparison. The 3D kinematic data were collected for each subject performing 5 trials of putts for each of these distances (random order): 1m, 3m, 5m The putting stroke was divided into 3 phases such as back swing. down swing and follow-through. In this study, it was assumed that there exist smoothness difference between elite and novice golfers during putting. The distance and jerk-cost function of Putting stroke for each phase were analyzed Results showed that there was a significant difference in jerk cost function at putter toe (at media-lateral direction) and at the center of mass between two groups by increasing putting distance. From these it could be concluded that jerk can be used as a kinematic parameter for distinguishing elite and novice golfers.

• 한국운동역학회지
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• 제31권2호
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• pp.148-153
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• 2021

Objective: It is to extract training items that have a high relationship with the improvement of weightlifting records through correlation and regression analysis between training methods used commonly in the field and Snatch records and jerk records. Through this, it is intended to promote training efficiency to improve the records of weightlifters. Method: For 90 elite weightlifters of the professional teams, 4 groups (lightweight (30 people): 61 kg, 67 kg, 73 kg., middleweight (30 people): 81 kg, 89 kg, 96 kg., heavyweight (30 people): 102 kg, 109 kg, +109 kg., the whole group (90 people)) were divided. At the significance level of 0.05, correlation analysis and linear regression analysis were performed between record of training methods used widely in the field and Snatch records and Jerk records. Results: First, the better the record in Jerk, the better the Snatch record. Second, the three training methods HS, ForceS and WP performed in the field were all found to be important factors related to the improvement of Snatch record. Third, In the jerk where there are more types of training than Snatch, three training methods (HC, ForceS, BPP) appeared to be an important training method for improving the jerk record. Conclusion: While many training methods have been devised and carried out in the field, 3 types of training (HS, ForceS, WP) for improving Snatch record and 3 types of training (HC, ForceS, BPP) for improving Jerk record was found to be the most influential training method. Since all of them showed a large value of explanatory power by regression analysis, it is considered that this study is meaningful in that it can promote training efficiency by simplifying although there are many types of training for athletes.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.785-786
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• 2010

• 한국자동차공학회논문집
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• 제19권1호
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• pp.17-24
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• 2011

TMED(Transmission Mounted Electric Device) parallel hybrid configuration can realize EV(Electric Vehicle) mode by disengaging the clutch between an engine and a transmission-mounted motor to improve efficiencies of low load driving and regenerative braking. In the EV mode, however, jerk can be induced since there are insufficient damping elements in the drive-train. Though the jerk gives demoralizing influence upon driving comport, adding a physical damper is not applicable due to constraints of the layout. This study suggests the jerk reduction control, composed of active damping method and torque profiling method, to suppress the jerk without hardware modification. The former method creates a virtual damper by generating absorbing torque in the opposite direction of the oscillation. The latter method reduces impulse on the mated gear teeth of the drive-train by limiting the gradient of traction torque when the direction of the torque is reversed. To validate the effectiveness of the suggested strategy, a series of vehicle tests are carried out and it is observed that the amplitude of the oscillation can be reduced by up to 83%.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1906-1909
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• 2005

This paper presents the acceleration optimization of a high-speed LCD (Liquid Crystal Display) transfer system for the minimization of vibration. To reduce vibration is one of key requirements for the dynamic control of a high-speed LCD transfer system. In this paper, the concept of finite jerk (the first derivative of acceleration) has been introduced for realizing input acceleration. The profile of finite jerk has been optimized using a genetic algorithm so that vibration effect can be minimized. In order to incorporate a genetic algorithm, the dynamic model of a LCD transfer system which is realized by using the $ADAMS^{(R){$ software has been linked to the simulation system constructed by the $MATLAB^{(R)}$. The simulation results illustrated that the duration of finite jerk can be optimized so as to minimize the magnitude of vibration. It has been also shown that the acceleration optimization with finite jerk can make the high-speed motion of a LCD transfer system result in low vibration, compared with the conventional motion control with trapezoidal velocity profile.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.604-609
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• 2005

This paper presents an experimental study for optimizing the acceleration of AC servomotor using finite jerk (the first derivative of acceleration). The acceleration optimization with finite jerk aims at generating the smooth velocity profile of AC servomotor by experimentally minimizing vibration resulted from the initial friction of servomotor. The stick-slip motion of AC servomotor induced by initial friction can result in the positional errors that are not good for high-precision devices such as the assembly robot arms to be used in a 300mm wafer or a LCD (Liquid Crystal Display) stocker system. In this paper, experiments were made by using a PM (Permanent Magnet) type AC servomotor with MMC(R) (Multi Motion Controller) programmed in Visual C++(R). The experiments have been performed for finding the optimal duration time of finite jerk in terms of the minimization of vibration displacements when both the magnitude of velocity and the allowable acceleration are given. We have compared the proposed control with the conventional control with trapezoidal velocity profile by measuring vibration displacements. The effectiveness of the proposed control has been verified in that the experimental results showed the decrease of vibration displacement by about 24%.

• 한국자동차공학회논문집
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• 제14권2호
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• pp.151-157
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• 2006

The passenger car drivers want in general to feel good driveability, but they sometimes feel uncomfortable by shock and jerk phenomena when they push or release acceleration pedal with clutch on state. In this paper, the shock and jerk characteristics are studied on the vehicles controlled by the throttle-by-wire system. Experiments and simulations were carried out on two vehicles which show different control characteristics. The engine torque control characteristics was analyzed by measuring cylinder pressure. Various specification factors of the vehicles and the torque control logic of the engines were simulated through experimental data basis. The result shows the spring effect of the trans-axle in the drive-train is one of the most important factors of the shock-jerk phenomena and the engine torque control method is also responsible for the reducing the shock-jerk amplitude. In this paper a new control logic of the engine torque is suggested for the better driveablility on the tip-in/out event.