• 한국운동역학회지
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• 제14권2호
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• pp.85-103
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• 2004

This study was conducted to determine what effects would the midsole hardness of running shoes have on shoe flex angle and maximum propulsive force. Furthermore, the relationship between the shoes flex angle and maximum propulsive force was elucidated in order to provide basic data for developing running shoes to improve sports performances and prevent injuries. The subjects employed in the study were 10 college students majoring in physical education who did not have lower limbs injuries for the last one year and whose running pattern was rearfoot strike pattern of normal foot. The shoes used in this study had 3different hardness, shore A 40(soft), 50(medium) and 60(hard). The subjects were asked to run at a speed of $4{\pm}0.08m/sec$, and their movements were videotaped with 2 S-VHS video-cameras and measured with a force platform. And the following results were obtained after analyzing and comparing the variables. 1. Although the minimum angle of shoes flex angle was estimated to appear at SFA4, it appeared at SFA2 except in those shoes with the hardness of 40. 2. The minimum angle of shoes flex angle was $145.1^{\circ}$ with barefoot. Among the shoes with different hardness, it was the smallest when the hardness was 50 at $149.9^{\circ}$. The time to the minimum angle was 70.7% of the total ground contact time. 3. Maximum propulsive force according to midsole hardness was the largest when the hardness was 50 at $1913.9{\pm}184.3N$. There was a low correlation between maximum propulsive force and shoes flex angle.

• 한국운동역학회지
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• 제17권4호
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• pp.27-36
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• 2007

The purpose of this study was to investigate the effect of the upper body in order to increase a propulsive force in the old's walking. The subjects were each 10 males, the latter term of the aged and former term of the aged. There were three walking speeds of slow(about 5km/h), medium(about 6km/h), and maximum speed(about 7km/h). The subjects walking 11m were filmed the 5m section (from 3m to 8m) by 2-video cameras using three dimensional cinematography. And we computed different mechanical quantities and especially computed the relative momentum in order to achieve this study's aim. In this study, we was able to acquire some knowledge. The step length and step frequency increased in proportion to the walking speed, and the faster walking speed, the shorter ratio of supporting time( both legs supporting time/one step length time). When it was one leg support phase, the torso was indicated to generate the momentum in order to produce the propulsive force of walking. The upper and lower body had a cooperative relation for walking such as keeping step rate with the arms to legs and maintaining the body balance. The opposition phase for upward-and-downward direction of the torso and arms in walking was functioned to prevent the increase rapidly toward vertical direction of the center of gravity. The arms had contributed to coordinate the tempo of legs and the posture maintenance of the upper body. And by absorbing the relative momentum from the upper torso with arms to the lower torso, it had the rhythmical movement on upward-and-downward direction reducing the vertical reaction force. On account of the relations of absorption and generation of the propulsive force and the production of vertical impulse in the lower torso when walking by maximum speed, it was showed that the function of lower torso was come up as important problem for the mechanical posture stability and propulsive force coordination.

• 로봇학회논문지
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• 제11권4호
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• pp.285-292
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• 2016

For articulated swimming robots, there have been no researches about controlling the motion or trajectory following. A control method for articulated swimming robot is suggested by extending a previous algorithm, ESPG (Extended Swimming Pattern Generator). The control method focuses on the situation that continuous pre-determined swimming pattern is applied for long range travelling. In previous studies, there has not been a way to control the propulsive force when a swimming pattern created by ESPG was in progress. Hence, no control could be made unless the swimming pattern was completed even though an error occurred while the swimming pattern was in progress. In order to solve this problem, this study analyzes swimming patterns and suggests a method to control the propulsive force even while the swimming pattern was in progress. The angular velocity of each link is influenced and this eventually modifies the propulsive force. However, The angular velocity is changed, a number of problems can occur. In order to resolve this issue, phase compensation method and synchronization method were suggested. A simple controller was designed to confirm whether the suggested methods are able to control and a simulation has affirmed it. Moreover, it was applied to CALEB 10 (a biomimetic underwater articulated robot) and the result was verified.

• 한국정밀공학회지
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• 제16권5호통권98호
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• pp.151-159
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• 1999

A self-propulsive polishing robot is proposed as a method which automates a floor polisher. The proposed robot with two rotary brushes does not require any mechanism such as wheels to obtain driving forces. When the robot polishes a floor with its two brushes rotating, friction forces occur between the two brushes and the floor. These friction forces are used to move the robot. Thus, the robot can move in any direction by controlling the two rotary brushes properly. In this paper, firstly a dynamics model of a brush is presented. It computes the friction force between the brush and the floor. Secondly, the dynamics of the proposed robot is presented by using the bush dynamics. Finally, the inverse dynamics is solved for the basic motions, such as the forward, backward, leftward, rightward motions and the pure rotaion. This paper will contribute to realize a self-propulsive polishing robot as proposed above, In addition, this paper will give basic ideas to automate the concrete floor finishing trowel, because its basic idea for motion is similar to that of the proposed robot.

• 한국운동역학회지
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• 제15권2호
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• pp.31-39
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• 2005

The Purpose of this study was to reveal the biomechanical difference of two soccer footwear(soft ground footwear and hard ground footwear). Secondly, the purpose of this study was to clarify how each type of soccer footwear effects soccer players, which will provide scientific data to coaches and players, to further prevent injuries and to improve each players capacity. The result of comparative analysis of two soccer footwear can be summarized as below. The comparison of the very first braking force at walking found distinctive factors in the statistical data(t=3.092, p<.05). Braking impulse of two difference footwear showed distinctive factors in the statistical data(t=2.542, p<.05). In comparing GRFz max(N), the result showed a statistically significant difference in the two soccer footwear at running(t=2.784, p<.05). In the maximum braking impulse(t=2.774, p<.05) and propulsive impulse for antero-posterior direction, there was a statistically significant difference between the two soccer footwear at running. In the maximum braking force(t=3.270, p<.05) and propulsive force(t=4.956, p<.05) for antero-posterior direction, there was a statistically significant difference between the two soccer footwear at running. Significant differences were not found in moment(rotational friction) with two difference soccer footwear(moment max; t=2.231, moment min; t=1.784).

• 대한조선학회지
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• 제38권3호
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• pp.88-92
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• 2001

H. Kim, B.K. Lee and C.K. Rheem have been experimentally studied to clarified the mechanism of thrust force generated by sculling motion for the propulsion of Korean small boats. The experimental investigations have been conducted under the bollard condition by installing a scull at the end of a trimming tank of towing tank. The sculling motion produced by the skilful fisherman and the resultant venerated forces have been measured in respect to the Cartesian coordinate fitted to the pivot point of the scull. ("An Experimental Study on the Propulsive Characteristics of Sculls". J. of the Soc. of Naval Arch. of Korea, Vol. 26, No. 3, 1989, pp.13-24) Through these experiments the trajectory of the blade tip and the angular displacement of the blade section have been measured as shown in Fig. 1 and 2 of this paper. And at the same time the resultant hydrodynamic force components are expressed in Fig. 3 and 4. These three dimensional data of sculling motion and generated real time force components are the unique experimental information which could clarify the thrust force generating mechanism of sculling motion. The experimental results have been reanalyzed by focusing the relation between instantaneous attack angle of blade section and the resultants real time force components. Through these investigation it is found out that the conventional imagination that the 7cull motion should be effective in generating lift force must be reconsidered because the attack angle of scull blade are too great to free from stall phenomena during the sculling operation.

• 대한기계학회논문집B
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• 제39권6호
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• pp.497-504
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• 2015

본 논문에서는 박테리아 편모를 모사한 스프링 모델을 이용하여 박테리아의 편모의 추진적 거동에 관한 연구를 수행하였다. 본 해석에서는 상용프로그램을 사용하였으며, 별도의 회전영역 설정에 따른 수치기법의 타당성 확인과 더불어 파라미터 연구를 수행하였다. 수치해석 결과는 전반적으로 Resistive force theory와는 잘 일치하지 않았지만, Slender body theory와는 잘 일치하였다. 그리고 스프링의 회전속도, 피치, 나선반경 및 유체의 점성의 영향을 확인하였다. 또한 벽과의 거리에 따른 효과도 분석하였다.

• 로봇학회논문지
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• 제12권2호
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• pp.228-238
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• 2017

The CALEB10 is a multi-legged biomimetic underwater robot. In the last research, we developed a swimming pattern named ESPG (Extended Swimming Pattern Generator) by observing diving beetle's swimming actions and experimented with a positive buoyancy state in which CALEB10 floats on the water. In this paper, however, we have experimented with CALEB10 in a neutral buoyancy state where it is completely immersed in water for pitch motion control experiment. And we found that CALEB10 was unstably swimming in the pitch direction in the neutral buoyancy state and analyzed that the reason was due to the weight proportion of the legs. In this paper, we propose a pitch motion control method to mimic the pitch motion of diving beetles and to solve the problem of CALEB10 unstably swimming in the pitch direction. To control the pitch motion, we use the method of controlling additional joints while swimming with the ESPG. The method of obtaining propulsive force by the motion of the leg has a problem of giving propulsive force in the reverse direction when swimming in the surge direction, but this new control method has an advantage that a propulsive moment generated by a swimming action only on a target pitch value. To demonstrate validity this new control method, we designed a dynamics-based simulator environment. And the control performance to the target pitch value was verified through simulation and underwater experiments.

• 제어로봇시스템학회논문지
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• 제5권4호
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• pp.454-461
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• 1999

A concrete floor trowel machine, developed in the U.S in 1990's, consists of only two rotary trowels, and doesn't need any other mechanism for motion such as wheels. When the machine flattens a concrete floor with its rotary trowels, the machine can move in any direction by utilizing the unbalanced friction forces occurring between the rotary wheels and the floor when the trowels are tilted in appropriate directions. In order to automate the trowels machine, this paper proposed the self-propulsive concrete finishing trowel robot which has twin trowels. For the control of the robot, this paper discussed the following. Firstly, the dynamics model of the driving frictional force applied on each trowel from the floor is derived. Secondly, the relationship between the driving force for the robot and the control variable of the robot is derived. Finally, the basic motion of the robot are realized by using the obtained relationship. This paper figures out how the concrete floor finishing robot with tow trowels moves and will contribute to realizing it.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.159-163
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• 2009

In this paper, the fluid dynamic forces and performances of a moving airfoil in the low Reynolds number flow is addressed. In order to calculate the necessary propulsive force for the moving airfoil in a low Reynolds number flow, a lattice-Boltzmann method is used. The critical Reynolds and Strouhal numbers for the thrust generation are investigated for the four propulsion types. It was found that the Normal P&D type produces the largest thrust with highest efficiency among the investigated types. The leading edge of the airfoil has an effect of deciding the force production types, whereas the trailing edge of the airfoil plays an important role in augmenting or reducing the instability produced by the leading edge oscillation. It is believed that present results can be used to decide the optimal propulsion devices for the given Reynolds number flow.