• 한국운동역학회지
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• 제32권2호
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• pp.37-42
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• 2022

Objective: The aim of this study is to analyze the effect of the strength of the ankle support on the walking characteristics and ankle joints when men with flexible flat feet walk. Method: 13 adult male subjects (age: 23.9 ± 2.4 yrs, height: 173.0 ± 5.0 cm, weight: 76.9 ± 13.2 kg, Navicular Drop Test (NDT): 10.2 ± 0.8 mm) participated in this study. Each participant had to walk with the 3 conditions, barefoot, soft arch support and hard arch support, along a walkway while their kinematics was recorded at 100 Hz. Results: Based on the results of this study, it is considered that men with flexible flat feet should use hard arch support rather than bare feet to induce normal arch shape, relieve foot damage caused by excessive ankle joint abnormalities and improve stability. Conclusion: Our results for men with flat flexibility, there was a significant difference in the value of step length when walking was performed using two arch supports with different strengths. The angle of ankle dorsiflexion was significantly increased, and the ankle eversion angle was significantly decreased.

• Structural Engineering and Mechanics
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• 제62권5호
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• pp.619-629
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• 2017

This paper focuses on the study of complete dynamic modeling and maximum dynamic load carrying capacity computation of N-flexible links and N-flexible joints mobile manipulator undergoing large deformation. Nonlinear dynamic analysis relies on the Timoshenko theory of beams. In order to model the system completely and precisely, structural and joint flexibility, nonlinear strain-displacement relationship, payload, and non-holonomic constraints will be considered to. A finite element solution method based on mixed method is applied to model the shear deformation. This procedure is considerably more involved than displacement based element and shear deformation can be readily included without inducing the shear locking in the element. Another goal of this paper is to present a computational procedure for determination of the maximum dynamic load of geometrically nonlinear manipulators with structural and joint flexibility. An effective measure named as Moment-Height Stability (MHS) measure is applied to consider the dynamic stability of a wheeled mobile manipulator. Simulations are performed for mobile base manipulator with two flexible links and joints. The results represent that dynamic stability constraint is sensitive when calculating the maximum carrying load. Furthermore, by changing the trajectory of end effector, allowable load also changes. The effect of torsional spring parameter on the joint deformation is investigated in a parametric sensitivity study. The findings show that, by the increase of torsional stiffness, the behavior of system approaches to a system with rigid joints and allowable load of robot is also enhanced. A comparison is also made between the results obtained from small and large deformation models. Fluctuation range in obtained figures for angular displacement of links and end effector path is bigger for large deformation model. Experimental results are also provided to validate the theoretical model and these have good agreement with the simulated results.

• 한국전자통신학회논문지
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• 제4권3호
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• pp.236-242
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• 2009

2관절 유연한 로봇 팔는 관절 축을 회전할 때 진동이 발생한다. 본 논문에서는 유연한 로봇팔의 진동 동력학은 bernoulli-Euler의 beam이론과 라그란지 방정식을 이용하여 구하였고, $\dot{D}$-2C가 skew symmetric이다는 사실을 사용하여 계산량을 줄이는 단순한 구조의 새로운 제어기를 제안한다. Lyapunov 안정도 이론은 관절을 조절하기 위한 안정한 확정적인 비선형 제어기를 성취하기 위하여 적용된다.

• 한국정밀공학회지
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• 제18권12호
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• pp.66-72
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• 2001

In this paper, by using pseudo-inverse matrix of the spatial redundant flexible manipulators, a position control method and its effect in vibration suppression was presented. Vibration suppression control was developed using lumped mass spring model of the flexible manipulators. With 2 elastic links and 7 rotory joint manipulator ADAM, (1)position control for no redundancy, and (2)position control for one redundant DOF(degree of freedom) were tested. The objective of this experiment is to show the effect of position control, using pseudo-inverse matrix. toward the improvement of operation, and at the same time, to reduce the vibration of the link and the magnitude of the joint torque.

• 제어로봇시스템학회논문지
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• 제12권4호
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• pp.371-379
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• 2006

Increasing requirements for the high quality of industrial robot performance made the vibration control issue very important because the vibration makes it difficult to achieve quick response of robot motion and may bring mechanical damage to the robot. This paper presents a vibration control solution for industrial robots which have flexible joints. The joint flexibility is modeled as a two-mass system. And we analyze the vibration problem of a classical P-PI controller when it used for the flexible joints of industrial robots. Then a state feedback controller is designed for vibration suppression of the two-mass system. Finally, a gain-scheduling method is designed for maintaining control performance in spite of the time-varying nature of each joint's load side inertia. Simulation and experimental results show effective vibration suppression and uniform properties in overshoot in spite of the variation of load. The result of this study can be applied to the appropriate gain manipulation of many other mechatronic devices which have the two-mass system with varying load side inertia.

• Structural Engineering and Mechanics
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• 제42권3호
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• pp.409-424
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• 2012

Since relatively low elasticity modulus of the FRP materials results in lower natural frequencies, it is necessary to study the free vibration of FRP transmission poles. In this paper, the free vibration of tapered FRP transmission poles with thin-walled circular cross-section is investigated by a tapered beam element. To model the flexible joints of the modular poles, a rotational spring model is used. Modal analysis is performed for typical FRP poles with/without joint and they are also modeled by ANSYS commercial finite element software. There is a good correlation between the results of the tapered beam finite element model and those obtained from ANSYS as well as the existing experimental results. The effects of different geometries, material lay-ups, concentrated masses at the pole tip, and joint flexibilities are evaluated. Moreover, it is concluded that using tougher fibres at the inner and outer layers of the cross-section, results in higher natural frequencies, significantly.

• International Journal of Precision Engineering and Manufacturing
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• 제5권4호
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• pp.50-60
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• 2004

A very flexible beam can be used to model various types of continuous mechanical parts such as cables and wires. In this paper, the dynamic properties of a very flexible beam, included in a multibody system, are analyzed using absolute nodal coordinates formulation, which is based on finite element procedures, and the general continuum mechanics theory to represent the elastic forces. In order to consider the dynamic interaction between a continuous large deformable beam and a rigid multibody system, a combined system equations of motion is derived by adopting absolute nodal coordinates and rigid body coordinates. Using the derived system equation, a computation method for the dynamic stress during flexible multibody simulation is presented based on Euler-Bernoulli beam theory, and its reliability is verified by a commercial program NASTRAN. This method is significant in that the structural and multibody dynamics models can be unified into one numerical system. In addition, to analyze a multibody system including a very flexible beam, formulations for the sliding joint between a very deformable beam and a rigid body are derived using a non-generalized coordinate, which has no inertia or forces associated with it. In particular, a very flexible catenary cable on which a multibody system moves along its length is presented as a numerical example.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1128-1130
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• 1996

A canonical form observer design method for nonlinear systems is studied. Through this method, an observer of single link robot system with flexible joint is proposed. It is shown through simulation that the system can be stabilized when using the nonlinear feedback linearizing controller and the supposed observer.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1999년도 제14차 학술회의논문집
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• pp.17-20
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• 1999

In this paper, we consider on hard contact transition control strategies. Hard contact transition phase can be divided into two definitely different phases,“Pre-Transition Phase”and“Transition Phase”. Here we focus on the“Pre-Transition Phase”and we propose three control methods. First, we propose a novel con-troller named as “Suppression Controller”which is not only stable but also simple to implement. Second, we present passive damper named as“Flexible-Damped Joint”Which is good solution in Circumventing pre-transition Phase. Third, We suggest a stable and simple controller which can maximize joint damping and minimize recontact velocity in flexible-damped joint. It is named as“Joint Damping Controller”.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.79-84
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• 1999

This paper focus on investigating the influence of the amount of water ingestion and the engine speed on the joint reaction force of the connecting rod in engine. The connecting rod was modelled by MSC/PATRAN, the modal informations of it were obtained by the DMAP module in the MSC/NASTRAN, and the dynamic force history was computed through the flexible multibody dynamic simulation in DADS. To analyze the joint reaction force acting on the connecting rod, the 48 cases were investigated. The engine speed varies with 200, 700, 1600, 2400rpm and the volumetric ratio of water to the combustion chamber varies with 0, 10, 20, ..., 90, 95 and 97.5% . As the engine speed decreases and the amount of water ingestion increases, the joint reaction force increase. Especially when the amount of water ingestion exceeds the 70% of the volume of the combution chamber, the joint reaction force acting on the connecting rod is over the design strength.