• 한국기계가공학회지
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• 제20권4호
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• pp.49-56
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• 2021

This paper describes the modeling and simulation of a four-axis dedicated robot that can attach and detach a workpiece on a computer numerical control (CNC) lathe. The robot was modeled as a Scarab robot for compatibility with CNC lathes. The advantages of such a robot are that an actuator with a small capacity can be used for the robot and the degrees of freedom of the robot can be reduced to four. For the simulation of the four-axis dedicated robot, a regular kinematic equation and an inverse kinematic equation were derived. Simulations were performed with these equations from the position of the loading device to the chuck position of the lathe before machining and from the chuck of the lathe to the position of the loading device after machining. The simulation results showed that the four-axis dedicated robot could be operated accurately, and they provided the joint angle of each motor (θ1, θ2, and θ3).

• 한국컴퓨터정보학회논문지
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• 제10권5호
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• pp.171-177
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• 2005

본 논문에서는 Forward Kinematics의 개념을 이용하여 각도변화에 따른 좌표계산 방법을 설명하고, Workspace 생성을 위한 반복적 방정식 (Recursive Equation)을 동차좌표계를 이용하여 수식으로 표현한다. 그리고 이 반복적 방정식(Recursive Equation)과 인체모델 관절의 한계 각도를 접목시켜 인체모델의 Workspace생성을 위한 알고리즘을 제시하고, 제시한 알고리즘을 이용하여 인체모델의 Workspace 생성결과를 그래픽으로 표현하였으며 알고리즘의 적절성을 보였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.661-665
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• 1996

An inverse kinemetics problem of a reclaimer which digs and transports ironstones or coals in the raw yard is investigated. Because of the special features of the reclaimer of which scooping buckets are attached around the rotating drum at the end of boom, kinematic redundancy occurs in determining the joint varialbes For a given reclaiming point in space the forward kinematics yields 3 equations, however the number of involved variables in the equations are four. A plane equation approximating the surface near a reclaiming point is obtained by considering 8 adjacent points surrounding the reclaiming point. One extra equation to overcome redunduncyis further obtained from the condition that the normal vector at a reclaiming point is perpendicular to the plane. An approximate solution for a simplified problem is first discussed, Numerical solution for the oritinal nonlinear porblem with a constraint equation is also investigated. Finally a closed form solution which is not exact but sufficiently close enough is proposed by exploiting geometric constraint.

• Journal of Biosystems Engineering
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• 제38권2호
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• pp.138-148
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• 2013

Purpose: Determining an appropriate path is a top priority in order for a robot to maneuver in a dynamically efficient way especially in a pick-and-place task. In a non-standardized work environment, current robot arm executes its motion based on the kinematic displacements of joint variables, though resulting motion is not dynamically optimal. In this research we suggest analyzing and applying motion patterns of the human arm as an alternative to perform near optimum motion trajectory for arbitrary pick-and-place tasks. Methods: Since the motion of a human arm is very complicated and diverse, it was simplified into two links: one from the shoulder to the elbow, and the other from the elbow to the hand. Motion patterns were then divided into horizontal and vertical components and further analyzed using kinematic and dynamic methods. The kinematic analysis was performed based on the D-H parameters and the dynamic analysis was carried out to calculate various parameters such as velocity, acceleration, torque, and energy using the Newton-Euler equation of motion and Lagrange's equation. In an attempt to assess the efficacy of the analyzed human motion pattern it was compared to the virtual motion pattern created by the joint interpolation method. Results: To demonstrate the efficacy of the human arm motion mechanical and dynamical analyses were performed, followed by the comparison with the virtual robot motion path that was created by the joint interpolation method. Consequently, the human arm was observed to be in motion while the elbow was bent. In return this contributed to the increase of the manipulability and decrease of gravity and torque being exerted on the elbow. In addition, the energy required for the motion decreased. Such phenomenon was more apparent under vertical motion than horizontal motion patterns, and in shorter paths than in longer ones. Thus, one can minimize the abrasion of joints by lowering the stress applied to the bones, muscles, and joints. From the perspectives of energy and durability, the robot arm will be able to utilize its motor most effectively by adopting the motion pattern of human arm. Conclusions: By applying the motion pattern of human arm to the robot arm motion, increase in efficiency and durability is expected, which will eventually produce robots capable of moving in an energy-efficient manner.

• Steel and Composite Structures
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• 제45권3호
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• pp.305-330
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• 2022

This article aims to investigate the static deflection and stress analysis of bi-directional functionally graded porous plate (BDFGPP) modeled by unified higher order kinematic theories to include the shear stress effects, which not be considered before. Different shear functions are described according to higher order models that satisfy the zero-shear influence at the top and bottom surfaces, and hence refrain from the need of shear correction factor. The material properties are graded through two spatial directions (i.e., thickness and length directions) according to the power law distribution. The porosities and voids inside the material constituent are described by different cosine functions. Hamilton's principle is implemented to derive the governing equilibrium equation of bi-directional FG porous plate structures. An efficient numerical differential integral quadrature method (DIQM) is exploited to solve the coupled variable coefficients partial differential equations of equilibrium. Problem validation and verification have been proven with previous prestigious work. Numerical results are illustrated to present the significant impacts of kinematic shear relations, gradation indices through thickness and length, porosity type, and boundary conditions on the static deflection and stress distribution of BDFGP plate. The proposed model is efficient in design and analysis of many applications used in nuclear, mechanical, aerospace, naval, dental, and medical fields.

• Journal of information and communication convergence engineering
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• 제8권2호
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• pp.145-149
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• 2010

In this paper, we propose a kinematic approach to estimating the real-time moving object. A new scheme for a mobile robot to track and capture a moving object using images of a camera is proposed. The moving object is assumed to be a point-object and projected onto an image plane to form a geometrical constraint equation that provides position data of the object based on the kinematics of the active camera. Uncertainties in the position estimation caused by the point-object assumption are compensated using the Kalman filter. To generate the shortest time path to capture the moving object, the linear and angular velocities are estimated and utilized. The experimental results of tracking and capturing of the target object with the mobile robot are presented.

• Journal of applied mathematics & informatics
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• 제26권1_2호
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• pp.45-60
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• 2008

Here we consider the evaluation of the the dynamic component of the second order force due to wave diffraction by a circular cylinder analytically and numerically. The cylinder is fixed, vertical, surface piercing in water of finite uniform depth. The formulation of the wave-structure interaction is based on the assumption of a homogeneous, ideal, incompressible, and inviscid fluid. The nonlinearity in the wave-structure interaction problem arises from the free surface boundary conditions, namely, dynamic and kinematic free surface boundary conditions. We expand the velocity potential and free surface elevation functions in terms of a small parameter and then consider the second order diffraction problem. After deriving the pressure using Bernoulli's equation, we obtain the analytical expression for the dynamic component of the second order force on the cylinder by integrating the pressure over the wetted surface. The computation of the dynamic force component requires only the first order velocity potential. Numerical results for the dynamic force component are presented.

• 대한기계학회논문집A
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• 제25권1호
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• pp.32-38
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• 2001

This paper presents an approximate synthesis of 5-SS multi link suspension for 2 D.O.F motions. In the proposed synthesis method, alteration curves of camber, toe, kingpin and caster angles are optimized during the bump rebound and the steering motions. And joint positions can be located within desired boundari es. Especially, steering motions are considered for control of kingpin offset and caster trail. Prescribed motions contain both wheel center positions and imaginary kingpin axes in the multi link type suspension. Constraint equations are formulated with di splacement matrix and velocity matrix using instantaneous screw axis.

• International Journal of Automotive Technology
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• 제6권4호
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• pp.375-381
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• 2005

This paper presents linear algebraic equations in the form of recursive formula to compute elastokinematic characteristics of a suspension system. Conventional methods of elastokinematic analysis are based on nonlinear kinematic constrant equations and force equilibrium equations for constrained mechanical systems, which require complicated and time-consuming implicit computing methods to obtain the solution. The proposed linearized elastokinematic equations in the form of recursive formula are derived based on the assumption that the displacements of elastokinematic behavior of a constrained mechanical system under external forces are very small. The equations can be easily computerized in codes, and have the advantage of sharing the input data of existing general multi body dynamic analysis codes. The equations can be applied to any form of suspension once the type of kinematic joints and elastic components are identified. The validity of the method has been proved through the comparison of the results from established elastokinematic analysis software. Error estimation and analysis due to piecewise linear assumption are also discussed.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.245-254
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• 2017

In this paper, deployment dynamics of large-scale flexible solar arrays with deployable mast is investigated. The adopted solar array system is introduced firstly, then kinematic description and kinematic constraint equations are deduced, and finally, dynamics equation of the system is established by the Jourdain velocity variation principle and a new method to deal with topology changes of the deployable mast is introduced. The dynamic behavior of the system is studied in detail. Simulation results indicate that the proposed model is effective to describe the deployment dynamics of the solar arrays and that the introduced method is applicable for topology changes.