• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3_1spc
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• pp.587-592
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• 2013

Until recently, the primary users of wheelchairs were people with lower body disabilities. However, the number of patients recovering from accidents or surgery, as well as the number of elderly people using wheelchairs, is constantly increasing. This study examined the design and manufacture of standing and gait assist wheelchairs that assist temporary gait disturbed patients to take rehabilitation training and elderly people to engage in walking exercise. A kinematic analysis was used to select a drive motor and design a four-bar linkage mechanism for lifting the backrest vertically. Using a multibody dynamic simulation, detailed design was performed taking into consideration the spatial motion and partial interference, and the necessary push force and stroke of the linear actuator were also calculated. To ensure structural safety, the von-Mises equivalent stresses of the upper and lower brackets of the linear actuator were verified through a finite element analysis. The manufactured wheelchair was shown to operate successfully as intended, using the developed controller for the drive motors and linear actuator.

• Agricultural and Biosystems Engineering
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• v.5 no.2
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• pp.45-49
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• 2004

Objective of the study was to develop a garlic clove metering device. The metering device consisted of a drum, a bucket and a bucket cover. A garlic clove simulator was designed to simulate motions of garlic cloves in the metering device. Simulation was performed using a multibody dynamic analysis program, RecurDyn version 5.1. Physical properties of garlic cloves such as mass and center of gravity were determined using 3D CAD modeler, IDEAS version 10.0. In order to compare the results of the simulation with actual movement of a garlic, movement of garlic clove was photographed by a high speed camera. A prototype metering device was built and tested under various metering speeds and metering guide angles. At the 12 rpm metering speed, rate of single-clove-discharge was $90.0\%$ and missing rate $1.3\%$ at $5^{\circ}$.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.137-146
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• 2001

A robust controller with the sliding mode is proposed for stable dynamic walking of the biped robot in this paper. For the robot system to be controlled, which is modeled as 14 DOF rigid bodies by the method of multi-body dynamics, the joint angle trajectories are determined by the velocity transformation matrix. Also Hertz force model and Hysteresis damping element are utilized for the ground reaction and impact forces during the contact with the ground. The biped robot system becomes unstable since those forces contain highly confused noise components and some discontinuity, and modeling uncertainties such as parameter inaccuracies. The sliding mode control is applied to solve above problems. Under the assumption of the bounded estimation errors on the unknown parameters, the proposed controller provides a successful way to achieve the stability and good performance in spite of the presence of modeling imprecisions of uncertainties.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.5
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• pp.82-91
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• 2011

In this paper, a planar model for mechanics of a vehicle/pedestrian collision incorporating road gradient is derived to evaluate the pre-collision speed of vehicle. It takes into account a few physical variables and parameters of popular wrap and forward projection collisions, which include horizontal distance traveled between primary and secondary impacts with the vehicle, launch angle, center-of-gravity height at launch, distance from launch to rest, pedestrian-ground drag factor, the pre-collision vehicle speed and road gradient. The model including road gradient is derived analytically for reconstruction of pedestrian collision accidents, and evaluates the vehicle speed from the pedestrian throw distance. The model coefficients have physical interpretations and are determined through direct calculation. This work shows that the road gradient has a significant effect on the evaluation of the vehicle speed and must be considered in accident cases with inclined road. In additions, foreign/domestic empirical cases and multibody dynamic simulation results are used to construct a least-squares fitted model that has the same structure of the analytical one that provides an estimate of the vehicle speed based on the pedestrian throw distance and the band within which the vehicle speed would be expected to be in 95% of cases.

• Journal of Biosystems Engineering
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• v.32 no.2 s.121
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• pp.69-76
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• 2007

This study was conducted to evaluate the sideways overturning stability of side loaded mini-forwarder. The model of a prototype was developed using a 3D CAD modeler and the performance was experimentally validated. The prototype model was run on the multibody dynamic analysis program, RecurDyn 6.0, to simulate motions when the model traversed over a circular bump on a inclined ground surface. The simulation was performed at a constant forward speed of 1.85 km/h under the loaded and unloaded conditions. The forward direction was also controlled to vary from 0 to 360 degrees with an increment of 10 degrees. Results of the simulation showed safe regions in which the mini forwarder could travel safely in terms of direction and slope of the ground. Even when the mini-forwarder was loaded by 20 logs of 3.6 m long and 12 cm diameter, it traveled safely within the ground slopes of 1 to 45 degrees by directions.

• Journal of the Korean Society for Railway
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• v.18 no.3
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• pp.194-202
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• 2015

In this paper, dynamic modeling with viscoelastic properties of a human body resting on a seat is presented to quantitatively analyze ride quality of passengers exposed to vertical vibrations. In describing the motions of a seated body, a 5 degree-of-freedom multibody model from the literature is investigated. The viscoelastic characteristics of seats used in railway vehicles are mathematically formulated with nonlinear stiffness characteristics and convolution integrals representing time delay terms. Transfer functions for the floor input are investigated and it is found that these are different in accordance with the input magnitude due to nonlinear characteristics of the seat. Measured floor input at the railway vehicle is used to analyze realistic human vibration characteristics. Frequency weighted RMS acceleration values are calculated and the effects of the seat design parameters on the frequency weighted RMS acceleration values are presented.

• Special Issue of the Society of Naval Architects of Korea
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• 2011.09a
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• pp.5-11
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• 2011

In this paper, the dynamic response analysis of a floating crane with elastic booms and a cargo is performed. The objective is to consider the effects of the elastic boom in the lifting design stage. Governing equations of the motion for the system which consists of interconnected rigid and flexible bodies are derived based on the formulation of flexible multibody system dynamics. To model the boom as a flexible body, floating reference frame and nodal coordinates are used. Coupled surge, pitch, and heave motion of the floating crane with the cargo which has 3 degree of freedom is simulated by solving the equation numerically. Finally, the effects of the elastic boom for the lifting design that the floating crane is required to lift a heavy cargo are discussed by comparing the simulation result between with the elastic boom and with the rigid one.

• International Journal of Railway
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• v.4 no.4
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• pp.97-102
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• 2011

In an EMS (Electromagnetic suspension)-type Maglev (Magnetically-levitated) vehicle, the flexibility of the bogie frame may affect the acceleration of the electromagnet that is input into the control system, which could lead to instability in some cases. For this reason, it is desirable to consider bogie frame flexibility in air gap simulations, for the optimization of bogie structure. The objective of this paper is to develop a flexible multibody dynamic model of 1/2 of an EMS-type Maglev vehicle that is under testing, and to compare the air gap responses obtained from the rigid and the flexible body model. The feedback control system and electromagnet models that are unique to the EMS-type maglev vehicle must be included in the model. With this model, dynamics simulations are carried out to predict the air gap responses from the two models, of the rigid and flexible model, and the air gaps are compared. Such a comparative study could be useful in the prediction of the air gap in the design stage, and in designing an air gap control system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1154-1163
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• 1996

This paper presents a three dimensional modeling and dynamic anlaysis of a hydraulic excavator. An excavator is composed of a ground, an under-frame, two idlers, two spockets, an upper-frame, a boom, an arm, a bucket two yokes, two connecting rods, two boom cylinders, an arm cylinder, and a bucket cylinder. Each cylinder is modeled with two separate bodies which are linked to each other by a translational joint. The three dimensioanl model of the excavator consists of 22 bodies and each body is assumed as rigid. This paper suggested the maximum lifting capability, a critical load and reaction forces at joints form the DADS simulation. It was presumed that the reaction forces due to a critical load are three times bigger than those due to the maximum lifting capacity.

• Journal of Drive and Control
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• v.19 no.2
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• pp.1-10
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• 2022

Field robots operate in various areas, including construction, agriculture, forestry and manufacturing. Typical tasks of field robots used in various areas include excavation, flattening, and demolition. Such tasks are often accomplished in narrow alleys or indoors. In the case of field robots, there is a limit to working in a small space. Thus, to compensate for these shortcomings, many field robots equipped with Tiltrotators have recently been observed. The advantages of Tiltrotator are improved task efficiency and reduced operating time by reducing unnecessary behavior. We need simulation models that can improve the ability of new people to work and simulate tasks in advance. Thus, in this paper, we developed a simscape-based simulation model and modeling of 6DOF systems for field robots equipped with Tiltrotator. Dynamic modeling of field robot 3D models using Simcape multibody and hydraulic systems of field robots using Simcape Hydraulics were modeled. We applied a PID controller to create a control system that operates along the input angle. Simulation results show that errors occur when comparing input and output angles, but overall, they move along input angles.