• The Journal of Korea Robotics Society
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• v.17 no.2
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• pp.183-190
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• 2022

Accurate kinematic parameters of mobile robots are essential because inaccurate kinematic model produces considerable uncertainties on its odometry and control. Especially, kinematic parameters of caster type mobile robots are important due to their complex kinematic model. Despite the importance of accurate kinematic parameters for caster type mobile robots, few research dealt with the calibration of the kinematic model. Previous study proposed a calibration method that can only calibrate double-wheeled caster type mobile robot and requires direct-measuring of robot center point and distance between casters. This paper proposes a calibration method based on geometric approach that can calibrate single-wheeled caster type mobile robot with two or more casters, does not require direct-measuring, and can successfully acquire all kinematic parameters required for control and odometry. Simulation and hardware experiments conducted in this paper validates the proposed calibration method and shows its performance.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2066-2071
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• 2003

In this paper, we identify the isotropic configurations of an omnidirectional mobile robot with three caster wheels, depending on the selection of actuated joints. First, We obtain the kinematic model of a caster wheeled omnidirectional mobile robot(COMR) without matrix inversion. For a given task velocity, the instantaneous motion of each wheel is decomposed into two orthogonal instantaneous motions of the steering and the rotating joints. Second, with the characteristic length introduced, we derive the isotropy conditions of a COMR having $n({\ge}3)$ actuated joints, which are imposed on two Jacobian matrices, $A{\in}R^{n{\times}3}$ and $B{\in}R^{6{\times}6}$. Under the condition of $B{\propto}I_6$, three caster wheels should have identical structure with the length of the steering link equal to the radius of the wheel. Third, depending on the selection of actuated joints, we derive the conditions for $A^t$ $A{\propto}I_3$ and identify the isotropic configurations of a COMR. All possible actuation sets with different number of actuated joints and different combination of rotating and steering joins are considered.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.427-427
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• 2000

In this study, singularity of two types of mobile robots for various input joints are investigated: One is the mobile robot with three caster wheels and the other is the mobile robot with two conventional wheels and one caster wheel. Kinematic models are derived via the transfer method of generalized coordinates. Then, determinants of the Jacobian of the mobile robots are used to identify the singularity configurations.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.12
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• pp.1235-1240
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• 2006

Previous isotropy analysis of a caster wheeled omnidirectional mobile robot(COMR) has been made under the assumption that the steering link offset is equal to the caster wheel radius. Nevertheless, many practical COMR's in use take advantage of the steering link offset different from the wheel radius, mainly because of improved stability. This paper presents the isotropy analysis of a fully actuated COMR with variable steering link offset, which can be considered as the generalization of the previous analysis. First, the kinematic model of a COMR under full actuation is obtained based on the orthogonal decomposition of the wheel velocities. Second, the necessary and sufficient conditions for the isotropy of a COMR are derived and examined to categorize three different groups, each of which can be dealt with in a similar way. Third, for each group, the isotropy conditions are further explored so as to identify all possible isotropic configurations completely.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1245-1246
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• 2010

• Journal of the Korean Society for Precision Engineering
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• v.14 no.12
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• pp.73-85
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• 1997

The rolling force and roll deformation behavior in the twin roll type strip continuous casting process has been computed to estimate the thermal charcteristics of a caster roll. To calculation of rolling force, the relationship between flow stress and strain for a roll material and casting alloy are assumed as a function of strain-rate and temperature because mechanical properties of a casting materials depends on tempera- ture. The three dimensional thermal dlastic-plastic analysis of a cooling roll has also been carried out to obtain a roll stress and plastic strain distributions with the commercial finite element analysis package of ANSYS. Temperature fields data of caster roll which are provided by authors were used to estimated of roll deformation. Roll life considering thermal cycle is calculated by using thermal elastic-plastic analysis results. Roll life is proposed as a terms of a roll revolution in the caster roll with and without fine failure model on the roll surface. To obtain of plastic strain distributions of caster roll, thermomechan- ical properties of roll sleeve with a copper alloy is obtained by uniaxial tensile test for variation of temperature.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.436-443
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• 2001

In order to investigate the mixing of dissimilar grades during the arbitrary grade transition in bloom caster, a computational model has been developed. The model is fully transient and consists of two sub models, which account for mixing in the bloom tundish, mixing in the strand. The developed model was verified using concentration histories measured on 1 : 1 scale bloom tundish water model. The result of numerical model showed good agreement with the experimental results of water model. By using this numerical model, the mixing of dissimilar grades in bloom caster has been simulated. As that result, the characteristics of the steel mixing in the bloom tundish and strand was showed and the amount of the intermixed grade bloom was predicted.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.443-448
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• 1998

As the strip caster system that produces a regular steel plate can be considered as a complicate nonlinear multi-variable system, it is not easy to obtain an effective control system. One way to overcome the difficulties is to apply the intelligent neuro-fuzzy fusion approach in developing the control scheme. The neuro-fuzzy control scheme possesses several distinct advantages, including the fact that it doesn't need the exact mathematical modeling of controlled plant and can provided some robustness in the control scheme. In this paper, an intelligent neuro-fuzzy for the stripe caster system will be proposed. The effectiveness of the proposed scheme will be demonstrated by computer simulation.

• International Journal of Control, Automation, and Systems
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• v.4 no.4
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• pp.486-494
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• 2006

In this paper, we present the complete isotropy analysis of a caster wheeled omnidirectional mobile robot (COMR) with nonredundant/redundant actuation. It is desirable for robust motion control to keep a COMR close to the isotropy but away from the singularity as much as possible. First, with the characteristic length introduced, the kinematic model of a COMR is obtained based on the orthogonal decomposition of the wheel velocities. Second, a general form of the isotropy conditions of a COMR is given in terms of physically meaningful vector quantities which specify the wheel configuration. Third, for all possible nonredundant and redundant actuation sets, the algebraic expressions of the isotropy conditions are derived so as to identify the isotropic configurations of a COMR. Fourth, the number of the isotropic configurations, the isotropic characteristic length, and the optimal initial configuration are discussed.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.11
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• pp.936-942
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• 2005

Recently the exoskeletal power assistive equipment which is a kind of wearable robot has been widely developed to help the human body motion. For the elderly people and patients, however, some limits exist due to the weight and volume of the equipments. As a feasible solution, a tendon-driven exoskeletal power assistive device fur the lower body, and caster walker are proposed in this research. Since the caster walker carries the heavy items, the weight and volume of the wearable exoskeleton are minimized. The key control is used to generate the joint torque required to assist motions such as sitting, standing and walking. Experiments were performed for several motions and the EMG sensors were used to measure the magnitude of assistance. When the motion of sitting down and standing up was compared with and without wearing the proposed device, the $25\%$ assistance was acquired.