Jae Heon Chung

The dynamic modeling and analysis for an omnidirectional mobile robot with three caster wheels

Recently quite a few applications of an omnidirectional mobile robot have been reported. However, understanding some fundamental issues still remains as further study. One of the issues is the exact dynamic model. Previous studies very often ignore the wheel dynamics of the mobile robot and suffer from algorithmic singularity. Thus, actuator sizing or control algorithms based on the incomplete plant model does not guarantee the control performance of the system. This paper deals with the singularity-free, exact dynamic modeling and analysis of an omnidirectional mobile robot with three caster wheels. Initially, the exact dynamic model of the mobile robot including the wheel dynamics is introduced. A natural orthogonal complement approach is also introduced. The joint-space and operational-space dynamic models are derived as analytical forms. Through simulation, the discrepancy of the incomplete dynamic model is shown by comparison with the exact dynamic model. Furthermore, the useful aspect of operational dynamics in terms of impact geometry is also discussed.

A Foldable 3-DOF Parallel Mechanism With Application to a Flat-Panel TV Mounting Device

This paper deals with a new 3-degree-of-freedom (DOF) parallel mechanism for a flat-panel TV mounting device with two rotations and one translation. The most important operational requirements of this device are that it should support the heavy weight of the flat-panel TV and should be foldable to save space between the flat panel and the wall. An asymmetric parallel structure that has three kinematic chains with internal four-bar linkage is proposed to meet such requirements. Kinematic modeling was performed along with actuator sizing. Finally, the mechanism was developed and tested to show its effectiveness as a flat-panel TV mounting device.

Compact design of a dual master-slave system for maxillary sinus surgery

The pathway to the maxillary sinus area is anatomically curved and narrow. Thus, using the conventional approach based on the straight endoscope and surgical tools, there are some limitations in inspection and treatment of the target legion of the maxillary sinus. To cope with such problems, a dual master-slave system is investigated in this work for general maxillary sinus surgery. Initially, the need for dual arm operation is explained. A compact design of two 4-DOF end-effector mechanisms for acquiring the endoscopic image and performing biopsy is introduced. Next, a dual master device to control the motions of the two end-effector mechanisms is employed and a motion scheduling algorithm for a proper master-slave control is also developed. Finally, the feasibility of the dual master-slave system is verified through experimental work.

Design of an antagonistically counter-balancing parallel mechanism

Much attention has not been paid to analysis of the open-loop stability for gravity counter-balancing of parallel mechanisms or closed-chain mechanisms. The open-loop stability is crucial especially in passively counter-balanced mechanisms where no actuators are involved. Passive hands-on device is such an example. A general stiffness model is derived for general closed-chain mechanism including counter-weight model. As a measure of the open-loop stability, we employ the determinant of the stiffness matrix. A parallel mechanism having 3 translational DOF (degree of freedom) is employed as an exemplary device. An antagonistically counter-balancing is found the most stable method. We conduct dynamic simulation and experiment to confirm the open-loop stability of the system.

Implementation of an embedded omni-directional mobile robot with active caster wheels

This work deals with a motion planning algorithm of an omni-directional mobile robot with active caster wheels. A typical problem occurred in the motion control, which has been identified through experimental experiences, is skidding of the mobile wheel. It sometimes results in uncertain rotation of the steering wheel. This is due to mismatching between the command and the mechanical hardware. To cope with this problem, a motion planning algorithm pursuing the natural configuration of the mobile wheel was mainly investigated, which resolves the skidding problem and uncertain motions of the steering wheel. Through simulations and experimentation, the feasibility of this algorithm was verified.

Design of a new spatial 3-DOF parallel mechanism with application to a PDP TV mounting device

In this paper, we propose a new 3-DOF parallel mechanism for PDP TV mounting device with 2-rotation and 1-translation. The most important operational requirement of this device is that the device should support large weight of the PDP panel and be foldable to save the space between the PDP panel and the wall. An asymmetric parallel structure that has three kinematic chains with internal four-bar is proposed to meet such requirements. The special four-bar mechanism is foldable and supports large weight structurally, which allows employment of small-sized actuators for motion. The kinematic modeling and kinematic analysis was performed along with actuator sizing. Finally, this mechanism was developed and tested to show the effectiveness as the PDP TV mounting device. It is believed that this device is a successful commercialized parallel mechanism.

Analysis of Internal Loading at Multiple Robotic Systems

When multiple robotics systems with several sub-chains grasp a common object, the inherent force redundancy provides a chance of utilizing internal loading. Analysis of grasping space based internal loading is proposed in this work since this method facilitates understanding the physical meaning of internal loadings in some applications, as compared to usual operational space based approach. Investigation of the internal loading for a triple manipulator has been few as compared to a dual manipulator. In this paper, types of the internal loading for dual and triple manipulator systems are investigated by using the reduced row echelon method to analyze the null space of those systems. No internal loading condition is derived and several load distribution schemes are compared through simulation. Furthermore, it is shown that the proposed scheme based on grasping space is applicable to analysis of special cases such as three-fingered and three-legged robots having a point contact with the grasped object or ground.

MODELING OF EXTERNAL AND INTERNAL IMPULSES IN CASE OF MULTIPLE COLLISIONS

When a robot system collides with environment, not only the contact point but also the joints of the robot system experience impulsive forces or moments. In the real environment, the structure collides with environment at multiple points. However, most previous modeling methods have assumed one point contact to environment. In this work, we propose external and internal impulse models in case of multiple contact. The case of one point contact is compared to the case of multiple points contact through simulation.

Modeling and analysis of a hybrid mechanism with kinematic and force redundancies

Redundancy problem in robotics can be classified as kinematic redundancy and force redundancy. However, they have been investigated separately. In light of the human mechanism that has simultaneous kinematic and force redundancies, this paper deals with kinematic and dynamic modeling of a hybrid mechanism that has simultaneous force and kinematic redundancies. Secondly, we proposed a motion generation algorithm that considers both force and kinematic redundancies. Finally, the performance of the proposed algorithm is shown by simulation.

Development of a 5-DOF Hybrid Micro-Manipulator and Implementation to Needle Manipulation Process in Medical Applications

This paper reports the development and preliminary experiments of a robotic system designed to perform needle manipulation tasks in medical applications. A hybrid type manipulator is designed to enlarge the workspace without loss of position accuracy. In this paper, we initially analyze the workspace and step resolution of the robotic system in the operational space. Then, we perform trajectory tracking experiment to verify that the developed robotic system could be employed to attenuate an unpredictable tremor of human operators and enhance position accuracy in neurosurgery or ophthalmic surgery, etc. It is shown through experimentation that the robothuman cooperation mode is effective for micro-manipulation tasks.