Sungchul Kang

Rough Terrain Negotiable Mobile Platform with Passively Adaptive Double-Tracks and Its Application to Rescue Missions

This paper presents design and integration of the ROBHAZ-DT3, which is a newly developed mobile robot system with chained double-track mechanisms. A passive adaptation mechanism equipped between the front and rear body enables the ROBHAZ-DT3 to have good adaptability to uneven terrains including stairs. The passive adaptation mechanism reduces energy consumption when moving on uneven terrain as well as its simplicity in design and remote control, since no actuator is necessary for adaptation. Starting from this novel design, dynamic analysis and simulation were conducted to verify the mobility of the double-track mechanism and to obtain significant design parameters such as a suitable track size and an allowable attack angle. Based on this novel mobile platform, a rescue version of the ROBHAZ-DT3 with appropriate sensors and a semi-autonomous mapping and localization algorithm is developed to participate in the RoboCup2004 US-Open: Urban Search and Rescue Competition. From the various experiments in the realistic rescue arena, we can verify that the ROBHAZ-DT3 is reliable in travelling rugged terrain and the proposed mapping and localization algorithm are effective in the unstructured environment with uneven ground.

Static balancing of a manipulator with hemispherical work space

This paper proposes a gravity compensator for the roll-pitch rotation which can be operated in hemispherical work space. The gravity compensator comprises two 1-dof gravity compensators and a bevel differential. It is revealed from analyses of energy and torque that the proposed gravity compensator can perform static balancing completely. The gravity compensation of a 4-dofs manipulator is briefly introduced for example. Experiments show that the proposed compensator can counterbalance the gravitational torques effectively and can be operated in hemispherical work space.

Design of a static balancing mechanism with unit gravity compensators

This paper proposes a design method of a static balancing mechanism using unit gravity compensators (e.g., 1-dof gravity compensator). In the design of a multi-dofs static balancing mechanism it is necessary to determine how many springs (or unit gravity compensators) are required and where they should be placed. This problem can be overcome by computing the mapping matrix between the joint space and gravity compensator space. The mapping matrix is obtained by analyses of the potential energy function. The number of rows of the mapping matrix indicates the amount of unit gravity compensators and linear joint constraints representing locations of unit gravity compensators. Example studies are presented to verify the effectiveness of the proposed method. Simulations are performed in that static balancing mechanisms designed by the proposed method can counterbalance the gravitational torques completely.

Design of a Haptic Stability Observer in Frequency Domain for Stable Haptic Interaction

Stable haptic interaction has been studied extensively by an energy-based approach. However, the energy in the haptic system is not directly measurable, but estimated from some measured quantities such as force and velocity; therefore, the estimated energy is occasionally inaccurate. Furthermore, haptic stability is difficult to observe by the energy-based approach for complicated virtual environments. To resolve this problem, a new observer, called a haptic stability observer, is proposed in this research. The empirical investigation of unstable haptic interaction in the frequency domain showed that the typical unstable behavior of a haptic system is different from random oscillations introduced by the hand motion of a human operator. The haptic stability observer working in the frequency domain quantifies the degree of instability of a haptic system. A double layered wall was implemented in the virtual environment to verify the validity of the HSO. Experimental results of the double layered wall show that the HSO is much faster than the passivity observer in detecting haptic instability

Mine Detecting Robot System

Humanitarian demining, the peaceful and non-explosive de-mining strategies, has been gaining worldwide acceptance lately. As the series of humanitarian demining, tele-operated mine detecting robot system was developed. This paper presents unique demining strategy of the demining robot system. There are two developed system called MIDERS-1 and MIDERS-2. The system is consisted of rough terrain mobile platform, multi degree of freedom manipulator, and the all-in-one mine detecting sensor module between ground penetrating radar and metal detector. We have focused that our cooperative demining procedure between the macroscopic and microscopic demining enhances the conventional human demining. With proposed methodology, the hardware configurations and functions are described.

Implementing Compact Tactile Display for Fingertips with Multiple Vibrotactile Actuator and Thermoelectric Module

In this paper, a compact tactile display which consists of multiple vibrotactile actuators with 4-different vibrotactile unbalanced mass and a peltier thermoelectric module is proposed. By stimulating 2 different sensory modalities including mechano-receptors and thermo-receptor simultaneously, surface texture and material composition can be displayed using the implemented device. With this implementing concept, the developed device can be used to display surface texture and temperature together, and it has the possibility of implementing a small-size, multi-fingered tactile display device

Learning robot stiffness for contact tasks using the natural actor-critic

This paper introduces a novel motor learning strategy for robotic contact task based on a human motor control theory and machine learning schemes. Humans modulate their arm joint impedance parameters during contact tasks, and such aspect suggests a key feature how human successfully executes various contact tasks in variable environments. Our strategy for successful contact tasks is to find appropriate impedance parameters for optimal task execution by reinforcement learning (RL). In this study recursive least-square (RLS) filter based episodic natural actor-critic is employed to determine the optimal impedance parameters. Through dynamic simulations of contact tasks, this paper demonstrates the effectiveness of the proposed strategy. The simulation results show that the proposed method successfully optimizes the performance of the contact task and adapts to uncertain conditions of the environment.

Sound Generation for the Haptic Perception using an Irregular Primitive Function

In this paper, a sound synthetic technique (SST) based on sinusoidal frequency modulations with irregular primitive function algorithms for tactile perception is suggested. Investigations of the benefits of real-time SST for haptic interaction were referenced. Performance was evaluated in two ways; 1) a unimodal analysis of synthesized sounds in terms of whether they can induce tactile perception, and 2) multimodal analysis of the relationship between tactile perception and the generated sound. The unimodal analysis of sound suggested that meaningful spectrum contents can be generated using the proposed SST. The result of the multimodal analysis showed that auditory-haptic multimodal perception increases human sensitivity of texture perception.