Abstract
Problem statement: Sensitization of robot hand is still remaining as crucial issue since most of robot hand systems nowadays are only capable to grasp a predefined specific object. It is still difficult for robot hand system to realize human-like tactile sensation. Some common problems in robot hand system are low accuracy sensing device, sensors are not robust enough for long time work and heavy duties, inconsistence tactile sensing detection and difficulties in control of sensing fusion with robot trajectory. These problems are apparently drawback the progress to commercializing robot hands as real consumer products. Approach: This study presented the application of optical three-axis tactile sensor to robot hand to improve sensitization quality in robotic hand system. The proposed tactile sensor system was designed with compliance modules to communicate with robot hand control system. The sensing principle used in this tactile sensor comparatively provides better sensing accuracy to detect contact phenomena from acquisition of three axial directions of forces. Methodology of force and slippage detection in the tactile sensor system was presented. Accordingly, the optimization of robot hand control algorithm to comply with the tactile sensor system was presented and verified in experiment of grasping and twisting. Results: The tactile sensor presented in this study is capable of detecting normal and shear force simultaneously. The proposed methodology was verified in experiment with paper cup and water, in which the result shows the robot control system managed to respond to the proposed object stiffness distinction parameters and effectively respond to sudden change of object weight during grasping. An experiment of grasping and twisting motions was conducted using a bottle cap. In order to perform simultaneous grasping and twisting tasks, optimization of the control algorithm was conducted with additional parameters to satisfy the desired tasks. Conclusion: Experimental result shows that the robot hand managed to perform grasping and twisting of bottle cap smoothly. The overall results revealed good performance of the proposed optical three-axis tactile sensor system and robot hand control algorithm for future application in a real artificial robot hand. In addition, slippage sensation measured in a robot control system could contribute a better maneuvering of the robot arm-finger system.
Highlights
Grasping and twisting are two common human abilities that support human’s daily life
Twisting motion by robot hand is an advanced ability that performed based on grasping technology
In order to contribute to this effort, the direction of our research has focused on development of high performance tactile sensing device for application in robotic hand
Summary
Grasping and twisting are two common human abilities that support human’s daily life. Computer Sci., 6 (8): 955-962, 2010 still remaining as crucial issue since most of robot hand systems are only capable to grasp a predefined specific object (Mouri et al, 2007) It is still difficult for robot hand system to realize human-like tactile sensation. Some common problems in robot hand system are low accuracy sensing device, sensors are not robust enough for long time work and heavy duties, inconsistence tactile sensing detection and difficulties in control of sensing fusion with robot trajectory These problems are apparently drawback the progress to commercializing robot hands as real consumer products. The sensing principle used in this tactile sensor comparatively provides better sensing accuracy to detect contact phenomena from acquisition of three axial directions of forces (Ohka et al, 2005) It is capable of measuring both normal and shear force simultaneously and suitable for application in dexterous robotic hands (Yussof et al, 2007). The total degree-of-freedoms for this robot arm is 11-dofs: 2-dofs at the shoulder joint, 1dof at the elbow joint, 2-dofs at the wrist joint and 2 units of 3-dof robot hands
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