Abstract
2 Faculty of Mechanical Engineering University Technology MARA, Malaysia Abstract: Problem statement: To advance the robust object recognition of robots, we present an algorithm for object exploration based on three-axis tactile data that is necessary and sufficient for the evaluation of contact phenomena. Approach: The object surface contour is acquired by controlling the finger position so that the normal force, measured by optical three-axis tactile sensors, remains constant as two fingertips slide along the object surface. In this algorithm, when the robot grasps an object, the tangential force increment is checked to judge the initial contact state because it is more sensitive than the normal force. After contact between the fingertips and the object, the normal force is adjusted to remain constant with a tolerant value between the upper and lower thresholds. Results: In the verification test, shape exploration experiments were conducted using a hand-arm robot equipped with our tactile sensor and a hard sinusoidal-shaped wooden object. Experimental results show that the hand-arm robot is capable of gathering the object contour having a concave or convex portion because its finger position controlled by three-axis tactile sensing information follows the object surface. Conclusion/Recommendations: We derive a control algorithm in robot fingers based on time tangential force increment and normal force detection to perform a shape exploration procedure.
Highlights
The requirements for autonomous service robots are the ability to detect, explore and recognize objects in their environments
In conjunction with the above studies, our research has focused on the development of high performance tactile sensing devices for robotic hand applications because there is no three-axis tactile sensor outside of our research (Ohka et al 2006 and Yussof et al 2008a; 2008b)
Fig. 1: 11-dof multi-fingered humanoid arm mounted with optical three-axis tactile sensors at fingertips consists of an acrylic hemispherical dome, an array of 41 sensing elements made from silicon rubber, a light source, an optical fiber scope and a CCD camera
Summary
The requirements for autonomous service robots are the ability to detect, explore and recognize objects in their environments Their modalities of applications highly differ from conventional industrial robots since they are deployed in a domestic environment and are usually not intended for repetitive tasks that require high precision or strong force. For such purposes, when a service robot must be equipped with sensors, vision sensors are popular choices. The optical waveguide sensing principle used in this tactile sensor provides comparatively better sensing accuracy to detect contact phenomena from the acquisition of the three-axial directions of forces (Yussof et al 2007) It can simultaneously measure both normal and tangential forces and is suitable for robotic hand applications. In our algorithm we apply the characteristics of tangential force to object exploration
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