The Development of an Efficient Grasp Master for Space Robotics Teleoperation

Abstract

This thesis reports on the development of an efficient grasp master for space robotics teleoperation that will complement the haptic human arm master X-Arm-2 (Schiele 2011). It should provide the hand and fingers of various operators with sensing and feedback functions, enabling bilateral teleoperation of various types of robotic end-effectors in different control architectures to perform a wide range of tasks. Analysis of the state of the art of reported grasp masters reveals issues that limit their use in combination with arm master devices. Two important factors involved are device placement w.r.t. the operator (e.g. arm coverage by actuators and arm workspace limitation by external transmissions) and structural complexity (bulky designs leading to uncomfortable operation and mechanical losses). Because of these issues, the device efficiency, defined as the user- and device performance achieved with respect to the resources expended, appears to be generally too low. It is the goal of this work to present on the development of an efficiency grasp master device that can be used by various operators in space robotics teleoperation without requiring device adjustments. By following a human-centric design approach, considering relevant space operation tasks, required operator grasp types, and psychophysical effects in human grasping, a reduction of the required number of DOFs of a possible master device was achieved. In combination with the separation of control and feedback channels this can constitute an efficient device concept and was elaborated into a detailed prototype design in this work. As a tool in the design of device geometry and workspace verification, an adaptable kinematic human hand model was constructed and partially verified. This model is based on human functional anatomy and is easily adaptable to various real human hand sizes by the use of body proportions. Verification of the grasp master workspace showed robustness against hand size variation from the 5th female- till 95th male percentile. Verification by analysis and simulation showed that key human factors- and performance requirements can be met. Verification using device efficiency indicators, proposed for the purpose, indicates that the grasp master design is relatively efficient w.r.t. other compared devices based on slave controllability, slave observability, and the quality of the reflected force. The proposed prototype design will be manufactured to enable further verification by testing and validation of real user interaction.