Research On Under-actuated Dexterous Hand For Biomimetic Robot

The multi-fingered dexterous hand is a highly integrated, miniture smart mechanism, whose design and research refer to machinery, computer, automation, electron, material etc. As the end effector, it, to some extent, has embodied the service ability of the robotic bearing it. Because the space inside the dexterous hand is lesser, adopting underactuated drive mechanism is the developing trend in future. Underactuated drive mechanism is a mechanism that independent drive number is less than free degrees. The research object of this paper is the multi-fingered dexterous hand used in the table tennis robot, and thorough study is carried out in three aspects:its structure, sports and function.First, the development history of the research on the multi-fingered hand and the current situation at home and abroad are introduced. For some representative multi-fingered hand models, the inherent characteristics are compared in their structures, freedom configurations and drive modes, etc, then, as the key to the underactuated drive structure commonly-used by most fingers, according to specific examples, several finger models just using this mechanism are introduced in detail and their transmission principles and merits and drawbacks are described. Then, a "cross" differential structure and a multi-fingered underactuated one are described.Secondly, as the size and the structure of existent dexterous hands and the principle of bionics for reference, the single finger model and the dexterous hand one are established, and their kinematics problems are analyzed and simulated, then, a specific grasp planning method is studied in consideration of the objects, the grasp tasks and merits and drawbacks of the two grabbing ways commonly-used, and the statics analysis on the dexterous hand grabbing a table tennis system is carried out.Thirdly, a tendon drive mechanism based on underactuated drive principle is put forward, which adopts the modular design and the tendon drive underactuated mechanism, it is simple and can realize bending and opening action. The multi-fingered hand made up by this finger has the ability grabbing object shape adaptively, then, the finger configuration design, joint drive and its rotation angle analysis, torsional spring design, motor power calculation, location/force sensor selection, as well as the control system design for the realization of the mechanism were introduced, and this method is verified through the finger physical model.Finally, a biomimetic dexterous hand with four-finger and one-motor is designed, because a actuator, which can drive four tendon ropes move with only one motor, has been assembled within the palm, and it can be very good with the fingers using the tendon rope underactuated drive mechanism, so that the number of the whole dexterous hand’s drive reduced to only one, and the production cost and the weight are greatly reduced. The dexterous hand finally designed could not only realize the envelope grab, but also the accurate grab, and it could grab reliably and independently by installing information collection structures, like limit switches on the finger and pressure sensors in the palm, etc.