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Chinese Robots and Applications
Edited by Professor Youlun Xiong
1 Introduction
Humanoid robot must use its hands to take actions like a human. A human hand has many advantages, small volume, more fingers, more degrees of freedom (DOF), strong grasp force, which make imitation of a human hand very difficult. In addition, all of the power supply, drivers, control system, sensors and information processing system are installed in the humanoid robot itself, which provides very strict requirement on many aspects, such as the weight, volume, power cost and real-time control as well as the humanoid appearance of the humanoid robot hand.
Many robotic hands focus on simulating the overall appearance and action of a human hand while neglecting other equally important features such as the size, weight and real-time control. Conventional robotic devices are relatively complex, large, cumbersome and difficult to be installed in a humanoid robot arm. The complexity of conventional robotic devices also makes the hand be more expensive and difficult to manufacture and maintain.
The special clamps in industry with 1 or 2 DOF are not competent in grasping objects with various shapes and sizes, since they have bad agility.
In the recent 30 years, many achievements have been made in the research of dexterous robot hands. A dexterous robot hand has three to five fingers with 2 ∼ 4 DOF in each finger, the joints of which are mostly active ones driven by actuators. Dexterous robot hands are capable of performing agile motions like human hands, including grasping objects and operating them. Examples of dexterous robot hands are Utah/MIT Hand ([1] Jacobsen et al. , 1986), Shadow Dexterous C5 Hand ([2] Dubey and Crowder, 2004), DLR Hand ([3] Butterfass et al. , 2001), Robonaut Hand ([4] Lovchik et al. , 1999), and domestic BH series hands by Beijing University of Aeronautics and Astronautics (BUAA) and HIT series hands by Harbin Institute of Technology (HIT).
In most cases, robot hands are only required to be able to perform grasping operations without being very agile. Thus, under-actuated robot hands are more and more important in recent 10 years. The so-called under-actuated mechanism refers to that with drivers (such as motors) less than DOF of the joints. Under-actuated robot hands use less motors to...