Manipulation by multifingered robot hands has been started in the early stage of the robotics research and is still actively studied.
Especially, dextrous manipulation using tactile sensation has been considered important for achieving human-like dexterity; however, the current stage of this research is far from the goal.
The `NAIST Hand project' has been started at Nara Institute of Science and Technology in 2002.
The purpose of this project is to develop a platform for the research of dextrous manipulation using tactile sensation.
Concepts for the NAIST Hand are as follows:
- The hand has 4 fingers, 12 DOF in total.
- Each finger has 3 DOF; 2 DOF for MP joint, 1 DOF for PIP joint, the DIP joint is couples with the PIP.
- All actuators are embedded in the palm.
- All joints are driven by specially designed gears and link mechanisms that does not use wires.
This mechanism
- relaxed the restriction of the space for actuators, and
- achieved good maintainability.
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Finger Module
A finger module has 3 joints (MP, PIP and DIP).
The MP joint has 2 DOF for adduction/abduction and flexion/extension motion.
The PIP joint has 1 DOF flexion/extension motion.
The DIP joint's flexion/extension motion is coupled with the PIP motion by a linkage.
This is based on the knowledge in physiology that human's PIP and DIP joint synchronize.
As a result, one finger has independent 3 DOF.
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Gear Mechanism
Generally, when the MP joint has 2 DOF, it is difficult to drive the PIP joint by link mechanism from an actuator embedded in the palm.
Therefore, in conventional hand mechanisms, the motors for the PIP/DIP joints have been embedded in the finger's link.
This imposes a severe restriction on choosing sufficient actuators.
It was a bottleneck to achieve a sufficient fingertip force even if the MP joint torque is enough.
According to the design concept, all 3 actuators of the NAIST-Hand are embedded in the palm; Motor 1, 2, and 3 for MP(adduction/abduction), MP(flexion/extension), and PIP(flexion/extension) respectively.
Two different pairs consisting of three bevel gears are combined in the MP joint.
The output shaft of the motor 3 passes through the gear and pulley connecting with the motor 2.
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Control System
Currently, Unilateral tele-operation is available by using CyberGlove. |
| Related research: Grip-force Control by Slip-margin Feedback |
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Tactile fingertip sensor for estimating slip margin
The fingertip sensor consists of a transparent semispherical gel, an embedded small camera, and a force sensor in order to implement the direct slip margin estimation.
We have proposed a vision-based grip-force control, which has the following advantages:
Highly accurate sensing by vision-based contact area measurement
Direct estimation of the slip margin without knowing the friction coefficient
A stabile grip force by a direct feedback of the slip margin
By estimating the slip margin during the incipient slip, a stable grasping is realized against the change of the traction force without occurring the gross slip.
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- Jun Ueda, Atsutoshi Ikeda, Tsukasa Ogasawara, "Grip-force Control of an Elastic Object by Vision-based Slip Margin Feedback during the Incipient Slip", IEEE Transactions on Robotics, Vol.21, Issue 6, pp.1139- 1147, December, 2005.
- Jun Ueda, Yutaka Ishida, Masahiro Kondo, Tsukasa Ogasawara, "Development of the NAIST-Hand with Vision-based Tactile Fingertip Sensor", Proceedings of the 2005 IEEE International Conference on Robotics and Automation (ICRA 2005),pp.2343-2348, Barcelona, Spain, April, 2005
- Jun Ueda (Project leader)
- Masahiro Kondo (Control system development, NAIST-Hand II development)
- Yuya Jikihara (Hand-arm system development)
