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This paper proposes a new bending mechanism with a screw drive mechanism, which enables omni-directional bending motion by rotating two linkages consisted of right-handed screw, universal joint and left-handed screw. We call this mechanism double-screw-drive (DSD) mechanism. DSD mechanism was applied to a robotic forceps manipulator for laparoscopic surgery. In the first prototype, by adding the third linkage to DSD mechanism and rotating this, opening and closing motions of a gripper was attained. In the second prototype, DSD forceps manipulator was enhanced so that its gripper can rotate. This is achieved by rotating the third linkage in DSD mechanism. On the other hand, the opening and closing motions of a gripper is attained by wire-drive. The developed DSD forceps manipulator realizes bending motion without using wires. Therefore, it has high rigidity, and it can bend 90 degrees in arbitrary direction. In order to control the developed DSD robotic forceps manipulator as teleoperation system, joy-stick type manipulator for remote control was built and servo system was constructed for each linkage. Servo experiments show the effectiveness of the constructed control system.

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[abstFig src='/00280003/12.jpg' width=""300"" text='Sensory feedback device for myoelectric hand' ] In this paper, a sensory feedback device was developed to improve the operability of a myoelectric prosthetic hand. The device is worn on the user’s upper arm and provides object hardness feedback to by winding a belt onto the upper arm using a motor. When the finger of the myoelectric prosthetic hand grabs the object, the contact force on the object is detected by a pressure sensor attached to a finger cushion on the myoelectric prosthetic hand. Based on the sensor’s input, the hardness of the object is calculated. According to the hardness of the object, a reference input to realize the corresponding winding speed of the belt is generated by a reference input generator. Then, the motor of the feedback device is controlled to track the reference input by using the self-tuning PID control technique, taking parameter variation into account. Thus, the belt of the feedback device is wound by the motor and tightens the user’s upper arm, thereby enabling the user to receive tactile feedback. Finally, confirmation tests are conducted based on a psychophysical method to verify the effectiveness of the feedback device and its control system. As a result, the difference threshold of the sensory feedback device was 0.59 N/mm.

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