Trade.Information

Topic Name: Active Flexible Cables for progress of the Robot’s ability to approach into Narrow Spaces: Tadokoro Laboratory

Category: Robotics

Research persons: Tadokoro Laboratory team

Location: Tadokoro Laboratory,Tohoku University, Japan

Details

Overview
Stuck or tangled cables are large issue for scope cameras and wired robots when they are inserted into a narrow space. Proposed new actuation mechanism realizes active or semi-active mobility for flexible long cables. By adding actuation mechanism to flexible cables, it is expected that progress of the robot’s ability to approach into narrow spaces and realization of actively release of stuck cables.

• Constitution method of actuation mechanism of active cables having devices which can generate distributional driving force
• Development of ciliary vibration mechanism
• Modeling of active flexible cables
• Establishment of control method for flexible cables with distributional forces

Actuation of active flexible cables

Ciliary vibration mechanism

Ciliary vibration mechanisms were focused and examined for the following two advantages: 1) those having distributional driving force; 2) those that are attachable easily to existing cables. The ciliary vibration mechanism has plastic or metal thin wires called cilia and achieve driving power through cilia vibration. As the cilia are angled and planted, by adding vibration to the cables, bending and rapid recovery occurs at the front edge of the cilia, which touch the running surface. Using energy stored by bending the cilia, the body can move very short lengths as the cilia recover their original shape. Repeating this bending and recovery motion very rapidly, a body can move forward through a falling-down and standing-up motion. Changing the angle of planted cilia can control the object's velocity and climbing ability. The active cable with this mechanism is covered with cilia all around. Therefore, it has distributive mobility throughout its body and it can generate driving forces in all directions around its body. See figure 3

Prototypes with ciliary vibration mechanism

Prototypes with ciliary vibration mechanism were produced to examine the capability of this mechanism.

A first prototype, using brass cilia 73 mm diameter 130 mm/s of driving speed. See figure 6

A second prototype, using nylon cilia 38 mm diameter 40 mm/s of driving speed can be bent by about 30degrees in four directions. See figure 1

Movies of these prototypes (Flash)

Numerical analysis using model

To elucidate the actuation mechanism and optimize the designing, the actuation mechanism is analyzed using modeling. See figure 4 and 5

Active scope camera developed

A prototype of an active scope camera was produced. The ciliary vibration mechanism was attached to a general industrial scope camera. The dimensions of the active scope camera are 30 mm diameter and 5 m in length. The driving speed is 11 mm/s and the maximum gradability was 11.5 degrees. See figure 2

Movie of the active scope camera (Flash)

Publications about active flexible cables

Kazuya Isaki, Akira Niitsuma, Masashi Konyo, Fumiaki Takemura, Satoshi Tadokoro,
Development of an Active Flexible Cable by Ciliary Vibration Drive for Scope Camera,
Proceedings of the 2006 IEEE/RSJ International Conference on Intelligent Robots and Systems, pp. 3946-3951, Beijing, Oct.2006,

K.Isaki, A.Niitsuma, M.Konyo, F.Takemura, S.Tadokoro, 
Development of an Active Flexible Cable Driven by Ciliary Vibration Mechanism, 
10th International Conference on New Actuators, Bremen, Jun.,2006.

Note for Flexible cables

Flexible cables are cables specially designed to cope with the tight bending radii and physical stress associated with moving applications, such as inside cable carriers.

Due to increasing demands within the field of automation technology in the 1980s, such as increasing loads, moving cables guided inside cable carriers often failed, although the cable carriers themselves did not. In extreme cases, failures caused by "corkscrews" and core ruptures brought entire production lines to a standstill, with high costs incurred as a result.

As a result, specialist, highly flexible cables were developed with unique characteristics to differentiate them from standard designs. These are sometimes known as “chain-suitable”, “high-flex” or “continuous flex” cables.

A higher level of flexibility means the service life of a cable inside a cable carrier can be greatly extended. A normal cable would typically manage 50,000 cycles, but a dynamic cable can complete between 1 and 3 million cycles.