CT-Arm (short for coupled tendon-driven arm) is an articulated arm driven by wires. Since the motors are all located in the base, the links can be light-weight, and less energy is needed to move the arm. Equipped with several 2-DOF joints, CT-Arm is also able to navigate inside narrow 3D spaces.



The concept was first proposed by Prof. Hirose several decades ago, but recently an improved version of CT-Arm saw action in an unexpected place: the No. 1 Fukushima Nuclear Power Plant.


The power plant was the stage of the nuclear accident of 2011, when some of the reactor building suffered catastrophic failure due to Hydrogen explosions. Even now, the No. 1 reactor building remains mostly untouched due to the complexity of the debris - attempting to remove the damaged structure may cause it to collapse and fall on top of the used nuclear fuel rods, which still remain inside the building.

The Fukushima version of CT-Arm was developed in cooperation with Shimizu Corporation, and consists of a base, from which CT-Arm is expanded. A large crane is used to support the base all around the outer perimeter of the damaged building, allowing the insertion of CT-Arm from several different points.
The tip of CT-Arm is equipped with several high-definition cameras and gamma ray sensors. These sensors have so far provided invaluable information about the damaged structure, from vantage points that cannot be reached with any other device.
Even though CT-Arm has seen much action in the harsh environment of the collapsed nuclear power plant, it can be applied also to other cases in which narrow entrances and debris make it difficult to enter and collect data.