A LIST robot for performing Megajoule Laser (LMJ) maintenance

The LMJ robot has reached a decisive stage in its development and commissioning for the MegaJoule Laser and is scheduled to enter service around 2012 for 30 years. The robot, which was designed in a joint project with Cybernetix and is based on original concepts developed by LIST, is mainly intended to perform protective panel fitting and removal operations and teleoperation tasks.
Its long reach (the ratio between its length and diameter), payload, deployment (the ratio between its minimum and maximum lengths) and accuracy all represent major technological advances. When inserted into the experiment chamber in line with its midpoint via a hatch 0.63 m in diameter, it can reach a point 10 m away at its opposite side while holding and positioning a 100 kg load, with 1 cm repeatability. Finally, it retracts into a mobile “package” 6 m long. All this is achieved by combining a telescopic structure with a yoke joint mechanism incorporating dual speed-reduction gearing in an assembly that is protected by two patents.
The CEA LIST teams have performed tests to study how the prototype of the robot’s second section (approximately half of the complete robot) behaves under strain. The computational models used to predict the complete robot’s behavior and enter the final phase of its testing and implementation have been revised as a result of these tests. Measurements were taken under different stresses by using a wide beam laser sensor to record the structure’s deformation. The purpose of these measurements is also to ascertain the robot model’s flexibility coefficients. This model is used in particular to calculate the internal constraints involved when a panel is inserted and improve the robot’s absolute positioning accuracy, which will be enhanced by means of visual servoing.

The results have been good enough for the robot to pass the final design review (RCD) performed by the CEA’s DAM. The LMJ robot has now entered the final phase in its development, includes all of its tools and is due to be used in the initial installation of the experiment chamber’s panels.