Design and flexible modeling of a long reach articulated carrier for inspection

This work concerns the development of advanced robotic systems for nuclear application. The manipulator will be used for light intervention in spent fuel management facilities. The robot must meet severe specifications: small diameter, long reach within a minimum range of 6 m, high dexterity to move in constrained environment and lots of degrees of freedom (DOF) for obstacle avoidance. In order to meet these requirements, a very challenging robotic carrier (called P.A.C.) which is able to perform light intervention tasks inside high range of blind hot cells using existing engineering penetrations is developed. This long reach multi-link carrier has 11 DOF and weighs less than 30 kg. The gravity effect in the manipulator is largely compensated by a special mechanical structure (the parallelogram) that helps reducing the size of the rotation actuators used to operate the robot. Also, a glass fiber epoxy equilibrium spring is used to compensate the gravity effect over the elevation actuators. A field test is made to measure the robot's repeatability and accuracy by using a laser tracker to measure the end effector's position. Due to its size and weight, this large robot manipulator holds lots of elastic and geometric deformations. Thus it possesses a very low accuracy. A mechanical model is developed to take into account the flexibilities of the structure. This flexible model will be used to improve the accuracy of the manipulator. Applications tests were made to evaluate the ability and performances of the system to meet the operational requirements. The operation took place in an existing decontaminated hot cell and it turned out to be successful.