Flexible Modeling of a Long Reach Articulated Carrier: Geometric and Elastic Error Calibration

The Interactive Robotics Unit of CEA LIST has developed a very challenging robotic carrier (called P.A.C.) which is able to perform high range intervention tasks inside blind hot cells. This long reach multi-link carrier has 11 degrees of freedom (DOF) and weighs less than 30 kg. Due to its size and weight, this large robot manipulator holds lots of elastic and geometric deformations. Hence, it presents very low position accuracy. A mechanical model is developed to take into account the flexibilities of the structure. A calibration method of the robot´s parameters is used to further reduce the positioning error of the end effector. This method is first tested by simulation. After encouraging simulation results, an experimental field is made for the calibration of the PAC manipulator. Results show that the adopted flexible model, with the new calibrated parameters, is indeed able to correct and reduce for the system errors.