Cooperative Robots

Sammanfattning: The topic of this master thesis is cooperative robots. The master and slave configuration is to be used for cooperative tasks and the task chosen is to move a flexible beam together. A trajectory is fed to the master robot to move it to the desired positions. The slave robot then follows the movement of the master robot by force control using force measurements from a force sensor. All experiments are performed in the Robotics Laboratory at the Department of Automatic Control at Lund Institute of Technology. The robots used are an ABB IRB 6 robot and an ABB IRB 2000 robot. The ABB IRB 6 robot is assigned to be the master robot and the ABB IRB 2000 robot as the slave robot. The ABB IRB 2000 robot is equipped with a force and torque sensor of type JR3 for force control. The thesis can be divided broadly into three parts. The first part is a background study of the robot systems and kinematics, on path and trajectory generation and also on the various robot force control schemes. The second part is about optimal trajectory generation. The desired path is first expressed in terms of path index in Cartesian space. It is then converted to joint space with variable step size to ensure that the deviation from the original path is kept within a given limit. The optimal trajectory is then generated using Linear Programming. The third part consists of the application of parallel force/motion control schemes to the slave robot to enable it to follow the master robot. The motion controller is simply the builtin controllers of the IRB 2000 robot. The force controllers used are direct force, impedance and admittance controllers. The schemes are first tested in Matlab Simulink where the robots are simulated by a first order system for each joint. The force measurements are generated by a contact model which simulates the contact forces and torques between the gripper of the IRB 2000 robot and the beam. The resulting joint values are then sent to a Java visualization program written in the platform Eclipse.