Robotic Surface Finishing of Curved Surfaces: Real-Time Identification of Surface Profile and Control

This thesis introduces a complete design framework for robotic surface finishing of curved surfaces. The system setup is subdivided into three key components: Real-time surface registration is accomplished by employing a proximity laser sensor mounted on the robot end-effector. The proximity sensor measurements coupled with the robot kinematics is employed to derive the coordinates of the projection points. The entire set of projection points is combined to form a grid upon which the surface normal and its normal profile are reconstructed. This surface normal profile description allows us to generate trajectories for both motion and force control. The trajectory generation is a variation of the time-scaling method to incorporate local surface normal information. Instead of using every local normal to form a trajectory, the trajectory is generated based on the local normal of a few sampled projection points. The local normal is estimated from the two consecutive sampled projection points to form the trajectory at the current time step while the end-effector is traveling between them. Therefore, a continuous stream of position goals is generated that would orient the robot end-effector to the local normal of the surface. Finally, this trajectory and a force set point are inputs to the force and position control loop that was synthesized using the simultaneous force and position control strategy; this strategy is based on the robot kinematics model using the product of exponential formula. Therefore the control strategy is robust to system uncertainties. The integrated robotic surface finishing system consists of a UR5 robot and a custom end-effector that includes a force/torque sensor, electromechanical sander, and the laser sensor. Robot Operating System (ROS) is utilized for real-time implementation, which will enable easy migration of the developed tools to other industrial robots. The effectiveness of the strategy is evaluated by conducting a number of experiments for flat and curved surfaces that includes force regulation and surface finishing on wooden surfaces; a representative sample of results is presented and discussed to validate the proposed approach