Robotic machining with a flexible manipulator

In a system having a robot and a tool held by said robot for machining a work piece a method for compensating for variability of height of the surface of said work piece during said machining comprising:

• determining a stiffness model prior to said machining by applying a load to said tool at one or more different robot orientations and measuring the displacement of said tool under load;
• using only said tool held by said robot to remove material from said surface of said work piece;
• setting a constant material removal rate for said tool to remove material from said surface of said work piece;
• generating from a force sensor mounted on said tool a signal representative of the force applied in real time to said work piece by said tool during said machining of said work piece by said tool;
• and
• using said force sensor signal and said stiffness model to modify the relative position between said tool and said work piece to maintain a constant material removal rate during said machining of said work piece by said tool.

A controller for controlling a robot having a plurality of joints and carrying a tool for machining a work piece, said controller having software executable to:

• obtain a stiffness model using joint angles only, said stiffness model relating the force applied at a tip of said tool to the deformation of said tool tip;
• obtain after said stiffness model is obtained a signal from a force sensor of a force applied by said tool to said work piece;
• use said signal and said stiffness model to determine the deformation of said robot due to said force applied by said tool to said work piece;
• and
• use said determined deformation of said robot to modify the relative position between said tool and said work piece to compensate for said deformation of said robot during said machining.