Displacement Analysis of Large-Scale Robotic Arm for Printing Cement Mortar Using Photogrammetry

The development of specialised equipment for three-dimensional printing of cement mortar requires the deployment of advanced design methods. The accuracy of printing robotic arms is influenced by the change in the position of the end effector, which is influenced by the stiffness of the arm, or deformation of parts of the arm and yielding in the place of rotation axes. Determining the actual change in the end effector position is often a difficult challenge. In this paper, we analysed the displacement on a large robotic arm by the non-contact optical photogrammetry method. We applied this method to a specialised 2.8 m long robotic arm SCARA with an added rotational axis. We compared the results from photogrammetry with the results from measurements with a mechanical deflection meter, and with the predicted displacement values from the FEM simulation. The results from both measurement methods showed maximum deviations of hundredths of a mm. The findings of the analysis thus indicate that photogrammetry meets the strict requirements for displacement measurement on a robotic arm for the 3D printing of cement mortar. A significant advantage of the method is the possibility of measuring almost all attainable arm positions and achieving results in hundreds of places.