Design and Force-Tracking Impedance Control of 2-DOF Wall-Cleaning Manipulator via Disturbance Observer

This article presents the design and force-tracking impedance control (FTIC) of a two degree-of-freedom (DOF) wall-cleaning manipulator. A novel 2-DOF wall-cleaning manipulator is designed not only to keep in good contact with different shapes of walls but also to avoid various obstacles on walls efficiently. By adopting two ball screws, 2-DOF motions of the manipulator, such as translation of 150 mm and tilting within <inline-formula><tex-math notation="LaTeX">$ \pm $</tex-math></inline-formula>13°, are achieved successfully. Also, the position-based FTIC is derived to enable the proposed manipulator to not only interact with walls in a desired impedance behavior but also maintain a desired contact force. The FTIC consists of a position-based impedance control (PIC) and a disturbance observer (DOB). While the PIC ensures the excellent force-tracking capability of the proposed manipulator in the steady state, the DOB is adopted to enhance its transient response, i.e., to effectively reject the disturbances caused by the various shapes of walls. The extensive experiments using the test bench equipped with the FTIC demonstrate that the proposed manipulator can maintain the desired contact force within <inline-formula><tex-math notation="LaTeX">$ \pm $</tex-math></inline-formula>4.5 N against the varying shapes of walls and the different types of roller brushes.