Calculation of Optimal Magnetic Force for Automatic Control Magnetic Force of the Window Cleaning Robot

This article describes a particular feature of the smart WINDORO, the successor of the first commercialized window cleaning robot, the WINDORO. The driving module of the smart WINDORO (which belongs to the inner unit) makes use of an autonomous magnetic force control mechanism. It automatically adapts the magnetic forces according to the thickness of the glass. This article focuses on the simulation of maximizing the friction on the surface of the window while minimizing the magnetic attractive force.

First the WINDRO is presented and emphasis is placed on the importance of the mechanisms for movement on and attachment to the windows. It is explained that the WINDORO uses permanent magnets for adhering to the window and that it is required to constantly change the magnetic forces to adapt to the thickness of the windows.

Because the first version of the WINDORO used a manual magnetic force controlling device, it is evaluated first. In order to let the inner and outer unit of the WINDORO adhere properly to the window, the user had to change the height of the magnet holders for every window. This was of course undesirable and introduced the risk that both units fall down. The minimum and maximum magnetic forces were calculated by means of software that implements a magneto static analysis.

After this, the magnetism controlling mechanism is verified by magnet movement. It is explained that the shape of the magnets were changed from rings to cubes to increase the contact area between the magnets and decrease the thickness of the magnets. Strength and strain analyses are done as well by means of software. Finally, it is concluded that the smart WINDORO has an average magnetic force that is 20% higher than the old WINDORO. Since the change of magnets reduced the weight, the new smart WINDORO has a higher magnetic efficiency.