Colloquia

Summary

This thesis brings together the field of cleaning robots for glass-roofs, solar-arrays and windows with the field of electrostatics. Primarily it is investigated how electrostatic attraction forces can be applied to increase the traction of cleaning robots on the slanted glass surfaces that they work on. In the course of the research, as an additional asset for this technology, the effect of the residual surface charge created by the use of cold plasma on the cleaning process is considered and looked into in a further section.

First the functioning of these cleaning robots and the current concepts of electrostatic actuators are described. Next the necessary theory of electrostatics is treated, shortly delivering the background to the effect of electrostatic attraction. Using this knowledge the physically available options are worked out. This delivers two design directions that are useful for this project. Both are treated in separate sections thereafter.

The first one concentrates on an in-contact adhesion solution and is evaluated on the basis of found literature and simulations. A design optimized for the attraction of glass is developed.

The second option is to enable an attraction force over a distance of multiple millimeters, which has some design advantages, as is further explained in the introduction. This part is done in a more experimental approach, as not much work on this topic was found. A suggestion for a demonstration setup for this design is described.

Both options are found to have their benefits and their disadvantages. In short the better researched in-contact adhesion - in contrast to the non-contact attraction - is found to inherently be capable of producing higher attraction forces that are at a useful level for these robots, while it is far more vulnerable to contamination and wetting, which are both involved in the cleaning process on glass roofs and solar arrays. The restrictively low limit to the attraction forces over an air-filled gap may explain the limited research on this topic.

Apart from the attraction effect of electrostatic charges, in a further section their effect on the cleaning process is also analysed. For this, contaminated samples are prepared to mimic the contaminated surface of glass-roofs and solar-arrays. The ease of removing this contamination with and without being treated with charges is then compared.

In total this report gives insight into the field of electrostatics and electrostatic attraction devices specializing on applying these to the described cleaning robots or other applications where temporary adhesion is required in combination with a cleaning operation.