Window Cleaning Robot ASME Design Competition
This report describes the design problems and findings with constructing window cleaning robot to compete in the American Society of Mechanical Engineers (ASME) Student Design Competition.
The design is described per section:
Mechanics:
For obvious reasons the robot was held as light as possible, making it more mobile and easier attachable to the window surfaces. Attachment was first done by windshield washer fluid pump to generate a negative pressure. This turned out to not be a suitable choice as it required a cooldown period and would quickly need membrane repairs.
After this the designers set on the use of a centrifugal blower that creates a pressure difference which ‘pulls’ the robot to the window. This also resulted in a higher air flow rate making it so that the robot would almost instantaneously stuck to the surface upon placing.
The robots movement came from a pair of high friction wheels at the back of the robot. The friction on these wheels create an additional ‘sticking’ factor for the robot to be able to stay on the window surface.
The biggest challenge was formed by the fact that the robot needed to be able to navigate multiple windows, and thus needed to be able to transfer over ledges to neighbouring window panes. The solution used in this design was the attachment of stilts to the side of the robot. When the robot approaches a window ledge, these stilts will support the robot whilst its ‘hanging’ from the safety cord attached at the top of the building. This safety cord would be able to navigate the top of the building, moving the robot over any ledges it may encounter. In order for this to work, the robot most only extend these stilts when it is needed to get over a ledge, otherwise the robot will lose suction and fall of the window.
Software and electronics:
The software of the robot was deemed to be fairly straightforward. The operational principle is to have the robot drive along the perimeter of the bottom window, then fill in missing area (having measured the window by means of wheel turns). The robot then lifts itself to the top window pane, and cleans it with the same pattern. It lowers itself down using the safety tether again, and waits at the starting point to be picked up by the operator.
It is important to maintain a straight heading using the accelerometer data (which essentially indicates the direction of gravity) and the encoder data (which indicates wheel speeds, which must be matched between the robots). This part of the system control is done on the motor control AVR, and is the bare-bones “low-level” functionality of the robot.