Now that the navigation functionality of the main chassis is mostly up and running, I’ve transitioned to designing modules that will fit into the chassis and give OpenADR all the functions it needs (see my last post). The first module I’ve designed and built is the vacuum, since it’s currently the most popular implementation of domestic robotics in the market. Because this is my first iteration of the vacuum (and because my wife is getting annoyed at the amount of dust and dog hair I’ve left accumulating on the floor “for testing purposes”), I kept the design very simplistic: just the roller, the body (which doubles as the dust bin), and the fan.
The brush assembly is the most complicated aspect of the vacuum. In lieu of finding an easily sourceable roller on eBay, I opted to design the entire assembly from scratch. I used the same type of plain yellow motors that power the wheels on the main chassis to drive the roller.
The rollers themselves consist of two parts, the brush and the center core. The brush is a flexible sleeve, printed with the same TPU filament used for the navigation chassis’s tires, that has spiraling ridges on the outside to disturb the carpet and knock dust and dirt particles loose. The center core is a solid cylinder with a hole on one end for the motor shaft and a protruding smaller cylinder on the other that is used as an axle. One roller is mounted on either side of the module and are driven by the motor in the center.
To print the vacuum module, I had to modify the module base design that I described in my last post. I shortened the front, where the brush assembly will go, so that the dust will be sucked up between the back wall of the main chassis and the front of the vacuum module’s dust bin and be deposited in the dust bin.
For the fan, I’ll be using Sparkfun’s squirrel blower. I plan to eventually build a 3D model of the fan so that it fits snugly in the module, but in the meantime, the blower mount is just a hole in the back of the module where the blower outlet will be inserted and hot-glued into place. In the final version, I will include a slot for a carbon filter in this mount, but given that I’m just working with a hole for the blower outlet in this first version, I cut up an extra carbon filter from my Desk Fume Extractor and taped that to where the air enters the blower to make sure dust doesn’t get inside the fan.
The blower itself is positioned at the top of the dust bin with the inlet (where the air flows in) pointed downwards. Once the blower gets clogged, the vacuum will no longer suck (or will it now suck?), so I positioned the inlet as high as possible on the module to maximize the space for debris in the dust bin before it gets clogged.
The rest of the module is just empty space that serves as the vacuum’s dust bin. I minimized the number of components inside this dust bin area to reduce the risk of dust and debris causing problems. With the roller assembly placed outside the bin on the front of the module, the only component that will be inside of the dust bin is the blower.
With a rough estimate of the dimensions of the dust bin, the vacuum module has the potential to hold up to a 1.7L! This is assuming that the entire dust bin is full, which might not be possible, but is still substantially more than the 0.6L of the Roomba 980 and 0.7L of the Neato Botvac.
There are a few things I’d like to improve in the next version of the vacuum module since this is really just alpha testing still. The first priority is designing a fan mount that fits the blower and provides the proper support. Going hand in hand with this, the filter needs an easily accessible slot to slide in before the fan input (as opposed to the duct tape I am using now).
I also want to design and test several different types of rollers in order to compare efficiency. The roller I’m using now turned out much stiffer than I’d like so, at the very least, I need to redesign them to be more flexible. Alternatively, I could go with something more like the Roomba’s Aeroforce rollers, which decrease the cross-sectional area of the air passage and thereby increase the air velocity. These rollers offer better suction and less opportunity for hair to get wrapped around the rollers but are a little less effective for thicker carpets.
Further, I need to make sure that the dust bin is in fact air-tight so that dust isn’t getting into the main chassis or back onto the floor. I included bolt mounts on the floor of the dust bin to connect the separate pieces together, but I don’t have mounts on the walls of the dust bin, and so I am using tape around the top of the bin to hold the pieces together for now. Since any holes in the dust bin provide opportunity for its contents to leak onto the floor, making sure I have a good seal here is critical. In the future I’d like to redesign these seams so that they are sealed more securely, possibly by using overlapping side walls.
Lastly, the vacuum module needs a lid. For the current version I intentionally left out the lid so that see everything while I’m testing. I plan to add a transparent covering to this version for that purpose (and so dust doesn’t go flying everywhere!). In the final version, the lid will need to provide a good seal and be easily removable so that the dust bin can be emptied.
But before we do all that, let’s test this vacuum!