[chbot] Robotic Sweepers

[Helmut Walle]

On 25/06/13 19:36, Richard Jones wrote:
> I noticed that Bunnings have a Robot Sweeper listed in their last 
> catalogue for $99. They seem to be out of stock in the Tower Junction 
> store at the moment. Anyone have views on this style of cleaner? Looks 
> more of a gimick than practical use to me, but it is a lot cheaper 
> than a Roomba and at first glance does the same job. Also not as quick 
> at clearing cans from the table as Lego Mindstorms for those with long 
> memories :-)
>
> http://www.youtube.com/watch?v=2eWeI59_Qpk
>
> Richard
[...]

Views? Yes, I have some general views on robotic vacuum cleaners for 
residential environments, and also some specific questions regarding the 
model shown in the video. Just some quick background: about a decade 
ago, I was a commercial cleaner for a few months, and in that role I 
spent ample time vacuuming (for the American readers: hoovering, or for 
the brand-aware: luxing) vast expanses of carpet, polished rock, lino 
and other surfaces. Now the beautiful thing about this kind of job is 
that it doesn't require much thinking, and so you have your mind 
available to contemplate and consider whatever you want. And obviously 
the natural thing for an old telecommunications and embedded systems 
engineer to think about is how to improve the job he is just doing by 
adding a little bit of innovative technology, and that obviously means 
thinking about self-cleaning windows, catalytically cleaning ovens, 
cleaning robots and the likes.

So, at that time I didn't know much about cleaning robots, but I thought 
it would be great to have one to do all this mindless and under-paid 
work. I had a few quick ideas on how to develop suitable robots, but 
being marketing-minded I also went and did a bit of a market survey. I 
found at the time that there were several companies offering cleaning 
robots, some for residential use, some for commercial applications. The 
differences between the available machines were as great as the 
differences in requirements between the two: the robots for residential 
applications looked very much like show-off toys for people with too 
much money, who already have the Audi and the Porsche and the Boat etc. 
and need yet another gimmick to stand out among their equally 
possessions-saturated friends (oh, and if you have any doubt regarding 
the practical usefulness of these machines - Oprah actually gave one 
Roomba to each of the participants of one of her shows back then, and 
there were lots of "Ohs" and "Ahs" from the audience). The machines for 
commercial applications on the other hand were not only much bigger, but 
they clearly looked like they had been designed with one objective in 
mind: to get the job done, to do it well, and to do it fast.

So far, so good - now let's look at some general technical questions 
that I would like to raise, and you can probably answer them yourselves:

* A good vacuum cleaner (just a traditional one, like this model used 
commonly by commercial cleaners: 
https://www.nilfisk.com/en/products/Pages/product.aspx?fid=14963&Name=GD%201005%20220-240V%20EU 
- and, declaration of conflict of interest: I've got absolutely no 
stakes in Nilfisk, but I have used some of their products, and they were 
good and reliable for what I needed! ) has a rated power of somewhere 
above 1 kW, and according to the spec for this example it will suck with 
270 W at the end of the tube. Now this is some serious power, and it is 
actually needed when your kids have been playing dress-up party, and all 
the hair from the wigs has gone into the carpet... But with these small 
robotic home vacuum cleaners like the Dirt Devil and others, where is 
that power going to come from? Well, it isn't... Soooo... the suction 
power of these things is probably quite limited, and that will limit 
their ability to clean the more interesting areas.

* A good professional cleaner (a human, that is) actually sees what is 
dirty and what is clean, and they will quickly complete the less dirty 
areas, and treat the badly dirty ones (where the kids have trampled over 
the carpet with their muddy wellies, thus densely compressing the 
liquefied soil into the depths of the carpet) as long and intensely as 
necessary to get them clean. But how does a robot know what's clean and 
what's not? Well, I have a list of ideas of how a robot could know this, 
and I think several of them are quite feasible, but I doubt that many of 
them are implemented in these cheap home vaccuming robots. Soooo.... the 
robot may manage to get everywhere eventually, but does that mean 
everything will be clean?

* With a good vacuum cleaner (see above again for example) I can 
continuously vacuum moderately dirty carpets for several hours before I 
need to replace or empty the dust bag. Now that bag actually takes up 
quite a big volume inside the vacuum cleaner, certainly a multiple of 
the dust compartments of any of these home vacuuming robots. So even if 
they had the suction power to properly clean the floor, how often would 
you have to pick them up to empty the dust compartment? And it is not 
that manufacturers wouldn't have seen this issue: the Kärcher 
Robocleaner ( 
http://www.karcher.com/int/Products/Home__Garden/Vacuums/Robocleaner/12691010.htm 
) for example works with a base station, to which the mobile robot 
automatically returns when it either needs to recharge its battery or 
feels the need to empty the dust into the 2-litre dust compartment of 
the base station (that's about the size of the dust bag of a "normal" 
vacuum cleaner, well, the Nilfisk example above actually has even more 
than twice that much). So they have positively addressed some of the 
questions and concerns. If you are considering other models / 
manufacturers, check how they are addressing these issues...

And now a couple of points more specifically regarding the Dirt Devil:

* It's all very nice to see how clean it sweeps the already very clean 
looking tiled floor. BUT, how does it perform on high-friction 
moderately heavy carpet?
Oh... I've just looked it up and found that it's not meant to be used on 
carpet at all: it is officially called a "Hard Floor Vacuum" - well that 
means for me personally it's not even worthwhile looking at any further, 
because I am wiping and mopping hard floor, which produces much better 
results than any dry vacuum can. So no carpets with this one...

* If you are still interested, I would recommend reading the customer 
reviews on Amazon: 
http://www.amazon.com/Dirt-Devil-RoomMate-Robotic-Vacuum/product-reviews/B005I5OTTA/ref=dp_top_cm_cr_acr_txt?ie=UTF8&showViewpoints=1 

I haven't read them in much detail but the overall stats do look a bit 
sad to say the least. Look here for a fairly detailed review of the 
Kärcher Robocleaner 
http://www.robotreviews.com/reviews/k%C3%A4rcher-robocleaner-rc3000-review

Well, I could go on, but this is probably enough to give you an idea of 
the kind of points to look at (not meaning to be exhaustive in any way, 
but rather only providing some examples), and to show that a 
conceptually simple thing like cleaning floors actually is mildly 
complex when you look at the practical reality of environments to be 
cleaned and the respective requirements for machines that are supposed 
to do a good job.

Kind regards,

Helmut.