EEVblog #980 - RoboMaid Automated Vacuum Cleaner Teardown

[EEVblog]

Teardown of the RoboMaid RM-770 Automated Robot Vacuum Cleaner

[Brumby]

Ah......   Wrong link

Fixed!

[WattSekunde]

We use the LG VR64701LVMP working in our rooms. Very good basic every day cleaning! And the LG is relatively silent if you are at home until he works.
They do not replace but reduces the need of manual cleaning!
In our neighborhood there are around 10 dry and wet cleaning bots in use. All from different manufacturers. Nobody want's to miss them any more ;-)

PS: I wish you would power up, measure and analyze more of the parts until the teardowns. That's why I love the always fascinating video #284 on the electrical toothbrush.

[Zbig]

Those main wheels drive motors don't look like steppers to me at all. Just ordinary brushed DC jobs. I don't think they'd be using optical feedback on top of stepper motors in such a cost-conscious device. That's the reason for the worm-gear reduction as well - you wouldn't need that with steppers. Those belts also look toothed, aren't they?

[EEVblog]

PS: I wish you would power up, measure and analyze more of the parts until the teardowns. That's why I love the always fascinating video #284 on the electrical toothbrush.

It's not always possible or worth the time and effort to do so.

[W9GFO]

I don't think the led towers provide any position information beyond a zone to avoid. The robot drives randomly around the room bumping off stuff and staying away from the led towers. When the battery gets low it knows to keep a lookout for the charge base, but it has no idea where it is located. Only when it gets close to it will it see it, then the two leds on the base will guide it in to dock.

[rrinker]

 Whatever you do, don't hook the motor up backwards. Wouldn't want it to go from suck to blow.

[cgroen]

Maybe a coincidence, or not, but seems to be "8 bits" on both LED's....

[TheRevva]

I had a 'robo-maid' type device a couple of decades ago, so perhaps I was a 'trend-setter'? (But I seriously doubt it).
It had some kind of weird artificial intelligence that I never quite understood despite numerous attempts at probing it.
I must admit that it really did SUCK!!!, but It had an annoyingly nasal audible system!
I tried to flash it, but the noise persisted - seemingly getting much worse for about 1/4 of each month?  (I initially suspected some form of lunar linkage)
I ended up completely throwing it out once I became aware that similarly functioning units were available for hire without the negative feedback inherent in my unit.

If my memory serves me right, the make / model was wife-1.0

[mtdoc]

Nice teardown video Dave.

We love our Roomba.

There's an excellent video lecture/teardown by one of the developers of the original Roomba.  He goes into some of the design decisions they grappled with.

[Windfall]

Whatever you do, don't hook the motor up backwards. Wouldn't want it to go from suck to blow.

Only Mega Maid does that. Hail Skroob !



(Okay, I admit it, I watched that movie too many times).

[Windfall]

I have had a Roomba for a few years now. It can't entirely replace the vacuum cleaner, but almost.

What surprised me (as a software engineer) is that it, apparently, doesn't actually know where it is, and essentially follows a random pattern, with a bit of ad-hoc intelligence thrown in here and there. Some other brand (I forget which) does know where it is, maps the area, and tries not to visit the same place twice. Before I bought one, I thought all vacuuming robots did that ! But not Roomba. Also, I think the Roomba's homing is based on radio rather than infrared (but I stand to be corrected).

[Zbig]

I have had a Roomba for a few years now. It can't entirely replace the vacuum cleaner, but almost.

What surprised me (as a software engineer) is that it, apparently, doesn't actually know where it is, and essentially follows a random pattern, with a bit of ad-hoc intelligence thrown in here and there. Some other brand (I forget which) does know where it is, maps the area, and tries not to visit the same place twice. Before I bought one, I thought all vacuuming robots did that ! But not Roomba. Also, I think the Roomba's homing is based on radio rather than infrared (but I stand to be corrected).

Neato uses lidar to map the rooms. Some others (Samsung?) use video cameras to navigate using the view of the ceiling.

[ErikTheNorwegian]

I got two Roomba 615, excelent machinery. Im disabeld, so vacuming is a tonn easier having these robots, they dive under beds and furniture and  do a excelent job. Only need a torrow cleaning with the vacum once every 14 days. Parts, like brushes etc are cheap from E Bay, china sellers.

[ajm8127]

I agree with an above poster that the infrared LEDs are emitting an 8 bit code using pulse length encoding

I wonder how the robot distinguishes the codes from each other in the room where there must be interference between the emitters. I doubt it's as sophisticated as CDMA such as is used in mobile phone air links. I suppose the byte could be arranged such that certain bits are not reused between two emitters so it would know that a particular bit being a 1 or 0 means it must be receiving a unique signal.

For instance if it received 11111100 it would know that it must be seeing both emitters. 11110100 or 11111000 would mean only one emitter it visible.

I guess it uses the different carriers to distinguish between the dock and the "wall". Does it use separate receivers on the bot?

It might be interesting to analyze the circuit a bit more which receives the signals on the robot and see how it connects to the NXP micro. Is it a digital setup that just relies on the threshold between high and low state for the cutoff. Or is it a more sophisticated analog circuit that is sampled by an ADC and then processed on the ARM?

I am guessing this is as simple as possible.

 

[james_s]

I have a couple of 400 series Roombas, they've served me well and I've rebuilt them more times than I can count. The real weak spot on these is the brush deck drive motor gearbox as well as the brush deck itself. The motor area gets full of lint and the motor overheats and melts the gearbox. Other times the gears strip out and iRobot has never offered just the gears or even the whole gearbox as a replacement part. The next issue is that the drive sockets that engage the beater bar and main brush are far too shallow and strip out easily, especially when cat hair gets wound around the end of the brush.

Other failures I've had, the mosfet that controls the brush deck motor burns out, this happens particularly when the motor wears and starts drawing too much current but it can happen on thick carpet as well. I finally got some protected mosfets I'll try the next time this happens. The wires to the front wheel that detect rotation break from the suspension action flexing them. Several times I've had IR LEDs in the drive wheel tachometers get weak, same happened once to one of the cliff sensor LEDs. Brush deck and vacuum motor bearing failure, clay based kitty litter is especially hard on these, I found suitable replacement motors from Jameco IIRC. Speakers have failed on both of mine, I replaced them with small paper cone speakers, they sound better too, not that it matters. Side brush gearbox gets hair wound around the shaft and eventually has to be taken apart for cleaning.

In a nutshell, I'd have a hard time recommending one to someone who was not technical because they are maintenance intensive, unless you have so much money that you can buy a new one when it breaks, in which case you should just hire a human maid. Personally I'd much rather tinker with robots than vacuum the house though, and the Roombas significantly reduce the frequency I have to do a proper manual vacuuming.

[HwAoRrDk]

(Okay, I admit it, I watched that movie too many times).

Don't let Dave catch on to it, he might start getting some funny ideas about EEVblog merchandising.

"EEVblog the T-shirt! EEVblog the colouring book! EEVblog the lunch box! EEVblog the breakfast cereal! EEVblog the flame thrower! Last but not least, EEVblog the doll - me, Dave Jones. <pulls string> 'I'm innnn like Flynn'"

[mtdoc]

have a hard time recommending one to someone who was not technical because they are maintenance intensive

We've had exactly the opposite experience with our Roomba 595.  I was skeptical about these but my sister in law raved about theirs (and she and my brother have no mechanical skills) so I got one several years ago and it has been great. We have a large dog with long fur and despite this, we have not needed to do any maintenance other than cleaning out the rollers, etc. It just keeps trucking along. We have it set to run automatically 3x a week and then use it manually probably once a week as well. It's been going for about 3-4 years like that with no issues. I keep expecting to need to get a new battery but so far it's still doing fine.

[james_s]

Perhaps they've made improvements. My mom has a 500 series and it has been marginally more reliable than my 400s but even so I've had to replace the complete brush deck once. I also had to disable the cliff sensors by removing the sensors and relocating them inside because it kept getting confused on the bamboo hardwood flooring and thinking it was going over an edge. She has a single floor house so they're not necessary anyway. I also am at a bit of a loss as to why the computer portion in the 500 is so powerful, it's a big ARM chip IIRC, even plays verbal messages, seems overly complex for what it does and the things are obscenely expensive given the plastic gears and toy-like construction.

None of the competing robotic vacuums are nearly as good despite the flaws though.

[Zbig]

None of the competing robotic vacuums are nearly as good despite the flaws though.

Have you tried Neato?

[madires]

Maybe a coincidence, or not, but seems to be "8 bits" on both LED's....

The virtual wall has the same protocol. My guess is that the first two pulses are the start bits, the short pulses are 0 and the long pulses are 1 (about 4 times the short pulse). Nothing fancy.

[rrinker]

(Okay, I admit it, I watched that movie too many times).

Don't let Dave catch on to it, he might start getting some funny ideas about EEVblog merchandising.

"EEVblog the T-shirt! EEVblog the colouring book! EEVblog the lunch box! EEVblog the breakfast cereal! EEVblog the flame thrower! Last but not least, EEVblog the doll - me, Dave Jones. <pulls string> 'I'm innnn like Flynn'"

 
We're not doing this for the money. We're doing it for a shitload of money!

The sad thing is, if there really were a Dave doll that said some of Dave's catchphrases, I'd probably buy it. The modified See 'n Say was too damn funny.

[james_s]

I'd consider buying the EEVblog flamethrower.

[rrinker]

 If you think Dave has problems shipping multimeters around the world.... 

[ErikTheNorwegian]

What?
A  EEVBlog branded  scope?