Powerbot VR7000 mods

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Powerbot VR7000 mods

Postby HiTec » July 1st, 2019, 11:32 am

Hey.

I have two powerbots. They are "Limited Edition" Star Wars bots (Vader and Stormy).

I disappointed about their battery life on turbo mode and suction power on normal/auto mode.

I just disassembled the Storm Trooper and realized that it uses basic brushed motor on its suction system instead of brushless.

I was thinking that i could try to mod brushed to brushless conversion to it, as suction motor only has two wires going on it. Has anyone tried this before? Does someone know how many amps and what voltage the suction motor is pulling through the motherboard on normal/turbo mode? (What are to motherboards suction motor drive system limits).

As for the battery life, has someone modified the stock battery pack to have more capacity available and can this robot benefit from it or is its battery usage logic some kind of "blind type" just like first Botvacs with NiMh:s had?
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Re: Powerbot VR7000 mods

Postby glnc222 » July 1st, 2019, 7:03 pm

Those are very unusual mod proposals for vacuum robots, as the motor and battery specs are deeply involved with the electronics design. A fundamental logic governs the use of battery capacity as once observed here about Neato products: the charge usage for maximum run time is programmed in the firmware, because the system is not equipped to measure the capacity of an unknown battery, and must assume the specification of the designed battery -- absent some firmware option for users to input capacity data. The charge usage must be measured to maintain a reserve for returning to base for recharging, as well as some unused capacity buffer against damaging deep discharge. (Batteries will charge to their maximum capacity, but only a programmed amount of it will be used, with charging terminated just from the voltage reached; the system has no data on the original charge condition of the battery.)

I do not know about the 7000 series owning a 9000, but the suction I measured was no worse than the Neato brand previously used. The battery powered bots depend on brush action for most of the cleaning anyway, as there is no way they can match the kilowatt fan power of a corded regular vacuum. The Samsung bots are interesting in having a cyclone extraction system, similar to the Dyson bots (where the cyclone was a signature feature of the entire brand), which does consume some of the suction power. But I enjoy not buying replacement filters, still on the original after four years.

I am not sure why replacing the fan motor with a brushless induction type would be any more efficient; the induction process might actually take more power, engineers would have to report. Anyway, the motor control system installed involves several components and firmware content all specific to the type of motor, so I would think it very difficult to change any of that. The original 9000 series had some sort of special warranty on long life for the fan motor, so maybe an induction type, not sure, their "digital inverter", and there could be differences in the warranty on these other models.
lower-end models such as VR20J9040WG and VR20J9020UG consist of the standard motor, instead of Digital Inverter (VR20H9050UW). Standard motor is not covered with 10 year manufacturer warranty.

"digital inverter" is vague but suggestive of the kind of motors developed by Dyson with digital control of the magnets for more power etc., compared to simple commutator magnet switching.

I did explore fan motors a little when reading the cyclone system could reduce effective cleaning suction, revealed by member Third_Deg, the original designer of Roomba's for iRobot, after he left that firm and posted about his exploratory Third Degree company (never realized at this late date). He designs fans and motors. See his remarks and some data I collected in thread at
http://www.robotreviews.com/chat/viewtopic.php?p=136798#p136798
A major conclusion is that the aerodynamics and motor characteristics create a diminishing returns situation, an inflection point where additional fan power adds little to effective suction. There is a kind of optimization in the design used.
The biggest takeaway is the sharply diminishing returns of adding fan power in terms of more airflow, at least with the cyclone, the way the aerodynamics work. Perhaps that inflection point in the curve [shown in graph of experiment] is how the Normal mode got defined for the design.


Sorry cannot be of more help. In general one does not see much discussion of engineering in the Samsung bots, perhaps because not of as much interest to engineer hobbyists, perhaps from the original higher prices (since more competitive). Also maybe because they are more durable with less opportunity to repair.
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Re: Powerbot VR7000 mods

Postby glnc222 » July 1st, 2019, 7:24 pm

On Normal vs Turbo or max fan power options: after my experiments with fans and suction I noticed some degradation of the battery capacity from wear, seen in reduced Max option run time. I noticed from the specs that the Max mode places a much higher load on the battery than the Normal mode (and I had placed even higher loads by removing the cyclone air flow limiting components -- hard to say if that was the real culprit). But with the ratios involved I have to wonder if the Max mode involves shorter battery life, pushing the limits of the batteries used, and these are very expensive batteries. However, mine did last about 400 charging cycles, owed to the lithium vs older tech NIMh batteries (most robots today have all switched to lithium with advances in that kind of battery for safety etc., tinkering with chemistry). I prefer to let the robot activate Max mode on its own from the dirt detection system (optical sensors in the intake flow), floor type detection etc. I notice the Max comes on every now and then briefly in certain spots on the floor, such as near windows sometimes, where there might be expected more exposure to dirt.
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