Future FRC Technologies?

[ratdude747]

Originally Posted by pilleya

There are two main types(most commonly used) of LiFePO4 cells 18650’s and A123’s

Laptop Batteries, cordless tool batteries(lithium ones), Tesla car’s etc.
Use 18650 cells.18650 cells look like big AA batteries.

The safety of 18650 cells is well documented, like all high capacity batteries they have the potential to be very dangerous. Most battery packs which use them, such as in laptops or cordless tools, have a lot of protection/safety measures built in to prevent problems. If FRC was to move towards LiFePO4 batteries, for safety reasons I would say that the some elements of the electrical system would have to be redesigned, to limit the potential for injury/error.

Not really, you make the controller part of the pack, just like with laptop packs and the like. Even add a push button charge indicator for extra functionality at a low marginal cost. The hardest part would be the current sense circuit, as we're talking pretty high peak currents compared to most packs. Not to say it's not doable (it almost certainly is), but it would take a corporate partnership for this to happen in FRC. Unless somebody already makes rated packs with a sufficiently robust casing, in which case, half the work is done.

[lynca]

A Backup Battery.
Supplies power to the cRio and Router as backup to the main battery. Less time lost in router or cRio reboot.

The VEX cortex has a backup 9V battery that behaves in a similar manner.

[AllenGregoryIV]

Originally Posted by lynca

A Backup Battery.
Supplies power to the cRio and Router as backup to the main battery. Less time lost in router or cRio reboot.

The VEX cortex has a backup 9V battery that behaves in a similar manner.

I'm not sure what problem that would fix anymore. We could get rid of the brownout conditions if we had one, but most radio and roborio reboots are from physical disconnections and which aren't immediately solved by a backup battery.

I do think backup batteries are a good idea because you could then switch out batteries during demos without needing to reboot the radio/RoboRIO.

Originally Posted by ASD20

I think the hardest problem is convincing teams to all scout in a similar way. Right now, every team scouts differently and collects different data, but for a system like this to work and be accurate, you would need multiple people per event collecting the same data set. I think a lot of teams will not like the data that the system would collect and will end up doing their own thing instead.

As far as ensuring accuracy, the thing with a similar problem that comes to mind is Waze and their crowdsourced road condition reporting. They also have a relatively small (I presume) amount of reports for each event and need to make sure they are as accurate as possible. I don't know exactly what their system is, but I think it would be a good starting point for anyone who is interested in making this happen. FRC has the advantage of being able to also reference the FIRST match API for some things (Ex: If someone reports that each robot on an alliance makes 5 high goals in a match and the API reports 7 total, you know something is wrong).

This system doesn't have to completely remove redundancy, in fact it works better when more teams are scouting. What this would do would allow teams to see real stats from events they aren't attending, as well as the general public.

This system wouldn't be comprehensive, teams are free to track whatever stats like personally but many of them could be added to the this central database. Largely teams track things such as high goals made the same way or at least can easily produce that stat for every robot they scout. There are other similar stats that most people agree on each year and if there are some less tracked stats, the system could show how many people/teams have submitted for that stat and possibly have some way to rank if you should trust that stat or not.

[Joe Ross]

Originally Posted by AllenGregoryIV

I'm not sure what problem that would fix anymore. We could get rid of the brownout conditions if we had one, but most radio and roborio reboots are from physical disconnections and which aren't immediately solved by a backup battery.

The IFI control system's backup battery relied on a different connection to the robot controller. Thus you had to have two connection failures for a disconnect to occur, greatly decreasing the probability of occurrence.

[IndySam]

Originally Posted by Joe Ross

The IFI control system's backup battery relied on a different connection to the robot controller. Thus you had to have two connection failures for a disconnect to occur, greatly decreasing the probability of occurrence.

Could that be duplicated by giving power through the RJ45 and the power plug? I wonder how the radio would react?

[AllenGregoryIV]

Originally Posted by IndySam

Could that be duplicated by giving power through the RJ45 and the power plug? I wonder how the radio would react?

They are redudant that is how we powered the radio, all year and it worked flawlessly.

And yes the old backup battery did have another connection but it added completixty, in having keep another battery charger and replacing it when needed. The main problem it solved was avoiding brown outs, the current system does that well without the need for the backup battery. (at least that is how I believe the system is intended to work).

[GeeTwo]

Originally Posted by AllenGregoryIV

And yes the old backup battery did have another connection but it added completixty, in having keep another battery charger and replacing it when needed. The main problem it solved was avoiding brown outs, the current system does that well without the need for the backup battery.

While it may not be as truly redundant as a separate power circuit, I agree that it makes more sense from the volunteer inspection standpoint (which needs both simplicity and safety) to allow robust voltage regulators (and boosters where needed) to ensure a steady voltage rather than a separate power source.

[Kevin Ainsworth]

Originally Posted by AllenGregoryIV

Hom many lumens was the projector that you all ended up using?

1000-1500 Lumens
The student/alumni that came up with this concept doesn't remember the exact specification. He said it was or was similar to the NEC LT260 DLP Projector with an old bulb. Something he picked up at a school auction.

Adding a coating to the 45 degree viewing window or reflective car tinting might also help, we used clear polycarbonate.

The one thing about this setup was it was very heavy and awkward to carry around between matches.

Originally Posted by frcguy

Any chance you have a photo from the driver's perspective? I saw several requests in the other thread but no photo.

Also, have you considered using a "pico projector or something smaller?

No pictures that I can find, sorry.
We did try a smaller projector but it wasn't bright enough to be usable.

[Drakxii]

For more complex games, like stronghold, project the relevant game data on the driver station window. That way the drivers/coach don't need to rely on the audience screen, which may or may not be blocked by field elements.

A simple game, in the kit off software bundle, that allows a person to walk through the game field. Allowing teams to get a clearer understanding of the field elements before building them. Also if the move part could be animated and/or have it set up for VR, that would be great too.

[scottgoering]

Originally Posted by Drakxii

For more complex games, like stronghold, project the relevant game data on the driver station window. That way the drivers/coach don't need to rely on the audience screen, which may or may not be blocked by field elements.

FYI, FIRST did try something similar to this in 2014 Aerial Assist. They used a spare ref panel screen to display zones credited for possession. From here:

Each ALLIANCE STATION has one (1) flat panel display centrally mounted above the middle PLAYER STATION. The
display shows the ALLIANCE each ZONE where the ALLIANCES’ ROBOTS have been granted credit for
POSSESSION. Further, the panel highlights the unique ROBOT-ZONE pairs that are recognized as ASSISTS.

Not quite the game data in each DS window, but at least they tried

I don't think it was used very much.

[Christopher149]

Originally Posted by scottgoering

FYI, FIRST did try something similar to this in 2014 Aerial Assist. They used a spare ref panel screen to display zones credited for possession. From here:



Not quite the game data in each DS window, but at least they tried

I don't think it was used very much.

I find it ironic that at MSC, I found myself looking at the arena jumbo-tron for the score instead of that panel even though the panel was only a couple feet from my head.

[AdamHeard]

I've been reading this thread all weekend on Mobile and it's been killing me... On desktop now and can reply.

Working at the system level, I'm responsible for designing and implementing (often lithium based) battery systems for motion control applications.

Lithium ion as a generic name, and Lithium Iron Phosphate (LiFePo4) as a specific chemistry are two very different things. Lithium ion is to dog as LiFePO4 is to german shepherd.

Lithium ion is commonly used as the name for most 18650s and cell phone cells, which I believe are commonly Lithium Cobalt Oxide, Lithium Manganese Oxide or some combo of the two. These cells are optimized for energy density (not power density) and not safety. There is a relatively low temperature thermal runaway condition that can be caused by physical damage (as this allows the anode and cathode to directly short) or temperature increase.

Lithium Polymer batteries (very popular in RC industry, and make a great show on battlebots) are different in that they use a polymer electolyte instead of a lithium salt. They are capable of higher power density than the cobalt and Mn lithium ion, but are often less energy dense. These also are not optimized for safety, and have the same thermal runaway condition.

Both of the above are used far more commonly than LiFePO4 and are made safe by the system design. They are spec'd where overcurrent is not a concern, they are balanced during charging (and sometimes during use), often have external current monitoring to prevent over current, temperature monitoring, etc... All of this with the goal of preventing thermal runaway.

Now let's get to the good stuff!

LiFePO4 is a very safe chemistry as compared to above, and comes in cell and pouch style. Some 18650s are LiFePO4, and a 26650 size was popularized by A123 Systems... but they do come in all shapes and sizes. LiFePO4 are far safer (which mostly comes from about 1/3 the energy density of the above). They are optimized for power density and safety.

LiFePO4 are commonly penetration tested (nail, etc... inserted entirely through the cell and out the other side) without any flame event, and often with the cell remaining perfectly functional. There will be some capacity loss, but it will keep trucking. They can be overcharged and discharged to 0V and recovered without safety issue (do not try this with other chemistires...), just some capacity loss.

LiFePO4 is a great option for FRC batteries as they are commonly used in SLA replacement applications where you you do 2/3 as many SLA cells with LiFePO4 cells, and use the same equipment. This isn't what I would recommend for FRC, as I believe we should still have a balance unit but it would work.

Considering the SLA batteries we use are essentially 4-5Ah batteries (see spec and explanation of law), a LiFePO4 pack could be made that would safely run an FRC robot for 4-5 matches and have a retail price of $200-250. The battery would last for a great deal more cycles than the SLA batteries as they aren't affected by the deep discharg nearly as much. Our team goes through 12 SLA batteries per year, and would we switch to probably 3-4 LiFePO4 batteries and one new one every other year. Most teams could just run 2 and buy a new one every 3 years.

Lithium Titanate would also be another safe option if we stay in the stone ages long enough and price comes down...

[Bryce2471]

Originally Posted by AdamHeard

I've been reading this thread all weekend on Mobile and it's been killing me... On desktop now and can reply...
...LiFePO4 is a very safe chemistry as compared to above, and comes in cell and pouch style. Some 18650s ...

Great information! Thanks for that.

It also may be worth noting that these batteries could potentially be charged from dead to full in a few minuets between matches.

[adciv]

Originally Posted by ratdude747

Not really, you make the controller part of the pack, just like with laptop packs and the like. Even add a push button charge indicator for extra functionality at a low marginal cost. The hardest part would be the current sense circuit, as we're talking pretty high peak currents compared to most packs. Not to say it's not doable (it almost certainly is), but it would take a corporate partnership for this to happen in FRC. Unless somebody already makes rated packs with a sufficiently robust casing, in which case, half the work is done.

The primary issue is a sufficiently robust casing is it would have to be built out of metal (work experience). Then again, I also have a different view on what I consider safe with regards to batteries since we sometimes do our penetration testing with bullets (conventional workplace hazard).

I am seeing integrated controllers as pretty common and one option a number of them do provide is current charge limiting. Some of the options allow you to provide the battery a straight 14.4 volts and the battery will current limit to whatever is programmed.