Possible Applications of new Brushless Motor?

Technical Technical Discussion
1

With the release of the new brushless motor legality for 2018, I think this is a huge win for the first community and a shift in the right direction.

Now if we can just get true stepper motors approved ::ouch:: ::ouch::

However, glancing over the specs of this BLDC motor, with a max power output of 44 Watts Peak, it really is one of the weakest motors we have available to us in first. The power of all other approved motors can be seen at motors.vex.com.

The closest motor which has similar power output is the Andymark 775-125 (AM-2194) according to the testing done by vex.

On our team we really like to do some physics calcs first, and size our motors, and number of motors required based on energy required for the tasks, and then we always apply a safety factor of 1.5x or 2x, to overcome simplifications. This definetly always puts us out of the AM775 power range, but has worked well for us. Especially when during gearbox design we try to be higher up on the efficiency curve, which reduces the power available.

This puts us in a realm where we typically use 775Vpros, bag motors, or banebots 775, or pneumatics for anything not DriveTrain related.

In an effort to understand how we can better incorporate these new motors into our designs (if at all), I am curious what applications teams have used for similar powered legal motors with high success, and reliability.

So in a nutshell, if you have used the NeverRest Motor (25W) or the AndyMark 775 (43W) motors in an FRC application, would you please share what that application was, and how well it worked for you. Preferably only 1 motor, but if you used more than one to multiply the power, that would be cool too.

The idea is, where previous AM775 motors (43 Watt) were successful, this new BLDC motor may be as well (without knowing too much about its interface or reliability or cost). I would imagine outside of those applications, this new BLDC motor may not be so well suited.

I am hoping this information can also provide more information to a lot of teams whom may be excited that a BLDC motor is now available.

Thanks,
Kevin

2

This year CyberTooth used an AndyMark 775 into a BaneBots 16:1 gearbox to spin our turret. We found it had the slowest output RPM of any legal motor that year, so it required the least amount of reduction (weight) to get it to a usable speed for a turret which required very little torque. It worked fantastically. (once we figured out a chain tensioning setup, side note, never use chain on a turret, way too much backlash >.> )

3

Turret was the first application that came to mind for me.

4

I see the introduction of this motor as a stepping stone to decent high-power Outrunners and Inrunners, rather than final solution. In fact I see very little practical use for this motor, in which it actually provides a performance benefit for teams.

I would like to see maybe 1-2 legal Brushless motors, with one type being a low-Kv outrunner which could be used to drive intake rollers (by sitting inside the tube), there would be sufficient market for FIRST to have them custom designed and wound. For other stuff the 775pro already has decent power density. Also a CAN brushless controller would be important, I recall CTRE having the Cyclone at Champs a few years back.

I think comparing this motor to the AndyMark 775 and NeveRest is a great idea. The two main reasons I have seen teams using those motors is for moving turrets/shooters or because they can’t afford anything else and only have what came in the KOP.

In regards to Nathans point, a 775pro run at 4 volts will be pretty much the same RPM and Power output as the AndyMark 775. Using the 775pro in this application would allow easy increase of motor RPM through a simple voltage increase, rather than requiring a gearing change (which is easy with a multiple stage custom gearbox or VersaPlanetary Gearbox if required anyway.) The integrated encoder on the AM 775 is a good advantage over the 775pro however.

In my opinion for the vast majority of applications (turret moving etc is the exception), using a motor less powerful than the BAG/9015 is a waste of time and is putting you not only at a direct performance disadvantage but also makes alliance captains look poorly upon you.

This season I saw dozens and dozens of teams trying to use AndyMark Gearmotors and KOP window motors to climb, a task in which they are woefully underpowered and unreliable for. I hope that this new motor does not end up being utilized in a similar fashion.

I hope VEX are able to get hold of some of these motors before kickoff for testing.

5

Perhaps I am in a minority here, but can we please not introduce high-power brushless motors into FRC? FRC bots are pretty terrifyingly powerful as is, and also plenty expensive as-is. This is a direction in which I honestly believe the meta-game does not need to go.

Brushless motors are cool, and it’d be nice for our students to have some experience with them; but it is not as if they are totally unprepared to deal with them from working with brushed motors, either (the physics are the same…).

I could get behind convenient, small outrunners for intakes, as you have suggested, but I really, really would rather not see it go past that.

6

Yes, cost is a big factor but maybe not in the way you are thinking. In order to be able to score large amounts of fuel this season you needed to have multiple motors, most successful fuel scores used 4 of the most powerful motors available, in fact 1986 were even using 5! at the start of season.

With the 2019 control system refresh( and potentially a redesign of the PDP), 1 high power brushless motor could replace maybe 2 775pros. The cost for the motor and controller will end up being higher if you are comparing it to a single CIM or 775pro( lets say $115 total for SRX+motor) then the more powerful motor and esc combo could cost $200 and still be competitively priced( because of what it replaces). In the quantities in which they would be produced and sold I can see a good quality brushless ESC comparable with the Talon SRX in terms of functionality being maybe $120 leaving $80 for the motor.

7

254 turret confirmed for 2018.

8

Could you please point me to the reference for this information?

9

The current control system was originally intended for use between 2015-2019( stated by FIRST in the proposal). This does not necessarily mean that a a whole new system will be introduced but modifications are likely.

I will edit my wording but by “redesign of the PDP” I meant that the introduction of brushless motors to replace multiple high-power motors would require a design of the PDP to increase current handling capacity, not necessarily that it is being changed for the 2020 season.

10

If you look outside of the FRC bubble you’ll quickly see that running 2 or 4 or even 6 motors + controllers as one motor is highly atypical. The power limit in FRC is set by the battery. With the latest basically unlimited motor rule set there isn’t a whole lot in the way of giving a function as much power as we’d like.

The benefits of brushless is efficiency and therefore power density. Huge swaths of FRC DT are taken up by motors and with FRC robots getting smaller and evermore complex this space could be utilized for more functionality. Think of all the electrical panel space that could be saved by just having one motor controller per function.

It’s kinda like moving from incandescent light bulbs to LED, light output has the potential to be far higher but in most cases it will stay relatively the same. We see the real benefits in efficiency and adaptability, bright LEDs can be used for cellphone camera flashes and cheap, compact head lamps that can stay on for hours. It unlocks tons of new possibilities.

11

A big advantage for the brush-less motor is that you can save on slots at the PDP.
We struggled with that this year and ended up replacing 2 of our not high power mechanisms from 775pro to the AndyMark motor, who both shared a PDP port (illegal with 775). The same could be used with the brush-less motors.

12

That is true if the GDC lets us use multiple brushless motors in the same PDP slot (like the AM775 and a few others). There is a real possibility that that will not be the case.

13

Can you share what application you used for the AM motors?

yep, though of turret as well.

We had a turret this year, and choose to use a bag motor for it, due to the small profile, and speed, although we only drive it no more that half power on a bag, we did throw around the idea of using a NeverRest motor, but I also have a rule about using a new product, we tend to wait at least one season before “trying something newly released”, so that all the bugs can be worked out in the first year, so we went with a bag for our turret, through a vp gear box, knowing it would be overkill and more weight, but had proven reliability.

And we never had to touch it all season.

Most likely we would avoid using this new BLDC motor for the same reasons, but just curious where most people could find use for it, if they did.

Yep, because they are so close in power, and so much smaller than the next strongest FRC legal motor comparing them in this way makes a lot of sense.

14

Not sure if I missed it, but does anybody know the weight of the new motor? It looks fairly bulky.

15

Through playing around with this site and entering the specs from the FIRST supplied datasheet. Looks to be around 15oz or 430g, although it includes the motor controller as well which are usually about 3oz depending on your preference.

http://www.3dcontentcentral.com/PremiumSSS-Download-Model.aspx?catalogId=11051&name=dynamoproduct

16

Different team, but we have used the AM PG gearmotors for internal feeders, doors, “deploy once per match” extensions, and latches. We even used a NeveRest this year to grip the gear and push it onto the peg. Not every application requires hundreds of watts.

17

Seems to me there was similar discussion about how much power can be packed into a given volume and concerns there-of when mini-cims and 775pros were made legal. Granted this is a bit different, but take the viewpoint of a build team from 2002 vs a 2017 build team. Most of those 2002 members would be awestruck by the amount of power we can get out of a robot 15 years later. I suspect FIRST is introducing this small offering as a test. In a few years teams will be comfortable with brushless mechanisms and we won’t have to worry about a COTS drivetrain/gearboxes having to deal with the extra power input as they will have caught up over the next few years as well.

18

I’m not so much worried about the drivetrains themselves holding up as I am the prospect of how much faster/more dangerous FIRST robots might become if drive motors become significantly more efficient (and, therefore, powerful). I’m already barely comfortable with our drivers practicing with our 6-CIM autoshifting drive from this year (and, even through our portable carpet, we’ve done a number on our school’s floors while practicing). Said drive was an important part of getting our team to Worlds this year; if everyone had access to more powerful drive motors, we’d probably have had to have used them or else risked being outcompeted. Such is the metagame.

I suppose appropriate limits on the number and manner of use of these motors may help avoid this issue, if FIRST does eventually go in that direction. But I really do think that we absolutely do not need FIRST robots going any faster than they do now.

19

That’s true regardless. Given a high power BLDC comparable in power to, say, 2x 775Pros takes up exactly 1 PDP slot the net effect is a savings on PDP slots. Maybe a worse example - How many slots on the PDP are taken up by your DT? For a lot of teams that’s 4 or for a few 6. If you could drop that number to 2? Massive savings.

20

I don’t think the change in top speed will be that dramatic. We are still limited in electrical power by the roboRIO brownout condition and the 120A main breaker. More powerful motors will not increase drivetrain speed. More efficient motors can increase drivetrain speed, but I don’t think the increase will be that dramatic. Moving from 4CIMs to 6CIMs is a 20% increase in power. The peak efficiency of a CIM is around 65%. Let’s say a new brushless motor has a peak efficiency of 85%, for a 30.8% increase in mechanical power. So, changing to brushless motors is comparable to switching from 4CIMs to 6CIMs, which is negligible enough that many teams don’t run 6 CIMs and still do fine.

*source: whitepaper)
**source: vex
***of course, drivetrains don’t run at peak power all the time, but I don’t know how else to do a comparison without actual specs for a brushless motor and then directly comparing 2 drivetrain designs