New AndyMark product: L16-R actuator

[jnicho15]

Interesting new product from AndyMark: linear servos. They are available in both 150:1 and 35:1. The 150:1 has a max force of 250N and the 35:1 a max speed of 35mm/s. Looks like a good replacement for something like a DART in lower-load applications. The DART can provide around 3.5x as much force, but costs over 4x as much. The L16-R s only cost $70 each! But will they be legal?

150:1 : http://www.andymark.com/product-p/am-3516.htm
35:1 : http://www.andymark.com/product-p/am-3517.htm

[GeeTwo]

As servos, they would have been last year, presuming they are reasonably efficient (peak output power is a bit under a watt, so input current is probably a few hundred milliamps).

Added: With the addition of the REV servo power module as a legal controller, it is likely that the servo limits will be going up, not down.

[dradel]

Was wondering about the legality as well. Part of me thinks seeing as it is marketed as an actuator it is going to cause issues with the legal motor tid bit, but is also a servo. Oh the horror 😲

[Cothron Theiss]

I can't say anything about the legality, but I can vouch for the quality of these actuators. I used one of the same brand for a work project, and they work very well. We mounted it with a load cell and used it with control loops so it was always exerting about 20 lbs. of force on an extruder. That's not exactly a typical FRC application, but I'd certainly go to these for tasks too small for a DART.

[cadandcookies]

Highly recommend that teams reach out to Actuonix/Firgelli if you're interested in these servos. They offer a considerable discount if you're shipping to an educational facility.

[Bkeeneykid]

Slight resurrection, but the just posted two more versions of this actuator:
http://www.andymark.com/product-p/am-3514.htm
http://www.andymark.com/product-p/am-3515.htm
Some reason they say "CIM NOT INCLUDED" despite the fact that they use built in servo motors (paging billfred?). Seems mostly the same, just smaller.

[otherguy]

Any consensus on whether or not this is legal for FRC 2017?

I could see them being legal if they were considered to be a servo.
I guess my holdup is that when I think servo, I'm picturing a rotary RC hobby type servo (Futaba/HiTec)

They don't look like a traditional servo, but electrically they are effectively equivalent (A DC motor w/ built in potentiometer for feedback). And the rules do not specify that a servo should be rotary/linear. The manufacturer of these components (actuonix) sells them as linear servos.
The only real constraint on servos in the rules appear to be cost (<$75) and they meet that. They also don't draw more than 2.2A in stall, so no immediate concerns about brownout. I think I've convinced myself they are a servo... I'm just not sure every inspector would see it the same way. Thoughts?

[Bkeeneykid]

Originally Posted by otherguy

Any consensus on whether or not this is legal for FRC 2017?

I could see them being legal if they were considered to be a servo.
I guess my holdup is that when I think servo, I'm picturing a rotary RC hobby type servo (Futaba/HiTec)

They don't look like a traditional servo, but electrically they are effectively equivalent (A DC motor w/ built in potentiometer for feedback). And the rules do not specify that a servo should be rotary/linear. The manufacturer of these components (actuonix) sells them as linear servos.
The only real constraint on servos in the rules appear to be cost (<$75) and they meet that. They also don't draw more than 2.2A in stall, so no immediate concerns about brownout. I think I've convinced myself they are a servo... I'm just not sure every inspector would see it the same way. Thoughts?

I see these pretty much legal. There's no definition of servo explicity mentioned for FRC, so the usual course is to go to Merriam-Webster:

a power-driven mechanism that supplements a primary control operated by a comparatively feeble force (as in a servomechanism)

Power driven mechanism? Check. Supplements primary control? Interprets the PWM signal from the RIO. Operated by a compartively feeble force? I think electrical signal would follow that. I see no reason why these wouldn't be legal, and especially with the REV servo board, you could have a servo up to 7.5 Amps.

[Kevin Sevcik]

Firgelli/Actuonix market these as linear servos on their webpage. I didn't have any qualms about using them last year under the typical "commonly marketed as" interpretation of the rules. As long as it's normal 3-wire PWM servo control and powered by 6V, it should be fine.

[GeeTwo]

Nowhere in the 2017 rule book are rotary vs linear servos called out. The AndyMark page refers to it as a linear servo. According to the AndyMark page, it's powered by 6V through the appropriate connectors and signals to be a servo. It retails for $70. I don't see any question here. If you do, go to the Q&A.

Edit: I suggest that you phrase your question such that you are asking if linear servos are permissible provided they meet the servo and electrical component requirements, otherwise the answer may be less specific than you would like, because the GDC doesn't usually rule on specific COTS items.

[JesseK]

Likely legal since it's an assembly powered by a continuous rotation servo. Relevant rules:

Originally Posted by R32

PWM COTS servos with a retail cost < $75

Originally Posted by R32 Blue Box

For servos, note that the roboRIO is limited to a max current output of 2.2A on the 6V rail (12.4W of electrical input power). Teams should make sure that their total servo power usage remains below this limit at all times.

Italics are researched specs/questions:

Originally Posted by R36

Servos must be connected to, and only to, one of the following:
A. PWM ports on the roboRIO ($0, 2.2A max across all channels)
B. PWM ports on a WCP Spartan Sensor Board (P/N: WCP-0045) [$120, 200mA max?]
C. REV Servo Power Module (P/N: REV-11-1144) ($40, 15A total across 6 channels)

The AM specs include current draw in the 'datasheet'. 650mA at 12V stall ===> 325mA at 6V stall, right?

I'm interested since it may prevent us from needing another PCM, cylinders, and a hard stop for two low-load internal mechanisms.

[ahartnet]

Originally Posted by JesseK

I'm interested since it may prevent us from needing another PCM, cylinders, and a hard stop for two low-load internal mechanisms.

Just keep in mind that even the faster one only moves at a rate of 1.25 inches per second, which is much slower than a cylinder.

[JesseK]

Originally Posted by ahartnet

Just keep in mind that even the faster one only moves at a rate of 1.25 inches per second, which is much slower than a cylinder.

Yea I know. But the amount it needs to move is about 3/4", and it isn't critical that it happens instantly.