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Unread 28-01-2017, 10:03
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Legality of Linear Actuators

Our team is planning to use a Actuonix L16 Micro Linear Actuator for the competition, and we were wondering under what conditions is this legal? Or is it legal at all to use it?
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Unread 28-01-2017, 10:16
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Re: Legality of Linear Actuators

It is legal, provided that its motor is legal. Take a look at R32 for the allowed motor list.

Chances are that the stock motor isn't legal and will need to be replaced with a legal one. Unless you can count it as a servo, but it's really close to the cost limit and isn't sold as one by default.

Your best bet is to use the actuator, but remove the motor for one listed in R32.
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Unread 28-01-2017, 10:18
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Re: Legality of Linear Actuators

You have to use one of the legal motors to operate the actuator. Please see Sections 8.6 Motors and Actuators in the Game Manual for legal motors. This also includes the AndyMark NeverRest Motors.
See below:
http://www.firstinspires.org/resourc...nual-qa-system

AndyMark Motor:
http://www.andymark.com/Search-s/545...errest&Submit=
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Unread 28-01-2017, 10:27
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Re: Legality of Linear Actuators

it looks like it is designed to work as a servo. I haven't read the rules about servos....are they required to be rotational, or can you use linear servos?

(if you replied without googling the part, maybe you ought to rethink your answer?)

(and to the original poster, maybe you ought to include a photo of the item in question, when it's something really weird like this?)

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Unread 28-01-2017, 10:51
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Re: Legality of Linear Actuators

From what I read in R32, the PWM COTS servo would apply here, so you would have to be able to purchase the motor for <$75. The R32 blue box may provide some insight. The RoboRIO is limited to 2.2A on the 6V rail. It may be beneficial to investigate using one of these

Q&A may have some answers as well. All I could find for "servo" was this.

I also assume you are interested in the 6V RC Control version such as this. You may want to consider this (also available here) if you are not already.
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Unread 28-01-2017, 10:53
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Re: Legality of Linear Actuators

Quote:
Originally Posted by MrForbes View Post

(if you replied without googling the part, maybe you ought to rethink your answer?)
I googled it. It's sold as a linear actuator, with a control pack for servo use sold separately (for an additional $40). That, to me, would take if off the "servo" list. Also, it's anywhere from $5 under the FRC servo cost limit to $5 over (manufacturer's price). Borderline at best, IMO.

But if you swap out the motor for a legal one, it's a linear actuator that has a legal motor in it.



http://www.actuonix.com/L16-Linear-A...rs-p/l16-p.htm
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Unread 28-01-2017, 11:05
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Re: Legality of Linear Actuators

From the actuonix website: L16-R Minature Linear Servo

There, it's marketed as a linear servo, it's PWM controlled, it's powered by 6V, it's under $75. It's a legal COTS servo if you use this version. You're welcome.

NB: We used one of these last year under last year's servo rules and had no problems.
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Last edited by Kevin Sevcik : 28-01-2017 at 11:07.
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Unread 28-01-2017, 11:11
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Re: Legality of Linear Actuators

Quote:
Originally Posted by Kevin Sevcik View Post
From the actuonix website: L16-R Minature Linear Servo

There, it's marketed as a linear servo, it's PWM controlled, it's powered by 6V, it's under $75. It's a legal COTS servo if you use this version. You're welcome.

NB: We used one of these last year under last year's servo rules and had no problems.
Yeah, I can see where the differing answers are coming from. I linked to the L16-P--which would be a linear actuator and over the servo budget--first result that came up on Google (other than images/ads for the L16-R).

OP, you will need to make sure you get the right version of the L16. L16-R = servo, legal. L16-P = linear actuator, needs legal motor to be legal. Just as a thought, you may want to make sure that the label with the type is visible for inspection in case an inspector asks questions.
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Unread 28-01-2017, 11:22
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Re: Legality of Linear Actuators

Quote:
Originally Posted by EricH View Post
Yeah, I can see where the differing answers are coming from. I linked to the L16-P--which would be a linear actuator and over the servo budget--first result that came up on Google (other than images/ads for the L16-R).

OP, you will need to make sure you get the right version of the L16. L16-R = servo, legal. L16-P = linear actuator, needs legal motor to be legal. Just as a thought, you may want to make sure that the label with the type is visible for inspection in case an inspector asks questions.
Realistically, if it works when it's plugged directly into a PWM port, it's legal. If you have to plug it into something else and plug the something else into a PWM port, it's not going to be legal.
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Unread 28-01-2017, 21:46
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Re: Legality of Linear Actuators

Quote:
Originally Posted by Kevin Sevcik View Post
From the actuonix website: L16-R Minature Linear Servo

There, it's marketed as a linear servo, it's PWM controlled, it's powered by 6V, it's under $75. It's a legal COTS servo if you use this version. You're welcome.

NB: We used one of these last year under last year's servo rules and had no problems.
What gear did you use and how was you experience with these?
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Unread 28-01-2017, 22:48
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Re: Legality of Linear Actuators

To cover yourselves, bring along the manufacturer's data sheet where it is called a SERVO and not a linear actuator. Get the version that has the same part number as the data sheet you have and be prepared to show an invoice with the price less than the limit given in this year's rules for a legal servo.

Do all this, and you should be good to go. I haven't used one of these yet, but I really like the concept.
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Unread 28-01-2017, 23:08
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Re: Legality of Linear Actuators

Quote:
Originally Posted by Retired Starman View Post
To cover yourselves, bring along the manufacturer's data sheet where it is called a SERVO and not a linear actuator. Get the version that has the same part number as the data sheet you have and be prepared to show an invoice with the price less than the limit given in this year's rules for a legal servo.

Do all this, and you should be good to go. I haven't used one of these yet, but I really like the concept.
This is, in fact, exactly what we did. Hard to argue with a manufacturer's website declaring it's a servo.

Quote:
Originally Posted by IndySam View Post
What gear did you use and how was you experience with these?
We actually used the L12-R, not the L16-R. It was to shove a piece of surgical tubing into a gear mesh to act as a brake on a lift, so it wasn't anything sensitive to force or speed. Just needed a small, easy to implement, non pneumatic linear actuation. Ours was a 30mm, 50:1 L12-R.

They worked fairly well, but it's definitely not a digital control in there. There's distinct overshoot past the eventual commanded position if you give it a step change. Even the 50:1 seemed slow-ish. Check the specs to make sure it's going to move fast enough for your needs.

I can tell you that while it's possible to unscrew the clevis from the end, you need to do it with the actuator extended, and rubber faced pliers on the rod to resist the torque. If you don't grab the rod, the servo internals aren't strong enough to resist the torque without damage.

I pulled ours apart to see what the students broke, but all I could tell is the wiper occasionally losing contact with the tracks of the linear pot it uses for feedback. So try not to repeat our mistake.
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Unread 28-01-2017, 23:21
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Re: Legality of Linear Actuators

It's sold as a servo, and I see no reason that it does not fit the servo rules (sale price is the only rule requirement, and it also fits the current requirements). How is this a question?

Edit: Just in case, Q369 asked.

Edit 2: answered.

Quote:
Q369 Is a servo a servo a servo?
To me this is simple, but there seems to be some difficulty on Chief Delphi, so here are the questions: Traditionally, servos are rotational devices which provide rotation-angle internal closed-loop control but do not provide feedback for "external" control. Are devices sold as "linear servos" which provide linear motion using servo standard PWM controls but producing linear rather than rotational motion considered servos under the 2017 rules?

Answer: If it is sold by a VENDOR as a "servo", linear or otherwise, it's a servo.
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