Help with CIM motor locking system?

[MAXOFLIFE]

Sirius Reveal: https://www.youtube.com/watch?v=zxG7JpejR4g

Can someone tell me the name of the device that the robot Sirius uses in this video to control their arm? Their arm device is rotated using a CIM motor. If I'm not mistaken, CIM motors do not stay in place as Sirius's arm does when lifted off the resting position. Are they using some sort of gear box that locks the arm in any position in the given rotation? Or does a CIM motor have some kind of idle when powered and connected to a motor controller?

Thank you for taking the time to read this post! Any help is greatly appreciated .

[jojoguy10]

I'm pretty sure they are using the Dart Linear Actuators. You can find them on their website: http://dartactuators.com/

Or, on Andymark: http://www.andymark.com/DART-s/540.htm

[MAXOFLIFE]

Originally Posted by jojoguy10

I'm pretty sure they are using the Dart Linear Actuators. You can find them on their website: http://dartactuators.com/

Or, on Andymark: http://www.andymark.com/DART-s/540.htm

According to a comment left on the youtube video, a CIM motor powers the arm and controls its angle. Do you know what we would need in order to replicate what they're doing? I was under the impression that this wouldn't work since a CIM motor doesn't lock into place when not power.

[Knufire]

Originally Posted by MAXOFLIFE

According to a comment left on the youtube video, a CIM motor powers the arm and controls its angle. Do you know what we would need in order to replicate what they're doing? I was under the impression that this wouldn't work since a CIM motor doesn't lock into place when not power.

Sometimes it does, sometimes it doesn't. It's all dependent on the efficiency (friction) in the components (gears, belts, chain, etc) between the CIM and what you're trying to rotate.

[MaGiC_PiKaChU]

they could be using sensors to read the arm's angle. You just have to apply a small portion of the available power using motor controllers (Talons, victors, sparks, etc.) to overcome gravity and keep it at the right angle.

I recommend you read about sensors and motion control for your personal knowledge

[zinthorne]

I believe the dart actuators are a worm drive system, and it's is very difficult or impossible to back drive a worm drive.

[Chak]

Originally Posted by zinthorne

I believe the dart actuators are a worm drive system, and it's is very difficult or impossible to back drive a worm drive.

Actually, the DART actuators use a ACME lead screw. Nevertheless, it's very difficult or impossible to backdrive a lead screw. On the other hand, efficiency goes down (Andymark says it's 52%).

[rich2202]

There is a setting on the Motor Controller that allows or resists free wheeling of the motor. It is called "brake" or "coast" mode. That mode may provide enough resistance to prevent the arm from moving.

You can also use encoders on the motor to PID control the position to hold the arm in place.

[adciv]

Placing a CIM in brake will not stop it completely. Brake mode turns the permanent magnet motor into a permanent magnet generator.

What you can do is operate the CIM at stall (using a PID for instance) and hold an arm in place. We did this a few years ago with our drive train a few years ago.

[CryptoStorm]

If you look at the video its clearly a cim connected to a standard gear box. a chain and sprockets deliver torque to a shaft going through the arm..

Its too hard to follow, however, if it were me and i was using this setup:

I'd attach a single turn pot to the end of the arm shaft and create a PID program to control the CIM output to match the analog value of the pot to a user defined value. pressing up increases the user defined value, pressing down decreases it.