The folks at iR3 Creative Engineering are excited to announce a new line of products called DART Linear Actuators, linear actuators developed specifically around the CIM motor.
DART Linear Actuators were optimized to be used by FIRST robotics Teams. The DART’s packaging offers 3 gear ratios, 1:1, 2:1 and 2.5:1 and comes in 2 stroke lengths 6" and 12". The DART actuators utilize a precision lead screw assembly which can offer position control over it’s range of motion, something that FRC pneumatic systems struggle to achieve. The DART Actuators are both strong AND fast providing forces greater than 200lbs or speeds over 12 in/s.
The DART Linear Actuators will be distributed by AndyMark.com and will be available in time for the 2015 build season! We will be updating the website with more information in the coming weeks and we’re hoping that this new product will help FRC teams in the seasons to come.
For more information, videos and CAD files please visit: DARTActuators.com
One question though… will the actuator backdrive? Using the arm in the video as an example, when you put the arm up, can you just turn off the motor off and the arm will stay in position, or do you need to power the motor to some amount to keep it there?
I think I know the answer, but want to make sure as it’s not specified in the video or website
Generally, we did not see back-drive with the actuators during testing. Technically, because the screw offers greater than 50% efficiency it is not considered self locking and may back-drive especially under high load and high vibration. That said, the additional resistance of the the motor and gear system limits the screw from back-driving.
During our testing the screw did not back-drive under the calculated loads and in many different configurations including the arm in the video.
Depending on the game, I was planning on making an adapter to join one of these actuators with an FRC legal motor. Depending on your price, you may save us a lot of engineering.
We will certainly do our best to meet market demand. AndyMark will have a sizable inventory to start the season and we will have many of the components on hand if demand is higher than expected.
We agree! This is actually one of the places we started. We looked at the actuator you linked along with larger alternatives like this one which is built to handle a more comparable motor power density to the CIM.
For reasons of weight, speed, packaging, etc. we decided we needed a ground up solution for FRC. We wanted to target a faster, lighter assembly for these applications. In our research, we found that one of the common complaints in regards to linear actuators is that they are slow and we wanted to break that mold with this product.
We wanted to land on something that could provide the force of a 2" bore pneumatic actuator at 60 psi AND still have enough speed to allow bots to be competitive.
The DART Linear Actuators will be introduced at around $380.
This is the closest thing FRC has ever had to a single piece, COTS solution for controlling a long robot arm. This is a huge development and a really cool product. I wouldn’t be surprised to see one of these on a 2791 robot next season!
I would imagine it is the repeatable accuracy of the potentiometer, which depending on the type/implementation, will be a number significantly less than 1.
I think a more appropriate question is how much end play is there in each direction under load. I.E., how much backlash does the geartrain have. Of course, if you always put it in compression is isn’t that much of an issue.
Lash in the potentiometer gear mesh will also be a factor in repeatability, with the ones mentioned in the preceding posts. Of course, lash/play in the mechanism powered by this actuator will be (at least) equally important.
Can someone involved in making the demonstration arm shown in the linked video please measure and post the unpowered vertical play at the end of the arm? I think tape measure accuracy would be enough to give us all a good idea of what to expect.
A fully laden 12" Stroke Length, that’s including the pot, CIM and limit switches it’s 5.8. According to AndyMark the CIM is 2.8lbs so that would put the DART at 3lbs.