Dart Linear Acuator

[Type]

So I am wondering if any other teams have ran into an issue when using the Dart Linear Acuator? We didn't put the limit switches in yet because we just got our robot working and wanted to drive a bit, but a driver of ours bottomed out and extended too far with the Acuator messing it up. We thought we fixed it but now one side (one on each side) is just slipping, putting a lot of strain on the other side. Has anyone else had issues with these?

[swraight]

We're also using a Dart, and have had similar issues when overrunning the stops. Use of the hall effect sensors to restrict the stroke really is essential. We have also found it necessary to use software to decelerate the motor as it approaches the limits. When running at high speed near the limits, the motor would not stop quickly enough to prevent overrunning the limit and hitting the mechanical stop.

Unfortunately, the mechanical stops inside the Dart are not strong enough to withstand the full force the Dart is capable of putting out. If you've over extended the actuator and now find that it's slipping, the only solution we have found is to completely disassemble and reassemble with new E-clips (and new Loctite on the threads of the lead screw nut).

We're planning on purchasing a spare Dart to swap out quickly if the one on our robot is damaged so we can still play while we repair the damaged one... Expensive, but it'll keep us in the game.

Good luck with it!

[Type]

Originally Posted by swraight

We're also using a Dart, and have had similar issues when overrunning the stops. Use of the hall effect sensors to restrict the stroke really is essential. We have also found it necessary to use software to decelerate the motor as it approaches the limits. When running at high speed near the limits, the motor would not stop quickly enough to prevent overrunning the limit and hitting the mechanical stop.

Unfortunately, the mechanical stops inside the Dart are not strong enough to withstand the full force the Dart is capable of putting out. If you've over extended the actuator and now find that it's slipping, the only solution we have found is to completely disassemble and reassemble with new E-clips (and new Loctite on the threads of the lead screw nut).

We're planning on purchasing a spare Dart to swap out quickly if the one on our robot is damaged so we can still play while we repair the damaged one... Expensive, but it'll keep us in the game.

Good luck with it!

We may be doing the same thing but it is a 2 and a half rebuild process due to the way our robot is built. It is compact, low bar robot so we have to move our electronics boards to fully pull the actuators out. I think we are adding physical limit switches so it doesn't go too low and it doesn't go too high. Thanks for the help!

[ruralrobotics]

Are any of you using LabView to program it? If so can you help us? We can use a talon sr or talon srx but aren't sure which one to go with. I'm guessing we write it the same way you would a limit switch? Any help would be greatly appreciated. Screen shots are even better.

[Coach Seb]

Originally Posted by ruralrobotics

Are any of you using LabView to program it? If so can you help us? We can use a talon sr or talon srx but aren't sure which one to go with. I'm guessing we write it the same way you would a limit switch? Any help would be greatly appreciated. Screen shots are even better.

Did you guys figure out how to wire and program this potentiometer? Looking to do the same... any help would be appreciated...

Coach Seb

[Type]

We decided the potentiometer wasn't worth the hassle and we put in physical limit switches. With the way our robot is designed we can do that but I'm not sure if all robots with Acuators could.

[Hitchhiker 42]

We used Darts in 2015 with potentiometers. We set software stops on these, as well as an equalling-out program (we were using 2, and 1 one would move faster than the other) that made it so both moved at the same speed.

The implementation can be done in 2 ways.

1.) You can set up a case structure that stops the motor (values: 0) if the pot values are over the limits (you'll have to find these experimentally)

2.) You can use the built-in Talon software to set limits in Begin (I'm pretty sure that's possible). Don't quote me on this, though.

[Matt-T-FRC]

Originally Posted by Hitchhiker 42

2.) You can use the built-in Talon software to set limits in Begin (I'm pretty sure that's possible). Don't quote me on this, though.

I completely forgot about this. In begin, place a Talon SRX Set Ref with feedback type wired as Analog POT and a Talon SRX Set POT Turns with the number of turns set to the right turn value and it should work.

[Coach Seb]

I am assuming this will be connected on the analog port on the Roborio right ?

[Coach Seb]

We are using Talon SRX as our motor controller, could i use the data port to connect the potentiometer wires?

[swraight]

We are also using a Talon SRX to control our Dart, and we have both the potentiometer and the limit switches connected to the data port on the Talon. I'm sorry that I cannot help with the specifics of the code - I'm just a knuckle-dragging mechanical guy - but I do know that it is possible to wire it as such.

We've also found that by roughening the shaft of the lead screw and using red loctite on the shaft collars (between the collar and the shaft, not on the clamp screw of the shaft collar) we have been able to absorb several high-speed impacts against the hardstops without jamming the actuator. We are still using software to limit the speed of the actuator as we approach our limit switches, but it's good to know that a small glitch won't result in us doing a complete tear-down of the Dart.

[Matt-T-FRC]

Originally Posted by Coach Seb

Did you guys figure out how to wire and program this potentiometer? Looking to do the same... any help would be appreciated...

Coach Seb

We are using Labview and the potentiometers with our Dart Actuators with decent success. I don't have our robot near me at the moment but I believe that the top Pin (Pin 3) was Negative, the center Pin (Pin 1) we used as Positive, and the bottom pin (Pin 2) was the pin that we used as our signal pin.

When programming the POTs we sent the values from the robot to the smart dashboard. From there, we slowly ran the actuator up and down between full up and full down and recorded the values with a few hundredths as leeway on each end to use as limits. I attached a few pictures of our begin, telop, and periodic tasks vis. Let me know if you have any questions.