Arm goes down too fast?
 

Hello all,

Our team is running into a problem with our arm for the robot. As of now the arm raises up slowly, which is what we want. However when we try to lower the arm, the movement is very fast, violent and erratic. For the moment we have an old bumper hooked up to the supports to stop the arm from crashing down into the vitals, but we really just need to make the arm lower more slowly. Any advice would be much appreciated.

Re: Arm goes down too fast?
 

Could you add surgical tubing or a gas shock, say as a counterbalance?

Re: Arm goes down too fast?
 

We have bungie cords on the back end of the arm but its too bouncy and doesn't really do much. They were super tensioned

Re: Arm goes down too fast?
 

Don't give the robot any more Mountain Dew.

Blake

PS: Are you actively trying to control the arm when it goes down, or is it just settling under the influence of gravity?

If you are trying to actively control it, how does the arm behave when it is disconnected from the active devices?

How do the active devices behave when they are diconnected from the arm?

Is some individual part of the machine acting erractically, or are several parts combining in some odd non-linear way to create the behavior?

Re: Arm goes down too fast?
 

Check if your Jaguar/Victors have the brake jumpers installed. It can help.

Re: Arm goes down too fast?
 

It does it when were powering it in a downwards direction. Without power it stays up fine, and with power up it goes up fine. Its only about .3 power in the programming and it just slams down

Re: Arm goes down too fast?
 

We're using window motors for the arm.

Edit: Does it matter? The window motors don't backdrive.

Re: Arm goes down too fast?
 

Add more surgical tubing -- lots more. The arm isn't neutrally balanced yet. This is one way to make it much more controllable.

It is easier to use software to limit the upward speed than the downward speed. Something about gravity... Use surgical tubing to take gravity out of the equation.

-John

Re: Arm goes down too fast?
 

Would bungie cords work?

Re: Arm goes down too fast?
 

Yes... make sure you get ones that will work in a way that you can apply force for the entire arm travel. Surgical tubing is great because of how much is stretches, in a manageable way. We tried bungies... learned to hate them.

Re: Arm goes down too fast?
 

We have the same problem. Our arm currently falls really fast once it starts going downwards.

What is the best and most efficient way to attach surgical tubing to the arm? We added surgical tubing to it but the arm is still falling out of control.

Re: Arm goes down too fast?
 

We have the same problem. Our arm currently falls really fast once it starts going downwards.

What is the best and most efficient way to attach surgical tubing to the arm? We added surgical tubing to it but the arm is still falling out of control.

Re: Arm goes down too fast?
 

I can't answer your question with any sort of specificity without seeing your design.

In general, attach the surgical tubing in between a stationary point on your robot, and a torque lever which affects the rotation of your arm. The longer your torque lever, the more effective the surgical tubing will be, the less you need to use.

Re: Arm goes down too fast?
 

Ok so, we no longer have the arm going down superfast but when we stop it from moving in the downward direction, its still super bouncy. Is there anything at all we can do to fix this? We bent up some of our arm parts from the bouncing..

Re: Arm goes down too fast?
 

can you post a picture of the arm?

need more details.
Usually
-increase gear ratio
-balance
-reverse powered lowering(requires some programming knowledge
-increase the strength of the joints and materials used.