Dr4B Program

[sbarrij135]

how do you program a DR4B to stay equal to the other side going up if its behind the other side?

[Doctortictac]

Welcome to forum!
You could use encoders, but just moving at same time at same speed with a backup button(s) (in case one falls behind) are easier

[ThirdDegree]

If you have proper cross bracing, this also becomes less of a problem. Connecting the gear boxes with an axle across also helps, but isn’t really necessary most cases.

[PortalStorm4000]

Instead of moving the motors up and down when pushing buttons, have them increase and decrease a variable instead. If the target variable goes outside of bounds of your lift, set it back. Then use PID to move the left side to that variable, and then do the same for the right side. Some pseudo code below. You’ll have to convert it to whatever language you are using.

int dTarget = 0;
while(true){
  if(buttonUp.get()) {dTarget += 1;}
  else if(buttonDown.get()) {dTarget -= 1;}
  
  if(dTarget <  0) {dTarget = 0;}
  if(dTarget > 100) {dTarget = 100;}

  leftArm.moveTo(dTarget);
  rightArm.moveTo(dTarget);
}

[V5isbetter]

Do any of you guys know how to build a DR4B or a good step by step video?
https://www.google.com/imgres?imgurl=https%3A%2F%2Fi.pinimg.com%2Foriginals%2Fe6%2F75%2F58%2Fe67558248fe349a1a3fee6d7bc815e9f.jpg&imgrefurl=https%3A%2F%2Fwww.pinterest.com%2Fpin%2F504403227015648673%2F&docid=98d0hV3UsINvFM&tbnid=l_1hn4px8nOPYM%3A&vet=10ahUKEwiw6fWV6uzlAhXFmVkKHftRDjsQMwhcKBIwEg..i&w=1280&h=720&safe=active&bih=609&biw=1366&q=DR4B&ved=0ahUKEwiw6fWV6uzlAhXFmVkKHftRDjsQMwhcKBIwEg&iact=mrc&uact=8

[enothecool]

The Kepler Electronics Guide to the DR4B

This video is a good guide on how to make a dr4b
All these threads involve people fixing or improving their dr4b. I would recommend reading over them to gain helpful tips.

DR4B Rubber Banding

So I know that the general consensus for rubber banding a DR4B is that a triangle is the best shape. However, I have a few questions about some more technical aspects on the choices that teams make when rubber banding their lifts. For one, why do most teams only rubber band the bottom part of the DR4B? I’ve been rubber banding both the top and bottom four bars and it works just fine, so is there a particular reason that the bottom is usually the only part rubber banded? Also, why do most teams…

DR4B Tips

I’m currently building a DR4B, and I am encountering many problems. my lift keeps leaning, but it isn’t because of weight, since it sometimes leans left, and sometimes leans right. The lift is also generally unstable, and wobbly, despite multiple, tight screws into the base, and support bars wherever I could put them. Are there any particular tips for these kind of issues?

Refining our DR4B

So two questions: We only have room to crossbrace our top four bar on the DR4B and were wondering whether it would really be necessary? Our DR4B seems sturdy enough for now. Is there a big difference when using pulleys with the rubberbands? I’ve heard it helps even the tension across each section of the rubber band triangle. Right now we are just using spacers that can roll but not wiggle around.

Heavy DR4B

We are attempting to use a double reverse four bar, but it is extremely heavy and barely lifts even with 2 motors and a TON of rubber bands. The screws attaching the gears to the channels are bending (even with standoffs there) and making the bars not parallel as well. Any suggestions? [image] [image]

[technik3k]

Kepler electronics video has very good explanations about workings of DR4B, however it features shaft based joints, which are not easy to build a stable lift with.

The best step-by-step building instructions for building a good DR4B lift is Team 333 tutorial:

DR4B Tutorial by 333A

It is that time of the season when beginner teams are searching for resources to assist them with building their first DR4B lift, and senior teams are looking for new ways to build taller, stronger, and more stable DR4Bs, improving on their designs from past seasons. Hence, we decided to make this DR4B Tutorial by 333A. In our guide, you will learn how Double Reverse Four Bar (DR4B) works. New teams will find step-by-step instructions how to build a good DR4B. It explains the main factors of …

[lerker100]

I control both motors with one button like normal then I get there position and calculate the difference and make one of the motors move the distance. But if your using V5 and it’s way off you need to fix your hardware by moving motors or metal around to make it better. Good software can’t fix bad hardware.