My team decided to do a broken dr4b (or 4bar-4bar) for our lift. Now obviously, the lift will be overwhelmed by gravity and slowly fall back down. I can’t do the traditional PID loop for a dr4b because a regular has both 4 bars mechanically linked. Will I have to run two separate PID loops for the bottom 4 bar and the top 4 bar? Also, many people use potentiometers for their lift, so is it fine if I use encoders and never reset the value? Thank you in advance!
What is a broken dr4b?
Since they are in principle two separate lifts ofc you need two different targets, etc.
Really just rubber band the four bars.
It has been the going name for rd4b where the top and bottom are not linked and are controlled separately.
not the best name the forum has adopted for something but not the worst either
but wouldnt that removed the mechanical efficiency and advantage of a rd4b?
Well it removes the motors sharing the load across both halfs of the rd4b. But in exchange you get the ability to create perfectly vertical motion without being forced to only have vertical motion. The original 8059 reveal is a good example, you guys needed a chain bar to reach forwards when picking up cones, you didn’t want to always be linear.
Ok… got it now.
So it is something like 62a latest 2dof lift.
Anyways, back on the main topic here…
Sure, main annoyance is you can’t calibrate bottom values or absolute heights (you need a relative height starting point) since every time you turn on the robot it resets the encoders.
Most likely. Both parts of the lift are totally independant of each other, powered by different, unconnected motors, and have a different feedback device. They will need separate control for accuracy on both halves. Also, it could be to your advantage to have seperated control on both. (See 62a early-season reveal)