I have been thinking a lot about arm designs, and I have realised that most arm designs I have seen (including ours) do not allow the robot to carry the tetra above itself, it has to hold it out, which could make for some interesting tipping problems :eek: .
Where do you carry tetras?
We carry them between ~2 and 6 feet from our shoulder joint which is located near one of the upper corners of the robot.
Our first design was a 2 jointed arm much like many people are talking about, but before finalizing it, I ran some calculations I should have done much earlier to see how tippable we would be. The results were unacceptable to me, so we decided to drop the second joint in exchange for a slider carrying our tetra manipulators on our arm.
We have a long “lance” that we use to spear the tetras, then we use a pneumatic to pull that lance up. It brings the Tetra closer in and allows us to cap higher.
Thats like what we are doing.
We have a pneumatic on our arm with a 2 foot stroke. We can rotate it about 270 degrees around the lateral axis. When we hold it straight up with the cylinder in the extended position, our bot’s about 12 feet tall. We need to do a tippability test.
Our arm has both a shoulder and elbow joint. Our “end-effector” (which is our undisclosable top secret design) is such that we can leave the shoulder all the way down, drop the elbow, grab a tetra, and then lift the elbow back into a vertical position and one face of the tetra nests nicely at about 2 feet above the ground directly above the front end of our robot.