Looks great guys! I like the way the way the lift comes out.
Right now we weigh just over 26 pounds.
Is you limit of 18 pounds because your lift doesnât have enough force for anything more, or is it because it causes you to tip over?
The chassis itself can support over 32 pounds without tipping or bending.
Right now we have a pneumatic lock that holds the lift down during the game because we have a significant amount of lift aid. Even with all of the pneumatics pulling the lift down, the lift aid still causes upward force. Adding lift aid would specifically risk not being able to release the arm lock and/ or throwing lighter robots (<10 pounds).
Right now we have 2 lifting options.
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Release lock, and make all 6 pneumatics push upwards at the same time. (heavy)
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Release lock, trigger pneumatics in 4 stages with manual delays. (light)
Our 18 pound limit is mostly due to things just becoming more difficult and problematic as more force and stress is applied. We can however low lift things heavier than 18 pounds. We will continue to try to improve our lifting compatibility and will post all changes in detail in our final reveal. Subscribe to the reveal video for competition footage.
Very impressive robot! Is there any reason that you use a red encoder on the flywheel itself rather than a motor encoder on the motors that control the flywheel? Thanks!
Actually, We originally used IMEâs (Internal Motor Encoders) on the thrower. We ended up using the red encoder chained 1:2.4 from the flywheel axle both so we could sense the changes in speed faster, and so that we had more counts per second so that we could allow for more checks of the speed per second.
By having a quadrature rather than an IME, we where able to slightly increases our aggression, consistency and fire rate. Especially because we are mostly working with chain and sprockets. Here is why.
Between the gearing in the gearbox of the motor and the external gearing of the thrower, you have 7 or more compound gearing sets. Your IME only reads the first gear speed. This is where the discrepancy is hidden. Depending if you are accelerating or decelerating, your IME speed will shift up and down the actual value.
I would actually really like to graph the speed of an IME V.S. a quadrature to see the difference.
We shoot off the 4 pre-loads and grab a stack from the wall and shoot it. That makes 45 points. If we keep that autonomous, we will have a video of it in our final reveal. I am also hoping to have links from our reveal to explanations of individual mechanisms so that we donât have a super long reveal.
Interesting. I have some minor issues with recovery rate and a competition in a week, so I will have to try this. Thanks!
What does bang bang controller mean? Does that mean you only put it at like 90 power all the time without PID/TBH?
A bang bang controller uses 3 motor powers. The largest is when you are under the target value, and outside the acceptable threshold you set. The middle value is when you are inside a threshold of tolerable error, and is enough to maintain the velocity without increasing it. The smallest value is used when the flywheel has accelerated to be faster than the setpoint, and is little enough to slow down the flywheel. If your system is durable enough (HS gears, and your motors can take the abuse), you can set that to 0, and the largest value to 127.
The code looks something like this:
task main {
while(true) {
if(error < target - thresh)
setFly(127);
else if(error > target + thresh)
setFly(0);
else
setFly(63);
}
}
The most basic bang bang controller only uses 2 motor powers. It seems that a lot of throwers canât take the abuse of a bang bang controller or just have really bad accuracy when using it. Chain seems to be the secret weapon as it allows âgiveâ in the system without decreasing power transfer. Obviously a lot of other things come into play too though.
How does your intake mechanism manage to intake an entire stack during autonomous? It doesnât seem like your intake mechanism is capable of modifying itself to open up to a whole stack.
If you look carefully at the photo of the front of the robot, the rollers are probably lifted up to intake a stack of balls by the elastic band using a release mechanism or pistons or a winch and pulley of some sort.
I wish I could say we had an intricate system like this, but the intake is a set system. Rather, our intake is designed to intake things off the wall by trapping the balls between the funnel and the wall. We grab all four by âflinchingâ foreword and backwards a couple of times. This allows the balls to fall apart and be in took without loosing control of the balls. It works quite well.
When my robot shoots full court(uses two 5 in traction wheel on each side), it seems to vary a lot depends on the softness of the ball, i had to have 3 settings for soft,normal and hard. And even then, i can only get around 17/24. Do you have this problem?
Yes, in this thread, we explain a good way to solve this. Most of the time it comes down to compression. Sometimes it can take a lot of tuning. I know it did for us.
It didnt really work for me 
Increase one is too wide, decrease one is too narrow
P.S. When we get the right point for full court(soft ball and hard ball land in same location), the near court is not good
It is really hard to know exactly the problem with this little of information. I have also not spent as much time with the 5 inch wheels, and have never actually seen a very good one.
I would maybe recommend trying to optimize your thrower for a mid or close shot rather than the far by maybe spacing your wheels out similar to what we have done. You should still be fine with full court shots.
I think the problem with 5 in wheels may be the tread. It reduces the surface area that can make contact with the ball. I donât know though.
Good luck!
My team uses 3 stacked 5" wheels, and that works for us. Our single flywheel is very consistent, and we only miss when we ignore the robotâs warning lights telling us not to load balls (happens remarkably frequently, by the way). I think part of what helps us with compression is the springiness of our polycarbonate backplate. Because polycarb is flexible, it adjusts the distance between the flywheel and the hood ever so slightly, so as to cause the same compressive force on soft and hard balls. We also wrapped our flywheel in rubber bands, so the balls touch rubber bands, which have a high friction coefficient (or so it seems to us), rather than the tread, which we noticed can also shred the balls, and the backplate in friction padding (the thick black rubbery sheets) so the ball has enough traction against the backplate, and doesnât get torn against the cut, rough edges of our polycarb (we use tin snips, so we donât have to buy more tools).
Edit: I apparently am terrible at reading stuff, since I didnât notice that you use a double flywheel. The concept is a bit different, because things that bend outward while spinning really fast are not always the best things to use. This post is here for anyone with a single flywheel who needs help, but with a double flywheel, ignore it. My bad.