That could certainly help. I still recommend reducing the stall force somehow, through current limiting and/or a high-current cutoff when bringing CARGO in if not less reduction/lower throttle.
Ok, we will try lowering the RPM in the code and test.
With the redline and a 12:1 you are running roughly 500 RPM at full speed, right?
For 4" wheels, 5:1 at 0.4 throttle would get you 3010/5.4 = 24 ft/s free speed and a stall force of 315/10.4, or 6.2 lb. If 2" wheels, 3:1 would make sense.<
Are you calculating based on a 5:1 ratio here? We have 10:1, or we can go to 4:1 if necessary, but we don’t have any 5:1 ratios.
No. Faster than that. That only equates to 8.3 rev/s.
I do all my calculations based off of end-effector ft/s. I’ve been told by people I respect to keep ball manip speeds around 20-30ft/s and all will be fine.
Currently our intake specs are:
free load = 31 ft/s
max efficiency = 25 ft/s
max power = 14 ft/s
Those numbers seem good to me in theory. And so far so good in practice.
We did a lot of testing to avoid this specifically. We popped a ball on our intake prototype and instantly pivoted our design to specifically avoid this. We took slow-motion video of the popping to find the cause, and we eventually figured it out. What causes the popping is the complying material, whether it be a compliance wheel, and rubber roller, etc, rubbing against the ball when it is unable to move, causing the roller to spin up against the static material and build up a lot of heat really fast, causing the heat to melt a hole in the ball’s material and cause it to deflate.
There are a few ways to solve this problem.
Prevent overspinning. You can put a presence sensor (ultrasonic, touch, etc.) sensor in your intake to prevent it from moving the rollers once the ball is at the back of the intake. The problem: it’s active. If that sensor fails or misdetects, it could compromise your ability to intake properly, plus it’s added complexity.
A different material. You could avoid using a rubber, sticky material and switch to something softer that complies but absorbs the heat. (think foam/paint roller)
Yes I was, not knowing what speeds you had available. at 4:1, at about 1/3 throttle, you could get 24 ft/s free and about 4lb stall force on each axle, which would be better than the high stall forces at 10:1.
Yes I was, not knowing what speeds you had available. at 4:1, at about 1/3 throttle, you could get 24 ft/s free and about 4lb stall force on each axle, which would be better than the high stall forces at 10:1.<
Ok, so we should change to 4:1 and run at 1/3 speed? How are you finding the ft/sec and stall torque numbers? I have the calculator spread sheet, but I can’t seem to find those numbers
It’s the exact same math that @GeeTwo and I shared earlier about linear intake speed and stall torque, except you work the problem backwards from your linear speed to rpm, to given speed to linear intake speed, just max rpm of motor times the power reduction scalar times the ratio times the circumference of intake wheel for speed, and for torque its the motors peak stall torque times your ratio times your power reduction scalar.
We found that the sharp edge of the compliant wheels regardless of color slice thru the ball, we filed/sanded the edges to round them over and have not had any issues since
My team popped 3
Does the math change since we are not moving when intaking cargo?
No the moving factor would just be used to determine what would be an ideal linear intake speed if we’re collecting while moving, everything else is the same.
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