Problems with parking

We have problems parking with 2 mogos. we simply stall out as if the drive train doesn’t have enough power. The bot is 17 lbs, and has 8 motor drive diirect 600 rpm with 2.75 wheels. the drive has low friction.

Please show us your code / photos of the drivechain

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17 pounds seems like a lot for a 600rpm direct drive, even with 8 motors. Are you getting this weight with the robot by itself or does 17 pounds include the goals?

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I think you know how to solve your own issue. Reduce the weight, or make your drive slower. 8 motor 600rpm is fast, but has a low amount of torque.

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Like people before me have said, If your bot is 17 pounds with goals, you must be excellent at weight reduction but at that point your bigger worries would be breaking your robot at the slightest collision. If your robot is 17 pounds without goals, the extra weight from them is definitely going to put a strain on your drive. 600rpm on 2.75s has extremely low torque. You might benefit from making custom traction wheels or something alone those lines.

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By itself
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I’ve heard that it has the same torque as 360rpm with 6 motors on 3.25 in wheels

This is about true. It’s also about the same torque as 4 motor direct drive 200 on 4" wheels.

from my experience you shouldn’t be having issues. i’ve parked with two goals on 6m 600 being about 16 pounds? pics/vids would help a lot.

8m 600 should have more than enough torque to climb with 2 mogos. It’ll be good if you can provide some images of your robot. I am guessing that weight distribution might be the problem.

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8 motor drive? Wow. You’ve accomplished my dreams. Take off as much of the robot as you can with as little screws as possible, like our lift system was held up by 4 standoffs, and we took it off once for testing. If you can’t then idk you’ll have to post a video.

here is my bot

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You posted a video of your robot parking with two goals a few weeks ago. What changed since then?

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It only parks when the motors ore completely cool. if I even move it around, it just stalls out. I suspect that it might be a motor problem, but I’m not sure.

Have you checked if your motors are over temp when you can’t park? It should say on the event log
https://kb.vex.com/hc/en-us/articles/360036231591-Accessing-the-V5-Brain-Event-Log

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The “motor problem” is that you are asking too much of them and they heat up to the point that they throttle their power to 75% then 50%. If they only do this after > 2 minutes, you can probably get away with it at worlds. Matches are relatively far apart. Students tend to loose track of time while practicing in my experience. Driving for 10 minutes is a whole different thing than driving for 2 – especially if you are doing something like parking practice.

edit: if you have built a drivetrain that cannot park after 1:45 of driving then you have built a drivetrain that cannot park.

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I noticed that when I try to park, the brain says “Motor power output error” It also says “battery low cell 1 voltage”.
Could this be the problem? If so, is it a brain or motor or wire problem?

@jpearman, do you know?

Then, it never said motor power output error. Now, if I look in the event log, it says “motor out put error every time I try to park”

My organization recently discovered that when using speed to drive the motor sometimes a motor stops spinning ( I can give full explanation if you want). The soultion is to use volts instead of speed.

full explanation

The reason is that when you use speed drive the motors have internal PID to reach their target speed effeciently. When you have motors geared together one motor may go over speed and try to slow down because motors go slightly different speeds. This results in that motor slowing down and eventually stopping because eit realizes it doesn’t need to do anything to get to it’s target speed

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just to clarify, your saying i should use volts instead of pct for the user control commands