Chief Delphi - Safety Issue: Robots Moving in Pits

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Re: Safety Issue: Robots Moving in Pits

Quote:

Originally Posted by Alan Anderson (Post 1458499)

Indeed, for much of the development of the TechnoKats' mecanum software this year the wheels would have a fit if they were lifted from the ground. The robot would jerk back and forth as the wheels convulsed, and it could easily have rocked itself off a set of blocks. Using closed-loop speed control does not play well with unloaded motors.

This makes sense in your build site not your pit. Yea trying to run PID's on blocks doesn't work, I know (our bot didn't shake it self of the blocks though).

What would you tell a team trying to test a drive running PID in their pit? Put it on the floor?

Quote:

Originally Posted by Chris is me (Post 1458525)

You totally missed what makes building one of these difficult. The floor of your testing stand isn't the same height relative to the robot frame as the floor of the field would be. On your model, the floor of the stand sits *above* the robot frame! You need a platform at floor level, supports that hold your frame above the ground such that your wheels are exactly tangent to that floor, and holes in the floor so they don't touch the wheels. Big ones, so they don't catch if the robot shakes.

It's really not as simple as some 2x4's with a plywood surface in the front. I'm not saying it's necessarily a crazy complex engineering challenge, but it's not trivial, the design is different for every robot, it's a big part that takes up a ton of pit space, and it's just far less effort than unplugging some breakers. If you don't trust your team's electrical practices enough to be able to do that, your electrical system may be a much bigger safety issue than wheels on the ground.

I see your point and I may try to make some improvements. This model does work with our robot because our elevator doesn't go lower then the top of the chassi. I may put a sideways 2x4 on top of the existing 2/4 to make it so it's completely level but that would be for other teams. I'm the electrical guy and I see why you would just pull breakers but those things are kinda hard to pull off in a hurry (if they are properly installed they are tight) and this is more of a proof of concept then a done project.

Re: Safety Issue: Robots Moving in Pits

Quote:

Originally Posted by jman4747 (Post 1458526)

What would you tell a team trying to test a drive running PID in their pit? Put it on the floor?

Our interim "fix" at the time was to clamp some thick paper (packing material) to the frame so that it rubbed on the wheel and provided some load to the motor being tested.

Back in the IFI controller era many years ago, we did run a robot on the floor in the pit in order to tune and test the autonomous drive routines. We didn't run the actual auton code, just some test commands through the serial "program port" link to tell it to drive forward or backward six inches, or to rotate left or right ten degrees at a time. We did a six foot run once or twice, with advance warning to our pit neighbors and a couple of lines of students making sure nobody was going to be in the danger zone. And always there was someone prepared to slap the big red Emergency Stop mushroom on our auton/disable dongle.