Safety Issue: Robots Moving in Pits

[robochick1319]

Originally Posted by Alan Anderson

I don't understand how this is supposed to help. If the chassis is intended to sit on the 2x4 frame, the bottom plane of the robot's wheels will be well below the raised platform on which the tote is sitting. Unless I'm missing something basic about how you are expecting this to work, you've taken the problem of the robot being higher than the floor and turned it the other direction. Am I simply failing to see what it's meant to do?

But even if I am missing something basic, robot frames are not all at the same height off the ground. I'm afraid that this "solution" would not work for a large fraction of the robots I have seen this year.

Perhaps not but if it works for his team and even one other that is progress, right?

[jman4747]

Originally Posted by robochick1319

Perhaps not but if it works for his team and even one other that is progress, right?

+1

Just make one for your own robot guys.

[Siri]

Originally Posted by robochick1319

Perhaps not but if it works for his team and even one other that is progress, right?

Only assuming that it doesn't not work for some other team so spectacularly that it actually adds to overall the safety risk. For instance, one of the hypothetical teams in this thread that makes mistakes pulling breakers or disabling code may position it improperly, or do a test that shifts robot CG such that it launches off the rig. Among other potential failure modes.

To be clear, this is at least slightly tongue-in-cheek. But there seems to be a lot of "my solution is foolproof, but here, let me build a better fool to break yours" going on. I have no reason to believe that this rig will actually harm anyone at SBPLI, and commend the effort towards what I hope and believe is a full spectrum attempt at safety culture. Kudos.

At the same time, I think we're all simply cautioning that, regardless of your solution, common sense/safety culture is still necessary to implement it properly. Raising the wheels is by no means an entirely safe solution. In fact, I can think of specific cases in which allowing the wheels to spin under power is more dangerous than actually controlling that power digitally or electrically. Again, it takes critical thinking. Anything anywhere in life that is sold as a perfect solution comes with the danger that users will stop thinking about its risks.

[Alan Anderson]

Originally Posted by Siri

Raising the wheels is by no means an entirely safe solution. In fact, I can think of specific cases in which allowing the wheels to spin under power is more dangerous than actually controlling that power digitally or electrically.

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.

[robochick1319]

Originally Posted by Alan Anderson

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.

Really? We've used mecanum (even this year) and never had this "jerking" issue that rocked solidly placed blocks.

I guess I'm picturing jacking the robot up like a car then testing the wheels. Is there really that much sideways movement when your run the wheels off the ground?

[jman4747]

Originally Posted by Alan Anderson

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?

[Alan Anderson]

Originally Posted by jman4747

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.