E- Stop and The New FRC Control System

[Ken Streeter]

Originally Posted by Kevin Sevcik

... True E-Stops should rely on a normally closed connection. ...

So, if the new DS always disables the robot without a (preferably normally closed) switch connected to the competition port, then all is well with the functioning of the new system. It can obviously still be jumpered around with a soldering iron, etc., but it generally makes it much more difficult to kill yourself.

That is exactly the behavior of the competition port on the Driver Station. You've also done an excellent job explaining the rationale behind the reason to change to a "normally closed" switch (for enable) from the prior behavior with the IFI operator interface. Thanks!

This does mean, however, that a team always has to have their switch on hand in order to enable the robot.

[Kevin Sevcik]

Originally Posted by Ken Streeter

This does mean, however, that a team always has to have their switch on hand in order to enable the robot.

Which is the entire point. Can't operate safely without a safety switch and all that.

An additional good safety system, if not necessarily for FRC robots, is the deadman switch. It's (usually) a 3-position switch that's only closed when squeezed half way. Released or gripped tightly, the switch is open and the robot should cease operation. The reasoning being that humans are likely to release something OR grip something tightly in a panic situation, but likely won't maintain a calm, light grip on something. Probably annoying to have an over excited driver kill your robot in the middle of a match with a death-grip.... but it might make a good training tool for encouraging the drivers to stay calm in practices.

[Mr. Freeman]

Seems to me like a switch that requires a light grip would be more of a pain in the neck than a safety feature. If you aren't trained to "click the button if something bad happens" and are incredibly likely to panic in the event of an emergency, you probably shouldn't be the one holding the e-stop switch.

I do like the fact the new behavior of the e-stop this year (NC). I've nearly been run over a couple of times due to the lack of an e-stop button.

[Kevin Sevcik]

Well, deadman switches aren't just a backup for E-Stops. They're often there specifically as enable switches for manual controls. So you have to active the switch before you can start moving around a large and dangerous robot, and you can't easily accidentally operate it.

Plus, how much use is an E-Stop button going to be if the machine you're operating electrocutes you, knocks you unconscious, or bores you to sleep? All of these situations leave the E-Stop button unpressed and the machine merrily humming away. Deadman switches don't just protect against machine operating dangers, they also protect against operator inattention.