So I recently learned what slew control was, and I think it would be a good idea to have it on our lift (DR4B). But it also seems like it would slow down the stacking a little bit. Does anyone here who has a good DR4B use slew control, and if so, does it slow your stacking any?
(I’m assuming slew control is the same thing as slew rate)
I think that I can say with confidence that most teams would not use slew rate for a lift, but rather a drive (Explained below) Most would prefer a regular PID or PD loop. Slew control is basically so that your robot does not trip the PTC. Your lift is not as likely to trip the PTC this year due to the minimalistic load you have to hold (118 grams). Even if you don’t want to risk it, a big downside to slew rate, as you mentioned, is speed. Slew control is more for controlling the bot, rather than going fast, a necessity for every game.
TLDR, Use it for your drive or another subsystem that stalls easily. PID is better for lift. It’s not really necessary this year.
TLDR: The main point is that slew rate control benefits every motor/servo system of any electromechanical system.
Slew rate control is applicable everywhere. Done properly, you won’t see significant human discernible difference in responses to control changes. You are just much less likely to mechanically and electrically stress the mechanisms.
Even when not using the smart motor library, I often use a simple set of functions, motorPowerSetWS, and the redundant motorStopWS, where “WS” means “With Slew.” Then, I write a task controlMotorsWS, that applies the requested changes at the max slew rate. It’s only a few lines of code, but doesn’t do any of the PTC prediction stuff of the smart motor library. Sometimes I throw in the remapping through the power linearization array TrueSpeed found here: https://vexforum.com/t/24cs-motor-control-value-remapping/23959/1
And if I’m feeling particularly technical, I also put in power scaling to account for battery charge level. That’s more complicated, since you have to account for which motors are wired through a power expander. And its best if you do testing to find a sweet spot of battery charge to use as your reference charge against which to scale. But I digress.