How can we get the exact position of our elevator carriage?


#1

We are having trouble with figuring out the position of our carriage on our elevator and I was wondering if there are any ways we could do this.


#2

Use an encoder on your elevator drive system. We use VP and the integrated encoder works great.


#3

There’s a multitude of ways you can do this. The most common would be to throw an encoder onto whatever motor you’re using to drive. Alternatively, you could angle a proximity sensor vertically, or use a series of limit switches for certain set levels, but this wouldn’t track in between. Each has it’s own advantages, but an encoder is most likely the most accurate and applicable.


#4

Encoders. If you are using Talon SRX’s, CTRE provides an extremely easy way to implement their MAG encoders. We use them for everything.


#5

If you already have an encoder you can throw some limit switches along the carriage (ideally one at the bottom, one at the top, and one in the middle) this will eliminate encoder drift and will effectively re-calibrate itself every time it passes one.


#6

What is the mechanism that you use to move the carriage? Chain? String wrapped around a spool? How high does it go?

Most people will tell you to use an encoder, which will tell you, basically, how far your shaft has turned and in which direction. You do some math, and you can convert that into a distance.

That works better with some mechanisms than others – if you’re using the REV elevator kit, for example, you’re probably driving the elevator with a spool. And, the spool will change diameters as you roll string on/off. That might make the math complicated – it won’t be linear any more. And, it gets worse if you have up/down spools on the same shaft, as they will be raveling/unravling at slightly different rates.

There are a variety of proximity sensors that you can use to measure the distance directly.

You might also look into using analog potentiometers instead of encoders (depending on how many times your shaft is going to rotate). One advantage of potentiometers is that you don’t have to do the math to figure out distance – tell your motor “Go until the potentiometer reads this position” and it does it.