Tuning PID Constants Over a Range

[AustinSchuh]

Originally Posted by thatprogrammer

Thanks for the advice! I spent my study period learning about how cross vectors worked and then went over a few of the concepts with my Physics teacher. I now have a good understanding of what's going on with the feedforward.
Two questions:
1. Shouldn't torque_linear = J* d^2(theta)/dt^2? *

Yea, yea, yea, that's what I get for going fast late at night. I updated my post. Thanks for catching that!

Originally Posted by thatprogrammer

2. Is the goal of the voltage scalar to be as close as possible to so that it becomes the non-linear part of the equation when multiplied by cosine(theta)?

*I start calculus next semester and have learned only the very basics from the edX class I have started taking to prepare for it (only 1 week in). Apologies if I am missing something obvious.

Linearizing systems ends up being in control systems classes, which you won't see for a while. It takes a while to wrap your mind around control systems properly.

By voltage scalar, do you mean F_gravity * r, which is then scaled by the gear ratio, the torque constant of the motor, and the resistance of the motor (motor constants not included here)? If so, yes. Your goal is for the term which you add to your motor command to cancel out as much of the problems created by gravity as possible. This leaves you with a small disturbance, and effectively a linear system. A linear system in this case means that applying a voltage at any angle should result in the same amount of angular acceleration. (To make your head hurt more, look at my previous post about efficiency and try to think about how you'd deal with that here )