Talon FX Configuration - Slot Configs, kA, kV, kS Feed Forward

The following is the quadratic regression curve (and linear) for velocity as input and desired output voltage for feedforward as output.

Per usual, but just for clarity, we collected the velocity after outputing voltages, then flipped the voltage to the output, for anyone that is unfamiliar.

image

In this equation, which has a great fitment, the coefficient for kV is negative.
According to CTRE SlotConfigs javadoc, the minimum value is 0 for kV.

I know about arbitrary feedforward, but I was hoping to not have to do that, considering the TalonFX motor controller has a faster loop time.

I figure this isn’t super uncommon. Can CTRE allow for negative kV values for situations like this?

Can you describe your data collection procedure in more detail?

Why not use SysId?

I believe I’m doing what SysId does, but manually. I know, probably not ideal, but it also helps students students understand how the values are calculated.

I used chatGPT, and it was able to give me an even better quadratic regression, with all positive coefficients

voltage=0.29911×(velocity) 2 +13.22432×(velocity)+0.17841 ​

ChatGPT is not going to be of much help here.

The regression is the least important part of the process; data sampling and choice of driving signal matter much more.

I do not think your procedure here can work, regardless; the system is not quadratic. You are fitting noise. Further, you cannot pull the linear term out of a quadratic fit and use it effectively in isolation.

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SysId fits a completely different model. Let x be the velocity, dx/dt be the acceleration, u be the voltage, and τ be the timestep.