paper: joystick sensitivity (gain) adjustment

[Roger]

Oh dear, I'm way behind, aren't I? We were using the original y = a(x^3) + (1-a)x formula. That "2parm" looks interesting for Monday's programming session.

I think we might be running out of joystick buttons. We've got 2 buttons already for switching gear speed up and down -- yet another parameter in the mix, as "Full cubic" in first gear is really slow.

Another thing I might mention is that we are changing only the "forward/backward" axis of the joystick, and the "left/right" axis is not being changed. (The robot is a standard drive left/right sides.) General thought of the group is that this gives full turning power always.

[Ether]

Originally Posted by Roger

...the "left/right" axis is not being changed...General thought of the group is that this gives full turning power always.

Perhaps this is the result of a misunderstanding. Just to be clear: You would still have "full turning power" if you used this sensitivity adjustment for the turn axis.

Look carefully at the figures and the associated narrative. This filter does not reduce the maximum available output. It just changes the response curve to reduce the gain for small commands. The maximum output of the filter is +/-1 regardless of the values selected for the tuning parameters.

What kind of drivetrain are you using, and what type of driver interface?

[AustinSchuh]

This probably should go in another paper, but it helps handling a lot if you get some speed vs PWM data, and then curve fit it so that you can convert the nonlinear response of the Victors to a nicer linear response. I ended up using a 7th order polynomial last year to do that, and it helped quite a bit.

[Ether]

Originally Posted by AustinSchuh

This probably should go in another paper, but it helps handling a lot if you get some speed vs PWM data, and then curve fit it so that you can convert the nonlinear response of the Victors to a nicer linear response. I ended up using a 7th order polynomial last year to do that, and it helped quite a bit.

Would you be willing to post your data? (Or maybe you already have?)

[AustinSchuh]

Originally Posted by Ether

Would you be willing to post your data?

Sure. I only tested it one direction and duplicated the data as you can see. The data isn't quite as clean as I would have liked, but it's not bad and worked well enough. I exploited the symmetry when I fitted it to avoid getting answers that didn't make much sense.

# Speed Power	Data on blocks.
0.103448	0.020000
-0.103448	-0.020000
0.252874	0.043000
-0.252874	-0.043000
0.333333	0.059000
-0.333333	-0.059000
0.454023	0.082000
-0.454023	-0.082000
0.517241	0.098000
-0.517241	-0.098000
0.614943	0.145000
-0.614943	-0.145000
0.724138	0.184000
-0.724138	-0.184000
0.793103	0.223000
-0.793103	-0.223000
0.885057	0.363000
-0.885057	-0.363000
0.965517	0.559000
-0.965517	-0.559000
1.000000	0.918000
-1.000000	-0.918000