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Ardurover Traxxas Nav Tuning

Hello to the forum! First time posting (so exciting), but have been perusing and learning for the past few years.

TL;DR: First time with Rover. Two issues with Traxxas X-Maxx, log/ params at bottom:

  1. Seems to be tuned well in Throttle and okay in Steering, but the nav tuning seems off. Large overshooting when approaching a turning WP – instead of inscribing the turn, it overshoots and has to perform an opposite turn to go back to the path. 50m squares look like diamonds.
  2. ESC (VXL-8S) allows braking, but braking only works when in reverse (even in Manual mode). Definitely works when ESC connected directly to RC receiver.

More background if interested…

I’m very familiar with ArduCopter and the tuning steps involved with that, but this is my first foray into Rover. I was hoping someone could provide some guidance on what I might be doing wrong here…

I have a (modified) Traxxas X-Maxx that I’ve shoved a Pixhawk 4 on. Currently running 3.5 because that’s what I’m used to with my copters, and I don’t think there are any upgrades in 4.0 that help me here (but if I’m wrong please let me know).

From Copter I’m used to the vehicle inscribing and not overshooting WPs (a square planned flight path should look like a rounded square when the vehicle performs it, not a diamond or oozing square). Should this behavior also be expected from Rover? Could it be due to rough terrain (chunky grass) and not-perfect steer tuning?

I’ve attached the log and params from a recent auto route here. How can I make the path inscribe and not overshoot these types of missions? I’ve tried the following extreme settings (seen in params):

  • WP acceptance high (5m, have tried 8m)
  • Nav period extremely low (1.0)
  • Nav dampening extremely high (0.95)

I also do not fully understand how these params affect the planner (not standard PID params). Currently running at 5m/s but would like to get up near 10 if possible.

I’ve seen the following post and, except for the above, much of the params suggested are similar to what I have: TRAXXAS MAXX ArduRover PID Tuning Help

Would greatly appreciate any pointers/ obvious things I’ve missed!
https://drive.google.com/drive/folders/1VpXyYuqiFAb9HBCt89wscjb-slNEC6o6?usp=sharing

I have a MAXX 8S as well and wanted to also add Pixhawk. What were you able to salvage from the original system in terms of the receiver, Traxxas VXL 8S and the battery interfaces? Could you take a picture of what you did?

@rrr6399 unfortunately not easy to take a picture as it’s pretty sealed up at this point, but in short I created an extension cable (I found solderable plugs online) with an XT30 splice off of the battery terminal which I connected to a separate 5V BEC (the VXL-8S outputs 6V which the PH cannot handle). I used a RadioLink RC6GCS receiver as it outputs SBUS connected to the PH and crimped my own cabling—the default Traxxas receiver does not support SBUS. Hope that helps some!

@rwalte25 Thanks for the reply. What did you have to do to connect the throttle and steering PWM output from the Pixhawk to the VXL 8S?

Just used the 8-pin PWM
JAT-GH to servo cable from PWM output, could also use the PMB if you’re already going that route. I have the PH, BEC, servo connections, and GPS in a separate side-mounted enclosure (pretty much Tupperware with a hole cut in it).

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