Autopilot use of servo trim overriding minimum speed value

ArduRover Rover 4.0
1

Hello ArduRover Community!

Introduction: I’ve been using Mission Planner a lot recently for my newly built rover, but one problem I have run into has been too challenging for a rookie, like me, to solve. The rover I am working with has two wheels and is servo-powered. I have gotten it to drive pretty well along missions I have made, but now it’s all down to the tuning.

Background: I really want this rover to be able to move through grass, but due to its small size, such a task is quite daunting and requires a continuous rotation of both wheels in the forward direction to avoid stalling and losing too much momentum. That being said, I tried to achieve such a behavior by going into the Servo Output menu and setting the servos like this:

Servo 1: Throttle Right – Min 800 – Trim 1475 – Max 1137
Servo 2: Throttle Left – Min 1737 – Trim 1475 – Max 2200

This worked as expected, but some PID Steering tuning was required, which I did (boy, what a pain it was).

Problem: When taking tight turns (180 deg U-turns, for example), the rover autopilot decides to use the servo trim value to stop one servo while maintaining a high speed on the other, completely disregarding my minimum that I set. Is there something I’m missing, or is it not coded to deal with something like this?

Best regards,
Ariel

2

You could use WP_SPEED_MIN to set a minimum speed during a mission. You could also set PIVOT_TURN_ANGLE to zero to disable pivot turns (and thus maintain speed through way point transitions)

1 Like
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Thank you very much for the quick reply! I will try those two things. I was eyeing WP_SPEED_MIN earlier, but I was worried that if I set it too high the vehicle would never reach it and therefore cause problems. These servos are very, very slow.

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I was able to test today and it worked! PIVOT_TURN_ANGLE was the key and after a bit of PID tuning it’s to the point that I’m satisfied. Thank you very much @jimovonz, I guess this topic is now closed.

1 Like
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You are most welcome - I am glad you have got the outcome you were after.