Servers by jDrones

Tighter 180 deg turning needed for rover at WP


(Max Birley) #1

I have a pixhawk (1) with rover firmware (latest) with a Roboteq 2260 motor driver. The Roboteq is driving 2 independent 24 volt motors. The chassis measures 4 ft by 2 ft and can turn on a dime. The unit goes forward and backward. Manual is working fine. However Auto has a few quirks.

  1. At the end of a mission it goes into reverse (not desirable) I would like it to just stop
  2. I have arranged a lane like mission pattern. The turns are 180 each time. In auto it makes turns that are too large. I need them to be much tighter.
  3. In learning mode the wp are being recorded without any lat/long data. Older versions were fine! is there a fix for this
    4 Lastly can I control the direction the unit turn when making a 180. i.e. I would like the unit to consistently turn to the left. Can this be fixed?

I have made the way points as small as 0.5 meter as I want accuracy. I am using rtk and the navigation is excellent. The tracking between the wp’s is good the as unit is on the edge of wavering. However when I get to the waypoint the unit is turning less crisply than it physically could do.

I have read the “Tuning steering and navigation for a Rover” section on the wiki however I am a little confused with the some of the parameters

Which of the parameters have the most affect on the turning response when you require it to make a 180?

Also is this a pixhawk issue of is it a Roboteq issue i.e. it may be limiting the motors in some way and there restricting the pixhawk to t lazy turn

I can not provide more data at this time as the pixhawk is not with me at the time of writing this post. I will be able to supply more info in the next few days

regards
Max


(Max Birley) #2

No-one has responded to these questions. If I need to provide more info please advise. So feedback regarding these issues would be appreciated.


(Max Birley) #3

I guess I am going to keep adding to the post until some knowledgeable person also decides to chime in and help out

I am trying to sort out some basics. They may seem simple to the experienced however I still find these concepts a little challenging

From my reading it seems that there are 2 ways to set up the steering on a rover.

Method 1. Esc for Forward Back and a servo for left Right. these will be controlled by the rc radios from aileron and throttle

Method 2 The ESC and servo are replace by a dual motor controller and two motors
The motor controller can be set up either mixed or independent modes. If mixed is selected the the behaviour of this is very much like method 1. ie the rc sticks aileron controls L/R and the throttle controls F/B. The motors are coordinated

If independent is selected then the aileron controls one motor and the throttle controls the other motor .So now we are controlling the motors individually and not coordinated together. If this is the case then you need to select Skidsteer for the Pixhawk to make the system produce coordinated F/B and L/R commands. ( I think this is the case)

I am discussing this because I am trying to improve the turning capability of my Bot in auto mode. It works well in manual and learning. As explained before the Bot can turn on a dime in manual however in Auto it make large turns around the way point when I want a crisp 180 degree turn.

I am enclosing a list of my parameters

I would appreciate if someone would engage and assist me to set up is Bot.

regards
MaxRover Ublox Roboteq 20 Nov 2017.param (8.7 KB)


(Esa Attia) #4

Hi Max,

What version are you using . I’m currently working a skid steer project too.

I believe there has been many improvements to how skid steering works in version 3.2-rc2 .

Did you give that a go?

I’m currently using the latest version from the master branch.


(Max Birley) #5

Hi Esa
I am using 3.1.2 so I will look into upgrading to 3.2.
I tested skid steer on a smaller chassis and changed the motor controller from MIXED to INDEPENDENT and it works well in manual mode. Still have not tried it in Auto as waiting for some better weather.
I will let you know what I find.

In the meantime can you share the key parameters that cause the rover to turn on a dime
ie tight turns around a waypoint when doing a 180 degree turn


(Esa Attia) #6

This is as far as I got … parameters in the link below

https://discuss.ardupilot.org/t/need-help-with-tuning-rover/23192


(Leonardo) #7

any progress? I’m trying to get my ASV (skid steer, too) and to PIVOT turn seems to be at too high speed and start oscillating…

Thank