zig zag motion between waypoints

Posted by BMS on January 18, 2015 at 5:51am

Hi All,

I built a 25ft arduboat to test it's abilities at such scale.

- Manual mode works great

- auto, hits way points quite accurately but goes along the path between one way point to another in a zig zag Fashion.

Can anyone provide any help with solving the zig zag issue?

Regards,

Basel Shuhaiber

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Replies

  • BMS January 23, 2015 at 11:48pm

    Hi All,

    I ran many tests, and things are looking much much better, I thank you all for that and the input provided was very useful.

    What i had to change that made the biggest difference was the steering angle, it was at 1500, for the Jet boat that was too sensitive of a swing so i reduced it to 1100 and it started hitting the way points relativity well. I have two issues left before i can consider this a successful build.

    1 - From start to way point # 1, it is offset by about 60 meters off track and sometimes misses or ignores the first way point. I understand the boat is trying to get up to cruise speed but i am wondering if anyone can assist in making the first way point more accurate

    2 - Final way point, the boat seems to always miss it, it goes close enough then just goes into hold mode. otherwise it hits the rest of the way points quite accurately.

    3 - I have spend few hours now trying to get the way points to show on the Tlog. but for some reason it just wont.. i hit play, it shows the path of the boat and everything moving, but it does not show the yellow way points. This happened after updating mission planner... 

    I want to take some screen shots to show how the boat behaves in general and have your feedback.

    Any thoughts?

    Basel

     

    • mb300sd > BMS March 31, 2015 at 1:46pm

      I have a 20ft jet boat and this looks amazing. Would you mind sharing what actuators you used to control steering and throttle? 

  • BMS January 18, 2015 at 11:46pm

    Hi Guys

    thank you for your response, I really am keen on getting this project in full motion.

    I think the trick would be to slow down the speed of the rudder servo actuator, I don't know which parameter could do that. In any case rather than sending a full list, I put the parameters below and hopefully you can help me figure this out.

    NAVL1_PERIOD: 16

    NAVL1_DAMPING: 0.85

    STEER2SRV_P: 1.8

    STEER2SRV_D: 0.005

    STEER2SRV_I: 0.2

    Waypoint Radius: 50

    The other question I have is, if I cant get it accurate enough after all the tuning, is it possible to assist the path by overriding the steering when in auto mode, is this possible? and what parameter is used to set that? With a boat of that size, overriding in Automode would be wise and when I let go of the joystick it could continue on its route.

    Your thoughts?

    • Admin
      Thomas J Coyle III > BMS January 19, 2015 at 5:03am

      Hi basel,

      Why is your waypoint radius 50 meters?

      Try reducing STEER2SRV_P a little at a time.

      You also might try increasing the NAVL1_PERIOD above the default value of 8. Try going up to 20 or more and then start reducing the value lower until you just start to get the weaving then bump it up some for margin.

      Regards,

      TCIII AVD

    • BMS > Thomas J Coyle III January 19, 2015 at 5:11am
      When I had it at 25 meters it would miss the way point due to the large zig zag manouvers, so I made It bigger.

      Do you recon with it being too wide it could effect performance from one way point to another?

      I'm testing again on wed, I'll reduce the steer2srv P alittle as you recomend and I'll post my results. Hopefully a video of it all worked out.
    • Admin
      Thomas J Coyle III > BMS January 19, 2015 at 7:56am

      @basel,

      The weaving is caused by the steering function overcorrecting (under damped) the boat's direction and then overcorrecting the other way.

      I would try reducing the waypoint radius once you get the weaving reduced to an acceptable level. 

      Also, try the STEER2SRV_I at 0.4.

  • Admin
    Thomas J Coyle III January 18, 2015 at 10:03am

    Hi basel,

    To help the Group members troubleshoot your issue it might be good to provide some technical details concerning your Arduboat like the navigation controller, firmware version, type of propulsion, type of rudder control, etc. in use.

    Also you might want to provide your configuration parameter file so that members can view your parameter values in relation to the suggested default values.

    If you feel that you have your NAVL1_PERIOD and NAVL1_PERIOD parameters adjusted to your liking then I suggest that you start experimenting with the STEER2SRV_  parameters. Particularly what value do you have the STEER2SRV_P value set to?

    Regards,

    TCIII AVD 

  • David Boulanger January 18, 2015 at 9:56am

    Basel,

    I don't know how your control surfaces are actuated but the NAVL1_PERIOD parameter most likely needs to be tuned.  I think the default value is 7 or 8..  What I did was start with a value of 30 and then turn it down until the weaving started again.  My boat is using a value of 14.  I have yet to mess around with the NAVL1_DAMPING but probably will in the near future.

    Regards,

    David R. Boulanger

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