Folks, here is what I want to do: an autonomously driven snowmobile.  I have the mechanical parts working well for the directional control (I can turn the handlebar left and right with the linear motor - I hope you can see it in the picture).  The throttle also works, though not shown in this picture.  What I would like to do is use the APM board to control this, to give the snowmobile a set of waypoints to navigate to, and then return.

The purpose is to drive the snowmobile in a grid to measure properties of the snow and ice (the picture is from Antarctica) - and to free up a scientist from driving in a grid for hours.

Right now I control the snowmobile over a radio - manually turning left or right - not very satisfying.

- The steering is controlled by an H-bridge that puts either +12V or -12V on the motor to extend or retract it.  When there is 0V on the lines, the motor doesn't move. (I use a 500Hz 50% duty cycle PWM wave to control the speed at which the arm moves).

- The throttle is a PWM servo motor (1ms for zero throttle, 2ms for full throttle).

I imagine the latter of these (the throttle) should integrate easily with the APM board.  How to drive the steering from the APM board?  Do I need to have an interface board between the APM and my H-bridge?

Doable?  A lot of hacking of the code?  I don't know Arduino, though it looks relatively straightforward.  I am using a propeller ( to communicate with the radio, to read the GPS, and to drive the steering and throttle.

(right now the GPS is ignored, but hopefully with APM board it can be used to control the steering).

I'm new to this community (wish I had stumbled on this about a year ago!!)




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  • Hmm, ...... maybe I should hack my Dads Mobility Scooter :)


  • Admin

    @Hi All,

    I think that we have hijacked Sridhar's discussion with our posts about the RoboMagellan effort. So it might be wise if we start a separate discussion concerning a RoboMagellan effort.



  • Admin


    I think that three Sharp IR sensors, one looking forward and two at 45 degree angles to the front will be sufficient based on my MINDS-i Parallax PING sensor experiments. The three IR sensors can be read by the Atmel 2560 Analog A0, A1, and A2 their detection indications used by the code to steer right or left. Couldn't be more simple. I think that you are making your obstacle detection overly complex in relation to what is required for effective obstacle avoidance.

    Just a thought.



  • Developer


    another thing you probably can try the ROV_AWPR_NAV function from Jean Louis Naudins 2.20 release but im not realy aware how this works.

    gave it a try once and programmed a simple rectangle course. could get my rover running much faster but it would drive in circles instead making sharp turns on the waypoints.

    dont be confused, the shown waypoints dont match up with the programmed course.



  • Developer

    Hi Sridhar,

    the rover currently does not account the turning radius of the vehicle.

    the apmrover for now is primarily used for much smaller projects and i can unfortunately not help so much with code because im just a aspiring junior developer for now.
    were actually lacking people jumping in.

    one thing you can do is tune the NAV_ROLL_P to adjust steering behavior according your vehicle and setup your waypoints for larger turns manually.

    it also depends on the speed you want to go and how large the grid is.



  • Developer

    wow what a vehicle!

    Mission Planner has a map tool that might be interesting.


    thought already about using skids on my rover in the long winter hehe



  • Admin


    You are going to need a way to convert the PWM steering output of the APM into a signal that can be used by the H bridge. I suspect that you could use an Arduino Uno to decode the steering PWM into right (CW) and left (CCW) steering commands for the H bridge. I suspect that the code already exists on the Arduino Forum for converting PWM to H bridge motor direction commands.



  • How good is GPS down there?  And compass? 

    Sounds workable!  What a project!

    Alan  KM6VV

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