First Rover build and troubles with Skid steering

Posted by FD on August 15, 2014 at 5:36am

Hi all,

this is my first official rover post after following the discussions for quite a while. I have built multicopters before, but got interested in rovers now.
My setup is a wild thumper 4wd with APM2.5 and X45 ESCs from HK. Until now I used it as a "FPV-rover" to play around with the components. The Rx was directly hooked up to the ESCs. Worked perfectly.
So now my next step is setting up APM, but I can't get it to work. APM's outputs don't really do what they should. I have gone through all the wikis and forums, but it didn't help.
 
So here’s my problem (running APM Planner v2.0.14 and ArduRover v2.45):
Once you turn the Rover on (manual mode) the wheels start spinning and any Input from RC-Tx either only slows down one side or abruptly changes direction. 
APMrover2:SKID_STEER_OUT is set to 1. I took a screenshot from the APM planner, which shows RC input, as well as what APM puts out.
Any ideas what’s going on? 
BTW where can I find some information about the drive modes? Didn’t find anything about what they do.

Apologies if I missed something obvious, which may very well have happened...

Regards,
FD 

photo-4WD-Crawler.JPG

Untitled3.png

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Tags: 4wd, apm25, rover, skid
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Replies

  • Admin
    Thomas J Coyle III August 16, 2014 at 6:07am

    @FD,

    The RCMAP parameters tell the navigation firmware on what channels it can find the PITCH, ROLL, THROTTLE, and YAW inputs to use in the differential steering function and provide the necessary steering outputs to the corresponding channels on the APM output.

    Glad to be of help in getting your issue put to bed. Good luck with your rover.

    Regards,

    TCIII Autonomous Vehicle Developer

    • FD > Thomas J Coyle III August 17, 2014 at 5:17am

      Ah ok. Now I get it. 

      It's quite confusing - at least for me. Maybe should be clarified that this has been taken over from APM's aircraft/copter history and does NOT refer to the Tx (since Tx-throttle is actually not connected, instead we have Tx-elevators connected to the RCMAP-throttle channel).

      And RCMAP Roll actually means "steer"(or yaw for that matter). 

      Are RCMAP_PITCH and RCMAP_YAW even used?

      I don't want to complain, rather suggest an update to documentation to save others from making the same mistake. 

      Apart from that, Rover's now running fine in manual mode. Thanks again for the help.

    • Admin
      Thomas J Coyle III > FD August 17, 2014 at 6:16am

      @FD,

      Normally the Aileron (ROLL) joystick is used for steering and the Elevator (PITCH) joystick is used for speed control.

      Therefore if you have the receiver aileron output connected to the APM input channel 1 and the receiver elevator output connected to the APM input channel 2 the RCMAP would be RCMAP_ROLL 1 and RCMAP_PITCH 2 while RCMAP_THROTTLE and RCMAP_YAW can be any value as long as the value is not 1 or 2.

      You need to understand that this is DIY which assumes that you are willing to experiment and explore to gain knowledge about the system you are using.

      Regards,

      TCIII Autonomous Vehicle Developer

  • Admin
    Thomas J Coyle III August 15, 2014 at 6:09am

    @FD,

    Please provide a full parameter file as a text file to help troubleshoot your issue.

    You can save a Full Parameter List file by using the Config/Tuning Tab in the MP and selecting the Full Parameter List on the left side of the screen.

    You must have the Advanced View checked to view the Full Parameter List.

    The Save button is on the right side of the Full Parameter List screen.

    Regards,

    TCIII ArduRover2 Developer

    • FD > Thomas J Coyle III August 15, 2014 at 6:18am

      Hi Thomas, thanks for the quick feedback. Find attached my parameters.

      config4WDrover

    • Admin
      Thomas J Coyle III > FD August 15, 2014 at 10:00am

      @FD,

      A quick look at your Full Parameter File indicates that you do not have an inputs on APM channels 7 & 8.

      The ArduRover2 firmware is expecting the Momentary Switch input to be on channel 7 and the Three Position Mode Switch on channel 8. You appear to have inputs on APM channels 10 & 11.

      You appear to have inputs on APM channels 1 & 2 which I assume to be aileron (ROLL) and elevator (PITCH) inputs.

      Your RCMAP_PITCH is on channel 2 and ROLL is on channel 1. Therefore the APM outputs to your ESCs should be the left motor on output 1 and the right motor on output 2.

      Regards,

      TCIII Autonomous Vehicle Developer

    • FD > Thomas J Coyle III August 15, 2014 at 11:09am

      Yes correct, only APM Input channels 1.3.5 are connected.

      Input on APM channel 10 & 11 ?? APM has only 8 Input channels. Not sure what you mean. 

      I have nothing connected to APM Input channel 2.

      As listed above:

      Rx CH1 (Aileron) --> APM Input CH3

      Rx CH2 (Elevator) --> APM Input CH1

      [I'm aware they are switched, RxCH1 should be APMCH1 and RxCH2 should be APMCH3 don't think it impacts the problem though]

      RCMAP_PITCH and RCMAP_ROLL: see above posting

      Shouldn't ESC left be connected to APM Output 1 and ESC right to APM Output 3?

      That's at least according to the manual in http://rover.ardupilot.com/wiki/setup/

      Didn't realize that Ardurover expects mandatory inputs on 7 & 8

      Note that I have my mode switch on APM Input CH5 (MODE_CH = 5) so that should be ok.

      Will hook up a switch to APM Input CH8 then.

      Thanks so far.

    • FD > FD August 15, 2014 at 11:42am

      Ok what I did now is:

      - switched RxCH1 to APM Input CH1 and RxCH2 to APM Input CH3 as it should be

      - attached a temporary switch to APM Input CH8

      But it's still the same weird pattern of outputs (see attached graph).

      What I realized though, that switching to other assigned modes (LEARNING or STEERING) doesn't change the behavior of the APM Outputs with respect to Tx Inputs.

      Another note: I don't have a GPS connected since I plan to use the rover indoors. However as far as I checked, there are no Arducopter-type safety switches at Ardurover so this shouldn't have an impact, correct?

      Still puzzled about the outputs...

      CH-graph2.png

      https://storage.ning.com/topology/rest/1.0/file/get/3702826411?profile=original
    • Admin
      Thomas J Coyle III > FD August 15, 2014 at 12:26pm

      @FD,

      Here are your RCMAP parameters based on your Full Parameter File:

      RCMAP_PITCH,2

      RCMAP_ROLL,1

      RCMAP_THROTTLE,3

      RCMAP_YAW,4

      What does the above tell you in relation to your receiver inputs to your APM?

      According to your Full Parameter List, RC3 is not calibrated:

      RC3_MAX,1500

      RC3_MIN,900

      RC3_REV,1

      RC3_TRIM,1500

      Without a GPS input, the APM may not start a mission in the Auto Mode.

      Regards,

      TCIII Autonomous Vehicle Developer

    • FD > Thomas J Coyle III August 15, 2014 at 2:04pm

      Not sure what RCMAP does really, so I left it at default. 

      So assuming this defines APM's Input Channels I hooked my Rx CH2 (Elevator) to APM Input CH2 to comply with RCMAP_PITCH,2

      Where are APM Output channels defined? Is the right ESC (Skid mode) on APM Output CH3 (as in http://rover.ardupilot.com/wiki/setup/) or on APM Output CH2 as you mentioned above?

      Good catch on calibration, I have obviously not updated this during some of my playing with parameters. Have calibrated all my channels (CH1, CH2, CH5 and CH8) now.

      Still no joy on the outputs though...

      Attached new parameter file.

      config4WDrover_v02

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