Comments

• Mark Halliwell March 4, 2014 at 10:40pm

  @Gary,

  Downward looking Optical Flow could be an interesting addition to the Rover code as it would give us the opportunity to try optical flow odometry for hi-res localization. As a glorified optical mouse (field mouse?) it could offer supplementary information to be read along with GPS data. As I understand it, the major challenge of optical flow to the flying community is the measurement of height to include in the calculations. On a rover, unless it's doing wheelies or similar, the height would be more or less fixed and known. That said, ground surface might be an issue with long grass affecting  the height.

  As I understand it, the current PX4FLOW would need a different lens to get the focal length down to a level better suited to a rover.

  Mark
• 

  Gary McCray March 4, 2014 at 9:05pm

  @Thiago, At this time I do not believe Optical Flow of either type is enabled for Rover and only Copter has optical flow enabled and only for simple Optical Flow system not for PX4FLOW.

  In fact Optical Flow as it is enabled for Copter is not really applicable to Rover.

  It is down looking and establishes a horizontal displacement / correction only.

  Ostensibly, optical flow from a rover might be forward looking and that is a whole different kettle of fish.

  For this use, PX4Flow would probably be mandatory and more likely 2 of them and a lot of custom programming of the PX4Flow itself. They are also serial, daisy chainable and have considerable on board processing power so 2 could be used in a binned stereo vision application to good effect on a rover, requiring only a seriously large firmware development.  

  Best Regards,

  Gary 
• Admin

  Thomas J Coyle III March 3, 2014 at 4:24am

  @Thiago,

  Here is a link to the APM: Rover Wiki: Rover

  You might want to post your questions concerning using the optical flow sensor in the Sensor & IMU Discussion Forum: Sensors GPS support can be found here: GPS

  Regards,

  TCIII
• 

  Antonie Kruger March 3, 2014 at 12:57am

  @Thomas - sorry, I missed the important questions.

  I tried to use the skid steer implementation on the APM2. I installed 2.45 again after a complete erase and reset.

  I activated the skidoutput, but left the skidinput as disabled and disabled the skid mixing on the Wild Thumper controller board. So the WT Controller takes Left and Right input and APM should give Left and Right output mixed from 2 channel receiver input. I re-checked my wiring twice and still had strange results. My rover starts to run at about 50 to 60%. All wheels with some direction change when moving the sticks. Yes, it was in manual mode.

  I'm using a 6P uBlox chip to get the best possible results position wise. I use the rover under open skies and always have 6+ sats. I have applied the declination, so it should not be a hassle. It makes sense though that at startup and slow speeds the weaving is more because of a short GPS baseline - would it not be prudent to rely more on the mag at this point?

  When the weather clears up I'll head out for some tuning, thanks for your help. If I have a thunderbolt of brilliance and get this sorted, I send you the final settings for the next noob.
• 

  Antonie Kruger March 3, 2014 at 12:45am

  @Thomas - I hear you : "For those of you with Pixhawk equipped rovers, the Pixhawk code with the EKF function can be found here: Pixhawk firmware with EKF Set AHRS_EKF_USE to 1 to enable."

  The problem with this is that the PixHawk pricing => African country GDP. So replacing any of the APM's at this time whilst the $ and OPEC are killing our R, we'll have to be content with APM. I think Gary might have the only PixHawk in RSA. What I do find odd is that the sum of the parts is less than 25% of the price of the whole (Stone in the bush).

  I was unable to go out this morning - farmer friendly weather has moved in.
• Thiago Gabriel March 2, 2014 at 9:16pm

  I'm Thiago Gabriel, Mechatronic Engineer. I'm working with a Masters of Mechanical Engineering, where I have to apply a ardupilot automodelismo Firehammer Duratrax DTX. My question is: have some step by step (tutorial) how to ride a rover? Another question is also how I can connect the optical flow in ardupilot 2.6? 
  I was watching a tutorial where one connected the optical flow in ardupilot 2.6, but he cut a contact there. That's right or have another way to connect? 
  I would also like to know if you communicate with the GPS ardupilot NTRIP network. 
  I'm waiting and I thank you for your attention
• Admin

  Thomas J Coyle III March 2, 2014 at 2:54pm

  @Michael,

  That would be a question for Tridge as he is more familiar with how the operating parameters interact with one another.

  My rover has a turning circle value of 1.3 m, but I have found that a value of 1.0 is optimal.

  A PERIOD of 6 - 7 is the best for my Slash rover that has a fast and tight steering system.  NAVL1_PERIOD values of less than 8 can improve steering response, but can cause dithering in the steering for fast steering vehicles. Less maneuverable rovers using skid steering can probably use a higher value as they cannot turn as rapidly as a normal steering rover.

  Regards,

  TCIII ArduRover2 Developer 
• MikeRover March 2, 2014 at 2:33pm

  @Thomas, without diving ito the code, do you know how the L1 period should relate to the turning circle, or what it corresponds to in "reality"?  From some of the doco it seems to be the distance in front of the vehicle/along the track that the "fake" waypoint sits.  Does that mean less maneuverable vehicles should have a higher period?
• Admin

  Thomas J Coyle III March 2, 2014 at 8:35am

  Hi All,
  
  Paul Riseborough's latest version of the Pixhawk EKF code works very well. Course repeatability is excellent and there is reduced overshoot at the end of sweeping turns.
  
  I found only two issues:
  With EKF enabled, the rover is not as aggressive in the turns as the DCM.

  
  The Pixhawk LED never went green when everything is a go, yet the rover performed flawlessly in all aspects.
  
  For those of you with Pixhawk equipped rovers, the Pixhawk code with the EKF function can be found here: Pixhawk firmware with EKF Set AHRS_EKF_USE to 1 to enable.
  
  Regards,
  TCIII ArduRover2 Developer
• Admin

  Thomas J Coyle III March 2, 2014 at 7:51am

  @Antonie,

  I have vetted the ArudRover2 firmware skid steering function with a Pixhawk. I have not tried it with an APM, but it should work okay.

  How many sats do you see and what is your HDOP before you go into the Auto Mode.

  Also, on the Thumper that I was working with, I had to raise the GPS/Compass module about 3" above the top of the Thumper chassis to avoid the motors' electromagnetic affect on the compass when under power. The compass would vary about 40 deg from the true heading when under power. Are you using the APM2.0 internal compass or an external compass?

  Regards,

  TCIII ArduRover2 Developer