Replies to This Discussion

DeveloperPermalink Reply by Linus on February 5, 2013 at 1:27pm

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

Regards,

Linus

Permalink Reply by Sridhar Anandakrishnan on February 5, 2013 at 1:45pm

@Linus: How does the code deal with turning radius of the vehicle?  Because of the skis and the throw of the linear motor, I can't make sharp turns.  Or do I deal with that in the ordering/positioning of the waypoints and put the waypoints "outside" the grid that I really want?

@TCIII - I think I can use my existing board to interpret the PWM from the APM into the proper drive for the H-bridge.

@KM6VV - GPS is great, compass needs the declination (can be anything up to 180degrees! - in other words North is thataway and Magnetic North is... exactly the other way!!)

Sridhar

Permalink Reply by KM6VV on February 5, 2013 at 2:19pm

@Sridhar

I think I'd steer around the waypoints, (maybe use a couple) allowing for the turning radius.

Yeah, I'd heard about the usefulness of a compass down there!

Alan  KM6VV

AdminPermalink Reply by Thomas J Coyle III on February 5, 2013 at 4:08pm

@Sridhar,

The present code makes really sharp right angle turns whether you are using skid steering or standard front wheel steering. I know because I have both kinds of rovers and have tested the code recently.

Regards,

TCIII

DeveloperPermalink Reply by Linus on February 5, 2013 at 2:14pm

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.

Regards,

Linus

AdminPermalink Reply by Thomas J Coyle III on February 6, 2013 at 10:30am

@Linus,

I could not find a definition of the NAV_ROLL_P in the ardupilot-mega APM_Parameters. Could you point me to where it is defined.

Regards,

TCIII

DeveloperPermalink Reply by Linus on February 6, 2013 at 11:13am

Hi Tom,

i have lowered the NAV_ROLL_P with the mission planner because one of my rover did not like hard steering.

So far thats the only thing it had changed in terms of of the steering.

I have found 0.400 to be a good value for my 1/16 4WD vehicle.

Regards,

Linus

AdminPermalink Reply by Thomas J Coyle III on February 6, 2013 at 11:35am

Hi Linus,

Thanks for the info, much appreciated.

How about the Rover Turn Gain? I am tempted to experiment with this value. Is there a definition as to what this parameter affects concerning turning?

Regards,

TCIII

DeveloperPermalink Reply by Linus on February 6, 2013 at 2:15pm

Hi Tom,

ROV_GAIN need to be set to about 5 so as to increase the gain of the wheels servo.

i had lowered it to 4 and got no moving servos anymore and took the NAV_ROLL_P instead.

Regards,

Linus

DeveloperPermalink Reply by Linus on February 6, 2013 at 11:28am

@Sridhar

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.

Regards,

Linus

Permalink Reply by Sridhar Anandakrishnan on February 6, 2013 at 9:45pm

Linus - thanks.  I looked in the code and there does seem to be a provision for limiting the turn radius, so I think almost everything I need is in the code...

Stay tuned...

Sincerely, Sridhar

AdminPermalink Reply by Thomas J Coyle III on February 6, 2013 at 1:49pm

@Alan,

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.

Regards,

TCIII

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