Mission to move without GPS or Mag

Hi all,

I have tried to set up a rover using the skid steering but its driving me crazy.

I have managed to get it to drive but the controls are very delayed which makes all movements overcorected, its impossible for me to drive in a straight line but i can wiggle around the garden.

When i try a basic mission the rover just spins around, or goes off in the wrong direction for a few feet then spins again. It might be something to do with the compass too near to the motors but i want to find out if my motor directions are correct first.

I would like to know if i can program a simple mission without GPS or compass, this mission will be to drive straight forward for 3 seconds, stop right motor and turn on left motor for 2 seconds, then stop left motor and turn on right motor for 2 seconds.

After running this mission i can see what directions the motors are moving and then hopefully get this thing sorted.

Is it possible?

No you can’t control the motor’s directly as you have requested i.e. turn motor on for a number of seconds.
Can you attach a tlog or bin log file so I can see how you have it setup.
Can you describe what transmitter you are using and what the setup on your skid steering rover is? Is it just one motor each side or something more complex?
Photo’s always welcome :slight_smile:
Thanks, Grant.

Thanks for your reply. I have only just noticed it.

Im sitll having issues.

Can you tell me what the pixhawk sends out on output 1 and 3 when using skid steer, eg. servo 1 2000pwm = full forward, 1000pwm = full backwards.
Once i know this I can modify my code on the custom motor controller i made.

Here is a video of the rover mindlessly spinning on the spot while in guided mode, it should have just driven straight to the destination. Please note that i could manually control the rover correctly.

I have also messed around with channel reversals, and i could get the rover to drive forwards, but not in the correct direction towards the waypoint, also the manual controls seem like they are 90 degrees out. obviously this is incorrect.

It seems that APM rover is designed for the sabretooh motor controller. I wonder what PWM values it expects.

Here is my motor controller code, it works really well with a radio RX directly connected and using skid steer mixing on the taranis

The code does a differential output so if PWM 1500 is centre and you go left at say 30% then RC1 will be 1700 and RC3 will be 1300 or the other way around depending on which motor side you have on which channel. If you look at this video (just after half way through) it will show you how to graph the live values and you can use this to graph almost anything including the input and output channels from ardupilot. You can then move the sticks and see the values change for yourself.

I can assure you Rover isn’t designed specifically for the sabertooth ESC - I don’t have one :slight_smile:
Is your transmitter doing the skid mixing when you drive in manual?

Thanks, Grant.