Comments

• Developer

  Andrew Tridgell February 16, 2014 at 3:41pm

  @Gary,

  No, we don't do reverse in auto yet. If you have skid steering and the next waypoint is behind you then the new code will stop and pivot in place then go forward. Adding support for reverse in auto modes is a separate issue. We will add it, but it isn't done yet.

  Cheers, Tridge
• 

  Gary McCray February 16, 2014 at 3:37pm

  I just heard from Tridge that he has stand in place turning implemented for Skid Steers.

  I presume this means reverse is now actually being used in an auto mode.
• 

  Antonie Kruger February 16, 2014 at 3:12am

  Michael, OK, thanks - will do. I suspect you are right in the MANUAL mode pass-through, but I'll check anyway.

  I still have the wild thumper controller board between the APM and motors with a arduino processor. I can implement a low pass filter there or implement some sort of throttle softening - Ramp Speed implementation.

  Thanks for your help and suggestions.
• MikeRover February 16, 2014 at 3:02am

  Antoine, the "philosophy" of MANUAL mode appears to be a direct pass-through.

   

  STEERING mode may apply ramping, but I'm not sure.  You can bench test it easily enough - just set SPEED2THROTTLE_P, I and D to zero, and watch what happens as you push throttle up.
• 

  Antonie Kruger February 16, 2014 at 2:31am

  Thanks Michael - do you think it would be possible to implement policing/managing of the MANUAL mode inputs to soften the outputs as AUTO would do?
• MikeRover February 16, 2014 at 2:15am

  Antoine, I forgot there's also a throttle ramp rate in APM:Rover you can use. That should be easier than any kind of filter and you can then do your necessary settings on the Sabertooth with DIP switches only.

   

  The only downside is that the throttle ramp in APM only applies to AUTO mode - you can still hurt the motors in MANUAL mode. 
• 

  Antonie Kruger February 16, 2014 at 2:08am

  Hi Michael, thanks - Ramp Time is what I'm after.

  It just occurred to me that applying a low pass filter on the output lines with a adjustable cutoff rate will have the desired effect. The lower the cutoff, the less rapid the change in output.
• MikeRover February 16, 2014 at 1:42am

  @Bruce, the current ratings are at 25C, and they de-rate from there. From the specs, it looks like the motors shouldn't pull more than 7A, but if your chassis is enclosed, or you're somewhere where the ambient temperature is 30+C, the extra margin may be useful. I'd assume Thomas went for the 25s for a reason, unless he had it lying around.

   

  @Antoine, the Sabertooth can do ramping internally, but you need the DEScribe software and DELink USB converter to set it.  I don't know if you can substitute another USB/serial converter.

   

  "Ramp Time

  This is the time the driver takes to go from full reverse to full forward or vice versa. High ramp rates give a slower-acceleration, softer feel."
• 

  Antonie Kruger February 16, 2014 at 1:21am

  HI Guys, thanks TC3, great job. Would you be porting the skid steer implementation to the APM2 boards? I have a few questions that I need some help with. I have a wild thumper 6wd chassis with the wild thumper controller board. I fitted my apm2 board with telemetry.

  Q1. When the controller is instructed to apply 50+% speed to the motors from 0, a lot of stress is placed on the gearboxes in the motors. It is not long before the drive gear in the gearbox strips. Would it be possible to manage the application of power to the motors over a longer period. I'm not sure if I'm explaining this right. The effect I'm after is : When I instruct 100% power forward the controller should not apply 100% immediately. It should accelerate from 0 to 100% over a time period to reduce the torque forces on the gearboxes to lengthen the life of the hardware.

  Q2. Does anybody know of better quality motors for this chassis or just gearboxes. The stock boxes sucks. Seems like the gears are mild steel or cast iron. Real cheap crap.

  Q3. Can the APM2 rover software take a NMEA string from a serial port for navigation. The reason for asking is that I use a robotic survey instrument to lock onto a 360 prism mounted on the rover. From here I transmit the coordinate to a FEZ Cerb40 netmf board that translates the coordinate into the needed NMEA strings, alternatively using a RTK GNSS receiver mounted on the rover to feed the needed NMEA strings to the controller.

  Thanks,

  Antonie
• Bruce D. Sidlinger February 16, 2014 at 12:39am

  Beautiful, and I was just tonight ordering that chassis, the high gear ratio (low speed) version. Question, would this controller have been enough, do you think? http://www.dimensionengineering.com/products/sabertooth2x12rc