Servers by jDrones

Dual Motor controller selection advice

(Christopher Milner) #1

Building a robotic lawn mower, skid steer. Propulsion with Electric Wheelchair Motors. 24V system for the motors. All up weight about 250 lbs.

I’ve combed through the forums and it seems that either a RoboClaw 2x30A Motor Controller or a Sabertooth dual 32A will work with my Pixhawk 4 running Rover 3.5. Aside from price it seems the Roboclaw has integrated decoders, hence off-the-shelf closed loop control, while the Sabertooth requires the Kangaroo x2 motion controller if I decide I need the controller to do the closed loop control. I’m planning on building encoders on the motor shafts directly (shafts turn 3600rpm). My thinking is to build and run without closed loop control, then, start by feeding encoder data directly to Rover (which I understand it will use in position estimation if I’m running EKF3).

Aside from price, does anyone know of any pluses or minuses or considerations I should be aware of when choosing the motor controller? Any experience with cheap no-name brands?

Thanks in advance…

(Christopher Milner) #2

After sifting through the overwhelming number of votes/opinions (not…) I went with the roboclaw.

(RoboBill) #3

Some years back I had a smaller 10 pound robot driven by fours craftsman drill motors and experienced some sort of clipping with the 2X25 .

My current robot is 75+ pounds. I went with the 2X60. I wanted the driver to be something I would never worry about.

Their customer service is great. Just be careful to avoid ground loops. The folks at Dimension Engineering can help you with this.

(Jeffrey Berezin) #4

Dimension Engineering has great support. They have helped me multiple times since I started using them in 2011. I use both the Sabertooth and Syren series and have fried things with “ground loops”. Now I know how to design better thanks to their tech support team. I can’t say anything about Roboclaw because I haven’t used them. Let us know how it goes!

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(Christopher Milner) #5

The Roboclaw 2x30a is working fine. In fact the whole mower is working fine - I mowed my first 1/2 acre or so this evening. A video from a few days ago is here https://photos.app.goo.gl/rrNTHjFD2JTFJ7Kt6

The details

  • 42" 2-blade deck off a donor mower driven by a Motenergy ME0709 motor powered by a 13S (about 48V) 100Ah pack of Thundersky LFP100s, an Elithion Lite BMS and an Alltrax controller. About 25amps (x50v=1250 watts) to run the deck blades @ 2,000 rpm. I expect about 3-4 hrs runtime.
  • DIY chassis
  • Wheelchair motors powered by a 24V, 15ah SLA battery pack and a Roboclaw 2x30.
  • Yes there are 2 separate battery systems onboard, one for the autopilot+motors, and one for the blades.
  • Pixhawk4 running Rover 3.5.1. No encoders.
  • Ardusimple GPS, receiving RTK corrections sourced from an NTRIP caster about 21km away (giving about 10cm accuracy, plenty for my application), forwarded to the Pixhawk using Mission Planner.

385 lbs all up weight. All those batteries are heavy. I think the 2x30 roboclaw may be slightly underpowered for this vehicle and am considering upgrading to the 2x60HV.

Next: The Rasbperry PI to control the deck (via the Alltrax) and the BMS and the Pixhawk 4…

Thanks @rmackay9 @ktrussell @Jeffrey_Berezin @RoboBill for your help thus far.

2 Likes
(Kenny Trussell) #6

Looking good! Thanks for sharing your progress.