How to implement skid steering using the APM

ArduRover Chassis -- deprecated
1

When using skid steering then is it just using two separate ESC and motors or is it something more? Simple ESC-s do not have encoder input. Is skid steering using encoders?

2

@Riff,
There are two ways to accomplish skid steering:

  1. Use the APM normal steering (Ch 1) and throttle (Ch 3) outputs to control an ESC, like the Sabertooth 2X12 or 2X25, that can perform the skid steering mixing function in the ESC. There are ESCs, like the RoboClaw, that can perform mixing and have encoder inputs. However, if you read about the quality of the RoboClaw hardware you might not want to use one.

  2. Use the APM in the skid steering mode and use each output channel to drive either a dual ESC like the Saberthooth in the non-mixing mode (two single channel motor controllers) or two individual ESCs with each one driving the motors on each side of the skid steering chassis.

Regards,
TCIII Developer

3

Can anyone help me understand the best path forward. I am trying to use a PixHawk to build a tracked machine.

I used the tracks from a small bobcat. They are heavy steel rollers with a heavy track. About 500 pounds just for the undercarriage. I tried it with 2 wheelchair motors and a sabertooth 2x60. Unfortunately I keep burning out fuses under any kind of moderate load.

Link to short video…youtu.be/wrDD5GnMvj4
[youtube]http://youtu.be/wrDD5GnMvj4[/youtube]

I am thinking of switching to electric powering hydraulic motors.

Any idea if the PixHawk can be used to power 2 hydraulic actuators using servos. So that to go forward the Pixhawk would move both servos forward. For backwards = both servos back, and for steering move one servo more than other. Is the pixhawk capable of that?

Thanks

4

I teach in a heavy equipment program at a local community college. I know the type of undercarriage that you are talking about. Your idea of going to a hydraulic motor to power the tracks will probably make matters worse. If you are blowing fuses it is because you just don’t have enough power to drive such a high resistance track system. We have built a hydrostatic drive simulator in our shop from a Cat skid steer. I powered this with a 5hp 230 VAC motor and I can trip a 30 amp breaker if I push it hard enough. These machines take a fair amount of energy just to get past the weight of the components. If you are still wanting to try and drive your rover hydraulically, I suggest going to a hydrostatic drive pump and controlling the swash plates with an ardupilot and electric actuators. I have done this once already and made a full sized skid steer into remote control.