Hi,
I’m building a 3 or 4 wheel robot with differential 2 wheel steering, that is going to be outdoor on grass.
The robot will weigh around 10kg and is not necessarily needed to go uphill. Even though i calculated with a 10 degree slope in your tool for having the possibility. The robot is going to have a speed around 0.5 m/s and 0.2 m/s^2 in acceleration.
Battery pack is a 3 cell LiPo 11,1V 4000mAh, I have access to a second one for parallel or serial for increase of either voltage or Ah.
The robot is going to be self-driving in a limited area with the help of some sort of sensors, how this will be done is not decided.
So my question is about suitable motors and controllers.
With the controllers I was thinking to have a Kangaroo controller to help with the control that will be done with either Raspberry pi or Arduino.
Is the Kangaroo a good choice to help the robot maintain a straight path, or is it better to try and make a solution with encoders and programming? robotshop.com/eu/en/self-tun … oller.html
Secondly with the controller alternatives, The robot will rarely have a current over 5A according to calculations. Could i then choose the smaller controller or should i go with the larger?
In alternative to the Sabertooth controllers i was thinking of the Devantech controller instead. Is the encoders from the motors compatible with that controller? Is this controller for 24V motor only? robotshop.com/eu/en/devantec … river.html
The named controllers are of interest because of the apparently easy control and feedback for control. The other controllers of PWM type seemed like the Arduino had to make all calculation to get current speed and direction. But maybe that isn’t such a hard task, maybe there is some Arduino library for that?
]The Self-tuning Kangaroo can be used in your application for feedback motion control to keep your robot in a straight path since you will be driving the four motors in differential two wheel steering. You will only need two encoders input for a pair of motors from each side of the robot. Each output channel from the dual motor controller will drive two motors simultaneously relying on one encoder input from the Kangaroo./:m] ] The RB-Wtc-07 stall current is 10Amps. Therefore, the consumed current at full load can be approximated at 2A-2.5A (20%-25% of the stall current). The RB-Dfr-439 consumed current at full load should be around 0.72A-0.9A (20%-25% of stall current 3.6A). It is always better to choose a motor controller that can provide at least the double of the full load current consumption to be safe. If you are planning to go with RB-Wtc-07, it is probably better to choose RB-Dim-42 that can provide 12A continuous current per channel (as each channel will be driving two RB-Wtc-07). If you prefer the RB-Dfr-439, you can go with RB-Dim-19. The Devantech MD49 is rated for 24V. There is no information if this controller can take a voltage range and yes, the hall effect encoders on the motors should be compatible with the encoder inputs on the controller. Also note that Sabertooth controllers offer more flexibility in term of controlling method than the Devantech (Analog, RC, Serial on Sabertooth vs only serial on Devantech)/:m]Regards,
I think i was a bit unclear on what i meant, the robot is supposed to use only two wheels with motors. The other two wheels is only for support.
Can i run the lynxmotion motors with the smaller 5A controller if current at full load is 2-2.5A or is it too close? When I will use one just one motor per channel.
For the controller, having lithium protection, thermal and over current control, do I need to have a fuse? Or should you always have a fuse no matter what?
Is there something else to think about supplying power for both motors and arduino from the same battery, current or voltage spikes or something like that?
If you are driving only two RB-Wtc-07 (one on each channel), the Sabertooth Dual 5A 6V-18V Regenerative Motor Driver should be fine.
It is always good to have a fuse with the appropriate current rating in series with the motor. This will add another layer of protection to the motor controller if, somehow, one of the motors (or both) are stalled.
It is very suggested to separate the Arduino and motors power supplies. Motors will generate noises on the power line which might affect the Arduino if they share the same power source.
