Hey all!
Im trying make a robot for my garden, its purpose will be cutting grass like husqvarnas robots, however my garden is quite small (around 8 metres by 15 metres) so Im trying to make a robot that will be smaller than husqvarnas.
Ive divided this project into steps, first one would be 3d printing the robot chasis (which is partially designed) and making the robot drive, second would be adding a charging station, third would be the grass blade, however Im focusing on the first one only (at least for this thread 
:o )
The robot will have 2 wheels at the back (which will be powered and push the robot) and 1 wheel in the front, which will be connected to a servo and change direction as needed in order to make the robot turn.
A small diagram: (excuse me for how it looks 
)
XXX
| -------- |
|---|
| ---------- |
| --------- |
| -------- |
| XXX |
| *where XXX is a rear pusher wheel, and Y is the pivoting wheel. |
Im trying to figure out the best way to do so, so far Ive thought about 2 configurations for the robot:
-
having 2 motors, each for each wheel. however doing so will require an encoder on each one so that theyll match their RPM in order for the robot to steer purely based on the rotation of the front wheel (correct me if im wrong please! )
-
having 1 motor, connected by a gear to a shaft, the shaft will be connected to both wheels and by doing so the problem of matching the motors RPM will be eliminated and so will the use of encoders (which will be cheaper and easier to implement programming-wise)
Ive thought about using those brushed motors with wormgear reduction system, however Im not quite sure how to calculate the needed torque to move my robot.
some info about the robot:
-the weight of the robot should be around 2.5KG (probably less)
-the rear wheel diameter will be 6cm, this will advance the robot 18.85cm for every wheel rotation.
-the robot will be driving over short grass, so itll be moving over higher friction surface (compared to a flat, smooth, and hard floor)
so, after breaking my head over this for a while Ive turn here for help
heres my questions,
- which configuration will suit the robot more? 2 motors at the back or 1 with a shaft?
- which motors should I be using? does such a robot require higher power motors or can a cheap one from ebay manage just fine?
- can you guys think of a better configuration for that sort of robot?
thanks a lot!