easiest way to drive a small outdoor robot ?

Projects General Guidance
1

I plan to mount my sensors and chargers on a small platform (say 20/40 cm at maximum) to be operated outdoor.

I have no experience at all in motor drivers.

Since the best method is to use tracks, if I can make the tracks - I will go for that. If not, I have to use 4 wheels.

At this time, I have on my desk some fairly cheap motors 3-6V, brushed (toys motors or similar). I can start by them and eventually replace them by some more expensive and effective motors.

The reductors is one problem (although I can buy geared motors to work it out).

I need:

  • forward - variable
  • backward - variable
  • brake

I guess I will have to use PWM to obtain variable speed, but I am also thinking to a sort of 3-speeds digital control, since I only need very slow speed.

+++

What motor drivers /controllers would you recommend, in order to start with (to learn) in this case, please?

Thank you!

2

study up on H-Bridges, build & test one to drive one of your motors. if successful, duplicate and go from there.
use MOSFETs instead of BJTs for better power efficiency.

H-bridge will give you forward, backward, & brake. one for each side will give you left & right.

3

You might like to consider using continuous rotation servos. They have all the gearing and motor-drive electronics included.

You can also get cheap geared motors like this

1000×1000 36.4 KB
.

This one comes with a wheel, but they are widely available without wheels.

These motors will need a h-bridge.

...R

4

If outdoor means rough surface, don't count on being able to reduce much speed with PWM. Make sure you can use your motor top speed and adapt a suitable gear according to that.

5

Outdoor=very rough surface.

I suppose I have to do something to increase torque as much as possible when required.

H-bridge can do that?

I found this:

http://www.modularcircuits.com/blog/articles/h-bridge-secrets/h-bridges-the-basics/

Looks very straight forward. Except the PWM part - which I need to study.

7

@Delta_G

For a similar project (a demo about tracks, no electronics) I could not find any suitable track.

I came across a couple of DiY solutions that I found either to difficult or to un-reliable.

So I think I will plan myself the tracks and find a way to make them somehow. The most difficult part is to find a way to have them driven by the motor wheel, keeping tracks in place.

9

@Delta_G

Thanks! Indeed, all those chassis look very cool. Not to expensive, considering the stuff they include, I may say.

I wonder whether the tracks can take a really rough surface (forest floor).

11

falexandru:
Outdoor=very rough surface.

I suppose I have to do something to increase torque as much as possible when required.

H-bridge can do that?

No. An H-bridge can only switch current direction. Add PWM to it and you get speed control. Without PWM you get full speed. With PWM you can only decrease speed, but you will decrease torque at the same time. And a PWM of 50 % duty cycle doesn't mean half speed and half torque. It might mean full stop and motor only beeping the PWM frequency.

A gear box on the other hand might drop the speed to 50 % and raise the torque to 200 %. While the motor runs at full speed, of course.

12

Is there any way to control torque without a gearbox?

A Brushless motor maybe?

14

@Delta_G
That would be nice to know, indeed.
As far as I know (and I know very little), the electric motors needs a sort of "push" to start, namely a "power burst" , in terms of significantely more current to start than to move.

http://myelectrical.com/notes/entryid/77/motor-starting-introduction