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Four wheel differential drive

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I did a search here to try and find out if anyone has done a four wheel differential drive robot with four servo motors.  I am wanting to build a robot lawnmower that will go up and down and sideways across steep slopes and over rough terrain.  Knowing this terrain when dealing with human driven vehicles, four wheel drive is a necessity.  I am not sure if this translates to the device I want to build but if it does my thinking is four motors .... with each side's motors wired in parallel for control and to perform skid steer type of operations.  Or I could possibly use two motors in differential drive and use a belt or chain transfer to the other wheels on the same side of this machine.  Besides power and extra battery (and weight)  needs for the extra two motors ..... what other drawbacks am I looking at?  If someone has done this ...is the alternative of using a belt or chain situation better for four wheel drive?  Thanks for any input you can give on this.

The Dagu Wild Thumper rovers do four-wheel and six-wheel differential drive steering, one motor per wheel.
They are a bit smaller than real lawn mowers, though -- it may be that differential steering something heavy enough to mow the lawn would actually rip up that same lawn when turning...

Also, DC motors with a gear reduction would be a better choice than Steppers.

Four wheel drive, differential steering has been discussed on the forums here. Try widening your search and searching for discussion of DC motors verses stepper motors separately.

Why not make a hexabot type lawn mower wouldn't that be great (and almost impossible ) :-)

My plan is to use DC motors with gear reduction.  Just trying to decide if four motors versus two motors with belt or chain transfer to the other wheels on each side of the machine is a better idea.  Tracks would be ideal but add significantly to the cost.  The Dagu is neat ...but I have a feeling it may not be able to what I want to do.  If you have ever bush hogged tall brambles and small saplings I think you will know what I mean.  This things has to be like a little tractor ...or ATV ..able to deal with hauling or pulling around some type of self powered mowing attachment and that weight is going to be at least a hundred pounds.


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