Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: airman00 on October 26, 2007, 12:45:31 PM
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If you have a robot with two motorized wheels and one caster wheel, should you have it drive with the motorized wheels in front and the caster in back , or caster in front and wheels in back?
What are the advantages of each?
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Simple physics... it is allways better to pull than push... motors in front of the casters. Better conrtrol, less strain on the motors.
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Then why is it that most robots do the reverse, ( caster in front of wheels) , surely there is some advantage
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Don't take my word, but I think it just looks better and normal with the caster in front. However, there might be some other reason...
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i found answers when i saw a bus outside the house.
backwheel drive is good and better. come to think of this, if you have a car with two motorized wheels at the back, and have the car fully loaded. and let the car move on inclined plane say about 30 degrees. where is the concetration of the force/weight? .. yes, physics comes in, but even with a simple look you know that as the angle of inclination increases the force acting on the Y axis increases. so to compensate the weight that would be concentrated at the back of the car, the motor should be at the back of course. another thing, it is always better to do turns with back wheel differential drive.
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For a tall robot (high COG), having the driving wheels at the back is not so good. It will tend to flip on it;s back when starting to move forward. This kind of robot would be best to have the driving wheels in the middle and one caster in the front and one in the back, the front one being spring loaded.
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I'd rather use 4-wheels for differential steering, but that makes localization harder to deal with... but to each their own I guess.
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Ive seen robots with both a front and back castor (not to complicate your decision or anything)
It affects not just control and stability, but you should also consider sensor locations . . . for example, for a line follower you want the sensors in front, meaning a castor cannot be located there (and many other examples) :P