I want develop a robot able to carry 2kg of stuffs. Shall I buy what kind of motor DC?
Thank you
You need to figure out the torque needed at the wheels, and the maximum speed, and then think about motor and gearbox that can together supply at least that torque and speed. If its on the flat the weight is less important, it is has to climb an incline or rough terrain then more torque will be needed. You need some reasonable estimates of friction in the system as well.
I think the quick answer is to look at other robot designs out there that look about the same size and see what they are using...