The torque required to overcome the inertia of a mobile robot can be much greater than the torque needed to keep it in motion.
To properly size a motor for a wheeled mobile robot, it is important to focus on the situations prevailing in the topography where the robot will accelerate from rest to full speed. This leads to asking pertinent questions as follows: Is the surface on the topography an inclined plane and by how much angle is the surface inclined? Is it on a smooth or flat surface? Is the topography on an undulating one? What number of wheels will provide motion for the robot and how many of those wheels will be driven by DC motors? Immediately following the number of wheels is the wheel diameter. Then it is necessary to decide on the maximum speed to be attained by the robot in one second.
Furthermore, it is a good design practice to determine the mass of the robot before sizing or selecting a motor. After selecting the motor, it is important to estimate the overall efficiency of the mobile robot which involves the product of the wheel, motor, and gearing efficiencies. This helps to establish a limiting condition above which the robot may not function optimally.