Which of the following does NOT affect the ability of a robot to run straight?

The ability of a robot to run straight is influenced primarily by factors that directly affect its movement and stability, such as how evenly both wheels are powered, the distribution of weight across the robot, and the design of the robot's chassis.

Wheel speed uniformity is crucial; if one wheel spins faster than the other, the robot will veer off course instead of traveling in a straight line. Weight distribution can also impact running straightness; uneven weight can create imbalances that cause the robot to tilt or turn in unexpected ways. Additionally, the type of robot chassis influences the overall dynamics of movement. For instance, different chassis designs may perform differently based on their construction and the distribution of their components.

On the other hand, the distance of an obstacle does not inherently affect how the robot runs straight; rather, it might require the robot to change its path or speed, but it does not directly influence the robot's ability to maintain a straight trajectory under normal conditions. This makes the distance of obstacles the factor that does not impact the robot's straight movement in the same way as the other options mentioned.