What can be added to a robot's arm to increase capacity without altering the rated load?

To increase a robot's arm capacity without altering its rated load, adding a supplementary load is a viable option. A supplementary load is designed to support the existing load by redistributing forces and enhancing stability without exceeding the pre-defined limits of the robotic system. This approach allows for efficient use of the robot's capabilities while maintaining safety and adherence to operational specifications.

In contrast, the other options do not effectively achieve the desired increase in capacity without manipulating the rated load itself. A secondary rated load, for instance, would ambiguously imply an adjustment to the load rating, which is not the goal. Mechanical resistance focuses more on opposing motion, thus not contributing to increased capacity. An external weight balancing system may aid in offsetting loads, but it does not necessarily increase the capacity of the arm in a way that maintains compliance with the existing rated load specifications.