Examination of Balancing in a Real-World Inverted Pendulum
Human motor control is often studied using virtual tasks that simplify object mechanics. We examined the stabilization of a physical underactuated cart-pendulum and its relation to passive dynamics. Twelve adults balanced three pendulum configurations (short, 0.31 m; medium, 0.64 m; long, 1.03 m). Free-decay measurements showed progressively lower oscillation frequencies from short to long, while passive-fall durations to {+/-} 30{degrees} were longer for the medium and long pendulums than for the short one. Participants trained with the medium pendulum for 30 trials and completed 20 test trials per configuration. Balance duration increased from the first four to the final four training trials, whereas no detectable start-to-end change occurred within any test block. Late-block balance duration was shorter for the short pendulum than for the medium and long pendulums, which did not detectably differ. Estimated peak pendulum angular speed was highest for the short configuration and lowest for the long, whereas peak cart speed did not mirror balance duration. The short configuration, which had the fastest passive dynamics, was balanced for less time than the longer configurations. These results provide a quantitative benchmark for autonomous controllers using a comparable physical linear-rail cart- pendulum under matched mechanical and task constraints.