The controlled system is a pendulum with mass <i>m</i> hanging from a weightless rod of length <i>L</i>.

The angle between the pendulum and its vertical axis is denoted by θ, where θ = 0 rad indicates the pendulum’s downward position. The goal of the task assigned to participants is to swing the pendulum in order to balance it in its upright position for as long as possible (i.e., θ ≃ π rad and ).