Event-Based Closed-Loop Control for Path Following of a Purcell’s Three-Link Swimmer

Purcell’s three-link swimmers, characterised by segments connected through one-degree-of-freedom joints, exhibit a difficulty in following precise paths. This is attributed to their motion primitives, which do not inherently generate displacement in a singular, predictable direction. To overcome this limitation, this paper proposes a closed-loop control strategy on the basis of event-based control. This control approach enables the robot to perform a specific motion primitive when the deviation from the desired trajectory exceeds a predefined threshold. In other words, an asynchronous strategy is used to adjust the motion of the swimmer, thereby ensuring tracking of the desired path with a limited error. The effectiveness of this closed-loop control strategy is demonstrated through experiments with a motor-driven 30 cm-length prototype. These tests show that this event-based control strategy allows the swimmer to follow specific paths with a tracking error of less than 30% of its length.