As part of an undergraduate internship program, I simplified the lab’s earlier flea-inspired jumping robot—which featured an insect-shaped body and a flea-mimicking torque-reversal mechanism—while retaining the key torque-reversal principle.

In this principle, the catapult stores a large amount of elastic energy while the leg linkage is held in an over-center (near-singularity) latched configuration, where the extensor generates a latching torque that presses the structure against a mechanical stop. A small trigger actuation then shifts the force line across the joint center, reversing the joint torque (latching → extending); once the mechanism passes the over-center point, the leg rapidly rotates and releases the stored energy to produce an impulsive takeoff.

Based on this principle, I designed a rhombus-shaped structure. The mechanism is mechanically latched near the over-center configuration, and elastic energy is stored using an extensor SMA spring. A weak trigger SMA actuator then drives the system across the over-center point; immediately after crossing, the structure rapidly unfolds and releases the stored energy. Experiments confirmed that the simplified robot was easier to build than the previous flea-inspired design while achieving improved jumping performance.