Quasi-zero stiffness vibration isolator for turtle-like limbs: High bearing capacity design and low-frequency vibration isolation performance analysis

To address the challenge of low-frequency vibration isolation, this study proposes a novel bionic quasi-zero-stiffness (QZS) isolator inspired by the load-bearing capacity and stability of turtle limbs. The bionic turtle limb structure (BTLS) employs rigid rods and linear springs to mimic the femur–tibia configuration and replicate the negative stiffness of muscles and tendons. By integrating BTLS with a positive-stiffness parallel mechanism, QZS characteristics are achieved. A nonlinear mechanical model is developed through static analysis and parametric investigation. The theoretical model is validated using ADAMS simulations, demonstrating that the proposed isolator enhances load capacity by 46.02% and broadens the isolation bandwidth by 30% relative to a conventional three-spring QZS isolator. Dynamic analysis based on Newton–Euler equations and the harmonic balance method yields amplitude– and phase–frequency responses. Experiments confirm improved low-frequency isolation, with a 45.86% reduction in initial isolation frequency relative to a linear isolator. This work innovatively applies turtle limb biomechanics to QZS design, demonstrating high load capacity, broadband isolation, and enhanced low-frequency performance.