A novel bio-inspired kangaroo leg structure for low-frequency vibration isolation

Inspired by the vibration mitigation effect of kangaroo’s legs, a novel bio-inspired kangaroo leg structure (BKLS) is proposed for low-frequency vibration isolation. The BKLS is composed of two main rods with different lengths (simulating the calf bone and thigh bone), two linear springs (simulating the internal and external muscles) and two auxiliary rods. Based on the Lagrange principle, the dynamic model is established to describe the nonlinear effects of BKLS, which are mainly contributed by the internal and external springs and the rotary joints. The corresponding displacement transmissibility derived with the harmonic balance method. The equivalent nonlinear stiffness shows that the proposed BKLS possesses favorable of high-static and low-dynamic stiffness (HSLDS) properties over a wide displacement range. The HSLDS range and bearing capacity can be tuned easily by initial assembly angle, rod length ratio, and spring stiffness ratio. Moreover, experiments were carried out to verify the dynamic predictions and demonstrate that the proposed BKLS indeed possess superior low-frequency isolation performance without sacrificing the carrying capacity, which can effectively suppress vibration with frequencies higher than 1.06 Hz. Regardless of the vibration isolation quality and excitation conditions, it can be designed/adjusted on demand by selecting appropriate structural parameters to achieve the best isolation performance. The innovative and simple BKLS provides an effective method for low-frequency vibration isolation.