Backpack with a nonlinear suspension system designed for low walking speeds

The most common injuries caused by carrying a backpack used by different strata of society are caused by the dynamic force applied to the body by the backpack. The application of vibration isolation is one of the proposed methods to reduce this force. This study has introduced a nonlinear mechanism to reduce the dynamic forces applied to the body, considering the shortcomings of common linear vibration isolators. Low dynamic stiffness and high static stiffness are the advantages of the proposed system. This feature leads to a much lower natural frequency in backpacks compared to conventional systems; thus, it will be effective at low speeds. High static stiffness prevents the initial deformation due to the backpack mass. This mechanism includes one horizontal and two oblique springs. The dynamic equations of this mechanism are extracted using the Newton method, and the analytical results are compared to those obtained from Adams software. Then, the design parameters for the proposed backpack are optimized using the transmission force objective function and the results are compared with the previous studies.