Development of a Suspension Backpack With Quasi-Zero Stiffness and Controllable Damping

Previous research has shown that load-bearing with elastic suspension backpacks improves human biomechanics and reduces human energy expenditure. Constant-force suspension backpacks (CFSB) with zero stiffness were developed to minimize the inertial force of loads. However, there is a mismatch between the load and the constant force mechanism due to the user's non-fully upright waist while moving. The load will exert inertial forces on the human body, increasing energy expenditure. In this letter, a suspension backpack with quasi-zero stiffness and controlled damping (CQFB) is developed. The position of the load can be adjusted by the electromagnetic damping force from motors without consuming additional electrical energy. A Q-learning based variable damping controller is proposed to keep the load in the middle of the slide with a small external force. The results of the load disturbance rejection experiments show that the CQFB effectively prevents the problem of collision limit after the load is subjected to the bias force and reduces the net metabolism by 11.4% compared with the ordinary backpack (OB). The results of the peak accelerative vertical force experiments show that the CQFB can reduce the peak accelerative vertical force of the load at three speeds, with a maximum average reduction of 86.8%. The controllable damping device has no significant effect on the levitation effect.