Energy performance analysis of a backpack suspension system with a timed clutch for human load carriage

This work theoretically investigates methods of reducing the energetic cost of bipedal walking while carrying a backpack with a suspension system. We extend a previous 2DOF model proposed by Ackerman and Seipel (2014) by adding a timed clutch to the suspension mechanism. The clutch allows the mechanism to switch between states of elastic or rigid connection of the backpack and the body. Periodic switching between the two states of the mechanism is either event-based or timing-based, and may result in inelastic impacts. We study the hybrid dynamics induced by the action of the clutch mechanism, analyze energy expenditure and stability of periodic solutions, and seek for optimal values of stiffness and switching times that minimize the energetic cost. It is found that in many cases, the clutch mechanism can significantly reduce energy expenditure compared to both rigid and elastic suspensions. (C) 2017 Elsevier Ltd. All rights reserved.