Adjustable stiffness artificial tendons: Conceptual design and energetics study in bipedal walking robots

This paper explores the effects of the elastic elements with the adjustable stiffness at the ankle joint on energy efficiency of a bipedal walking robot during the collision phase. A mechanism design approach is elaborated to study the energetics through two major efforts. For the first effort, three different conceptual designs of the adjustable stiffness artificial tendons (ASAT) are proposed and the mathematical model of each conceptual design is developed. For the second effort, each conceptual design of ASAT is added at the ankle joint of a bipedal walking robot model. Lagrangian equations and impulsive constraints are used to implement the dynamic modeling of the bipedal walking robot during the collision phase. The simulation results show significant improvements in the energetics of the bipedal walking robot by proper stiffness adjustment of ASAT.