A Comparative Study on 2-DOF Variable Stiffness Mechanisms
This provides design guidelines for engineers working on variable stiffness mechanisms, but is incremental in nature.
The paper compared different 2-degree-of-freedom variable stiffness mechanisms using parallel kinematic machines with redundant actuators and non-linear springs, developing a stiffness formulation and optimization approach that resulted in a quantitative stiffness metric for design comparison.
Based on the idea of variable stiffness mechanisms, a variety of such mechanisms is shown in this work. Specifically, 2-DOF parallel kinematic machines equipped with redundant actuators and non-linear springs in the actuated joints are presented and a comparative overview is drawn. Accordingly, a general stiffness formulation in task space of all mechanisms is given. Under fixed geometric parameters, optimization of task space stiffness is carried out on the designs comprising all kinematic solutions. Finally, a stiffness metric is introduced that allows a quantitative comparison of the given mechanism designs. This gives rise to design guidelines for engineers but also shows an interesting outline for future applications of variable stiffness mechanisms.