Exploiting natural dynamics for energy minimization using an Actuator with Adjustable Stiffness (AwAS)

In repetitive trajectories, adaptable compliance actuators can minimize energy consumption thanks to their ability to adjust the level of stiffness which allows the exploitation of the natural dynamics of their link based on the desired motion´s frequency. However for most of these actuators in case of a variable frequency motion, it is not energetically beneficial to exploit the natural dynamics in the real time due to the considerably high amount of energy needed to change the stiffness. AwAS (Actuator with Adjustable Stiffness) achieves the stiffness regulation not through the control of the spring pretension (as in most of the existing variable stiffness joints) but by controlling the location of the spring elements. An important consequence of this mechanism is that the displacement needed to change the stiffness is perpendicular to the forces generated by the springs which in turn helps to minimize the energy/power required to regulate the stiffness. It is experimentally shown that AwAS is capable of minimizing energy consumption through exploiting the natural dynamics in real time for both fixed and variable frequency motions.