Design and Dynamic Modeling of Variable Stiffness Joint Actuator Based on Archimedes Spiral

Traditional rigid actuators are not applicable to robot applications involving explosive actions. Solutions suggested by previous studies have mainly focused on the concept of stiffness variation, its design and verification, and the explosive actions of variable stiffness joint actuators. This paper proposes a variable stiffness actuator that features a leaf spring as the elastic element and a pair of disks with two Archimedes spiral grooves as the stiffness adjusting mechanism, maintaining φ114 mm×130 mm overall dimensions and a full range (i.e., 127-2095 Nm/rad) of stiffness variation driven by a 7.2-W motor and, therefore, creating a competitive advantage in both compactness and energy saving capacity. The proposed actuator is intended as a dynamics model to predict the exact kicking speed under any given initial conditions of joint stiffness, kicking time, and load mass and for uses in the joints of industrial and/or service robots that frequently involve explosive actions.