Research of power modulation characteristics of elastic actuators

Elastic actuator is one type of advanced actuators composed by the traditional stiffness actuator and the transmission mechanism with more than one elastic elements. It is also the core component with the function of achieving motion, force and energy transformation in various robot systems. Designing a bionic robot joint with the characteristics like animals' muscle-tendon system is an urgent demanding but difficult issue. Natural muscle-tendon system has the short-term high-power density output characteristic. But it is a tricky problem to realize the short-time high-power density actuation by means of the engineering techniques. Hill proposed the classical three-element muscle model to reveal the relationship between the skeletal muscle contraction velocity and the tension force, but not to analyze the mechanism and design method of the short-term high-power density output of biological elastic actuators. In this paper, the mathematical models of elastic actuators are established based on three-element Hill muscle model. Five kinds of elastic actuator models are compared and analyzed to reveal the influence of the stiffness parameter on the maximum output and power modulation characteristics. The proposed designing methods and procedures also can be extended to more complex elastic actuators of various robot systems in the engineering applications.