Article

Energy-Efficient Variable Stiffness Actuators

IEEE Transactions on Robotics (Impact Factor: 2.43). 11/2011; 27(5):865 - 875. DOI: 10.1109/TRO.2011.2150430
Source: IEEE Xplore

ABSTRACT

Variable stiffness actuators are a particular class of actuators that is characterized by the property that the apparent output stiffness can be changed independent of the output position. To achieve this, variable stiffness actuators consist of a number of elastic elements and a number of actuated degrees of freedom, which determine how the elastic elements are perceived at the actuator output. Changing the apparent output stiffness is useful for a broad range of applications, which explains the increasing research interest in this class of actuators. In this paper, a generic, port-based model for variable stiffness actuators is presented, with which a wide variety of designs can be modeled and analyzed. From the analysis of the model, it is possible to derive kinematic properties that variable stiffness actuator designs should satisfy in order to be energy efficient. More specifically, the kinematics should be such that the apparent output stiffness can be varied without changing the potential energy that is stored in the internal elastic elements. A concept design of an energy-efficient variable stiffness actuator is presented and implemented. Simulations of the model and experiments on the realized prototype validate the design principle.

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    • "Interactions between a manipulator end-effector and the environment occur in many applications, such as assembling or grasping operations. Consequently, considerable attention has been paid to the analysis, modeling, optimization, and control of robotic system stiffness and compliance3456789101112131415161718. Generally, such interactions occur in dynamic conditions and depend on the compliance of the systems in contact, i.e. both the robot and the environment. "
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    • "Still following the first approach, actuators are designed in order to have variable impedance. So-called variable impedance actuators (VIA) can show a behavior where the output stiffness can vary independently from the output position (Vanderborght et al., 2009; Visser et al., 2011). "

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