Article

Energy-Efficient Variable Stiffness Actuators.

IEEE Transactions on Robotics 01/2011; 27:865-875. DOI: 10.1109/TRO.2011.2150430
Source: DBLP

ABSTRACT Variable stiffness actuators realize a particular class of actuators characterized by the property that the apparent output stiffness can be changed independently of the output position. This is feasible due to the presence of internal springs and internal actuated degrees of freedom. In this work, we establish a port-based model of variable stiffness actuators and we derive an energy efficient control strategy. In particular, when the variable stiffness actuator acts on a mechanical system, the internal degrees of freedom are used to achieve the desired nominal behavior and the internal springs are used as a potential energy buffer. The release of energy from the springs, as well as the apparent output stiffness, are regulated by control of the internal degrees of freedom. Simulation results on a robotic joint illustrate the effectiveness of the control strategy during the tracking of a periodic motion in presence of disturbances.

0 Bookmarks
 · 
115 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Research effort in the field of variable stiffness actuators is steadily increasing, due to their wide range of possible applications and their advantages. In literature, var- ious control methods have been proposed, solving particular problems in human-robot and robot-environment interaction applications, in which the mechanical compliance introduced by variable stiffness actuators has been shown to be beneficial. In this work, we focus on achieving energy efficient actuation of robotic systems using variable stiffness actuators. In particular, we aim to exploit the energy storing properties of the internal elastic elements.
    01/2010;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Variable stiffness actuators (VSAs) are currently explored as a new actuation approach to increase safety in physical human–robot interaction (pHRI) and improve dynamic performance of robots. For control purposes, accurate knowledge is needed of the varying stiffness at the robot joints, which is not directly measurable, nonlinearly depending on transmission deformation, and uncertain to be modeled. We address the online estimation of transmission stiffness in robots driven by VSAs in antagonistic or serial configuration, without the need for joint torque sensing. The two-stage approach combines (i) a residual-based estimator of the torque at the flexible transmission, and (ii) a recursive least squares stiffness estimator based on a parametric model. Further design refinements guarantee a robust behavior in the lack of velocity measures and in poor excitation conditions. The proposed stiffness estimation can be easily extended to multi-degree-of-freedom (multi-DOF) robots in a decentralized way, using only local motor and link position measurements. The method is tested through extensive simulations on the VSA-II device of the University of Pisa and on the Actuator with Adjustable Stiffness (AwAS) of IIT. Experiments on the AwAS platform validate the approach.
    The International Journal of Robotics Research 11/2012; 31(13):1556-1577. · 2.86 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Variable Impedance Actuators (VIA) have received increasing attention in recent years as many novel applications involving interactions with an unknown and dynamic environment including humans require actuators with dynamics that are not well-achieved by classical stiff actuators. This paper presents an overview of the different VIAs developed and proposes a classification based on the principles through which the variable stiffness and damping are achieved. The main classes are active impedance by control, inherent compliance and damping actuators, inertial actuators, and combinations of them, which are then further divided into subclasses. This classification allows for designers of new devices to orientate and take inspiration and users of VIA’s to be guided in the design and implementation process for their targeted application.
    Robotics and Autonomous Systems 01/2013; 61(12):1601–1614. · 1.16 Impact Factor

Full-text

View
1 Download
Available from