A new variable stiffness actuator (CompAct-VSA): Design and modelling

Abstract

This paper describes the design and modelling of a new variable stiffness actuator (CompAct-VSA). The principle of operation of CompAct-VSA is based on a lever arm mechanism with a continuously regulated pivot point. The proposed concept allows for the development of an actuation unit with a wide range of stiffness and a fast stiffness regulation response. The implementation of the actuator makes use of a cam shaped lever arm with a variable pivot axis actuated by a rack and pinion transmission system. This realization results in a highly integrated and modular assembly. Size and weight are indeed an open issue in the VSAs design, which ultimately limit their implementation in multi-dof robotic systems. The paper introduces the mechanics, the principle of operation and the model of the actuator. Preliminary results are presented to demonstrate the fast stiffness regulation response and the wide range of stiffness achieved by the proposed CompAct-VSA design.

Robust Tracking Control Of The Variable Stiffness Actuator Based On The Lever Mechanism

“…Although many control strategies have been proposed for the tracking control of the VSAs, there are still exist some problems. The robustness is not considered in . For the backstepping controller presented in , the model errors and the unmodeled dynamic effects will lead to nonvanishing control errors.…”

“…The robust tracking control scheme that simultaneously regulate the position and stiffness of the VSA based on the lever mechanism needs further study. The input saturation problems are not considered in . The presence of the unavoidable constraints on the control inputs, if not fully considered in the design process of the controller, may have effects on the tracking performance or even the system stability.…”

“…The presence of the unavoidable constraints on the control inputs, if not fully considered in the design process of the controller, may have effects on the tracking performance or even the system stability. In addition, a state space model of the VSA, which considers the parameter uncertainties, the unknown friction torques acting on the driving components, the unknown external disturbance acting on the output link, and the input saturation constraints, is not found in . The robust tracking control problems for other types of systems (non‐VSAs) are addressed in .…”

Torsion MACCEPA: A novel compact compliant actuator designed around the drive axis

“…Research into new compliant actuation principles is closing the gap towards the torque-to-weight ratios and efficiency requirements of novel applications. Furthermore, several compliant actuators have been developed and their current progress consists of increasing compactness for a better integration in multi-degree-of-freedom robotic systems [12]. The MACCEPA [13] is a VSA developed at the Vrije Universiteit Brussel (VUB).…”

A User Study on Kinesthetic Teaching of Redundant Robots in Task and Configuration Space

“…A new generation of adept manipulators has recently become more widely used, combining two technological advancements: advanced force-torque sensing integrated into compact actuation units (Albu-Schäffer, Haddadin, et al, 2007) with variable stiffness (Tsagarakis, Sardellitti, & Caldwell, 2011) leading to fully compliant robot manipulators Grzesiak, Becker, & Verl, 2011) and the tendency to increase the degrees of freedom towards kinematically redundant (Conkur & Buckingham, 1997) manipulators. While these robots provide a great degree of flexibility for the realization of complex applications -for example, in industrial (Daimler AG, 2009) or service robotics (Akgun, Cakmak, Yoo, & Thomaz, 2012;Breazeal et al, 2008) scenarios -the gained flexibility generates the need for additional modeling steps and the definition of criteria for redundancy resolution.…”