International Journal of Advanced Robotic Systems ARTICLE Conceptual Design and Analysis of Four Types of Variable Stiffness Actuators Based on Spring Pretension Regular Paper Jishu Guo1 and Guohui Tian1* 1 School of Control Science and Engineering, Shandong University, Jinan, Shandong, China *Corresponding author(s) E-mail:
[email protected] Received 12 November 2014; Accepted 17 March 2015 DOI: 10.5772/60580 © 2015 The Author(s). Licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract between the output stiffness and the angular deflection is fairly linear. The conceptual layouts and working princi‐ The variable stiffness actuator (VSA) is an open research ples are elaborated for the four actuators. The characteris‐ field. This paper introduces the conceptual design and tics of torque and stiffness of the VSAs are presented, and analysis of four types of novel variable stiffness actuators the mechanical solutions are illustrated. (VSAs). The main novelty of this paper is focused on the convenience control of the torque and stiffness of the Keywords Variable stiffness actuator, Approximate actuator. We do not need to design complicated control quadratic spring, Characteristics of torque and stiffness, strategies to achieve the desired actuating torque and Convenient to control, Mechanical solution output stiffness. This feature is beneficial for real-time control. In order to achieve this advantage, three types of approximate quadratic springs and four types of stiffness regulation mechanisms are presented.