Reflexive stability control framework for humanoid robots
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Reflexive stability control framework for humanoid robots Tadej Petriˇc · Andrej Gams · Jan Babiˇc · Leon Žlajpah
Received: 15 February 2012 / Accepted: 28 February 2013 / Published online: 19 March 2013 © Springer Science+Business Media New York 2013
Abstract In this paper we propose a general control framework for ensuring stability of humanoid robots, determined through a normalized zero-moment-point (ZMP). The proposed method is based on the modified prioritized kinematic control, which allows smooth and continuous transition between priorities. This, as long as the selected criterion is met, allows arbitrary joint movement of a robot without any regard of the consequential movement of the ZMP. On the other hand, it constrains the movement when the criterion approaches a critical condition. The critical condition thus triggers a reflexive, subconscious behavior, which has a higher priority than the desired, conscious movement. The transition between the two is smooth and reversible. Furthermore, the switching is encapsulated in a single modified prioritized task control equation. We demonstrate the properties of the algorithm on two human-inspired robots developed in our laboratory; a human-inspired leg-robot used for imitating human movement and a skiing robot.
Electronic supplementary material The online version of this article (doi:10.1007/s10514-013-9329-0) contains supplementary material, which is available to authorized users. T. Petriˇc (B)· A. Gams · J. Babiˇc · L. Žlajpah Department of Automation, Biocybernetics and Robotics, Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia e-mail: [email protected] A. Gams Biorobotics Laboratory, École Polytechnique Fédérale de Lausanne, Vaud, Switzerland e-mail: [email protected] J. Babiˇc e-mail: [email protected] L. Žlajpah e-mail: [email protected]
Keywords
Humanoids · Stability · Skiing robot
1 Introduction In this paper we propose a modified prioritized task control applied to stability control of humanoid robots. Humanoid robotics is currently one of the most exciting fields in robotics (Shin et al. 2010; Sentis et al. 2010; Omrˇcen and Ude 2010; Asfour and Dillmann 2003). Different tasks, important for understanding human and human-like movements (Atkeson et al. 2000), are being researched and performed using humanoid robots and service platforms, yet they are all secondary to maintaining the postural stability. The postural stability problem may not be evident for such tasks as playing with different toys (Petriˇc et al. 2010, 2011a; Žlajpah 2006). However, this is not true for the full body tasks like walking (Ijspeert 2008; Righetti and Ijspeert 2006), jumping (Babic and Lenarcic 2006) or skiing (Lahajnar et al. 2009; Petriˇc et al. 2011b). An important criterion used in robotic stability is the zero moment point (ZMP) (Vukobratovic and Juricic 1969; Vukobratovic and Borovac 2004), which is commonly used to evaluate the center of mass (CoM) acceleration boundaries, i.e. to determine the highest possible accelerations of the CoM, whi
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