Additional DOFs and sensors for bio-inspired locomotion: Towards active spine, ankle joints, and feet for a quadruped robot. - Daniel Kühn; Felix Grimminger; Frank Beinersdorf; Felix Bernhard; Armin Burchardt; Moritz Schilling; Marc Simnofske; Tobias Stark; Martin Zenzes; Frank Kirchner (ROBIO, 2011)