“…When dealing with physical legged robots, the majority of studies only considers the evolution of un-driven walking controllers and, most of the time, the task consists in finding a controller that maximizes the forward walking speed (Zykov et al, 2004;Chernova and Veloso, 2004;Hornby et al, 2005;Berenson et al, 2005;Yosinski et al, 2011;Mahdavi and Bentley, 2006). Papers on alternatives to evolutionary algorithms, like policy gradients (Kohl and Stone, 2004;Tedrake et al, 2005) or Bayesian optimization (Calandra et al, 2014;Lizotte et al, 2007), are also focused on robot locomotion along a straight line.…”