Efficient Walking Gait Generation via Principal Component Representation of Optimal Trajectories: Application to a Planar Biped Robot With Elastic Joints. - Gian Maria Gasparri; Silvia Manara; Danilo Caporale; Giuseppe Averta; Manuel Bonilla; Hamal Marino; Manuel G. Catalano; Giorgio Grioli; Matteo Bianchi 002; Antonio Bicchi; Manolo Garabini (IEEE Robotics Autom. Lett., 2018)