Contact Wrench Cone-Based Stable Gait Generation and Contact Slip Estimation of a 12-DoF Biped Robot.

In general, the stability control of the biped robot is based on Zero Moment Point (ZMP) which excludes the foot-ground contact stability characteristics. The concept of Contact Wrench Cones (CWC) is introduced in the stable gait generation of Humanoid robots for incorporating contact stability in recent research. The CWC confines the contact forces within limits as well as controls the Center of Pressure (CoP). This paper presents a CWC-based optimum gait generation for the dynamic biped locomotion. The kinematic model for a 12 Degree of Freedom (DoF) Biped robot is developed in the Screw theory framework. The dynamic equations of motion are derived using the recursive Newton–Euler (N–E) method. Stable dynamic gaits are generated for flat and step surfaces. Controlled Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) is used for the optimization of the dynamically stable biped gaits. The contact forces and the variation in friction coefficient are estimated for all the above cases. The peak values of the friction coefficient are used for assessing the conditions for kinetic friction and slip. [ABSTRACT FROM AUTHOR]