A study of walking gait stability and gait efficiency of a cost-effective small humanoid bipedal robot: Analysis, simulation and implementation

This paper discusses the study of humanoid bipedal gait stability and the corresponding gait efficiency. The project involves the use of an open source humanoid robot, PLEN 2 to study the recently developed walking gait control system. The stability of a humanoid walking gait is studied from both static and dynamic point of view. Zero-moment Point or ZMP coupled with nonlinear feedback dynamic compensation method are employed to generate a stable walking gait, suitably implemented on a real humanoid robot platform. Nonlinear dynamics of the bipedal PLEN2 is considered in the walking gait analysis and control design. The primary contribution made in this work is the convenient verification of the enhanced walking gait control on a 3D printed small humanoid robot (PLEN2). The enhancement accomplished is the incorporation of pseudoinverse of the inertia mass matrix in the dead beat controller to guarantee numerical computation in the simulation. This facilitates fast iterative design process which involves both facets: the shaping of the joint trajectory in achieving bipedal gait and also the mechanical design variation which in this case, the length of the humanoid leg. Being a cost-effective open source humanoid robot platform, the mechanical design for the PLEN2's legs can be modified conveniently by the designer as to achieve a stable and yet efficient walking gait. The simulation result of the bipedal humanoid robot is verified by the real hardware implementation on the PLEN2.