Dynamic modelling and walk simulation for a new four-degree-of-freedom parallelogram bipedal robot with sideways stability control

The paper presents a simplified mathematical model of a two-leg walking robot with four degrees of freedom. It presents a novel method of sensing and balancing for the bipedal robot with the minimum possible number of degrees of freedom for the walk. The proposed method involves the design of a semi-rigid ankle to facilitate fast and accurate measurements of the sideways (sagittal) instability of the walking robot. The use of a new hip-mass carrying strategy in the forward direction and a system of two counter-masses for the sideways body balancing enables us to decouple the forward walking algorithms from the robot stability issues. The system of two different masses helps to improve the response time and efficiency of the balancing system. The control algorithms developed provide continuous stability of the robot while it walks in a forward direction by actuating its four DC motors. Smooth leg trajectory planning is implemented to minimize the foot–ground impact and jerky motions at the joints. The efficiency of the proposed control algorithms is tested and verified by using MATLAB Simulink computer tools.