Simulation of a Compliant Biped Multibody Model: walking and running

In the world of robotics, for many years, the study of the human-machine relationship has tried to build models based on human anatomy and on the movements that a normal man naturally performs. By imagining this, biped models that referred to human walking or running have been conceived and designed. The purpose of this thesis focuses on the analysis, study and simulation of human walking gait and running gait using as a basis a model of a bipedal robot. Some modifications have been made on it because of a different vision of how the joints positioned along the lower limbs perform their own work. The old model deals with the concepts of both compliance and variable stiffness: it uses revolute joints for both hip and ankle and a pin slot joint for the knee to simulate interposed springs with proper stiffness coefficient and damping. This operation lets to have compliant joints. So, in this new concept of the model, in addition to the revolute joints that are positioned on the hip, knee and ankle, a different type of joint has been used and inserted along each lower limb modifying the model structure. This last joint has the purpose of physically simulating a spring with a variable stiffness coefficient and a damping coefficient. After these changes in the model, it has been validated to make it as much as possible in line with a real system. Then, various simulations for walking gait and running gait have been made to obtain outputs to compare the trends due to the different stiffness values used and to the compliance of the joints. Once the results have been obtained, they have been compared with those of the old model to find any improvements, selecting the best situation among these. In consideration of that, many plots have been made, especially regarding the displacement of Centre of Mass, the power and torque values by the revolute joints, the trajectory of the Centre of Mass from the starting point.