MODELING OF VARIABLE COMPLIANT FOUR LEGGED ROBOT

Abstract

In the era of automation, the interaction of the humans with the robots is unavoidable. Hence, there is a need to improve the safety of humans that interact with the robots for the industrial as well as domestic purposes. Compliance in the body parts of the robot tends to provide safer human interactions. Compliance in the links also provides an energy efficient locomotion. Wheeled robots are limited in different types of terrain that they can navigate. In contrast, legged robots can navigate in a wide range of terrains. When compared to bipeds and hexapods. four legged walking robots provide a good trade off stability, load carrying capacity and mechanical complexity. Four legged robot is designed to travel in too steep, rutted rocky. wet muddy and snowy environment. In this paper we propose a variable stiffness four legged robot. The bottom link of leg is C- shaped. There is a moving appendage which can slide over C- shaped link and thus changing the stiffness of the link. The physical mapping of the C- leg into a linear geometry is achieved using the SLIP (Spring Loaded lnverted Pendulum) model. The SLIP model is a well-established description of bouncy gaits. While in the original SLIP model leg parameters are fixed, in this paper, we include variations of rest length and linear stiffness. Dynamic model of the leg is created using Lagrange method. For the said analysis, the dynamic model of the robot is simulated in MATLAB by assuming initial values of the masses of legs, friction, impact force and inclined ground surface. The modeling of the robot is carried out in sagittal plane and bounding gait has been considered for the simulation purposes. The dynamic model achieved can be further used for designing the controller.