Design of a quadruped robot driven by air muscles

This paper describes the development of Puppy, a canine-inspired quadruped robot driven by Festo air muscles. Puppy was designed to be a test bed for implementation and control of pneumatic muscles in legged locomotion. A two-dimensional kinematic model was developed using joint range of motion data and skeletal dimensions from large-breed canines, specifically the adult greyhound. This model was used to predict structural loads, required joint torques, muscle origin and insertion locations, and actuator lengths. Based on this study, the quadruped robot was designed with three degrees of freedom in each leg, all confined to motion in the vertical plane. Festo air muscles were mounted in antagonistic pairs and have been controlled using pulse-width modulation with closed-loop position feedback. Currently, the front legs and spine have been assembled and have successfully tracked position angles during air walking. The two legs can lift a 13.5 kg payload, nearly twice the predicted weight of the entire robot.