Determination of Artificial Muscle Placement for Biomimetic Humanoid Robot Legs

Abstract

Bipedal robotic leg kinematics and dynamics are a key component in designing biomimetic humanoid robots. This work describes the process of designing artificial muscle attachment locations of the legs of a bipedal robot utilizing pneumatic artificial muscles (PAMs). PAMs offer similar force and activation times to real muscles, while being lightweight and low power. However, not all properties are identical, and substituting artificial muscles in with the same attachment locations results in different torque profiles about each joint. This work analyzes muscle length, moment arm, and isometric force of muscles over a range of different joint configurations, based on muscle attachment and wrapping points of the Gait2392 model in OpenSim. These parameters are then used to find joint torques produced by each muscle. This process is repeated for a model of the robot actuated by PAMs. Joint torques for individual muscles and groups of muscles are then compared between the models. Results indicate that several muscles torque profiles in the robot model closely match that of the human model, however, many muscles fall far short of the human capabilities. Where appropriate, additional results demonstrate how muscle attachment locations on the robot have been modified to better match the torque capabilities demonstrated by the OpenSim model. Matlab tools created for this project will facilitate further design refinement before implementation on the robot.