CAREER: Muscle-Inspired Load-Adaptive Actuation for Compliant Robotics

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This Faculty Early Career Development Program (CAREER) project will advance the national health, welfare, and security through scientific advancements in the field of biologically-inspired robotics favorable for wearable technology and exoskeletons. The research will make important contributions to society by increasing robot energy efficiency and performance while simultaneously improving human-robot interaction compatibility and safety through the use of inherently soft actuators. Actuators are critical component of a machine or robot that are responsible for moving and controlling a mechanism or components of a system. Current robotic actuators are poorly suited to wearable or human-assistive applications because they are inefficient when used in slow, variable-speed motions like moving an arm or leg. In addition, they create human safety hazards due to their stiffness and rigid motions. This research will create a new type of actuator that is inspired by human muscle tissues, which contain thousands of fibers that are selectively recruited to provide only the amount of force needed for a given task. Engineering artificial muscles to incorporate this concept of selective recruitment will allow the robot to consume less energy, therefore increasing battery life and range. It will also allow the same actuator to generate both gentle, precise motion as well as high-force, high-speed motion, depending on the task, while also incorporating soft construction and controllable stiffness. This new approach will help make assistive robotics safer, more comfortable, and more compatible with human physiology, all of which will provide more rapid and effective recovery for those suffering from debilitating injuries or disabilities. This research lends itself well to outreach opportunities to work with young people who suffer from disabilities; the outreach activities will help inspire them and show them how engineering can be used to improve their lives and the lives of those around them.Improvements in actuator efficiency and performance can be made by implementing the biologically-inspired concept of orderly recruitment to create an integrated fluidic artificial muscle tissue that contains selectable actuation elements of different sizes. This tissue can dynamically adapt to changes in load by recruiting different combinations of actuators. This orderly recruitment scheme conserves energy by reducing working fluid consumption and minimizing throttling losses. It also allows for a wide gamut of force generation and fast response time due to reduced flow rate demand. The goals of this research are to (1) understand the relationships between recruitment state, pressure, force, contraction, and velocity for selective-recruitment fluidic artificial muscle tissues; (2) establish the effects of topology on performance and create a framework for optimizing tissues to robot operating tasks and requirements; (3) understand implications of recruitment control architecture; and (4) demonstrate bandwidth improvements, variable compliance, and energetic savings on a walking robot platform.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.