The Development of a Continuum Hydraulic/Pneumatic Actuator for Enhancing Gripping Function

This paper describes a research project being conducted to develop a flexible actuator to be used in orthotic and robotic devices. A unique Continuum Hydraulic/Pneumatic Actuator (CHPA) has been designed at the University of Wisconsin-Madison Fluid Power Research Laboratory (UW-FPRL). As the name suggests, the CHPA can be hydraulically or pneumatically energized to produce a pushing force. The actuator is being developed to flex fingers to assist the gripping capability of persons who have a combination of diminished strength and motor control. The CHPA is implemented within a powered hand orthosis (PHO) and can feasibly be used with end effectors. A glove-like, non-bulky, and non-patient specific PHO prototype was fabricated to be used in conjunction with the actuator. Test results indicate that with component development and improved fabrication methods, the performance of the CHPA can be optimized for common gripping tasks. At an operating pressure of 120 psi (830 kPa) an actuator 0.35 inches (9 mm) in diameter and 4.5 inches (114 mm) in length provides (distal) pushing forces between 5–6 pounds (22–27 N) and produces corresponding (palmar) finger-tip forces in the range of 2–5 pounds (9–22 N). Future efforts will focus on optimizing the CHPA mechanism, it’s configuration within the orthosis and integrating a suitable control interface.Copyright © 2007 by ASME