Fabrication, Characterization and Control of Knit-Covered Pneumatic Artificial Muscle

This paper presents the design, fabrication, characterization, and validation of three kinds of knit-covered pneumatic artificial muscle (called k-PAM) actuators, in which three different knits are made by braiding silver-plated (conductive) yarn and non-conductive yarns with different stitch methods. After a successful characterization process, these k-PAM actuators are able to provide feedback information on actuator length corresponding to the applied pressure. A complete fabrication method is proposed to make the actuator work for higher pressures (up to 300 kPa or more). Furthermore, since the force generated by the actuator is decoupled from the external force, ultimately, it can be directly used to measure both the length and the force. This paper contains the detailed characterization processes, the experimental validations of the sensing ability, and the several characteristics of the k-PAM actuators. It is expected that the k-PAM actuator can be used directly for robotic applications in higher pressure conditions, while the semi-permanent conductive knit cover provides the actuator with durability in highly repetitive situations.