Sensorized, Flat, Pneumatic Artificial Muscle Embedded with Biomimetic Microfluidic Sensors for Proprioceptive Feedback.

In recent years, soft components, such as pneumatic artificial muscles (PAMs), have been increasingly employed to design safer wearable devices. Despite the inherent compliance of the materials used to fabricate PAMs, the actuators are able to produce relatively large forces and work when compared to their weight. However, effective operation of these systems has traditionally required bulky external force and position sensors, which limit the maneuverability of users. To overcome these issues, inspiration was taken from organic muscles, which incorporate embedded sensors, such as Golgi tendon organs and muscle spindles, to provide real-time position and force feedback for muscles. As such, a sensorized, flat, pneumatic artificial muscle (sFPAM) with embedded force and position sensors was designed and fabricated. In addition, a hyperelastic model was developed and verified through comparison with the experimentally characterized mechanical and electrical performance of the sFPAM. Furthermore, a sliding mode controller was implemented to demonstrate the feasibility of embedded sensors to provide feedback during operation. Ultimately, a lightweight, compact actuation system was designed with the ability to be seamlessly incorporated into future wearable devices.

Design of a bio-inspired pneumatic artificial muscle with self-contained sensing.

Pneumatic artificial muscles (PAMs) are one of the most famous linear actuators in bio-inspired robotics. They can generate relatively high linear force considering their form factors and weights. Furthermore, PAMs are inexpensive compared with traditional electromagnetic actuators (e.g. DC motors) and also inherently light and compliant. In robotics applications, however, they typically require external sensing mechanisms due to their nonlinear behaviors, which may make the entire mechanical system bulky and complicated, limiting their use in simple systems. This study presents the design and fabrication of a low-cost McKibben-type PAM with a self-contained displacement and force sensing capability that does not require any external sensing elements. The proposed PAM can detect axial contraction force and displacement at the same time. In this study, the design of a traditional McKibben muscle was modified to include an inductive coil surrounding the muscle fibers. Then, a thin, soft silicone layer was coated outside of the muscle to protect and hold the sensing coil on the actuator. This novel design measures coil inductance change to determine the contraction force and the displacement. The process can be applied to a variety of existing McKibben actuator designs without significantly changing the rigidity of the actuator while minimizing the device's footprint.