Volume Transfer: A New Design Concept for Fabric-Based Pneumatic Exosuits

The fabric-based pneumatic exosuit is now a hot research topic because it is lighter and softer than traditional exoskeletons. Existing research focuses more on the mechanical properties of the exosuit (e.g., torque and speed), but less on its wearability (e.g., appearance and comfort). This work presents a new design concept for fabric-based pneumatic exosuits: volume transfer, which means transferring the volume of pneumatic actuators beyond the garment's profile to the inside. This allows for a concealed appearance and a larger stress area while maintaining adequate torques. In order to verify this concept, a fabric-based pneumatic exosuit is developed for knee extension assistance. Its profile is only 26 mm and its stress area wraps around almost half of the leg. A mathematical model and simulation is used to determine the parameters of the exosuit, avoiding multiple iterations of the prototype. Experiment results show that the exosuit can generate a torque of 7.6 Nm at a pressure of 90 kPa and produce a significant reduction in the electromyography activity of the knee extensor muscles. It is believed that volume transfer can be utilized prevalently in future fabric-based pneumatic exosuit designs to achieve a significant improvement in wearability.