Boosting Actuator Performance with Elastic Bands
To create bending of an inflatable textile actuator, an imbalance between two layers of fabric must be achieved. This imbalance is created by using pleating techniques, excess material of one layer is folded and stitched onto the other, and unfolds when inflated. This approach, however, has potential drawbacks, e.g. when the space between the layers is too small for the pleats to unfold (which, for finger sized designs, can become imminent). Another technique to create such imbalance is the use of different types of fabric with varying elasticity. This way, one layer stretches more when actuated and the structure will bend towards the less elastic one. Integrating braided elastic band to the stretch fabric option with the ruffles technique is proven more efficient in terms of blocking force and bending angle capabilities. Component view of the elastic band actuator can be seen on the left.
Two important parameters for soft bending actuators for wearables are flexion angle and blocking force. In example, for rehabilitation or assistive hand exoskeletons it is imperative that each finger is unrestricted in relation to its maximum angle, and actuators should apply 10-15 N blocking force to the fingers.
The elastic band integration boosts both of these critical parameters for the actuator. The force capability increases approximately from 10 N to 25 N, and maximum bending angle increases from approximately 180 degrees to 360 degrees.
Another quality of this actuator is it being pressure efficient. The actuator can apply about 15 N force to the environment with just 60 kPa pressure. So to actuate this structure a smaller air compressor can be used when compared to other soft pneumatic actuators.
The video on the left shows our novel elastic band integrated fabric actuator. This actuator is tailored such that it can apply high forces to the environment and can bend high angles even with low input pressure values.
To see how to fabricate the elastic band integrated actuator please check the video on the right. The method used to create the actuator is called "Ruffles". (Music by Kaspar Althoefer)
Check out more about the elastic band integrated actuator below.
To read more about elastic band integrated fabric actuators, see our soft hand exoskeleton prototype below.