Design and Analysis of a Novel Soft Actuator with High Contraction Ratio Based on Nested Structure

Considering the drawbacks of existing soft actuators used in narrow unstructured space, such as lower expansion ratio and smaller driving force, a soft actuator with high stretch-draw ratio is designed in this paper. Based on TPU(Thermoplastic polyurethanes) airbags, the actuator is designed by the use of nested structure combined with rope mechanism, which achieves a large expansion ratio (115%) on the premise of ensuring the rest size of the actuator. Then, according to the structural characteristics of the actuator, the static driving characteristics of TPU airbag and rope mechanism of the actuator are deduced by analytical and geometric methods. So the static model of output force of the actuator is obtained. Finally, a modeling method of using displacement-driven variable load instead of rope mechanism to construct simulation model is proposed. This research lays the foundation for the follow-up study of the actuator's dynamic characteristics and control strategy.