Soft Pneumatic Helical Actuator with High Contraction Ratio

Soft contraction actuator has always been an important research field in soft robotics. This paper presents a novel soft contraction actuator which can realize high-ratio contraction when pressurized by pneumatic power. This actuator can be easily made by soft materials including rubber tube, one-way extensible cloth, inextensible cloth and wire. 2 types of structures are presented based on different working circumstances. When pressurized, the actuator can curve and then coil to a helical shape due to the different extensibilities of its opposite sides, a high contraction length and large contraction force can be achieved synchronously. Experiments are conducted to show the relationship between contraction force and contraction ratio of this actuator. The high contraction ratio of this actuator is revealed by comparing with McKibben actuator under the same condition, the maximal contraction ratio reaches 78% and the actuation stress is 8.36kPa.