Soft origami tripod based on electrohydraulic actuator for twisting motion

The twisting motion is essential for its fundamental role in enabling efficient object manipulation. Motivated by this feature, this study proposes a novel soft origami tripod capable of twisting motion using electrohydraulic actuators. The soft origami tripod consists of an origami joint structure connected by three parallel Kresling pattern-supporters and electrohydraulic actuators. The actuator inflates instantaneously by an applied voltage and induces the deployment mechanism of the origami joint structure. By designing the origami joint structure according to the trajectory determined by the pattern, the proposed tripod stably achieves a helical twisting motion combining extension and rotation. At an input voltage of 10 kV, the tripod can accomplish a maximum linear strain of 265 % and a maximum rotation angle of 69°. Geometrical and kinematic mathematical models are presented to analyze the motion of the tripod. The model is experimentally validated to establish a relationship between strain and angle and to predict mechanical performances. Additionally, we conduct a series of experiments to investigate the continuous and stable twisting motion of the tripod.