Static Characteristic Analysis of a New Type of Pneumatic Bending Joint

Aiming at the bending angle limit of existing pneumatic bending joints at low pressure, an idea of using structural angle to implement the bending action is proposed. And a new type of pneumatic bending joints with two flexible pneumatic actuators (FPAs) as its drive source is designed. This joint includes one T-type structure, two rotating structures which can perform circular motion around the hinge, and two symmetrical FPAs. And two symmetrical FPAs are fixed on the T-type structure and the rotating structure. The two FPAs stretch to push rotating structure to move when inner air pressures are changed, which leads to an angle between rotating structures, and thus bending motion of the joints is achieved. The static characteristics of the turning end of FPA on the bending joint are analyzed based on the moment equilibrium principle. Simulation analysis and experimental results show that angle-pressure ratio of the new pneumatic bending joint is higher than traditional ones. It means that the larger bending angle can be gotten at lower pressure. Besides, the bending angle of the bending joint is nonlinear with the air pressure inside the FPA and the bending angle changes with the structure parameters.