Design, modeling and characterization of a joint for inflatable robotic arms

Abstract

This paper investigates the design and modeling of a joint for inflatable robotic arms (IRAs) towards long-range inspection. A primary trade-off design is elaborated in view of materials, fabrication and actuation through the detailed comparison of some existing IRAs. Antagonist pneumatic artificial muscles (PAMs) are selected to actuate each joint that is fabricated from low-cost fabrics or films. A novel static joint model is proposed by taking into account both the stiffness of irregular-shaped inflatable tubes and the nonlinear issue of PAMs, without the need for numerous experiments or computationally expensive algorithms. The proposed modeling approach, which aims to predict joint behaviors analytically, is experimentally validated on two different prototypes. Particularly, the integration of the beam and membrane models is introduced, so that the stiffness model achieves the most accurate prediction with a mean absolute percentage error (MAPE) of 21.60 % as compared to its separate counterparts. Following this, the model-based optimization of the IRA joint is carried out for a further trade-off among its motion range, payload capacity and weight. Experiments on the optimized prototype are conducted to characterize its bending modality and force output, showing the great potential of our method for some specific applications, e.g., disaster inspection, space exploration and domestic assistance.