Design and characterisation of a multi-DOF soft pneumatic module

Bending and elongation have been some of the most studied motions in soft actuators due to the variety of their applications. For that matter, multi-DOF actuators have been developed with the purpose to generate different movements in a single actuator, mainly bending. However, these actuators are still limited in mobility range, and some of them do not perform continuous curvatures. This paper presents the design, characterisation and implementations of a multi-DOF soft pneumatic module. The internal structure of the proposed module is composed of four channels, which generate bending in several directions. The finite element method analysis demonstrates that the actuator performs continuous curvatures for different pressure values. We present a repeatable and easy manufacturing process using the casting technique, considering the material Ecoflex 00-50; as well as the kinematic model of the actuator, taking into consideration two bending Degrees of Freedom (DOFs). Furthermore, we performed bending characterisation for all possible combinations of the four channels via computer vision, demonstrating a wide mobility range and performing continuous curvatures. Additionally, we evaluated the kinematic model with characterisation data, obtaining the angular and cartesian relationship between the pressure and continuous curvatures. On the other hand, the authors propose the design of a modular soft manipulator based on two multi-DOF modules. The kinematic model is reported. In addition, we implement a motion sequence in the manipulator to pick and place tasks.