# Flexible Design of the Connecting Plate in Pneumatic Soft Manipulators
### Related Works  
A pneumatic flexible manipulator achieves motion mainly through non-linear deformation of the silicone material, which is different from the rotational motion of a rigid robotic arm at the joints. Therefore, chambers become the most common actuators in pneumatic arms, which act like pneumatic artificial muscles and are realized by the expansion or contraction of the chambers [12; 13; 14]. The structural design of the chamber needs to consider a sufficient deformation capacity, and the structure of the bellows can provide redundant surfaces to ensure that the chamber can elongate and contract. Therefore, three chambers used in parallel to form a section of an arm are widely used in the structural design of pneumatic manipulators. An arm composed of multiple segments connected in series can achieve more flexible movements. It is necessary to fix these chambers with components such as a manifold to connect each section [15]. The novel flexible connection plate proposed in this paper has fine mechanical properties and can be used as a general design method for multi-segment structures [16]. A popular approach to modeling continuum robots has been already established to model rigid manipulators: researchers select the key kinematic parameters in a model--the arc, the curvature, and the orientation angle--to establish a transformation equation in the task space and apply it at every segment of the manipulator [17; 18; 19]. The shape and position of the soft manipulator are hard to describe because of the flexibility of the material. It is usually made up of silicone and shows nonlinear deformation. A robotic arm consisting of rotating or moving joints uses four linkage parameters to describe the mechanism's motion relationship, called the Denavit-Hartenberg method. However, obtaining accurate kinematic equations for flexible manipulators is usually challenging [20]. [PERSON] et al. presented a ball joint for a cable-driven soft manipulator considering the blocking effect [21]. It can be efficient in a cable-driven manipulator but is unsuitable for a structure that expands or contracts. Similarly, establishing a discrete model is essential to illustrating the change in parameters for dynamics modeling [22; 23]. Stiffness is not a constant factor in the model because of the nonlinear elasticity. The position of the connecting plate in relation to the chambers is relatively stationary, and this fact causes stress to easily accumulate due to actuation pressure from the chambers. Therefore, as the components of a soft manipulator, it could affect the accuracy of the position and shape via the conduction of actuation moment from chambers. Additionally, the connecting plate prevents stress from coupling due to the flexible deformation.  
To sum up, the development of soft manipulators originated from bionics, and their feasibility has been proven using kinematic modeling. However, further research is needed due to the limitations of the materials' characteristics and the structural design. Based on bionics, this paper aims to design a novel connecting plate as a flexible joint to achieve greater flexibility for the manipulator.