Compliant mechanisms are widely used in the design of medical robotics and devices because of their monolithic structure and high flexibility. Many compliant mechanisms derive their design ideas from nature, since the structure of biological organisms sometimes offers a better solution than the conventional mechanisms. However, the bio-inspired structures usually have very complex geometries which cannot be easily modeled and analyzed using traditional methods. In this paper, we present a novel finite element method (FEM) based modeling framework in Matlab to analyze the mechanics of different bio-inspired compliant mechanisms. Since the basic linear FEM formulation can only be employed to model small displacements of compliant mechanisms, a non-linear FEM formulation that integrates the modeling of large displacements, tendon-driven mechanisms and contact problems was implemented in the proposed framework to overcome the limitations. Simulations and experiments were also conducted to evaluate the performance of the modeling framework. Results have demonstrated the accuracy and plausibility of the proposed non-linear FEM formulation. Furthermore, the proposed framework can also be used to achieve structural optimization of bio-inspired compliant mechanisms.

Compliant mechanisms are widely used in the design of medical robotics and devices because of their monolithic structure and high flexibility. Many compliant mechanisms derive their design ideas from nature, since the structure of biological organisms sometimes offers a better solution than the conventional mechanisms. However, the bio-inspired structures usually have very complex geometries which cannot be easily modeled and analyzed using traditional methods. In this paper, we present a novel finite element method (FEM) based modeling framework in Matlab to analyze the mechanics of different bio-inspired compliant mechanisms. Since the basic linear FEM formulation can only be employed to model small displacements of compliant mechanisms, a non-linear FEM formulation that integrates the modeling of large displacements, tendon-driven mechanisms and contact problems was implemented in the proposed framework to overcome the limitations. Simulations and experiments were also conducted to evaluate the performance of the modeling framework. Results have demonstrated the accuracy and plausibility of the proposed non-linear FEM formulation. Furthermore, the proposed framework can also be used to achieve structural optimization of bio-inspired compliant mechanisms.

Purpose Compliant mechanisms are commonly used in the design of manipulator and surgical robotic tools for minimally invasive surgery (MIS) thanks to their compactness, ability of miniaturization and lower part count. However, conventional compliant joint has higher internal stiffness, which limits the bending radius. To overcome this problem, a novel tendon-driven manipulator structure based on monolithic compliant rolling-contact joint (CRCJ) is proposed. Methods The proposed rolling-contact mechanism is used to prevent cable slack during actuation, which occurs in conventional compliant joint design. By means of selective laser sintering (SLS) technique, the CRCJ can be fabricated in a monolithic structure, thus granting the CRCJ both the advantages of compliant joints and rolling-contact mechanism. Simulations with nonlinear finite element analysis (FEA) and experiments were conducted to evaluate and compare the mechanical properties of the proposed CRCJ with conventional leaf-type compliant joint including the bending and compliant motion. Results Experimental results showed that the CRCJ has lower bending stiffness, higher maximum bending angle (over $$180^{\circ }$$ 180 ∘ ) and a higher compliance compared to conventional compliant hinges, which allows a larger workspace and reduces the possibility of tissue injury. Agreement was also found between the nonlinear FEA and experiments regarding the relation between actuation force and bending angle. A primary prototype of a 3-DOF handheld laparoscopic manipulator with a diameter of 7 mm was further developed. Conclusion A dexterous tendon-driven monolithic manipulator structure based on CRCJ for MIS is proposed. A preliminary prototype of a handheld laparoscopic manipulator demonstrates the capability of the CRCJ for steerable medical devices. However, design improvements based on FEA and application-orientated prototypes considering anatomical requirements still show room for improvements.

The rapid development of digitalization and 3D printing is creating an ever-increasing demand for methods for the automated generation of 3D models from real components. Thanks to the progress and widespread use of computer vision, it is now possible to merge classical engineering tasks with image processing techniques. Computer aided design can therefore be automated using information from image data. In this work, we present a novel method for automated digitization of 3D structures using AprilTag fiducial system and Solid Geometry Library. The proposed design process is implemented in MATLAB. AprilTags are used to realize 3D coordinate measurements in order to digitally capture the 3D dimensions of real components. Based on these data, 3D replica models are generated with the Solid Geometry Library toolbox, which enables automated design of 3D surface models in MATLAB. The mathematical background of this procedure is described in detail. The capability of the proposed method is demonstrated on 3D structures composed of components with fixed cross-sections and fundamental 3D structures such as prisms, cylinders, and spheres. Further improvements in the coordinate measurement process using AprilTag and further implementation in MATLAB can extend the functionality for the digitization of more complex 3D structures.

Due to its monolithic structure and high dexterity, the compliant mechanism becomes an emerging solution to miniaturize surgical forceps for minimally invasive procedures. However, it is complicated and inefficient to use traditional rigid-link-based kinematic method to synthesize compliant forceps. In this paper, we present a topology-optimization-based method to automatically synthesize compliant forceps for robot-assisted minimally invasive surgery (RMIS). The basic geometry modeling tool and the automatic synthesis algorithm were both implemented in Matlab. Several synthesis examples were presented to show the performance of the proposed method. The realized forceps and a continuum manipulator have been constructed and 3D-printed, which demonstrated the application of the automatic synthesis method in RMIS.