Rixin Wang

Bio: Rixin Wang is an academic researcher from South China University of Technology. The author has contributed to research in topics: Topology optimization & Compliant mechanism. The author has an hindex of 5, co-authored 14 publications receiving 178 citations.

Topology optimization of a cable-driven soft robotic gripper

Abstract: Improving the functionality of soft continuum manipulators to expand their application space has always been an important development direction for soft robotics. It remains very challenging to calculate the deformations of soft materials and predict the basic structure of soft fingers under complex objective functions and constraints. This work develops a cable-driven soft robotic gripper with multi-input and multi-output using topology optimization considering geometric nonlinearity, which not only performs adaptive grasping but also enables finer manipulations such as rotating or panning the target. A scheme that can describe adaptive grasping behavior is proposed, which converts the contact between the clamping surface and the object into a boundary condition to circumvent complex contact nonlinearities. An additive hyperelasticity technique is used to overcome numerical instabilities, and the finite element analysis is performed in ANSYS. Numerical simulations and experimental results are performed to demonstrate the effectiveness of the optimization algorithm and to illustrate the application potential of the proposed gripper.

Structural Topology Optimization Using a Moving Morphable Component-Based Method Considering Geometrical Nonlinearity

Abstract: The moving morphable component (MMC)-based method is a newly developed approach for topology optimization. In the MMC-based method, the design problem is formulated using a set of morphable components, and the optimized structural topologies are obtained by optimizing shapes, sizes, and locations of these components. However, the optimization process often tends to break the connection between the load area and the supported boundary. This disconnection has a strong influence on the convergence, especially when the large deformation effects are considered. In this paper, a method is developed for topology optimization of geometrically nonlinear structures by using the MMC-based method. A scheme is developed to address the disconnection issue in the optimization process. Several numerical examples are used to demonstrate the validity of the proposed method.

An 89-line code for geometrically nonlinear topology optimization written in FreeFEM

Abstract: Topology optimization has emerged as a powerful tool for structural configuration design. To further promote the development of topology optimization, many computer programs have been published for educational purposes over the past decades. However, most of the computer programs are constructed based on a linear assumption. This paper presents an 89-line code for nonlinear topology optimization written in FreeFEM based on the popular SIMP (solid isotropic material with penalization) method. Excluding thirteen lines which are used for explanation, only 76 lines are needed for the initialization of the design parameters, nonlinear finite element analysis, sensitivity calculation, and updated design variables. Different design problems can be solved by modifying several lines in the proposed program. The complete program is given in the Appendix and is intended for educational purposes only.

Additive manufacturing of metallic lattice structures: Unconstrained design, accurate fabrication, fascinated performances, and challenges

Abstract: Lattice structures, which are also known as architected cellular structures, have been applied in various industrial sectors, owing to their fascinated performances, such as low elastic modulus, high stiffness-to-weight ratio, low thermal expansion coefficient, and large specific surface area. The lattice structures fabricated by conventional manufacturing technologies always involve complicated process control, additional assembly steps, or other uncontrollable factors. Furthermore, limited types of unit cells can be used to construct lattice structures when using conventional processes. Fortunately, additive manufacturing technology, based on a layer-by-layer process from computer-aided design models, demonstrates the unique capability and flexibility and provides an ideal platform in manufacturing complex components like lattice structures, resulting in an effective reduction in the processing time to actual application and minimum of material waste. Therefore, additive manufacturing relieves the constraint of structure design and provides accurate fabrication for lattice structures with good quality. This work systematically presents an overview of conventional manufacturing methods and novel additive manufacturing technologies for metallic lattice structures. Afterward, the design, optimization, a variety of properties, and applications of metallic lattice structures produced by additive manufacturing are elaborated. By summarizing state-of-the-art progress of the additively manufactured metallic lattice structures, limitations and future perspectives are also discussed.

A review on feature-mapping methods for structural optimization

Abstract: In this review we identify a new category of methods for implementing and solving structural optimization problems that has emerged over the last 20 years, which we propose to call feature-mapping methods. The two defining aspects of these methods are that the design is parameterized by a high-level geometric description and that features are mapped onto a non-body-fitted mesh for analysis. One motivation for using these methods is to gain better control over the geometry to, for example, facilitate imposing direct constraints on geometric features, while avoiding issues with re-meshing. The review starts by providing some key definitions and then examines the ingredients that these methods use to map geometric features onto a fixed mesh. One of these ingredients corresponds to the mechanism for mapping the geometry of a single feature onto a fixed analysis grid, from which an ersatz material or an immersed-boundary approach is used for the analysis. For the former case, which we refer to as the pseudo-density approach, a test problem is formulated to investigate aspects of the material interpolation, boundary smoothing, and numerical integration. We also review other ingredients of feature-mapping techniques, including approaches for combining features (which are required to perform topology optimization) and methods for imposing a minimum separation distance among features. A literature review of feature-mapping methods is provided for shape optimization, combined feature/free-form optimization, and topology optimization. Finally, we discuss potential future research directions for feature-mapping methods.