Conformal Topology Optimization of Ferromagnetic Soft Robots Using an Extended Level Set Method

Ferromagnetic soft active structures using embedded ferromagnetic particles in the soft polymer matrix can generate flexible locomotion and change configurations remotely, rapidly, and biologically friendly with an applied magnetic field. To achieve the desired motion, these soft active structures can be designed by tailoring the layouts of the ferromagnetic soft polymer. Structural topology optimization has become a promising method to achieve innovative structures by optimizing the material layout, opening a new path for architecting ferromagnetic-driven active structures. Given the widespread adoption of thin-shell structures for soft robots, the extended level set method (X-LSM) and conformal geometry theory are employed to perform topology optimization of the ferromagnetic soft active structures on manifolds. The boundary evolution on a freeform 3D surface can be transferred into a 2D rectangular plane by solving a modified Hamilton–Jacobi equation weighted by conformal factors. The design objective consists of a subobjective function for kinematic requirement and a subobjective function for minimum compliance. The proposed method was applied to design several ferromagnetic soft active structures. Topologically optimized designs have been printed using functional 3D printing technology, to physically realize soft active structures with built-in functionalities. The results of the numerical verification and experimental validation demonstrate the effectiveness of the proposed design and fabrication framework.

Methodology
Numerical Examples

Representative Publications:

  1. Tian, J., Li, M., Han, Z., Chen, Y., Gu, X. D., Ge, Q. J., Chen, S., Conformal Topology Optimization of Multi-material Ferromagnetic Soft Active Structures using an Extended Level Set Method, Computer Methods in Applied Mechanics and Engineering, 389, p. 114394, 2022.
  2. Tian, J., Zhao, X., Gu, X. D., Chen, S., Designing Conformal Ferromagnetic Soft Actuators Using Extended Level Set Methods (X-LSM), ASME Proceedings of IDETC/CIE, vol. 83990, V010T10A01, 2020.
  3. Tian, J., Zhao, X., Gu, X. D., Chen, S., Designing Ferromagnetic Soft Robots (FerroSoRo) with Level-Set-Based Multiphysics Topology Optimization, Proceedings, IEEE International Conference on Robotics and Automation (ICRA), 10067–10074, 2020.