Computational Design of Active Lattice Structures for 4D Printed Pneumatic Shape Morphing

Abstract

With advances in 3D printing and digital fabrication an opportunity is presented to realize highly customized designs whose shape can change and adapt to facilitate their functionality. A computational design method to determine the configuration of 2D pneumatic shape morphing lattices using a direct search method is implemented and assessed. The method is tested using a Kagome unit cell lattice structure, which is particularly well suited for shape morphing. To achieve shape change, beams are replaced by linear actuators such as those found in pneumatic 4D printing, whose number and placement are optimized to replicate a given target shape. The actuator placement and deformation accuracy are given for four main curvature changes: linear, convex, concave and the transition from one to the other. The results are assessed in terms accuracy of deformation and computational effort. It is shown that the method proposed produces structures that can replicate complex shape changes within 1% of the desired shape. Reducing the number of actuators for robustness purposes is shown to affect the results minimally.

Actuator placement optimization in an active lattice structure using generalized pattern search and verification

“…They offer similar shape morphing accuracy but have not verified their results with a physical prototype. The maximal range of deformation of this work is within the top three of the publications in table 4, considering that du Pasquier et al [16] shows only numerical results and Sofla et al [15] manually replaces nearly half its structure with actuators. Both of these authors achieve three target deformations, whereas this work achieves four.…”

“…However, as mentioned previously, statically and kinematically determinate structures are shown to need the least activation energy [12]. The accuracy of control can be compared only with Baker and Friswell [2] and previous work by the authors, du Pasquier et al [16], since only they optimize for a precise target shape change. They offer similar shape morphing accuracy but have not verified their results with a physical prototype.…”

“…Determining the layout of sets of actuators in a lattice structure to deform it into a target shape is a non-linear and discrete design problem whose complexity increases exponentially with the total number of elements in the lattice. It is possible to determine the actuator layout for certain simple target displacements experimentally through trial and error if the lattice is small enough [1,14,16]. However, this approach is not scalable and can only achieve an approximation of a target shape.…”

“…In SR, deformation and control are directly embedded into an actuator's design [28]. The compliant materials are generally light, highly deformable, and can be pressurized to carry significant loads [16]. Previously limited in design complexity by the available fabrication methods, due to advances in additive manufacturing (AM) these soft pneumatic actuators can now be 3D printed to meet the requirements of shape morphing structures.…”

A nonlinear optimization method for large shape morphing in 3D printed pneumatic lattice structures

“…In the cases where it has been validated, shape morphing has been demonstrated experimentally with the following actuation methods: shape memory alloys (SMAs) [8][9][10][11] or polymers (SMPs) [9,12,13], electromechanical components such as servo and stepper motors [14][15][16][17], and piezoelectric stacks. Previous work from the authors also introduced pneumatic linear actuators for 2D and 2.5D shape morphing structures [5,18].…”