Control-Based Adaptive Behavior for 4-D Printed Flexible Intelligent Structure

4-D printed structures have excellent application prospects in defense, aerospace, medical, and other fields due to their alterable shape and function. Current 4-D printed structures are limited to make predefined shape changes in response to particular external stimuli by the design of the materials and structures. However, it is crucial to achieve adaptive accurate control of its deformation in a dynamic environment, particularly in highly sensitive tasks. Therefore, we propose a deformation regulation strategy for a 4-D printed flexible intelligent structure based on an adaptive integral terminal sliding mode controller. The effectiveness of the algorithm is verified using a lab-made finger structure made of Liquid Crystal Elastomer as a 4-D printed structural part. Considering the condition of disturbed and nonpredetermined external excitation, the bending angle of the finger joint can be stable within $\mathbf {\pm 2.1\%}$ of the expected value based on the feedback of the self-sensing information, which enables collaborative tracking of the deformation state of the external human finger. This controller-based, adaptive, and accurate deformation regulation is not possible with the existing 4-D printed deformation structures and has not yet been reported nationally or internationally.