Responses of rings with light-activated shape memory polymers regulated by neural network and phase shift

Abstract

Light-activated shape memory polymer is able to hold the temporary shape and to change the permanent shape upon exposures of ultraviolet lights with specific wavelengths. The study aims to provide a non-contact and temperature-independent technique to suppress the vibration of rings using light-activated shape memory polymer. Forced responses of flexible rings laminated with light-activated shape memory polymer patches are evaluated. Dynamic equations of light-activated shape memory polymer–laminated rings are established first. With the modal expansion method, the modal force of light-activated shape memory polymer actuators is derived and then the modal responses (with or without control) are evaluated. A generic kth order and its simplified light-activated shape memory polymer constitutive equations are established based on the chemical kinetics. Light-activated shape memory polymer shows the dynamic stiffness when exposed to ultraviolet lights, and this feature is reflected in its constitutive equations influenced by light intensity, material constant, thickness, and so on. With these derivations, the relationship of light intensity and modal force is established and it exhibits a hysteresis phenomenon. The procedure of identifying the hysteresis model using the neural network is described. Then, the phase shift and neural network control techniques are, respectively, applied to enhance the control effects. The neural network vibration control (with a maximal reduction in 98.1%) is very effective to improve light-activated shape memory polymer’s actuation capability.