Dynamic Behavior Analysis Of Self-excited Oscillator Of Photoresponsive Liquid Crystal Elastomer

Liquid crystal elastomer is a kind of deformable and elastic cross-linked polymer intelligent material.It will undergo mechanical deformation under external stimulation,and its mechanical behavior is complex and diverse.Photoresponsive liquid crystal elastomer is a polymer material synthesized by doping photosensitive molecules into liquid crystal elastomer.It can deform or even bend under steady illumination.Studying the mechanical behavior of light responsive liquid crystal elastomers is of great significance for the design of new products in the fields of industry,biology,and medical treatment.Self excited oscillation is a phenomenon that which the system moves continuously and periodically under the stimulation of a stable external environment.It has the advantages of directly obtaining energy from the environment,autonomy,and equipment portability.It is widely used in mechanical engineering,acoustics,electronics,and biomechanics.Synchronization is one of the most basic phenomena in nature.It exists in every corner around us.The study of the self-excited oscillation coupling phenomenon and collective motion of two or more degrees of freedom is helpful to construct richer and more complex motion models and show more functions in microrobots.For complex micro-active robots or microrobots,it is very important to understand the coupling and collective motion of multiple self-excited oscillators.In view of this,based on the dynamic model of liquid crystal elastomer established by Finkelman et al.,this paper constructs a single degree of freedom liquid crystal elastomer self-excited oscillator and a two degree of freedom liquid crystal elastomer self-excited coupling oscillator system respectively.The phenomena of self-excited oscillation and synchronous motion of the two systems are studied in detail,which deepens the understanding of non-equilibrium dynamics and enriches the theoretical system of self-excited oscillation.Firstly,a novel single degree of freedom photoresponsive liquid crystal elastomer fiber oscillator is proposed,which can realize self-excited oscillation under steady illumination.Based on the established dynamic model of liquid crystal elastomer,the self-excited oscillation of the system is studied theoretically.The dynamic governing equations of the oscillation process are derived in detail and numerically calculated.The results show that there are two modes of motion of the elastomer vibrator,namely oscillation mode and static mode.At the same time,the mechanism of self-excited oscillation is also elaborated.Due to the mutual coupling of the photoresponsive deformation of the liquid crystal elastomer fibers and the motion of the mass block,the energy input into the system from the external environment compensates for the damping dissipation and thus maintains the self-excited oscillation of the system.In addition,the critical conditions for triggering self-excited oscillation under different physical parameters are discussed quantitatively.The results show that the fiber spring constant,contraction coefficient,light intensity,gravity acceleration,and damping coefficient can adjust the self-excited oscillation of the system,while the initial velocity does not affect the motion mode of the system.And it is further concluded that the amplitude of self-excited oscillations increases with the increase of elastic constant,contraction coefficient,and light intensity,or with the decrease of the damping coefficient and gravitational acceleration.Meanwhile,increasing the elastic constant decreases the period,while the other parameters have no significant effect on the period.The initial velocity,on the other hand,has no effect on the amplitude and period of self-excited oscillation.Secondly,in this paper,a self-excited oscillation coupled synchronous system with two degrees of freedom consisting of a photoresponsive liquid crystal elastomer fiber and an ordinary spring is constructed based on a single degree of freedom photoresponsive liquid crystal elastomer oscillator.The possibilities and situations of synchronization of two coupled oscillators under the influence of system parameters are theoretically investigated,and the control equations of the synchronized motion are derived in detail.The calculation results show that under the interaction of two mass blocks,the system has three synchronous motion modes: static mode,in-phase mode,and anti-phase mode.Meanwhile,by calculating the evolution of key physical quantities with time,it is found that the mechanisms of self-excited oscillations in the in-phase and anti-phase modes are similar,and the mechanism of self-excited oscillation in the in-phase mode is explained in detail.In addition,the effects of different physical parameters on the amplitude and limit cycle of self-excited oscillation under synchronous motion are discussed,and the critical conditions for two mass blocks to produce self-excited oscillation and realize synchronous motion are obtained.The results show that changing the elastic constant of the spring will affect the synchronous mode,amplitude,and limit cycle of the self-excited oscillation of the system.Changing the light intensity,contraction coefficient,and damping coefficient have no effect on the synchronization mode of self-excited oscillations but has an effect on the amplitude and limit cycle of self-excited oscillations.Different initial conditions have no effect on the synchronization mode,amplitude,and limit circle of self-excited oscillation.Figure[32] table[4] reference[90]...