Research Of Coupling Dynamics Of Swing Movable Tooth Transmission System With Shape Memory Alloys

Swing movable tooth transmission system with SMA is a highly integrated and innovative micro-electromechanical system,which integrates SMA sensing,control,driving and movable tooth transmission functions.Quantitative output torque is achieved by sensing temperature changes in complex environments or by precise temperature control.Compared with traditional motors,it has the advantages of simple structure,low speed,large torque and easy miniaturization.It is especially suitable for the cutting-edge technology fields such as micro-robots,micro-satellites and lunar probe,and has broad application prospects.In this paper,the working principle of swing movable tooth transmission system with SMA is analyzed,and the coupling mechanical model of SMA wire phase change drive and movable tooth transmission is established.The output torque equation of the system is deduced.It is found that swing movable tooth transmission system with SMA presents periodic large fluctuation.The influence of coupling parameters such as swing rod amplification factor and movable tooth eccentricity on the output characteristics of the system is investigated.On the basis of continuous body vibration theory,elastodynamics theory and SMA phase change theory,a coupled dynamic model of swing movable tooth transmission system with SMA is established.The natural frequencies and vibration modes of the system is solved,and the influence of parameters on the natural frequencies is investigated.Considering that external excitation and meshing stiffness excitation of the swing movable tooth transmission system with SMA,the forced response vibration equations of the SMA driving part,the movable tooth transmission part and the whole coupling are derived,and the influence of excitation frequency and system parameters on the forced response is analyzed.Considering the non-linear constitutive relation of SMA phase and the non-linearity caused by meshing stiffness change of movable tooth,the non-linear vibration models and equations of driving and transmission parts of swing movable tooth transmission system with SMA is established.The response equations of weakly nonlinear free vibration,forced vibration near resonance and far from resonance have been deduced.The natural frequency,response mode and amplitude-frequency characteristics of the system as well as the influence of the parameters on it is given.Based on the structure design of the swing movable tooth transmission system with SMA,the processing and adjustings of the prototype are completed,and the output characteristics and natural frequencies of the prototype are tested.By comparing the calculated values with the experimental data,it is found that the output speed of the prototype is consistent with the theoretical values.The maximum torque of the prototype is 7.36 Nmm,the error between the theoretical trough torque and the measured torque is 12.59%.The natural frequencies of the prototype are simulated and tested by ANSYS software and hammering method,and the maximum errors are 10.4% and 17.2% respectively.The feasibility of the system and the correctness of the theoretical analysis are verified.