Research Of The Movable Teeth Drive System Integrated With Shape Memory Alloys

The movable teeth drive system integrated with shape memory alloys is a new type of transmission,in which the movable teeth transmission is driven by SMA wires.The system output torque is achieved by the wave generator doing travelling wave motion.The system has advantages such as simple and compact structure,sensing function of SMA,and a big reduction ratio of the movable teeth transmission.It has wide application prospects in the high-tech field,such as the aerospace,the precision instrument,and the robot,etc.In this paper,the structure design of the system and the analysis of its working principle are carried out.Based on one-dimensional constitutive model of Brinson and the theory of the movable teeth transmission,the multi-field coupled mechanics equations of the system are established.The force and its output characteristics of the system are studied.When the system structure parameters are changed,changes of the forces in the drive along with the output shaft rotation angle are analyzed,and the influence of input current on the output characteristic is studied.The research shows that both rotational speed and output torque of the drive are fluctuant periodically.The simplified model of the free vibration for the drive is obtained by making appropriate assumptions.According to Newton’s second law,the free vibration equation of each component is derived.Considering the coupled boundary condition of the drive and the transmission,the free vibration equation of the system is established.The natural frequency and corresponding vibration mode is obtained.The influence of the structure parameters on the natural frequencies is analyzed.Based on 51 single chip micro-computer,the heating and cooling device is designed.The input control of the movable teeth drive system integrated with SMA is realized.According to choosing the appropriate hardware circuit,the platform of the system control has been set up and the control program is produced.By choosing different external resistances,the voltage source and the period of the software are controlled,and the amplitudes and frequency of control current can be adjusted.Thus,the current input control is achieved for the SMA wires which have various performance parameters.The overall structure design of the system is completed,and the verification of continuity conditions is done.The prototype of the system is produced and assembled.The tension test of the SMA is completed,and the traveling wave displacement of the system is tested.The output characteristic test of the prototype is carried out.The results show that the error between the test speed and the theoretical one is 2.5%.