Design And Research Of Shape Memory Alloy Buoyancy Actuator

Autonomous underwater glider(AUG)is one of the important means of ocean observation and detection.It can carry all kinds of mission sensors to independently complete the diving and floating movement in the sea water through buoyancy regulation,and collect the temperature,salinity and other data information of the sea water.The buoyancy drive is a key link in the buoyancy adjustment process of AUG,which is related to whether the AUG can reach the specified depth and collect data smoothly or float to the surface and be recovered smoothly after diving.Most of the existing AUGs adopt the variable volume buoyancy adjustment mode,and the motor drives the oil pump to discharge the oil.Generally,the buoyancy driving part has a large mass,complex structure and low buoyancy adjustment accuracy.Therefore,in order to make the buoyancy adjustment system lightweight and control the buoyancy adjustment accurately,a buoyancy actuator for AUG is designed based on the deformation mechanism of shape memory alloy(SMA).The main research contents and achievements are as follows:1.The deformation driving mechanism of SMA is studied and the appropriate SMA is selected.The phase transition temperature and basic mechanical properties of SMA are tested and the test data are used to guide the design of the SMA buoyancy actuator2.The offset and electric heating buoyancy drive scheme based on SMA is determined,and the dynamic model of buoyancy driver is established.The design method of buoyancy driver for different buoyancy adjustment depth is proposed.The s SMA buoyancy actuator structure is designed,and the designed buoyancy actuator has the characteristics of light weight,simple structure,and small volume.The SMA shrinks simply by electric drive,and it doesn’t need to rely on other moving parts to drive.The whole process can avoid the noise of AUG and make it easy to hide.The buoyancy driving process of SMA is discontinuous,and the single minimum adjustment is 1m L,which effectively improves the accuracy of buoyancy adjustment of AUG.3.The thermodynamic model of SMA buoyancy actuator is established.The influence of current intensity on the temperature change and deformation driving process of SMA is described by finite element simulation under the coupling of electric,thermal and mechanical fields.The driving characteristics of the designed buoyancy actuator are obtained,and the optimal current intensity is determined.The accuracy of the model is verified by experiments.4.The temperature control strategy of buoyancy actuator based on resistance feedback is proposed,and the PI(proportional,integral)controller is designed.By analyzing the relationship between resistivity and metallography,metallography and temperature in the process of SMA phase transformation,the relationship between resistivity and temperature is deduced,It can control the temperature of SMA by judging the resistance value of SMA,make it stable at the minimum temperature required for deformation,avoid the failure caused by SMA overheating,and realize the low power consumption control of the designed buoyancy actuator.