Basic Study On Valveless Micropump Driven By Shape Memory Alloy

Precision motion and position control actuators which can provide greater forces and torques within given volume and weight are in great need in modern industry. Nowadays, more and more functional materials can be adopted to generate mechanical moving. New kinds of actuators based on smart materials are paid more attention to. NiTi Shape Memory Alloy would have unique latent application in miniature or small scale robot because of some merits, such as great power rate, integration between sense and actuators, large strain etc.In this thesis, the crystal structure and shape variation mechanism of SMA are analyzed. The Martensite structure and the constitutive relation of SMA are presented. In this dissertation some main research works are presented as following: 50.8at%-Ni-Ti memory alloy is chosen for the best general property by the comparison with other several present smart materials in actuating properties. The relationships among strain, stress, and temperature and phase transformation of shape memory alloy (SMA) are presented as base theory of development and application of embedded SMA actuator.Next, the relationships among current, strain rate, displacement, phase transition temperature and working principle of the differential SMA spring actuator are discussed, and the operation principle of the differential SMA actuator is described also. A parallel-type differential SMA actuator are designed and made and its characteristics are studied, PWM electrical heating and liquid cooling are chosen for actuator in order to get best operation frequency for differential actuators. The experiments showed that, the actuator can output great force and displacement with a simple structure and control system. Displacement and deformation rate rise with the increase of current in a certain range. The differential SMA actuator with a special structure can operate on higher frequency, provide greater force and have a high efficiency.Finally, in this thesis, a valveless pump driven by the parallel-type differential SMA actuator is proposed. The design principle of the differential SMA actuator and the one-way flow mechanism and structure design of the valveless pump has been analyzed. A prototype and the control system have been developed successfully. The analysis of flow field has been finished, and the preliminary test has been taken. The feasibility of the operation principle and design method of the valveless pump driven by the SMA actuator has been proved by the analysis and test results.