Design and Characteristic Analysis of Actuators Made of Magnetically Controlled Shape Memory Alloy

Precision motion and position control actuators that can provide greater forces and torques within given volume and weight are in great need with the development of micro automation and computer control technology. The low power density and the complex power-driven and control system along with the relatively big volume of the traditional linear actuators make them hard to be widely used in the modern industry. New kinds of actuators based on smart materials are attracting more and more interests. The magnetically controlled shape memory alloy (MSM) is a new type of shape memory alloy, which has not only large shape variation and fast dynamic response but also high power density and high efficiency of electromechanical energy conversion. This material is particularly suitable for applications of high precision motion and position control actuators.In the paper, the shape variation mechanism of MSM is investigated. The work temperature range of MSM is measured by a differential scanning calorimeter (DSC). The relationship between the MSM strains and the varying of temperatures, magnetic fields and pre-stresses are ascertained by the static and dynamic test on equipments specially designed.Two new-style actuators-the inchworm MSM linear motor and the differential control MSM actuator are designed. The detailed design of them and their control systems are thoroughly discussed in this paper. The MSM linear motor based on bionics inchworm principle can output great force with a simple structure and control system. With these characters, there is a wide range of potential application of electric actuations in high-force precision positioning systems. The differential control MSM actuator with a special structure can operate on higher frequency, provide greater force and have a high efficiency. The differential control method used in MSM actuator provides new idea for the design of the future MSM actuators.