POSITION AND FORCE CONTROL OF A SMA SPRING BASED DIFFERENTIAL ACTUATOR

Actuators as a major component of all mechanical systems require improving in size, power; noise and simplicity. In most presented actuators, there is no such feature of suitable positioning of load, variable stiffness/force and active shock damping simultaneously. Shape Memory Alloys (SMAs) can be a suitable choice for providing the above capabilities in the systems. Especially the spring type SMAs are less utilized in the developed SMA based systems. SMA springs in comparison to SMA wires may provide much more deflection although less force is produced through them. This property may tend to a more flexibility in the developed mechanisms. Additionally the actuator capability in controlling position and force is not presented in the works. In this paper, an actuator with one DOF utilizing SMA springs with the above features is considered. The actuator mechanism is based on the antagonistic application of SMA springs that provide faster actuation response and controllable stiffness. It is shown that such an actuator demonstrates a good positioning accuracy in addition to a higher level force and stiffness control capability. As a result, the mechanical systems with such actuator behave more flexible with less bodily damage while encountering environment.