MSM Actuators: Design Rules and Control Strategies

Abstract

Magnetic shape memory (MSM) alloys are comparatively new active materials which can be used for several industrial applications, ranging from precise positioning systems to advanced robotics. Beyond the material research, which deals with the basic thermo‐magneto‐mechanical properties of the crystals, the design as well as the control of the actuators displacement is an essential challenge. This paper addresses those two topics, trying to give to the reader a useful overview of existing results, but also presents new ideas. First, it introduces and discusses in details some possible designs, with a special emphasis on innovative actuator design concepts which are able to exploit the particular potentialities of MSM elements. The second focus of the paper is on the problem of designing a controller, i.e., an algorithm that allows to obtain a required performance from the actuator. The proposed control strategies try to take into account two main characteristics of MSM elements: the hysteresis and the temperature dependence. The effectiveness of the strategies is emphasized by experimental results performed on a commercially available MSM actuator demonstrator.

Modeling and control of innovative smart materials and actuators: A tutorial

“…The restoring force, which must be higher than the twinning stress, is realized typically with a pre-stress spring, leading to the so-called MSMA spring actuator in Fig. 3a [3], [13]. This configuration has two disadvantages, namely, only a part of the maximum force generable from the active element is available for mechanical work, and the deformation is not self-supported, i.e., a persistent current must be applied in the coils to fix a defined position.…”

“…To start deformation, the magnetic stress M AG σ or the external stress σ should at least overcome the twinning stress. The twinning stress is the source of a hysteretic memory effect: the deformation is self-supporting as long as σ or M AG σ does not overcome the twinning stress of the material, therefore under certain circumstances the shape change can be hold without external excitation [3].…”

“…Considering the possibilities to achieve elongation and contraction, five different operating modes can be defined [3]. The two most common modes are depicted in Fig.…”

Electromagnetic and Thermal Analyses of High-Performance Magnetic Shape Memory Actuators for Valve Applications

“…All actuators are designed for magnetic field-induced elongation and mechanical contraction corresponding to operating mode 2 in [12]. A restoring force is produced by a return spring commonly used in MSM actuators.…”

Characteristics of the Improved Magnetic Shape Memory Alloy Actuator Test Stand

“…Terfenol-D). Ordinary SMA are activated thermally and in order to distinguish both groups of materials with shape memory, it is proposed to use names and abbreviations: TSMA for thermally activated alloys and MSMA for magnetically activated ones [4,5,12]. When external magnetic field is applied to the MSMA material sample, it elongates or contracts, accordingly to the direction of the magnetic field vector and initial state of the sample.…”