Linear motion is rather common in the industry, and linear electric motors (LEMs) can provide it directly (without a mechanical transmission) through electromagnetic field forces. LEMs may be considered counterparts of rotary electric machines, but specific topologies lead to characteristics that differ (in some cases notably) from those of the latter. This paper attempts an overview on recent progress of LEMs, from innovative topologies to advanced modeling, design, and control, with case studies and examples related to specific industrial applications from people movers to small compressors solenoids, speakers, and microphones.

Linear Electric Machines, Drives, and MAGLEVs: An Overview

The field of energy harvesting has grown concurrently with the rapid development of portable and wireless electronics in which reliable and long-lasting power sources are required. Electrochemical batteries have a limited lifespan and require periodic recharging. In contrast, vibration energy harvesters can supply uninterrupted power by scavenging useful electrical energy from ambient structural vibrations. This article reviews the current state of vibration energy harvesters based on magnetostrictive materials, especially Terfenol-D and Galfenol. Existing magnetostrictive harvester designs are compared in terms of various performance metrics. Advanced techniques that can reduce device size and improve performance are presented. Models for magnetostrictive devices are summarized to guide future harvester designs.

http://iopscience.iop.org/article/10.1088/1361-665X/aa8347/pdf

Review of magnetostrictive vibration energy harvesters

The supercoiled polymer (SCP) actuator is a recently discovered artificial muscle that demonstrates significant mechanical power, large contraction, and good dynamic range in a muscle-like form factor. There has been a rapid increase of research efforts devoted to the study of SCP actuators. For robotics, SCP actuators overcome specific challenges of artificial muscles such as shape memory alloy wires, where limited strain and slow dynamics, and power consumption had limited their use. It is known that hysteresis nonlinearity results from coiling the threads, and can cause up to 30% strain difference under the same voltage; however, no work has been reported to characterize the hysteresis in SCP actuators. In this paper, three new models are formulated to characterize the hysteretic relationship between three coupled variables (voltage input, strain, and load) of an SCP actuator, namely, the augmented generalized Prandtl-Ishlinskii model, the augmented Preisach model, and the augmented linear model. By incorporating the relationship between hysteresis curves and loading forces, the proposed models can efficiently characterize the hysteresis. Open-loop position control is further realized through inverse compensation. Experimental results show that the proposed schemes can effectively estimate and compensate the hysteresis. For the first time, the hysteresis characterization and compensation of SCP actuators are successfully demonstrated, such that accurate robot control can be realized.

Modeling and Inverse Compensation of Hysteresis in Supercoiled Polymer Artificial Muscles

Excessive vibrations in civil and mechanical systems can cause structural damage or detrimental noise. Structural vibrations can be mitigated either by attenuating energy from vibration sources or isolating external disturbance from target structures. Magnetostrictive materials coupling mechanical and magnetic energies have provided innovative solutions to vibration control challenges. Depending on the system’s tunability and power consumption, the existing vibration control strategies are categorized into active, passive, and semi-active types. This article first summarizes the unique properties of magnetostrictive materials that lead to compact and reliable vibration control strategies. Several magnetostrictive vibration control mechanisms together with their performance are then studied using lumped parameter models. Finally, this article reviews the current state of vibration control applications utilizing magnetostrictive materials, especially Terfenol-D and Galfenol.

https://iopscience.iop.org/article/10.1088/1361-665X/aadff5/pdf

Review of magnetostrictive materials for structural vibration control

Robotic artificial muscles are compliant and can generate straight contractions. They are increasingly popular as driving mechanisms for robotic systems. However, their strain and tension force often vary simultaneously under varying loads and inputs, resulting in three-dimensional hysteretic relationships. The three-dimensional hysteresis in robotic artificial muscles poses difficulties in estimating how they work and how to make them perform designed motions. This study proposes an approach to driving robotic artificial muscles to generate designed motions and forces by modeling and compensating for their three-dimensional hysteresis. The proposed scheme captures the nonlinearity by embedding two hysteresis models. The effectiveness of the model is confirmed by testing three popular robotic artificial muscles. Inverting the proposed model allows us to compensate for the hysteresis among temperature surrogate, contraction length, and tension force of a shape memory alloy (SMA) actuator. Feedforward control of an SMAactuated robotic bicep is demonstrated. This study can be generalized to other robotic artificial muscles, thus enabling muscle-powered machines to generate desired motions.

http://iopscience.iop.org/article/10.1088/1361-665X/aaa690/pdf

Liang Shu

Papers

Research on impedance network modeling and output characteristics of magnetostrictive electro-hydraulic actuator