Critical review of current trends in shape memory alloy actuators for intelligent robots

Abstract

PurposeThe purpose of this paper is to review the current application areas of shape memory alloy (SMA) actuators in intelligent robotic systems and devices.Design/methodology/approachThis paper analyses how actuation and sensing functions of the SMA actuator have been exploited and incorporated in micro and macro robotic devices, developed for medical and non‐medical applications. The speed of response of SMA actuator mostly depends upon its shape and size, addition and removal of heat and the bias force applied. All these factors have impact on the overall size of the robotic device and the degree of freedom (dof) obtained and hence, a comprehensive survey is made highlighting these aspects. Also described are the mechatronic aspects like the software and hardware used in an industrial environment for the control of such nonlinear actuator and the type of sensory feedback devices incorporated for obtaining better control, positioning accuracy and fast response.FindingsSMA actuators find wide applications in various facets of robotic equipments. Selecting a suitable shape, fast heating and cooling method and better intelligent control technique with or without feedback devices could optimize its performance.Research limitations/implicationsThe frequency of SMA actuation purely depends on the rate of heat energy added to and removed from the actuator, which in turn depends upon interrelated nonlinear parameters.Practical implicationsFor increasing the dof of robots, number of actuators also have to be increased that leads to complex control problems.Originality/valueExplains the suitability of SMA as actuators in smart robotic systems, possibility of miniaturisation. It also highlights the difficulties faced by the SMA research community.

Properties of Magnetic Shape Memory Alloys in Martensitic Phase

“…THE shape memory alloys (SMAs) have emerged as smart advanced materials in the recent past due to wide applications in bioengineering [1][2][3][4][5][6][7][8] , aerospace 1,[9][10][11] , robotics [12][13][14] , consumer products and industrial applications [15][16][17] , structures and composites 18 , automotive industry [19][20][21] , actuators and micro-electromechanical systems (MEMS) 1,2,[22][23][24] , and in fashion 25 . The SMAs are capable of memorizing their original shape.…”

Ternary β and γ phases in the Al–Au–Cu system at 750°C

“…Evidently, quenching suppressed the ordering reaction, as in the case of α-(Au,Cu)→AuCu [23]. The α-(Cu,Au,Al)→Cu 3 Au transformation occurred about 20˚C higher than that of a binary (Au,Cu) alloy of the corresponding Au:Cu ratio, indicating that the addition of 15 at% Al raised the ordering temperature. This should be contrasted to the findings of Chapman and Gillam who reported that the addition of as little as 1.3 at.% Al to Cu 3 Au lowered the transformation temperature by 40˚C [24].…”

“…There is a small exothermic signal at ~320˚C in the DTA scan of Sample 6, cooled at 10˚C per second, evidently generated by the α-(Cu,Au,Al)→ Cu 3 Au ordering reaction. However, the strong characteristic superlattice {100} and {110} peaks for Cu 3 Al were absent in the XRD patterns which had been taken on samples annealed at 750˚C and then quenched. These samples showed only the peaks expected for α-(Au,Cu) plus some evidence for a small proportion of a second phase, possibly the β-phase.…”

“…This has enabled a wide range of uses for these materials, with applications ranging from under-wires of bras to arterial stents and intricate jewellery [2][3][4][5][6]. However, there are some limitations due to the fact that many SMAs suffer from aging and martensite stabilization [7][8][9].…”

Elastomeric Tiles for the Fabrication of Inflatable Structures

“…[11] In microrobotics, [12] actuation may be achieved using materials that change shape upon stimulation. For example, shape-memory alloys (SMAs), [13] following mechanical deformation, recover their original shape when exposed to heat, and piezoelectric crystals expand (or contract) along specific axes when exposed to electric fields. [12,14] In macroscale machines/robots, shape-change actuation is demonstrated by the McKibben "air muscle," [15] which is driven pneumatically, and iRobot's "blob-bot," which operates by stiffening portions of an inflatable soft skin using jamming.…”