SMA actuators: theory, performance curves and design problems

Abstract

Purpose -The main purpose of the paper is to develop model basing on the modified and properly-adopted Fermi-Dirac equation which combines proper accuracy with adequate simplicity as well as to show how steady state and transient curves resulting from this model can be applied for solving design task. Design/methodology/approach -The standard Fermi-Dirac equation was modified and extended. Full performance cycle for the SMA actuator was characterized by double-valued function describing the actuator activation and the actuator deactivation. All these functions and parameters can be easily determined by analysis of measurement data or with use of Hooke-Jeeves optimization algorithm. Findings -SMA linear actuator can be used in mechatronic systems as a special non-standard drive when ultra-light mass and very simple mechanical construction of power feed system is required. The proposed steady-state and transient performance curves as well as operation diagram constitute sufficient base for effective designing SMA drive systems.Research limitations/implications -The greatest disadvantage of a SMA actuator is long time of deactivation resulting from slow self-cooling process. As far as efficiency is concerned as essential factor for choosing the most suitable linear actuator, there is no sense to take into account a linear SMA actuator because of its very low efficiency. Practical implications -Designer can use performance curve which determines proper length of SMA actuator and range of its motion. The proposed model can be implemented in SMA drive control unit for controlling position of the actuator. Originality/value -Similarities between change of martensitic phase during transition process and probability P of electron energy level distribution described by the Fermi-Dirac two-variable equation were taken into account. Such an approach seems to express in the most suitable way the physical nature of m-a transition. The authors decided to extend concept (proposed in Jayender et al.) and to adopt the Fermi-Dirac equation for describing behaviour of a SMA linear actuator.

State of the art of soft robotic applications based on magneto-rheological materials

“…Nowadays, various approaches are used to build soft robots, such as shape memory alloys (SMAs) [3], pneumatic muscles [4][5], dielectric elastomers [6], magnetorheological (MR) materials [7], etc. Each of these approaches has its own advantages and disadvantages and its potential application scope.…”

OpenWRT operating system based controllers for mobile robot and building automation system students projects realization

“…Traditional actuators like servodrives or DC motors are still most popular but up to date actuators like SMA became more popular. It is result of didactic and research in SMART materials [11] [12]. Generally robots work in autonomous way or they are controlled using wireless communication (e.g.…”

Analytical Description of SMA Actuator Dynamics based on Fermi-Dirac Function

“…After theoretical considerations and on the basis of the engineering intuition the authors decided to choose for further detailed analysis the so-called Fermi-Dirac function (which in some previous papers was applied effectively for the description of steady-state hysteresis curve of SMA linear actuators [11,12]), as well as to find analytical description of SMA actuator dynamics in the form of one-parameter family of functions: ∆L = f (t, F ). Such a family of curves are related to common equation so that all curves can be generated by varying parameter F in the equation.…”

“…An SMA actuator is an electromechanical converter in which electric energy is converted into mechanical energy via thermal energy [11]. The actuator (in form of a rod, a spring or a piston) made of shape memory alloy may be biased by another SMA actuator, spring or gravitational load (Fig.…”