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.

The Exechon 5-Axis Parallel Kinematic Machine (PKM) is a successful design created in Sweden and adopted by many producers of machine tools around the world. A new version of the manipulator is being developed as a component of a mobile self-reconfigurable fixture system within an inter-European project. The basic Exechon architecture consists of a 3-degree-of-freedom (dof) parallel mechanism (PM) connected in series with a two- or three-dof spherical wrist. The PM has two UPR (4-dof) legs, constrained to move in a common rotating plane, and an SPR (5-dof) leg. The paper presents the kinematic analysis of both the PM and the hybrid parallel-serial architecture. We describe the complex three-dimensional motion pattern of the PM platform, derive the kinematic equations and provide explicit solutions for the inverse kinematics.

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This paper reviews recent developments in nonlinear control technologies for shape memory alloy (SMA) actuators in robotics and their related applications. SMA possesses large hysteresis, low bandwidth, slow response, and non-linear behavior, which make them difficult to control. The fast response of the SMA actuator mostly depends upon, (1) type of controller, (2) rate of addition and removal of heat, and (3) shape or form of the actuator. Though linear controllers are more desirable than nonlinear ones, the review of literature shows that the results obtained using nonlinear controllers were far better than the former one.\ud Therefore, more emphasis is made on the nonlinear control technologies taking into account the intelligent controllers. Various forms of SMA actuator along with different heating and cooling methods are presented in this review, followed by the nonlinear control methods and the control problems encountered by the researchers

Abstract\ud Purpose – Aims to discuss how a Cartesian parallel robot with flexure revolute joints can effectively perform miniaturized assembly tasks.\ud Design/methodology/approach – The results of the test and validation phase of a Cartesian parallel robot designed for miniaturized assembly are\ud shown. The workspace volume is a cube with 30mm side and the target accuracy is 1mm. Each of the three robot legs has a prismatic-planar\ud architecture, with a cog-free linear motor and a planar joint realized using ten superelastic flexure revolute joints. Flexure joints are adopted in order to\ud avoid stick-slip phenomena and reach high positioning accuracy; their patented construction is relatively low-cost and allows a quick replacement in\ud case of fatigue failure.\ud Findings – The tests on the prototype are very encouraging: the measured positioning accuracy of the linear motors is ^0.5mm; on the other hand,\ud the effects of unwanted rotations of flexure joints and hysteresis of the superelastic material are not negligible and must be properly compensated for in\ud order to fully exploit the potential performance of the machine.\ud Practical implications – The introduction of this robotic architecture can fulfil the needs of a wide range of industrial miniaturized assembly\ud applications, thanks to its accurate positioning in a relatively large workspace. The cost of the machine is low thanks to its extreme modularity.\ud Originality/value – The combination of Cartesian parallel kinematics, cog-free linear motors and superelastic flexure revolute joints allows one to\ud obtain very good positioning performance