Purpose – The 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/approach – This 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. Findings – SMA 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/implications – The 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 implications – For increasing the dof of robots, number of actuators also have to be increased that leads to complex control problems. Originality/value – Explains the suitability of SMA as actuators in smart robotic systems, possibility of miniaturisation. It also highlights the difficulties faced by the SMA research community.

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. 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.

The paper discusses forward and inverse kinematics of a class of four-degree-of-freedom (DOF), four-legged parallel mechanisms providing three rotational and one translational DOFs. A fully parametric analytical form solution to the inverse-position problem is provided. All working modes of the mechanism are shown and discussed. The equations of the forward-position problem are obtained under different leg arrangements, and a numerical example is provided. New special geometries in the class are proposed, including one suitable for keyhole surgery.

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.