PurposeThe purpose of this paper is the optimisation of shape memory alloy (SMA) spring actuators. The purpose of these actuators is to control active endoscopes. The objective for such endoscopes is to minimize one patient pain during operation.Design/methodology/approachA range of recently published (1990‐2002) works, which aim to provide models for SMA actuators, do not focus on the simulation and on the design of such actuators. SMAs have two main characteristics, namely the phase change and non‐linear behaviour in each phase. The proposed model is based on a mixed approach combining an Euler‐Bernoulli beam model and a bi‐dimensional finite element model. It allows the modelling of plastic behaviour and drives the phase evolution in the beam cross‐section.FindingsThe physical properties of SMAs are described and modelled. A new beam model and a numerical algorithm are proposed. Preliminary results demonstrate the performance of our method on two problems and lead to determine the actuator capability. The resulting actuator model is then integrated into an optimisation process based on genetic algorithms. The overall approach provides a design tool for SMA spring actuator subjected to design constraints.Research limitations/implicationsThe proposed method is only validated for our practical purposes. However, we believe that the optimisation methodology may have other implications in structure design.Originality/valueThis paper provides an optimisation approach that is valuable for scientists and engineers in engineering computations.
The design and realization of micro robotic devices in the medical field enable the operating gesture to be assisted. So a polyarticulated device actuated with shape memory alloy (SMA) springs for endoscopy is developed in collaboration with the Laboratoire de Robotique de Paris. In this paper, a simulator realization, based on an original simulation platform (OpenMASK), of this structure is described. A numerical representation of the inspected network obtained by magnetic resonance imaging is used. A contact detection algorithm, which will be described, allows to determine the interaction forces between the endoscope and the duct thanks to a distance cartography of the space, in order to minimize the calculation time. An important experimental work shall be lead to determine the parameters of the contact model. Simulation results of virtual navigation through this duct representation by using an endoscope mechanical model including a behaviour description of the SMA actuators will be presented. Moreover, the efficiency of a command with the multi-agent approach is proved. Then the simulator interest is studied for the prototype amelioration by applying the techniques of virtual prototyping. Some results of optimization by using genetic algorithms with respect to the virtual navigation task will be shown.
Minimally invasive surgery progresses have allowed to greatly decrease patient suffering. A way to improve these techniques is to use active tools, which could adapt to the inspected environment. The development of these tools is very complex. So simulation methods can be significantly helpful in order to produce the most suitable tools while limiting the quantity of physical prototypes. We work on the design of a simulator for virtual coloscopy. Besides the virtual prototyping aspect for new active endoscopic devices, we can also use it as a training simulator once the device is designed. To do so, we have to address the simulation process of the colon. This article is mainly devoted to the description of the chosen models for the colon behaviour, which are used for the simulator. Some experimental results are presented which confirm the validity of the different choices. To finish, sigmoid untwisting operation is presented as a benchmark test to prove the efficiency of the simulator.
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