A practical approach to the design and control of active endoscopes

• Published in: Mechatronics (Oxford) Vol. 20; no. 2; pp. 251 - 264
• Main Authors: Sars, Vincent De, Haliyo, Sinan, Szewczyk, Jerome
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.03.2010; Elsevier
• Subjects: Active endoscope; Actuators; Biological and medical sciences; Endoscopes; Endoscopy; Engineering Sciences; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Genetic algorithms; Intermetallics; Investigative techniques, diagnostic techniques (general aspects); Mathematical analysis; Mathematical models; Medical sciences; Minimal invasive surgery; Nickel titanides; Physics; Shape memory alloys; Sliding mode control; Solid mechanics; Springs; Structural and continuum mechanics; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...); Minimal invasive surgery; Shape memory alloys; Active endoscope; Sliding mode control; Genetic algorithms; Energy consumption; Constraint; Sliding mode; Variable structure system; Modeling; Optimization; Endoscope; Finite element method; Elastic support; Shape memory alloy; Surgery; Endoscopy; Nitinol; Actuator; High performance; Vibration; Variable structure control; Experimental study; Spring; Vibration isolation; Dimensioning; Genetic algorithm
• DOI: 10.1016/j.mechatronics.2009.12.001
• ISSN: 0957-4158

Actual endoscopes and boroscopes, widely used in industry and in minimal invasive surgery, have considerable limitations, mainly due to their low number of degrees of freedom and their manual operation. Two different solutions for the electrical actuation of articulated endoscopes are presented in this paper. The technical constraints for this kind of application are very limited space for the actuators and high performance in terms of torque and angular reach. The first solution classically consists in a 2 d.o.f. structure steered by two pairs of antagonist shape memory alloy (SMA) wires. The sizing and preload determination for those actuators follow an original analytical approach. The second solution consists in a multi-d.o.f. structure actuated by thin NiTi springs mounted in an antagonist configuration and directly integrated in the structure of the endoscope. The geometry of the springs is obtained by optimization through genetic algorithms and finite elements method. Experiments show good adequacy between real behaviour and numerical model and also validate the approach. This study is also enhanced by a control scheme specifically developed for SMA actuators in an antagonist configuration. It is based on a first order sliding mode scheme, which has the advantage of a great structural simplicity. The experimental results show that this solution can reach a good compromise between the dynamic behaviour of the actuator, its energy consumption and the structural lifetime of the endoscope.