Team AVR - Control, Vision and Robotics Lab

ISIS - Robotization of flexible systems for minimally invasive surgery

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Flexible endoscopy has long been used for diagnosis purposes only. But with the general trend in surgery to try to minimize invasiveness it has come a major tool for surgical procedures as shown by the development of specific flexible surgical platforms. Unfortunately these systems are not directly adapted to surgery. Several surgeons have to coordinate to manipulate the available DOFs, which result in difficult operations and potential high functioning costs. We envision a solution in the development of robotic tools for flexible endoscopic surgery. The aim of the ISIS project is to show that by using robotics it is possible for a single surgeon to perform surgical procedures intuitively with flexible systems. The chosen path to this goal is to build on existing asserted medical systems, such as flexible endoscopes manufactured by Karl Storz, rather than developing complete new systems. Issues arise at several levels (see the following for more details) :

  • Small-size mechanical design for developing light, compact and modular slave systems
  • Low-level control of cable-driven systems with significant non-linearities
  • Cartesian control of flexible instrument made difficult by imperfect models and lack of measurement solutions

Overall the project includes mechanical development, low-level control, high level strategies and measurement solutions development.

Keywords: Flexible endoscopy, continuum robots, teleoperation

Persons working on the project

  • PhD students: P. Cabras
  • Research engineers: L. Zorn (mechanical design and realization), Ph. Zanne (Electrical desgin and realization)
  • Researchers: F. Nageotte, M. de Mathelin
  • Past PhD students: A. De Donno, B. Bardou, L. Ott


Florent Nageotte, Philippe Zanne, Lucile Zorn


The project is developed in collaboration with Karl Storz GmBH and surgeons from the IRCAD (Dr B. Dallemagne, Dr S. Peretta). P. Cabras is funded by CAMI labex and his thesis project is in collaboration with Agathe team (ISIR Paris). STRAS v2 realization has been partly outsourced to Sandmann company (Bennwihr Gare, France) and Opticab.

In details

Visual control of flexible endoscopes

STRAS : a robotic system for intraluminal surgery

During the ISIS project, we have developed a robotic prototype based on the Anubis platform from Karl Storz. The proposed system is modular and consists of three kinds of modules:

  • an endoscope module, which motorizes the four-ways deflection of the main endoscope tip
  • instruments modules, which enables the two-ways deflection of instruments. They come in two flavours: electrical instruments modules for instruments needing electrical pluging, such as electro-coagulation tools and mechanical instruments needing an opening / closing capability, such as scisors or graspers.
  • Translation and Rotation modules (T/RMs) which allow the rotation and translation of the instruments inside the channels of the main endoscope.

TR/Ms and the endoscope modules are mounted onto passive positioning arms, which can be attached to the operating table. With this structure only two T/RMs are needed, whatever the number of instruments required for the surgery.

The whole motorization is located at the proximal side, which makes the robotic system easily compatible with medical constraints.

This slave system can be teleoperated using two master interfaces, enabling a single user to control all degrees of freedom. First tests have been performed in the lab, which have shown that STRAS allows a better and more comfortable control of the flexible instruments than in the manual version.

Overview of STRAS
Motorization on the proximal part

Control of flexible systems

Flexible systems used in the STRAS prototype have very particular behaviours due to their kinematic properties (singularities at the straight position) and their mechanical actuation (cable driven systems) which makes their control difficult. We are investigating how to improve the control of these systems at two levels: At low level we try to understand the local behaviour of the flexible systems and at higher level we analyze the effect of the choices of master / slave control modes and mappings on the overall control capabilities.

Visual measurement

Because of frictions, backlash and deadzones, it is difficult to estimate the position of instruments using only internal sensors such as motor encoders. On the other hand there are no commercially available sensors which can be integrated inside small diameter instruments and which would allow to measure small enough radii of curvature. For improving the control of flexible instruments, we work on the use of the endoscopic images for measuring the positions and motions of the instruments. This information can be fused with encoders measurements to improve the obtained accuracy.

Major facts

  • Sep 2014 : Start of a new project called "EASE" for developing a clinical version of STRAS. EASE is funded by SATT Conectus with support of Karl Storz and IRCAD
  • Sep. 1/2 2014 : in vivo experiments at the IRCAD
  • Feb. 12 2014 : Alsace 20 (TV broadcaster) has filmed STRAS v2 for broadcast program Lab20 to be seen on friday feb. 14 and on the website of Alsace 20 from feb. 17.
  • Feb. 5 2014 : In vivo tests of ESD with a novice surgeon
  • Jan. 30 2014 : Demonstration of STRAS v2 to M. F. Hollande, president of the republic during his visit at IRCAD
  • Jan. 30 2014 : Demonstration of STRAS v2 to Mrs Storz, CEO of Karl Storz
  • Jan. 10 2014 : Demonstration of STRAS v2 to a Karl Storz delegation
  • Jan. 7 2014 : Demonstration of STRAS v2 to a delegation of Covidien
  • Dec. 19 2013 : Second operation tests on animals
  • Dec. 13 2013 : A. De Donno successfully defended his PhD. The defense took place in the "Salle des Actes" at the faculty of Medicine in Strasbourg. The jury was composed by Ph. Cinquin (President), A. Menciassi (reviewer), J. Szewczyk (reviewer), M. de Mathelin and F. Nageotte.
  • Dec. 5 2013 : First in vivo tests of STRAS v2. Our medical partners at IRCAD successfully performed an ESD in an animal.
  • Nov. 4 2013 : F. Nageotte presented control strategies for STRAS at IROS in Tokyo.
  • Oct. 29 2013 : First ex vivo tests of STRAS v2. Successful fake ESD in a pig stomach.
  • Oct. 24 2013 : First lab tests of the new version of STRAS (v2) on chicken breast.
  • Oct 2013 : Second version of STRAS has been assembled
  • May 2013 : A. De Donno presented STRAS at IEEE ICRA in Karlsruhe
  • Presentation of STRAS robotic system during visits of Siemens HealthCare CEO (march 12), Mrs Sybil Storz, CEO of Karl Storz (march 13) and M. Louis Gallois (Commissaire général à l'investissement) (march 14).
  • Nov. 30 2012 : Presentation of STRAS robotic system at the IRCAD during Sanofi CEO visit
  • Nov. 29 2012 : first trials by IRCAD surgeons
  • oct. 2012 : presentation of surgical simulator at the "Fête de la Science" in Strasbourg
  • Oct. 2012 : Paolo Cabras has joined the project as PhD student working on image processing tools for system control
  • 2011 : Presentation of STRAS system at the IRCAD lab during visit of Laurent Wauquiez, minister of research and higher education