Team: DEXTER, LIRMM Laboratory, Montpellier, France
Advisors: Cédric Girerd and Philippe Poignet
Contact: cedric.girerd@lirmm.fr, philippe.poignet@lirmm.fr

The topic of the internship detailed below can be downloaded in pdf format, see attached file.

Context:
Minimally invasive surgery (MIS) is revolutionizing medical operations by minimizing the impact of procedures on the patient. By entering the body through small incisions or natural orifices, the complication risk, pain and recovery time can all be decreased. However, entering the human body through small entry points and navigating tortuous paths around obstacles to reach surgical sites, requires a very specific set of surgical tools. Indeed, these surgical tools need to have a high degree of dexterity, while maintaining a small overall diameter. Continuum robots are particularly well-suited for such medical tasks. Unlike serial or hyper-redundant robots, which have a finite number of links and joints, continuum robots can be viewed as robots made of an infinite number of joints and links of zero length, forming a continuously bending structure in the 3D space.
Concentric tube robots (CTRs) are a particular subclass of continuum robots. They are made of a telescopic assembly of precurved elastic tubes, that interact in bending and torsion to reach an equilibrium. The resulting shape of the robot can be actively modified by proximal translations and rotations of the individual tubes. Such variations in shape are visible in this video: https://cgirerd.github.io/publication/girerd20tro/girerd20tro.mp4.
Compliance is a fundamental property of continuum robots and CTRs. It corresponds to a softness of its body, which deforms upon the application of external forces or moments. The compliance of a CTR depends on its design parameters (tube diameters, materials) and its joint values (tube rotation and orientation). In the context of medical and surgical applications, a modulation of the robot compliance can be desired. For instance, a high compliance can be required during interaction with soft and delicate tissue, while low compliance can be required for incisions, pulling or tissue cutting tasks.

Proposed work:
The intern will aim to achieve the following three tasks:
- The first task will be the maintenance and update of an existing CTR prototype in our laboratory. This maintenance and update will focus on both the mechanical aspects of the prototype, to enable the movement of the tubes, and the software and programming aspects, to control the motors associated with the tube movements. This first step will allow the intern to become familiar with the prototype.
- The second task will involve the development of an experimental setup to measure the compliance of the CTR. Physical methods will need to be implemented to apply forces at specific points on the robot’s body and to measure the resulting deflection.
- The third task will consist in conducting series of compliance measurements with the CTR prototype and the experimental measurement setup designed, for different sets of tubes and joint variables of the robot. These measurements will be compared to theoretical values derived from models proposed in the literature. Any potential discrepancies will be explained.
This work will pave the way for new reflections and ideas on the feasibility of implementing active stiffness modulation for CTRs, in order, for instance, to adjust the robot’s compliance during different phases of a medical gesture.

Work environment:
This internship will take place in Montpellier, a sunny and vibrant city located in the south of France, near the Mediterranean sea. The host laboratory is the Laboratoire d’Informatique, de Robotique et de Microélectronique de Montpellier (LIRMM). The LIRMM is a joint research unit between the CNRS and the University of Montpellier, and includes more than 400 employees, among which 192 permanent staff. It is divided in 3 research units: Computer Science, Robotics, Micro-Electronics, with additional centralized services. The intern will integrate the DEXTER team in the Robotics Department.

Candidate profile:
The student should be ideally in his/her last year of Engineering School or Masters (Bac +5), and must ideally have a major in Robotics/Mechatronics. He/She should feel comfortable with building prototypes, and with programming (Matlab, C++). He/She should be able to work in a pluridisciplinary and multicultural environment, and must possess good communication skills.

Application:
Interested candidates can apply by sending a cover letter and a CV/résumé to the following email addresses: cedric.girerd@lirmm.fr et philippe.poignet@lirmm.fr. Any questions related to this project can also be directed to these email addresses.