Publiée 3 juillet 2026
PhD Position F/M Singularity Detection and Analysis in Modular Parallel Continuum Robots
Inria
Villeneuve-d'Ascq, Hauts-de-France 59491, France
CDI
A propos du centre ou de la direction fonctionnelle
Created in 2008, the Inria center at the University of Lille employs 360 people, including 305 scientists in 16 research teams. Recognized for its strong involvement in the socio-economic development of the Hauts-De-France region, the Inria center at the University of Lille maintains a close relationship with large companies and SMEs. By fostering synergies between researchers and industry, Inria contributes to the transfer of skills and expertise in the field of digital technologies, and provides access to the best of European and international research for the benefit of innovation and businesses, particularly in the region.
For over 10 years, the Inria center at the University of Lille has been at the heart of Lille's university and scientific ecosystem, as well as at the heart of Frenchtech, with a technology showroom based on avenue de Bretagne in Lille, on the EuraTechnologies site of economic excellence dedicated to information and communication technologies (ICT).
Contexte et atouts du poste
Project context:
The RPC-JaM project aims at advancing fundamentally the development of parallel continuum robots, a class of deformable robots obtained by assembling slender elastic legs in parallel. Their natural compliance enables them, to a certain degree, to adapt safely to their environment in case of contact, making them particularly interesting in tasks with sensitive environments such as medical interventions and cobotics. Despite all their advantages observed and demonstrated in the litterature, developing these robots comes with challenges such as the presence of singularities and elastic stability deficiency, models with high computation time, and a complex design. To solve these issues, we propose to follow an original approach where the robot is seen as the assembly of modular limbs, each one having its own sensors, actuators and processing units. The objective of this project is first of all to tackle the previous scientific challenges, eventually simplified as they are considered as the limb level and not the entire structure, with an additional work on how the assembled legs cooperate. Our goal is also to federate french research on this strongly emerging topic, and to disseminate the results to the public. Indeed, instead of buiding demonstrators for specific applications, we propose to valorize these results through the development of interactive art with one or several parallel continuum robots, which will be exposed, and to observe and analyse the people's reactions. The RPC-JaM project is composed of 4 partners (Centre Inria de l'Université de Lille, LS2N in Nantes, FEMTO-ST in Besançon, ENSADLab in Paris) in relation with le Lieu Unique in Nantes).
PhD Context:
Similar to their rigid counterpart, Continuum Parallel Robots (CPR) can reach singular configurations in their workspace. They can encounter type 1 singularities, which correspond to the workspace boundaries and actuation limits, and type 2 singularities where the robot loses stiffness and stability, and buckles suddenly. Type 2 singularities result in dynamic snapping motions which are difficult to control and stabilize due to the high stiffness of the structure relative to its low inertia. The current approaches to manage them is either to avoid them, in cases where the robot shape must be controlled at every moment such as surgery through natural orifices, or to release them to create additional dynamic forces and compensate for others such as needle penetration or gravity [Nyloid art project, Cod.Act 2013]. In every case, the first step is to identify these singularities in the workspace offline and online, which is a challenge due to the computational cost of existing approaches. The existing detection criteria target changes of elastic stability, which can be computed either by using the optimal control theory or analyzing the Hessian matrix of the robot potential energy. Both approaches require knowing the CPR's full state, which is classically obtained with dynamic models that can be demanding in terms of computational resources. Indeed, the slender legs are typically modeled with non-linear rod models such as Cosserat rods and assembled using geometrical constraints. The resulting system of equations to solve, in its strong form, is a set of non linear partial differential equations with mixed boundary conditions that often require specific integration schemes and root-finding algorithms to solve. This problem of computational cost makes it challenging 1) to analyse efficiently and offline the workspace ans singularities of a given design of CPR, which is of great interest for design, planning and control, and 2) to detect online the appearance of singularities. When considering a single rod subject to known forces at their ends, however, it is possible in certain cases to obtain analytical criteria that are very fast to compute, such as the well-known equations of critical buckling force for clamped beams.
Environment:
The PhD will take place in the team Defrost of the Centre Inria de l'Universté de Lille, in collaboration with the ARMEN team of LS2N in Nantes. It will be co-supervised by Quentin Peyron (export in continuum and soft robotics modeling, design and singularity analysis), and Sebastien Briot (expert in parallel rigid and continuum robotics modeling and singularity analysis).
Mission confiée
Drawing inspiration from this, the main idea if this PhD is to explore potentially two research directions. A first direction concerns the use of sensors along one modular leg of the RPC-JaM to measure physical quantities instead of having to compute them through a complete model, and therefore obtain online singularity detection algorithms that are frugal enough to run on the local leg micro-controller. The second direction concerns the development of efficient numerical algorithms for workspace computation and characterization, considering tools developed in the applied mathematics field such as continuation methods.
Principales activités
Main activities :
Additional activities :
Compétences
Technical skills:
Languages :
Relational skills :
Avantages
Rémunération
Monthly gross salary: 2 300 €
Created in 2008, the Inria center at the University of Lille employs 360 people, including 305 scientists in 16 research teams. Recognized for its strong involvement in the socio-economic development of the Hauts-De-France region, the Inria center at the University of Lille maintains a close relationship with large companies and SMEs. By fostering synergies between researchers and industry, Inria contributes to the transfer of skills and expertise in the field of digital technologies, and provides access to the best of European and international research for the benefit of innovation and businesses, particularly in the region.
For over 10 years, the Inria center at the University of Lille has been at the heart of Lille's university and scientific ecosystem, as well as at the heart of Frenchtech, with a technology showroom based on avenue de Bretagne in Lille, on the EuraTechnologies site of economic excellence dedicated to information and communication technologies (ICT).
Contexte et atouts du poste
Project context:
The RPC-JaM project aims at advancing fundamentally the development of parallel continuum robots, a class of deformable robots obtained by assembling slender elastic legs in parallel. Their natural compliance enables them, to a certain degree, to adapt safely to their environment in case of contact, making them particularly interesting in tasks with sensitive environments such as medical interventions and cobotics. Despite all their advantages observed and demonstrated in the litterature, developing these robots comes with challenges such as the presence of singularities and elastic stability deficiency, models with high computation time, and a complex design. To solve these issues, we propose to follow an original approach where the robot is seen as the assembly of modular limbs, each one having its own sensors, actuators and processing units. The objective of this project is first of all to tackle the previous scientific challenges, eventually simplified as they are considered as the limb level and not the entire structure, with an additional work on how the assembled legs cooperate. Our goal is also to federate french research on this strongly emerging topic, and to disseminate the results to the public. Indeed, instead of buiding demonstrators for specific applications, we propose to valorize these results through the development of interactive art with one or several parallel continuum robots, which will be exposed, and to observe and analyse the people's reactions. The RPC-JaM project is composed of 4 partners (Centre Inria de l'Université de Lille, LS2N in Nantes, FEMTO-ST in Besançon, ENSADLab in Paris) in relation with le Lieu Unique in Nantes).
PhD Context:
Similar to their rigid counterpart, Continuum Parallel Robots (CPR) can reach singular configurations in their workspace. They can encounter type 1 singularities, which correspond to the workspace boundaries and actuation limits, and type 2 singularities where the robot loses stiffness and stability, and buckles suddenly. Type 2 singularities result in dynamic snapping motions which are difficult to control and stabilize due to the high stiffness of the structure relative to its low inertia. The current approaches to manage them is either to avoid them, in cases where the robot shape must be controlled at every moment such as surgery through natural orifices, or to release them to create additional dynamic forces and compensate for others such as needle penetration or gravity [Nyloid art project, Cod.Act 2013]. In every case, the first step is to identify these singularities in the workspace offline and online, which is a challenge due to the computational cost of existing approaches. The existing detection criteria target changes of elastic stability, which can be computed either by using the optimal control theory or analyzing the Hessian matrix of the robot potential energy. Both approaches require knowing the CPR's full state, which is classically obtained with dynamic models that can be demanding in terms of computational resources. Indeed, the slender legs are typically modeled with non-linear rod models such as Cosserat rods and assembled using geometrical constraints. The resulting system of equations to solve, in its strong form, is a set of non linear partial differential equations with mixed boundary conditions that often require specific integration schemes and root-finding algorithms to solve. This problem of computational cost makes it challenging 1) to analyse efficiently and offline the workspace ans singularities of a given design of CPR, which is of great interest for design, planning and control, and 2) to detect online the appearance of singularities. When considering a single rod subject to known forces at their ends, however, it is possible in certain cases to obtain analytical criteria that are very fast to compute, such as the well-known equations of critical buckling force for clamped beams.
Environment:
The PhD will take place in the team Defrost of the Centre Inria de l'Universté de Lille, in collaboration with the ARMEN team of LS2N in Nantes. It will be co-supervised by Quentin Peyron (export in continuum and soft robotics modeling, design and singularity analysis), and Sebastien Briot (expert in parallel rigid and continuum robotics modeling and singularity analysis).
Mission confiée
Drawing inspiration from this, the main idea if this PhD is to explore potentially two research directions. A first direction concerns the use of sensors along one modular leg of the RPC-JaM to measure physical quantities instead of having to compute them through a complete model, and therefore obtain online singularity detection algorithms that are frugal enough to run on the local leg micro-controller. The second direction concerns the development of efficient numerical algorithms for workspace computation and characterization, considering tools developed in the applied mathematics field such as continuation methods.
Principales activités
Main activities :
- State of the art of continuum robots models, workspace and buckling analysis tools, and continuum robot sensing strategies
- Prototyping of a simple continuum robot with the equipped sensors, and of the online detection algorithm
- Experimental study and validation of the approach.
- Investigation of efficient algorithms for offline workspace characterization.
- Redaction of scientific articles and the PhD thesis
Additional activities :
- Participation and involvement in the ANR project
- Scientific mediation and communication
Compétences
Technical skills:
- Fundamentals in Robotics
- Fundamentals in continuum mechanics and applied mathematics
- Training in mechanical design and engineering
- Experiences in sensors and instrumentation
Languages :
- A good level of English, written and spoken, is required
Relational skills :
- Ability to work in a team and will to participate in the research teams' life
Avantages
- Subsidized meals
- Partial reimbursement of public transport costs
- Leave: 7 weeks of annual leave + 10 extra days off due to RTT (statutory reduction in working hours) + possibility of exceptional leave (sick children, moving home, etc.)
- Possibility of teleworking and flexible organization of working hours
- Professional equipment available (videoconferencing, loan of computer equipment, etc.)
- Social, cultural and sports events and activities
- Access to vocational training
- Social security coverage
Rémunération
Monthly gross salary: 2 300 €
