[robotics-worldwide] Phd Position at IRCCYN/Institut Pascal (France)

Philippe MARTINET Philippe.MARTINET at lasmea.univ-bpclermont.fr
Mon Jun 13 01:06:31 PDT 2011

In the framework of the network of ROBOTICS called ROBOTEX, IRCCYN  
(From Nantes) and Institut Pascal (From Clermont-Ferrand) offer a PHD  
position in the following theme: "Modeling and control of  
reconfigurable parallel robots". Details on subject are given at the  
end of this email.

Before june 30th 2011, the interested candidates must send :
- one curriculum vitae
- the notes they have the last years
- one motivation letter
- two recommandation letters
to the following address : Philippe.Martinet at lasmea.univ-bpclermont.fr

This Phd will be done in collaboration between Irccyn and Institut Pascal.
We expect to start the PHD in september or october 2011.

Philippe Martinet
Blaise Pascal University
Phone +33 473407653, Fax: +33 473407262
Philippe.Martinet at lasmea.univ-bpclermont.fr

Subject : Modeling and control of reconfigurable parallel robots

Context :

Because of the heavy economic pressure, most of the companies are  
forced to quickly modify their means of production (manufacturing  
tools, machines, robots
) in order to ensure a high productivity, a  
high flexibility and to increase their production capacity. Therefore,  
the principle of reconfigurable manufacturing system answers the needs  
of agility and productivity and permits to substantially extend the  
tool use so as to be suitable for the production of a great range of  

According to this report, new machines, mechanisms and robots appear  
such as new parallel robots which are able to change their  
configuration or operating mode in order to increase their workspace  
and/or modify their kinematic structure. However, even if this kind of  
mechanisms could be used to increase the manufacturing system  
productivity and agility, new phenomena (parallel and serial  
) are introduced and locally reduce the robot  
controllability which affect the robot workspace and making the robot  
reconfiguration more difficult.

Thesis objectives :

The main objective of the thesis is to develop a new control law  
(based on advanced modeling) dedicated to parallel robots  
reconfiguration. The algorithm would permit the parallel and serial  
singularities crossing for both increasing the robot workspace and  
allow the change of robot configuration without using additional  
actuators (no redundancy). Therefore, it consists of using an optimal  
and/or variable modeling of the robot coupled with calibration  
algorithm, observers and advanced control laws (multi-model control  
) so as to ensure the robot stability close to the robot  
singular position. As a consequence, the main goal is to increase the  
robot workspace and to ensure the robot stability (mechanical and  
automatic stabilities point of view) by managing on-line the robot  
reconfiguration/change of posture in function of the task to be done.

The technical objective consists of carrying out the parallel and  
serial singularities crossing on each actual robots located at IFMA  
(French Institute of Advanced Mechanic): the parallel robots 3CRS[1]  
and 3RRR[2]. In the case of the 3CRS robot, the aim is to reconfigure  
the robot so as to modify its kinematical structure from 3CRS to 3PRR  
in order to permit the realization of new tasks. In the case of the  
3RRR robot, the goal is to show how the theoretical developments are  
used to improve the robot workspace in order to decrease product cycle  

Scientific locks identified give the thesis a multidisciplinary aspect  
which transcend mechanic, automatic, computer science and electronic.

·         Which mechanical modeling can be used for singularity crossing ?

·         How the quality of motion transmission close to a  
singularity point can be evaluated, which criterion is adapted ?

·         Which control law is adapted to ensure the robot stability ?

·         How many observers have to be used for motion variables estimation?

·         How the trajectory is modified or influenced by the  
singularity crossing ?

·         How the robot reconfiguration is managed according to the task ?

The thesis originality is also characterized by the formulation of a  
new control law algorithm (based on an advanced modeling) experimented  
on actual robots and used to manage on-line the robot reconfiguration  
according to the task so as to increase the manufacturing tool agility.

Scientific management :

PhD main supervisor: P Martinet (martinet at lasmea.univ-bpclermont.fr)

PhD co-supervisors: S Briot (Sebastien.Briot at irccyn.ec-nantes.fr), N  
Bouton (nicolas.bouton at ifma.fr)

The thesis will be in association with the Pascal Institute  
(Clermont-Ferrand) and the research laboratory IRCCyN (Nantes)

References :

1.             Bonev, I.A. Les robots parallèles de la recherche vers  
les applications. in Journées Nationales de la Recherche en Robotique  
2007 2007. Oberna, France.

2.             Gogu, G., Structural synthesis of parallel robots :  
Part I : Methodology. 2007: Springer.

3.             Merlet, J.P., Les robots parallèles. 1997: Hermès -  
Lavoisier. 370.

4.             Ji, Z. and P. Song, Design of a reconfigurable platform  
manipulator. Journal of Robotic Systems, 1998. 15(6): p. 341-346.

5.             Bonev, I.A., D. Zlatanov, and C.M. Gosselin,  
Singularity Analysis of 3-DOF Planar Parallel Mechanisms via Screw  
Theory. Journal of Mechanical Design, 2003. 125.

6.             Briot, S. and V. Arakelian. On the dynamic properties  
and optimum control of parallel manipulators in the presence of  
singularity. in In Int. Conf. on Robotics and Automation (ICRA). 2008.  
Pasadena, U.S.A.

7.             Alvan, K. and A. Slousch, On the control of the spatial  
parallel manipulators with several degrees of freedom. Mechanism and  
Machine Theory, 2003. 1: p. 63-69.

8.             Bhattacharya, S., H. Hatwal, and A. Ghosh, Comparison  
of an exact and an approximate method of singularity avoidance in  
platform type parallel manipulators. Mechanic and Machine Theory,  
1998. 33(7): p. 965-974.

[1] 6dof spatial robot composed of three identical legs. Each leg is  
composed of a cylindrical joint, a revolute joint and a spatial joint  
linked with the robot platform.

[2] 3dof parallel robot composed of three identical legs. Each le gis  
composed of three parallel revolute joints.

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