Marc Arsicault

Micro robots dedicated to small diameter canalization exploration

In this paper, three peculiar in-pipe microrobots are presented. They are the result of investigations of 3 laboratories involved in the microrobotics workgroup of the French National Centre of the Scientific Research (CNRS). They have been conceived to answer the locomotion problem inside industrial tubes of small diameter. Each of them is specific to a particular set of conditions.

A fast grasp synthesis method for online manipulation

This paper presents a new method for solving the grasp optimization problem by a multi-finger robotic hand; this method allows gripping an object using three articulated fingers, in order to manipulate it later. Because of the large number of operations and the high computation time, online grasp has not yet been reported. In this study, we propose a method that is able to provide an optimized initial grasp in a short time before online manipulation.

A real-time strategy for dexterous manipulation: Fingertips motion planning, force sensing and grasp stability

This paper presents a global strategy for object manipulation with the fingertips with an anthropomorphic dexterous hand: the LMS Hand of the ROBIOSS team from PPRIME Institute in Poitiers (France). Fine manipulation with the fingertips requires to compute on one hand, finger motions able to produce the desired object motion and on the other hand, it is necessary to ensure object stability with a real time scheme for the fingertip force computation. In the literature, lot of works propose to solve the stability problem, but most of these works are grasp oriented; it means that the use of the proposed methods are not easy to implement for online computation while the grasped object is moving inside the hand. Also simple real time schemes and experimental results with full-actuated mechanical hands using three fingers were not proposed or are extremely rare. Thus we wish to propose in a same strategy, a robust and simple way to solve the fingertip path planning and the fingertip force computation. First, finger path planning is based on a geometric approach, and on a contact modelling between the grasped object and the finger. And as force sensing is required for force control, a new original approach based on neural networks and on the use of tendon-driven joints is also used to evaluate the normal force acting on the finger distal phalanx. And an efficient algorithm that computes fingertip forces involved is presented in the case of three dimensional object grasps. Based on previous works, those forces are computed by using a robust optimization scheme. In order to validate this strategy, different grasps and different manipulation tasks are presented and detailed with a simulation software, SMAR, developed by the PPRIME Institute. And finally experimental results with the real hand illustrate the efficiency of the whole approach.

A design of slave surgical robot based on motion capture

The synthesis of movement and the biomechanics are introduced into the design methodology for the development of a minimally invasive surgery (MIS) robot manipulator : compact, lightweight and close to the surgical gesture. The goal of this study is progress toward a next-generation surgical robot system that will help surgeons deliver health-care more effectively. Based on an extensive database surgical measurements, the workspace requirements were clearly defined. The pivot point constraint in MIS makes the spherical manipulator a natural candidate. The kinematic model of the proposed structure is performed and singularities are avoided. A synthesis problem is formulated and as a result the optimal link lengths of a medical robot are determined.

Lms robotic hand grasp and manipulation planning (an isomorphic exoskeleton approach)

In order to widen the potentialities of manipulation of the Laboratoire de Mecanique des solides (LMS) mechanical hand, we developed a new planning approach based on the use of a specific exoskeleton. This one has kinematics architecture and dimensions identical to the mechanical hand. This feature allows us to obtain manipulation trajectories for the mechanical hand, very easily and very quickly, by using the exoskeleton, without complex calibration. Manipulations trajectories are replayed offline with an autonomous control, and, consequently, the exoskeleton is not used with any feedback strategy for telemanipulation. This paper presents the characteristics of this exoskeleton and the graphic interface that we developed. This one uses a method to determine the objects evolution during the manipulation with the exoskeleton, without using exteroceptive sensors. This new approach was tested for standard trajectories by simulation on a Computer-aided design (CAD) robotics system and by using the mechanical hand. Thus, we validate the use concept of an isomorphic exoskeleton to mechanical hand for manipulation planning with the LMS mechanical hand.

New Printing Robot for High-Resolution Pictures on Three-Dimensional Wide Surfaces

A novel five-axes robot for industrial large printing applications is presented in this paper. The robot was developed in the robotics team from PRIME institute and an international patent was deposited for this invention in 2006. It concerns large-format 3-D printing on a fixed surface, like trailer tarpaulin for example. The robot is composed of an inkjet printing block and a device to dry the ink sprayed onto the surface. Kinematics of the mechanical device with 5 DOF was studied to position and orientate the printheads onto the surface to be printed. The structure of the robot is simple with high-speed capability and printing resolution. The working principle and mechanical structure are described, and the geometrical model and surface following control of the robot are also discussed. Finally, printing results in a practical situation illustrate the efficiency of the proposed 3-D printing robot, and an analysis of how the task is carried out is provided.

A complete methodology to design a safety mechanism for prismatic joint implementation

The majority of recent researches have been focused on developing compliant joint for rotary motion. Few authors contributed to the problematic of safety in pure linear motion, i.e. prismatic joint. The contribution of this work is to present a new design capable of achieving, passively, a nonlinear elastic behavior for prismatic joint implementation, the so-called Prismatic Compliant Joint (PCJ). This new device is based on a six-bar mechanism equipped with a linear spring. Hence, this structure generates the desired nonlinear stiffness behavior under a specified external force. The elastic characteristic will comply with force safety criteria of physical Human/Robot interaction (pHRI); a Hunt-Crossley model based one. In order to fit the PCJ response curve to the established safety measures, an optimization based on genetic algorithm method tunes PCJ intrinsic parameters subject to the chosen constraints.

An in Vivo Experiment to Assess the Validity of the Log Linearized Hunt-Crossley Model for Contacts of Robots with the Human Abdomen

A key issue in Human-Robot physical interaction is the real-time perception of contact impedance by the robot. The Hunt-Crossley (HC) model is a popular model of contact force with soft biological tissues as it enjoys accuracy with low-complexity properties and its parameters are physically sound. Because the original HC model is non-linear, the current best known approach of real-time identification consists in identifying the parameters of a log linearized version of the HC model, by means of a Recursive Least Squares (RLS) algorithm. But, the final model used for exploitation in robot control, is the original non-linear HC model with the previously identified parameters. Hence, this approach may be questionable concerning the modeling accuracy and some authors prefer rejecting the HC model. This paper presents for the first time an in vivo experiment to assess the performances of contact models with the human abdomen. In particular we show here through a statistical analysis, that the log linearized HC model should be considered as a contact model on its own and replace the original non-linear HC model for both identification and exploitation.

Toward new minimally invasive surgical robotic system

This paper present a new laparoscopic surgical setup (minimally invasive surgery, MIS) with spherical serial surgical robot. The robot was developed at the PPRIME Institute in the ROBIOSS team from Poitiers University. Based on laparoscopic surgery, specification for workspace and constraints are outlined and the architecture selected for the surgical robots is presented and discussed. Analytical models of the inverse and forward kinematics are provided together with a detailed analysis of mobility and constraints. The proposed approach is based on motion capture of an expert gestures during which an anastomosis technique has to be performed. The evaluation of the workspace is based on the use of the Vicon Nexus motion capture system. The medical gestures were analyzed in term of position and velocities; the result has been used in the definition of the kinematics specifications of the proposed manipulator. The effective workspace size is determined through an experimental study on a simulator. The spherical serial robot (3R-T) has been selected because of its characteristics meeting the constraint requirements. The robot and its environment are described.

Forward Kinematic Model of a New Spherical Parallel Manipulator Used as a Master Device

The paper discusses the Forward Kinematic Model (FKM) of a special Spherical Parallel Manipulator (SPM). The special SPM is obtained by modifying one leg of a classic SPM. This new architecture eliminates the singularity from the workspace. The SPM is used as master device for medical tele-operation system. The FKM of the new SPM is calculated using the equation of spherical four-bar mechanism. A method to improve the FKM calculation using extra sensor is proposed in this paper.