Tanneguy Redarce

Sensor-based guidance control of a continuum robot for a semi-autonomous colonoscopy

Due to their compliance and high dexterity, biologically-inspired continuum robots have attracted much interest for applications such as medical surgery, urban search and rescue, de-mining etc. In this paper, we will present an application to medical surgery-colonoscopy by designing a pneumatic-driven flexible robotic manipulator, called ColoBot. The focus of this paper lies in the sensor-based position control of the ColoBot for guiding the advancement in a tubular, compliant and slippery environment. The kinematic model related the position of the distal end of the ColoBot to the actuator inputs which is firstly developed and formulated to control the shape of the ColoBot through position control of the distal tip. To achieve safe guidance, the ideal position of the tip should be in the central axis of the colon. A method based on a circumscribed circle is proposed to approximate the central position in real-time based on three sensor readings. This position will be used as reference position for the tip to adjust its shape in real time to avoid the contact with tube wall. This proposed approach can be extended to the control of continuum robots in the conditions of a dynamically confined space. The simulation results and experimental results with a curved tube will be presented in order to validate the proposed control strategy.

Automatic Lip-Contour Extraction and Mouth-Structure Segmentation in Images

Lip-contour extraction has great potential for human-machine interface and communication systems, but most existing techniques are inappropriate for changing poses, malformations, or whole-mouth descriptions. A new mouth-structure segmentation methodology uses pixel color classification, segmentation refinement, and fitted region-of-interest clipping to improve the speed and accuracy of mouth-structure segmentation using standard database images.

The design of a new type of micro robot for the intestinal inspection

In the last few years, we have observed a fast development of modern science and technology. In the field of medical engineering, the same evolution is observed, and the minimally invasive surgery (MIS) has became one of the most important research area. Medical endoscope is one typical medical instrument that complies with the requirement of MIS. This paper deals with the design of a new type of micro-robot for intestinal inspection. Because of the injuries caused by the colonoscope during the operation, and the long time spent at the hospital by the patient, we focus on a new type of intelligent colonoscope. The main purpose of this medical tool is to be in accordance with MIS by minimizing the contact between the colonoscope and the interior boundary of the colon, and to make the progression of the colonoscope easier for the surgeon. Our current prototype, which is twice the size of the final tool, is electro pneumatically driven. It is constituted by three metal bellows disposed 120/spl deg/ apart, and its position in the intestine is driven by three sensors positioned on the superior plate. Some experimental results are presented.

Development and kinematic analysis of a silicone-rubber bending tip for colonoscopy

In this paper, the authors describe the design of a bendable robotic tip for semi-autonomous colonoscopy called COLOBOT. It is a flexible robotic manipulator made of silicone rubber in view of the compact size and biocompatibility. The outer diameter of the tip is 17 mm which is lesser than the average diameter of colon (20 mm). Three servo-valves are used to control the pressure of each chamber of this tip to obtain its flexible movement. The experimental results of this new prototype show that it can bend until 120 degrees under the pressure of 2 bar. Based on the geometric deformation and a nonlinear analysis of the silicone behavior, a direct kinematic model analogous to the forward kinematics of a conventional industrial robot kinematics chain has been put forward. The proposed kinematic model of this bendable tip is an extended model of classical models found for such a mechanism. At first a polynomial approximation is used to characterize the non linear behavior of each chamber of the actuator. Next the coupling phenomena between each chamber are highlighted through experimental tests. A new correction parameter is then proposed to take into account these interactions and a non linear optimization is made to compute this coefficient. Finally, the proposed kinematic model is experimentally validated

CAD-based range sensor placement for optimum 3D data acquisition

The use of laser range sensor allows a very significant improvement in acquisition speed but does not equal the accuracy obtained with a coordinate measuring machine. In order to obtain a quality control close to that obtained in metrology we suggest improving the accuracy of the depth measurements by positioning the sensors head according to a strategy for optimum 3D data acquisition. We propose such a strategy to automatically produce a sensing plan for completely and accurately acquiring the geometry of a surface or of the whole piece whenever possible. The system requires the exact position and orientation of the part and its CAD model in IGES format. There is no limitation regarding the shape of the part to be digitized. An auto-synchronized range sensor developed at the NRCC was used, and for this sensor, the accuracy of the 3D measured points is a function of the distance and of the incident angle relative to the surface. Our strategy guarantees that the viewpoints found meet the best accuracy conditions in the scanning process.

Robotic Assembly by Slight Random Movements

In this paper we develop a compilant system that permits robotic assembly of chamferless pieces. The idea is to absorb the positioning error between parts to be inserted by giving one of them a planar random movement. An actuator consisting of two axes ( X and y ) operated by an electromagnetic System is fitted to the work table; when its inputs are pseudo-random binary signais (P.R.B.S.) random motion is obtained. The trajectories of the actuator are analysed depending upon the P.R.B.S. parameters and a peg-in-a-hole assembly task is carried out. Experimental results show that large positioning errors can be compensated for chamferless insertions.

A CAD-based 3D data acquisition strategy for inspection

Abstract.The use of a laser range sensor in the 3D digitalization process allows significant improvement in acquisition speed and in 3D measurement point density. However, if we want to use these 3D data in applications that require data with a high degree of accuracy like inspection tasks, it is mandatory that the 3D points be acquired under the best conditions of accuracy. During 3D capture of a part, several sources of error can alter the measured values. Thus we must find and model the most important parameters affecting the accuracy of the range sensor. This error model, along with the CAD model of the part, is used to produce a sensing plan to completely and accurately acquire the geometry of the part. The sensing plan is comprised of the set of viewpoints that defines the exact position and orientation of the camera relative to the part. There is no limitation with regard to the shape of the part to be digitalized. An autosynchronized range sensor fixed on a coordinate measuring machine was used. For this sensor, the accuracy of the 3D measured points is a function of the distance and of the angle of incidence relative to the surface. The strategy proposed to find the acquisition plan guarantees that the viewpoints meet the best accuracy conditions in the scanning process, solving the occlusion problems. It was found that the 3D data acquired by using the proposed strategy are around 30% more accurate than the 3D data obtained in a standard acquisition.

Biomechanical simulation of the fetal descent without imposed theoretical trajectory

The medical training concerning childbirth for young obstetricians involves performing real deliveries, under supervision. This medical procedure becomes more complicated when instrumented deliveries requiring the use of forceps or suction cups become necessary. For this reason, the use of a versatile, configurable childbirth simulator, taking into account different anatomical and pathological cases, would provide an important benefit in the training of obstetricians, and improve medical procedures. The production of this type of simulator should be generally based on a computerized birth simulation, enabling the computation of the reproductive organs deformation of the parturient woman and fetal interactions as well as the calculation of efforts produced during the second stage of labor. In this paper, we present a geometrical and biomechanical modeling of the main parturients organs involved in the birth process, interacting with the fetus. Instead of searching for absolute precision, we search to find a good compromise between accuracy and model complexity. At this stage, to verify the correctness of our hypothesis, we use finite element analysis because of its reliability, precision and stability. Moreover, our study improves the previous work carried out on childbirth simulators because: (a) our childbirth model takes into account all the major organs involved in birth process, thus potentially enabling different childbirth scenarios; (b) fetal head is not treated as a rigid body and its motion is computed by taking into account realistic boundary conditions, i.e. we do not impose a pre-computed fetal trajectory; (c) we take into account the cyclic uterine contractions as well as voluntary efforts produced by the muscles of the abdomen; (d) a slight pressure is added inside the abdomen, representing the residual muscle tone. The next stage of our work will concern the optimization of our numerical resolution approach to obtain interactive time simulation, enabling it to be coupled to our haptic device.

A new mechanical birth simulator: BirthSIM

This paper deals with a new mechanical birth simulator (BirthSIM). Currently available birth simulators provide manikins that include new-born head and maternal pelvis but they do not produce the movements of the new-born in the mothers pelvis. Furthermore available maternal pelvis do not include interface pressure and are not enough realistic to simulate maternal pelvic muscles. In summary, these simulators do not help students to practice the gestures they should safely use to help the new-born in normal and at-risk situations of delivery. The originality of our mechanical birth simulator, is to provide a system to mimic the last step of the instrumental delivery, to insure a safe training of junior obstetricians and to test new techniques in obstetrics practice. The new mechanical birth simulator is composed of three parts: a physical new-born head and a maternal pelvis manikin, an interface pressure system, and a pneumatic actuator that develops an active resistance. Driven by a computer, the simulator can simulate the contractions, the interface pressure applied in the new-born head and mimic birth complications.

Assessment of forceps blade orientations during their placement using an instrumented childbirth simulator

This paper aims to highlight the benefits of simulator training in obstetric manipulations such as forceps blade placement. The BirthSIM simulator is used to mimic operative vaginal deliveries. To characterise forceps blade placement, we studied the curvature of forceps path. The orientation of the forceps blades are studied in the quaternion unit space to ensure time‐independent analysis. The results showed progress for all novices in forceps blade placement. Simulator training helps them to develop their self‐confidence and acquire experience before working in the delivery room.