François Xavier Lepoutre

Optimization approach for the simulation of car accessibility movement

The objective of this study is to develop a numeric simulator able to quantify the discomfort during the automobile accessibility movement. An experimental protocol and device were set up in order to record the automobile accessibility movement using the motion analysis system Vicon. A biomechanical human model composed of rigid bodies articulated was also proposed to simulate it. After reconstruction of the ingress/egress movement, a position error exists between the simulated and the experimental trajectories of the hands and feet. This error could imply collisions with the vehicle. In order to correct this error, an optimization procedure is suggested. This method modifies the experimental joint angles so that the simulated trajectories of the limb extremities fit to the experimental data.

Enhancement of open-crack detection in flying-spot photothermal non-destructive testing using physical effect identification

This paper considers the images provided by a photothermal camera (flying-spot camera) dedicated to open-crack detection. In this type of active thermography, both thermal and optical effects contribute to the elaboration of photothermal images. Here the thermal effect is relative to the presence of open-cracks and the optical effects are due to surface conditions. In the case of open-cracks detection, the optical effects induce high magnitude perturbation signals, possibly masking the presence of open-cracks. In this contribution a signal processing method is proposed in order to identify both thermal and optical effects separately. The method lies uses multiple principal component analysis combined with a continuous wavelet transform. It is used to enhance the open-crack detection for the inspection of an industrial mock-up showing open-cracks and various surface conditions. The enhancement of the detection performance is characterized thanks to Receiver Operating Characteristic curves. The proposed method shows high detection performances and could be extended to a classification scheme.

Human articulation efforts estimation in the automobile vehicle accessibility movement: a pilot study

To build a criterion of discomfort evaluation, based on the kinematics and the dynamics of the performed movement, is an expectation of the car manufacturers. There is no reference concerning the evaluation of the articulation efforts during the automobile vehicle accessibility movement. On this point, we propose to give a first reference. Our method and our computation were verified by a well known movement, the walking. The automobile vehicle accessibility movement of a young and healthy subject is studied. The articulation efforts presented are coherent with the produced movements analysis.

Identification of alternative movement techniques during the car entering movement

The objective of this study is to develop a digital human model able to quantify the discomfort during the car entering/exiting movement. Simulating human motions for ergonomics analyses implies to consider alternative movement techniques. The aim of this paper is to identify alternative movement techniques during the car entering movement. A quantitative index called joint contribution vector (JCV) is used. The JCV is a motion in terms of contributions of individual joint degrees of freedom to the achievement of a task goal. The JCV is computed for 20 subjects. A k-mean clustering analysis and a multidimensional scaling analysis are conducted on the JCVs. The results suggest the existence of two motions clusters. The first group consists of 17 subjects and the second group consists of 3 subjects.

Experimental Platform to Assess the Weight Relief Lifting and Sitting Pivot Transfer Movements

Abstract Several times per day, manual wheelchair (MW) users perform weight relief lifting or sitting pivot transfer movements using only their upper limbs. These motions generate significant articular constraints that could lead to musculo-skeletal disorders. The geometry of the hardware configurations of manual wheelchairs influence the movements produced by these MW users. To evaluate this influence, it was necessary to design an instrumented and adjustable experimental platform that would allow the articular efforts of the weight relief lifting and sitting pivot transfer movements to be estimated. The experimental platform that we have developed is composed of 5 adjustable modules: 2 seat modules, 2 armrest modules, and 1 footrest module. These modules are instrumented to allow the effort exerted by the subjects on their environment to be measured, while a motion capture system records the position of reflective markers positioned on the subject. The measured data, coupled with kinematic, anthropometric and dynamic models, make it possible to estimate the articular effort. The results reported in the literature confirm our results, thus validating our method and our instrumentation.

AUTOMOBILE VEHICLE INGRESS/EGRESS MOVEMENT STRATEGIES ADOPTED BY ELDERLY AND/OR, HIP OR KNEE, PROSTHESIS HAVING PERSONS

Abstract This paper presents the automobile ingress/egress movement strategies adopted by 41 test subjects from a mixed population of able-bodied, elderly and/or disabled drivers when entering/exiting four stripped vehicles representing 90% of the automobile types presently on the market. Two general movement families were identified, those starting from a standing position on one foot or on two feet. Eight ingress/egress movement strategies were identified (5 ingress and 3 egress). This paper describes these strategies in terms of the population performing them and the vehicle tested. It appears that no one strategy is used systematically by a single person, since subjects tend to adapt their strategy to the tested vehicle.

Identification of a model to simulate the automobile accessibility movement

The presented works are a part of the realization of an automobile accessibility movement simulator. The aim of this paper is to propose an optimization step of the kinematic model representing the human body. This model is made of two rigid bodies representing the trunk (torso and pelvis) and 4 simple open kinematics chains, in a star-shaped topology, with 7 degrees of freedom constituting the arms and the legs. The reconstruction of the joint angles is computed from the spatial trajectories measurement of some particular points of the body. The criterion optimization is the difference between the experimental and reconstructed trajectories of the end effectors. In results, the best body of reference is the torso and the position of the joint between the torso and the pelvis is located at 20% of the trunk length (roughly at the 10th thoracic vertebra)

Shearographic imaging of the interaction of ultrasonic waves and defects in plates

We present shearographic imaging of the interaction of AO waves with defects in plates. The images are good when the plates are composite plates, due to some attenuation of the waves which prevents reflections. Those images contain information on the interaction between waves and defects. Nevertheless, this information is very difficult to extract and this extraction need numerical models. Here we show some examples of interaction. It is expected that this images will help to better understand the wave-defect interaction and will help to define and optimize health monitoring systems for carbon-epoxy plates and sandwich plates.

Laser-generated Lamb waves in carbon/epoxy composite structures using an embedded fiber optic delivery system

Health and usage monitoring systems for composite structures based on Lamb wave propagation are one of the most promising systems presently evaluated. Generally, they are constituted of a network of piezoelectric transducers. The various transducers generate and receive the Lamb waves. The diagnostic is based on the perturbation in the propagation of the waves due to the presence of the damage. In view to develop less intrusive actuators/sensors, the possibility of using a fiber optic delivery system for laser generation of Lamb waves is evaluated. 125 μm-dia. optical fibers are embedded in the composite during the process. The energy of the pulses are lower than a mJ allowing a good functioning of the system even after several hundred of thousands pulses. The out-of-plane displacement field on the surface of a carbon-epoxy structure equipped by such a system is reconstructed (B-scan) using point measurement from a very sensitive and wide-band (20 kHz - 30 MHz) interferometric probe. The analysis of typical B-scans by 2-D Fourier transform clearly demonstrates the generation of Lamb waves. Various modes are excited, from the fundamental ones to high order ones. Comparison to theoretical dispersion curves is presented.

Defects localization in metallic structures by Magneto Optic Image processing

The Magneto Optic imagery is a good alternative to detect and localize the possible presence of defects such as cracks and corrosion, in various metallic structures commonly used in aeronautical domain. This method, based on eddy currents and Faraday effect, allows obtaining some images of circular areas (∼50 cm2) of structure under test where the main defects are directly visible. This particularity allowing investigating a large structure with a short time, gives a great advantage for this method compared to classical eddy current testing process. However, the obtained images have not a good contrast, their interpretation is not easy and demands a specialist having a good practice. In order to facilitate the visual detection of defects, some algorithms of image processing allowing localizing immediately the main defects, have been developed. After a short description of the Magneto Optic Imager, the two main algorithms of image processing, respectively corresponding to the two main types of defect (crack and corrosion) are presented and discussed. Several images obtained on various real structures are shown. To conclude, the prospect of this method is discussed.The Magneto Optic imagery is a good alternative to detect and localize the possible presence of defects such as cracks and corrosion, in various metallic structures commonly used in aeronautical domain. This method, based on eddy currents and Faraday effect, allows obtaining some images of circular areas (∼50 cm2) of structure under test where the main defects are directly visible. This particularity allowing investigating a large structure with a short time, gives a great advantage for this method compared to classical eddy current testing process. However, the obtained images have not a good contrast, their interpretation is not easy and demands a specialist having a good practice. In order to facilitate the visual detection of defects, some algorithms of image processing allowing localizing immediately the main defects, have been developed. After a short description of the Magneto Optic Imager, the two main algorithms of image processing, respectively corresponding to the two main types of defect (crac...