Ecole De Technologie Research Articles

Flatness tracking control scheme of rehabilitation exoskeleton robot with dynamic uncertainties

Artificial limbs are new robotic devices created to help stroke victims in the rehabilitation process. In this article, we focus our work on applying passive, active or assistive control strategies to provide a physical assistance and rehabilitation by a 7-degree-of-freedom exoskeleton robot with nonlinear uncertain dynamics and unknown bounded external disturbances due to the robot user’s physiological characteristics. The flatness controller combined with time-delay estimation is designed for the 7-degree-of-freedom exoskeleton robot called ETS-MARSE (Ecole de Technologie Supérieure—Motion Assistive Robotic-exoskeleton for Superior Extremity) in order to ensure a passive rehabilitation exercises with a high level of tracking accuracy and robustness against the uncertainty constraints. The stability analysis of such systems is proven using the Lyapunov–Krasovskii functional theory. This approach is illustrated by experimental results with healthy human to highlight the efficiency of the suggested controller scheme.

Optimization of injectable scaffolds with enhanced mechanical properties for cell therapy and tissue engineering

Event Abstract Back to Event Optimization of injectable scaffolds with enhanced mechanical properties for cell therapy and tissue engineering Caroline Ceccaldi1, 2, Sepideh Samei1, 2, Yasaman Alinejad1, 2, Medeine Bucionyte2, Marta Cerruti3 and Sophie Lerouge1, 2 1 Ecole de technologie supérieure (ETS), Department of Mechanical Engineering, Canada 2 Centre de recherche du CHUM (CRCHUM), Laboratoire de biomatériaux endovasculaires (LBeV), Canada 3 McGill University, Materials Engineering, Canada Introduction: Injectable hydrogels present high potential for cell therapy and tissue engineering because they can ensure appropriate localization, retention and survival of seeded cells. They should also provide them with a mechanically resistant support despite injection through catheters and needles to minimize surgical incision. In this project we discovered and optimized thermosensitive chitosan hydrogels with enhanced mechanical properties and biocompatibility for cell therapy applications. Materials and Methods: Chitosan (CH) acidic solution was combined with a mix of sodium hydrogen carbonate (SHC) and phosphate buffer (PB) or beta-glycerophosphate (BGP) and compared to conventional CH-BGP gels[1]. The effect of formulation on rheological properties, injectability, macroporosity and mechanical strength were evaluated by rheometry (Physica MCR301), SEM, compression and tensile tests (Bose Electroforce).To assess potential for cell encapsulation, pH and osmolality were measured and survival and growth of encapsulated fibroblasts and mesenchymal stem cells were evaluated over 7 days by alamar-blue and Live/Dead. Hydrogels were injected subcutaneously in rats. Finally, the best formulations were further optimized using chondroitin sulfate and addition of catechol groups[2] to improve cell growth and tissue adhesion respectively. Results and Discussion: Mechanical characterization in tension and compression were drastically enhanced compared to conventional CH-BGP hydrogels, highest properties being observed for SHC at 0.075M and slightly decreasing as a function of PB concentration. Secant Young modulus at 50% rose from 6±1 for CH-BGP0.4M up to 158±11 kPa (25 fold increase) and the ultimate strength from 13 to 143 kPa (10 fold increase). Hydrogels presented clear thermosensitive properties (Fig.1a) with relatively stable complex viscosity at room temperature and drastic increase of the storage modulus (G’) around 35°C. This ensures easy and homogenous encapsulation of cells and drugs, injectability though small-diameter catheter and needles (Fig.1b), but rapid formation of a cohesive and load-bearing structure after injection in vivo. Cell survival was excellent thanks to isoomolality and macroporosity of the scaffold (Fig. 2). CS was found to further increase cell growth, while the effect of chitosan modification with catechol groups on tissue adhesion is under evaluation. Conclusion: These new injectable scaffolds present excellent mechanical properties and can be fine-tuned depending on the targeted application. They hold great promise for cell therapy and tissue engineering.

On the Optimization of the Aggregate Packing Characteristics for the Design of High-Performance Asphalt Concretes

ABSTRACT In the framework of a partnership between the European EIFFAGE Travaux Publics Group and the Ecole de Technologie Supérieure (ETS) from Montreal (Québec), some basic concepts associated with granular combinations and aggregate packing characteristics enabled the development and design of high-performance self-blocking asphalt concretes. The aggregate packing methods first developed in the field of high-performance cement concretes were successfully transposed to the field of asphalt concretes. Laboratory assessment in both laboratories of the ETS and EIFFAGE Travaux Publics consisted in the evaluation of the compactin g ability using the French gyratory shear compactor (GSC), the resistance to moisture using the so-called Duriez test, the resistance to rutting thanks to the French wheel tracking tester at 60°C, the secant stiffness modulus at 15°C and the fatigue resistance at 10°C. The paper concludes that the grading analysis concepts allow the design engineer new insights into the structure of aggregates. The proposed principles can be used to develop more specific guidelines for aggregate structure selection of high-performance asphalt concretes.

Application of visual analog scales (VAS) for the comparative evaluation of tool and equipment designs and work methods

For a few years now, researchers of the Equipe de recherche en sécurité du travail (EREST) at the Ecole de technologie supérieure have been using psychophysical methods, VAS in particular, in their research work, in order to make precise assessments of tools, equipments and working methods. In all studies conducted, using VAS enabled the researchers to carry out precise evaluations and to recommend solutions for validating a choice, or to make the required modifications to tools, equipments or working methods. When physiological and/or physical measurements were also recorded at the same time as the psychophysical evaluations, results have consistently shown excellent correlation between these measurements. In this article, we present a summary of the main studies where the psychophysical technique of visual analog scales has been used successfully.