The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. https://localhost:443/yetl1 2026-09-10T13:50:31Z 2026-09-10T13:50:31Z Pagès Sanchis, Carlos Maceratesi, Filippo Febrer-Nafría, Míriam http://yetl.yabesh.ir/yetl1/handle/yetl/4316949 2026-08-23T08:43:30Z 2026-01-01T00:00:00Z

Predicting the Effects of Walker Height and Weight Support on Assisted Gait Using Physics-Based Predictive Simulations Pagès Sanchis, Carlos; Maceratesi, Filippo; Febrer-Nafría, Míriam Abstract. Walker-assisted gait is widely used in clinical rehabilitation for individuals with muscle weakness and balance impairments. This study presents a first step toward developing a predictive simulation framework that integrates a 3D full-body musculoskeletal model driven by muscle torque generators within an optimal control problem. We calibrated the muscle torque generators model using experimental isometric and isokinetic data from a healthy participant, obtained from a biodex dynamometer equipment. To assess the predictive capability of the framework, we evaluated the effects of walker height and percentage of body weight support on walker-assisted gait patterns by running nine predictive simulations across varying walker configurations. Results showed that effects of walker height were well predicted (e.g., elbow flexion increased with walker height from a mean value of 81.59 deg to 93.86 deg), while effects of weight support were only partially predicted (e.g., upper body joints did not show a clear trend with changes in weight support). Results suggest that developing a detailed hand-walker interaction model would significantly improve the realism of the simulations. This study provides an important step toward optimizing walker-assisted gait through simulation-based design and personalization.

2026-01-01T00:00:00Z Ahmed, Rizwan Ferhatoglu, Erhan Tamatam, Lakshminarayana Reddy Firrone, Christian Maria Zucca, Stefano http://yetl.yabesh.ir/yetl1/handle/yetl/4316948 2026-08-23T08:43:24Z 2026-01-01T00:00:00Z

An Improved Experimental Validation of Nonlinear Forced Response Simulation of Shrouded Blades Ahmed, Rizwan; Ferhatoglu, Erhan; Tamatam, Lakshminarayana Reddy; Firrone, Christian Maria; Zucca, Stefano Abstract. Friction damping devices like tip shrouds are usually employed in low pressure turbine (LPT) blades to reduce their large vibration amplitudes. From an engineering point of view, experimental validation of the numerically predicted dynamic behavior of the blade is essential to demonstrate the damping performance of shrouds in LPTs. In accordance with this purpose, this study presents the comparison of experimental and numerical results for the detailed investigation of the dynamic behavior of shrouded turbine blades. A brief overview of the experimental test rig, which has been previously developed to measure both the nonlinear forced response and contact forces simultaneously, is first presented. The experimental results show the effect of different normal preloads and excitation force levels on the measured parameters. To compute the nonlinear forced response of the blade and the shroud contact forces, the test rig is modeled in a commercial finite element (FE) software, and the system matrices are extracted in a reduced order form. The harmonic balance method (HBM) is applied in a nonlinear solver developed dedicatedly with the implementation of a 3D contact model. The comparison of the experimental and numerical results is presented in particular cases where lower normal preload to excitation force ratio results in alternate stick and slip transitions. The results show that experimental dynamic behavior of shrouded blade is computationally captured in most of the cases. The nonmatching results are also highlighted for some cases in which the nonunique contact forces introduce the response variability. For these cases, response boundaries are numerically estimated by utilizing an optimization algorithm. The outcomes of this paper consequently exhibit a detailed validation procedure for the simulation tools and an understanding of the numerical concerns like convergence.

2026-01-01T00:00:00Z Nguyen, Tien Dung Nguyen, Tung Lam Le, Duc Thinh http://yetl.yabesh.ir/yetl1/handle/yetl/4316947 2026-08-23T08:43:21Z 2026-01-01T00:00:00Z

Robust Prescribed Performance Control for Heavy-Haul Freight Trains Under Actuator Faults and Input Time Delays Nguyen, Tien Dung; Nguyen, Tung Lam; Le, Duc Thinh Abstract. With the rapid development of autonomous vehicles, heavy-haul freight trains (HhFT), with their capability of transporting large volumes of cargo over long distances, are emerging as promising subjects for research in automatic control. One of the main challenges in operating HhFT lies in ensuring accurate trajectory tracking performance under the influence of adverse factors such as external disturbances, model uncertainties, and actuator-related issues, including actuator faults and input time delays. If not effectively addressed, these factors can significantly degrade the control performance of the system. This paper presents a robust trajectory tracking control system with prescribed performance for HhFTs using multiple electric locomotives. In this framework, a prescribed performance function (PPF) is designed to ensure that the position tracking errors of the locomotives remain within a predefined bound. Simultaneously, an extended state observer (ESO) is employed to estimate the states and the lumped disturbances representing the adverse effects. Based on the outputs of the PPF and the ESO, a robust sliding mode controller (RSMC) is designed. The stability of the closed-loop system is proven through Lyapunov stability theory, showing that all system states converge to a neighborhood of the origin in finite time. Computer simulation results clearly demonstrate the superior control performance of the proposed system compared to previously introduced methods.

2026-01-01T00:00:00Z Peloquin, John M. Newman, Harrah R. Elliott, Dawn M. http://yetl.yabesh.ir/yetl1/handle/yetl/4316946 2026-08-23T08:43:19Z 2026-01-01T00:00:00Z

Vertebral Body Kinematics Measured From T1-Weighted Magnetic Resonance Imaging With Optimized Rigid Registration Peloquin, John M.; Newman, Harrah R.; Elliott, Dawn M. Abstract. Magnetic resonance imaging (MRI) is a useful method to noninvasively measure vertebral kinematics (rotations and translations). Measurement of vertebral kinematics should be both fast and accurate, a need potentially satisfied by automatic registration of reference–deformed image pairs. So far, MRI registration has not been systematically optimized for this application. The objective of this study therefore was to apply automatic 3D image registration methods to the measurement of vertebral kinematics from MRI: first, to systematically optimize all registration parameters to minimize registration error across a representative dataset; second, to reanalyze a separate, previously published, MRI dataset of diurnal, flexion, and extension vertebral body (VB) mechanics using the optimized registration to reduce the dataset's measurement error and clarify its interpretation. Validation against manual registrations indicated that midsagittal vertebral body marker position error in the sagittal plane was 0.10±0.08 mm, well below the pixel size of 0.5 mm, with corresponding negligible errors in change in wedge angle (Δ wedge angle), change in disc height (Δ disc height), and A–P translation. Reanalysis of diurnal mechanics data revealed that diurnal Δ wedge angle, with subjects scanned supine, is essentially zero despite significant A–P translation and disc height loss. Distinct kinematics at the L5–S1 disc level were also observed. Relative to manual marker-based methods, use of this image registration method in future work would allow sample size to be halved with no change in statistical power. This optimized registration method will increase the efficiency of future research and may allow detection of effects that would otherwise be overlooked.

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