With increasing attention to physical human-machine interaction (pHMI), new control methods involving contact force regulation in collaborative and coexistence scenarios have spread in recent years. Thanks to its internal robustness, high dynamic performance, and capabilities to avoid constraint violations, a Model Predictive Control (MPC) action can pose a viable solution to manage the uncertainties involved in those applications. This paper uses an MPC-driven control method that aims to apply a well-defined and tunable force impulse on a human subject. After describing a general control design suitable to achieve this goal, a practical implementation of such a logic, based on an MPC controller, is shown. In particular, the physical interaction considered is the one occurring between the body of a patient and an external perturbation device in a dynamic posturography trial. The device prototype is presented in both its hardware architecture and software design. The MPC-based main control parameters are thus tuned inside hardware-in-the-loop and human-in-the-loop environments to get optimal behaviors. Finally, the device performance is analyzed to assess the MPC algorithm’s accuracy, repeatability, flexibility, and robustness concerning the several uncertainties due to the specific pHMI environment considered.

Thermosonic wire bonding is a common fabrication process for connecting devices in electronic packaging. However, when the free air ball (FAB) is compressed onto the I/O pad of the chip during bonding procedure, chip cracking may occur if the contact pressure is too large. This study proposes an effective simulation technique that can predict the wire ball geometry after bonding in an accurate range. The contact force obtained in the simulation can be used for possible die cracking behavior evaluation. The simulation in this study used the explicit time integration scheme to deal with the time marching problem, and the second-order precision arbitrary Lagrangian-Eulerian (ALE) algorithm was used to deal with the large deformation of the wire ball during the bonding process. In addition, the equilibrium smoothing algorithm in LS-DYNA can make the contact behavior and geometry of the bonding wire almost the same as the experiment, which can also significantly reduce the distortion of the mesh geometry after remeshing.

In the present paper, the low-velocity impact of an elastic rod with a flat end upon a viscoelastic Timoshenko type beam has been considered. Viscoelastic properties of the beam out of the contact zone are described by the standard linear solid model with integer derivatives, while inside this zone they are governed by the fractional derivative standard linear solid model. The contact force for a concrete target has been defined experimentally at the concrete age of 7, 14, 28, 56, and 91 days. It has been found that an average maximum of the contact force increases with concrete age, whereas the contact duration decreases. Moreover, the most remarkable changes of both, contact force and contact time, occur at the concrete age earlier than 14 days, after that the rate of changes slows down. Experimental results have a good coincidence with theoretical expectations.

In reality, clearances in the joints are inevitable due to tolerances, and defects arising from design and manufacturing. Therefore, poor dynamic performance, reduction in components component lifetimes and generation of undesirable vibrations result in impacts of mating parts in the clearance joint. In this study, the dynamic behavior of a planar mechanism with revolute joints, in the presence of clearances is investigated. A continuous contact force model, based on elastic Hertz theory together with a dissipative term, is used to evaluate the contact forces here. Moreover, using a contact model, the effects of working speed and clearance size on the dynamic characteristics of a planar mechanical system are analyzed and compared. Furthermore, numerical results for a 3RRR planar parallel manipulator with six revolute clearance joints are presented.

Currently, there exists a lack of confidence in the computational simulation of multiple body high-speed air delivered systems. Of particular interest is the ability to accurately predict the dispersion pattern of these systems under various deployment configurations. Classical engineering-level methods may not be able to predict these patterns with adequate confidence due primarily to accuracy errors attributable to reduced order modeling. In the current work, a new collision modeling capability has been developed to enable multiple-body proximate-flight simulation in the Loci/CHEM framework. This approach maintains high-fidelity aerodynamics and incorporates six degrees of freedom modeling with collision response, and is well-suited for simulation of a large number of projectiles. The proposed simulation system is intended to capture the strong interaction phase early in the projectile deployment, with subsequent transfer of projectile positions and flight states to the more economical engineering-level methods. Collisions between rigid bodies are modeled using an impulse-based approach with either an iterative propagation method or a simultaneous method. The latter is shown to be more accurate and robust for cases involving multiple simultaneous collisions as it eliminates the need to sort and resolve the collisions sequentially. The implementation of both the collision detection methodology and impact mechanics are described in detail with validation studies to demonstrate the efficiency and accuracy of the developed technologies. The studies chronologically detail the findings for simulating simple impacts and collisions between multiple bodies with aerodynamic interference effects.

In the present paper, the problem on normal low-velocity impact of a solid upon an isotropic spherical shell is studied without considering the changes in the geometrical dimensions of the contact domain. At the moment of impact, shock waves (surfaces of strong discontinuity) are generated in the target, which then propagate along the shell during the process of impact. Behind the wave fronts up to the boundary of the contact domain, the solution is constructed with the help of the theory of discontinuities and one-term ray expansions. The ray method is used outside the contact spot, but the Laplace transform method is applied within the contact region. As a result, the exact solution of the contact force is determined as a function of time. This model is intended to be used in simulating crash scenarios in frontal impacts, and to provide an effective tool to estimate the severity of effect on the human head and to estimate brain injury risks.

La connaissance de l'effort de contact entre le pantographe et la caténaire est un élément essentiel de l'évaluation de la qualité du captage du courant. La SNCF étudie cet effort pour qualifier le matériel et les infrastructures nouvelles, ou en vue de détecter les défauts dans la caténaire.La méthode de mesure utilisée jusqu'à présent, basée sur une hypothèse d'archet rigide, a une bande passante limitée bien en deçà de la première fréquence propre de l'archet.Pour franchir cette limitation, notamment pour les trains à grande vitesse, et pour la détection de défaut par analyse de la signature vibratoire, une nouvelle méthodologie, basée sur la prise en compte des modes propres de l'archet, est proposée. Vibratec développe depuis plusieurs années des méthodes inverses [6,7] pour remonter aux efforts injectés à partir des vibrations mesurées. L'originalité du contact pantographe caténaire réside dans le fait que la position du point de contact est une inconnue du problème. La méthode inverse utilisée est basée sur l'analyse modale des premiers modes de l'archet. L'écriture de l'équilibre dynamique de l'archet permet d'aboutir à un système d'équations dont la résolution donne le module de l'effort et son point d'application. Les résultats obtenus sur un dispositif expérimental de validation, à partir d'une base modale limitée aux 3 premiers modes de l'archet, montrent un gain important sur la bande utile de la mesure, qui passe de 45 Hz à 120 Hz. Par la suite, la bande passante pourra encore être étendue en considérant davantage de modes de déformation de l'archet. Un utilitaire a été développé sous Matlab pour la mise en œuvre de la méthode à partir de données expérimentales.