Search Results (4)

This letter derives and discusses the superiority of a simple dc-link capacitor voltage control configuration for multilevel neutral-point-clamped converters with any number of levels. The control involves n − 2 control loops regulating the difference between the voltage of neighbor capacitors. These control loops are inherently decoupled, i.e., they are independent and the control action of one loop does not affect the others. This method is proven to be equivalent to previously published approaches, with the added advantages of increased simplicity and scalability to a higher number of levels, all while imposing a lower computational burden. The good performance of such control is confirmed through simulations and experiments. Full article

Flexible 3D stretch bending (FSB) is a technology that uses multi-point molds instead of traditional integral molds to bend and deform profiles. Since the position of a multi-point mold can be adjusted in the horizontal and vertical directions, a set of molds can be used to form profile products with different contour structures. Due to the contact area and non-contact area between the multi-point mold and the surface of the profile, the forming accuracy of different areas is different. Thus, the axial normal stress and bending moment of the contact zone and non-contact zone between the profile and roller dies are studied in this article. By simulating the change in axial normal stress at the same position in the middle of a web along the axial direction, it is found that the axial normal stress shows little difference in the contact zone and non-contact zone. The value of axial normal stress in the non-contact zone is relatively stable, and there is a small increase on the side near the clamp. By simulating the axial normal stress of different cross-sections in the middle areas of three groups of webs, it is found that there is a linear relationship between the axial normal stress and the distance from inner curved surface. The bending moment of the profile in the contact zone is obviously greater than that in the non-contact zone, and the bending moment gradually decreases to near zero from the contact zone to the non-contact zone. The bending deformation of the profile in the contact zone is obviously greater than that in the non-contact zone, which results in the deviation between simulated bending displacement and theoretical bending displacement in the contact zone and non-contact zone. Full article

Vibrissae are an important tactile sense organ of many mammals, in particular rodents like rats and mice. For instance, these animals use them in order to detect different object features, e.g., object-distances and -shapes. In engineering, vibrissae have long been established as a natural paragon for developing tactile sensors. So far, having object shape scanning and reconstruction in mind, almost all mechanical vibrissa models are restricted to contact scenarios with a single discrete contact force. Here, we deal with the effect of multi-point contacts in a specific scanning scenario, where an artificial vibrissa is swept along partly concave object contours. The vibrissa is modeled as a cylindrical, one-sided clamped Euler-Bernoulli bending rod undergoing large deflections. The elasticae and the support reactions during scanning are theoretically calculated and measured in experiments, using a spring steel wire, attached to a force/torque-sensor. The experiments validate the simulation results and show that the assumption of a quasi-static scanning displacement is a satisfying approach. Beyond single- and two-point contacts, a distinction is made between tip and tangential contacts. It is shown that, in theory, these contact phases can be identified solely based on the support reactions, what is new in literature. In this way, multipoint contacts are reliably detected and filtered in order to discard incorrectly reconstructed contact points. Full article

Prototype monitoring techniques play an important role in the safety guarantee of mooring systems in marine engineering. In general, the complexities of harsh ocean environmental conditions bring difficulties to the traditional monitoring methods of application, implementation and maintenance. Large amounts of existing mooring systems still lack valid monitoring strategies. In this paper, an underwater monitoring method which may be used to achieve the mechanical responses of a multi-point catenary mooring system, is present. A novel self-contained assembled water depth-inclination (D-I) sensor is designed and manufactured. Several advanced technologies, such as standalone, low power consumption and synchronism, are considered to satisfy the long-term implementation requirements with low cost during the design process. The design scheme of the water resistance barrel and installation clamp, which satisfies the diver installation, are also provided in the paper. An on-site test has previously been carried out on a production semisubmersible platform in the South China Sea. The prototype data analyses, including the D-I value in the time domain (including the data recorded during the mooring retraction and release process) and spectral characteristics, are presented to reveal the accuracy, feasibility and stability of the sensor in terms of fitting for the prototype monitoring of catenary mooring systems, especially for in-service aging platforms. Full article