Increasing the Level of Automation in the Forestry Logging Process with Crane Trajectory Planning and Control

Working with forestry machines requires a great deal of training to be sufficiently skilled to operate forestry cranes. In view of this, it would be desirable within the forestry industry to introduce automated motions, such as those seen in robotic arms, to shorten the training time and make the work of the operator easier. Motivated by this fact, we have developed two experimental platforms for testing control systems and motion‐planning algorithms in real time. They correspond to a laboratory setup and a commercial version of a hydraulic manipulator used in forwarder machines. The aim of this article is to present the results of this development by providing an overview of our trajectory‐planning algorithm and motion‐control method, with a subsequent view of the experimental results. For motion control, we design feedback controllers that are able to track reference trajectories based on sensor measurements. Likewise, we provide arguments to design controllers in an open‐loop for machines that lack sensing devices. Relying on the tracking efficiency of these controllers, we design time‐efficient reference trajectories of motions that correspond to logging tasks. To demonstrate performance, we provide an overview of extensive testing done on these machines.     

Pseudoelasticity of Metal Nanoparticles Is Caused by Their Ultrahigh Strength

An assembly of hemispherical Ag nanoparticles is prepared by solid‐state dewetting of thin Ag film deposited on the sapphire substrate. The in situ nanomechanical compression testing of the particles with a flat diamond punch inside the scanning electron microscope demonstrates the deformation behavior typical for the nucleation‐controlled plasticity: high elastic deformation followed by an abrupt particles collapse. The latter is associated with the dislocations nucleation in otherwise pristine particle. The average contact pressure in the contact zone at the onset of dislocation‐controlled plasticity is about 8 GPa, and does not depend on particle size. This observation supports the hypothesis that the pseudoelasticity of much smaller Ag nanoparticles is intrinsically related to their ultrahigh strength. A stress‐induced diffusion along the particle–substrate and particle–punch interfaces is identified as a factor controlling the pseudoelastic deformation. The corresponding diffusion model allows estimating the room‐temperature self‐diffusion coefficient of Ag along the Ag–W and Ag–zirconia interfaces, which is quite close to the estimated value of the grain boundary self‐diffusion coefficient in Ag. Based on this finding, the map of pseudoelastic deformation of crystalline materials is proposed.     

Updated safety analysis of ITER

An updated version of the ITER Preliminary Safety Report has been produced and submitted to the licensing authorities. It is revised and expanded in response to requests from the authorities after their review of an earlier version in 2008, to reflect enhancements in ITER safety provisions through design changes, to incorporate new and improved safety analyses and to take into account other ITER design evolution. The updated analyses show that changes to the Tokamak cooling water system design have enhanced confinement and reduced potential radiological releases as well as removing decay heat with very high reliability. New and updated accident scenario analyses, together with fire and explosion risk analyses, have shown that design provisions are sufficient to minimize the likelihood of accidents and reduce potential consequences to a very low level. Taken together, the improvements provided a stronger demonstration of the very good safety performance of the ITER design.     

On the use of multi-path inductorless TIAs for larger transimpedance limit

This paper discusses the use of mutli-path inductorless transimpedance amplifiers (TIAs), consisting of several different second-order shunt-feedback sub-TIAs (SF-sTIAs) driven by the photodiode, to break the single-stage technology-dependent transimpedance limit. The advantage of the MP-TIA that is explored in this work is in its third-order transfer function, which provides additional degrees of freedom in tailoring the performance. Pole and zero locations of the MP-TIA transfer function are examined and verified with behavioural simulations. The theoretical transimpedance limit for MP-TIAs based on two SF-sTIAs is derived. The possibility of further increasing the transimpedance limit vs bandwidth trade-off by combining three and four sub-TIAs is investigated with simulations. A transistor-level design example of an MP-TIA is presented. The 0.13-μm CMOS MP-TIA achieves the largest figure-of-merit among published TIAs.