Enhancing Machine Learning-Based Feedforward Control of 2-DOF Flexure Manipulator: Benefits of Time-Delay Embedding

This research uses machine learning techniques to enhance a feedforward controller for a fully actuated 2 degrees of freedom manipulator with flexure joints. The foundation of the controller is a combination of the Lagrangian Neural Network to model the system’s conservative forces and the Feedforward Neural Network to simulate non-conservative ones. To address the limitations of both networks in precisely modeling the reproducible part of these forces, we introduce the weighted least-squares method with regularization, which maps the system’s configurations to the residue of control signals (error) and adjusts the model with rank-1 updates. Inevitable trade-offs apply when one uses Time-Delay Embedding, but the preliminary results indicate its feasibility in application to improve the used error learning approach

Index-3 divide-and-conquer algorithm for efficient multibody system dynamics simulations: theory and parallel implementation

[Abstract] There has been a growing attention to efficient simulations of multibody systems, which is apparently seen in many areas of computer-aided engineering and design both in academia and in industry. The need for efficient or real-time simulations requires high fidelity techniques and formulations that should significantly minimize computational time. Parallel computing is one of the approaches to achieve this objective. This paper presents a novel index-3 divide-and-conquer algorithm for efficient multibody dynamics simulations that elegantly handles multibody systems in generalized topologies through the application of the augmented Lagrangian method. The proposed algorithm exploits a redundant set of absolute coordinates. The trapezoidal integration rule is embedded into the formulation and a set of nonlinear equations need to be solved every time instant. Consequently, the Newton–Raphson iterative scheme is applied to find the system coordinates and joint constraint loads in an efficient and highly parallelizable manner. Two divide-and-conquer based mass-orthogonal projections are performed then to circumvent the effect of constraint violation errors at the velocity and acceleration level. Sample open- and closed-loop multibody system test cases are investigated in the paper to confirm the validity of the approach. Challenging simulations of multibody systems featuring long kinematic chains are also performed in the work to demonstrate the robustness of the algorithm. The details of OpenMP-based parallel implementation on an eight-core shared memory computer are presented in the text and the parallel performance results are extensively discussed. Significant speedups are obtained for the simulations of small- to large-scale multibody open-loop systems. The mentioned features make the proposed algorithm a good general purpose approach for high-fidelity, efficient or real-time multibody dynamics simulations.Ministerio de Economía y Competitividad; JCI-2012-12376Poland. National Science Center; DEC-2012/07/B/ST8/0399

Olbrzymi naczyniak jamisty móżdżku u 4-miesięcznego niemowlęcia. Opis przypadku i przegląd piśmiennictwa

Cavernous malformations (CMs) are rare vascular lesions that affect 0.4–0.9% of the population. The diagnosis of CMs is simple in most typical cases although some lesions may present unusual imaging features: localization, signal intensity, or size. Extremely rare giant CMs can mimic neoplastic lesion because of their size. We report a case of giant cerebellar CM that is more than 6 cm in size, diagnosed in 4-month-old boy. We discuss magnetic resonance findings and histopathological features of this lesion.Naczyniaki jamiste to rzadkie zmiany naczyniowe, występujące u 0,4–0,9% populacji. Ich rozpoznanie w większości typowych przypadków jest łatwe, ale niektóre zmiany mogą stwarzać trudności diagnostyczne związane z nietypową lokalizacją, ich intensywnością sygnału lub wielkością. Niezwykle rzadkie gigantyczne naczyniaki jamiste mogą imitować zmiany nowotworowe. Autorzy przedstawiają 4-miesięczne niemowlę, u którego rozpoznano olbrzymi naczyniak jamisty zlokalizowany w móżdżku o wymiarze większym niż 6 cm. Omawiają cechy naczyniaka w badaniu za pomocą rezonansu magnetycznego oraz wynik badania histopatologicznego

Modeling and control of a simplified high-speed vehicle moving in reduced-pressure conditions

In times of rapidly progressing globalization, the possibility of fast long-distance travel between high traffic cities has become an extremely important issue. Currently, available transportation systems have numerous limitations, therefore, the idea of a high-speed transportation system moving in reduced-pressure conditions has emerged recently. This paper presents an approach to the modelling and simulation of the dynamic behaviour of a simplified high-speed vehicle that hovers over the track as a magnetically levitated system. The developed model is used for control system design. The purpose of passive and active suspension discussed in the text is to improve both the performance and stability of the vehicle as well as ride comfort of passengers travelling in a compartment. Comparative numerical studies are performed and the results of the simulations are reported in the paper with the intent to demonstrate the benefits of the approach employed here