1,213 research outputs found

    Closed-loop controller for post-impact vehicle dynamics using individual wheel braking and front axle steering

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    This paper presents a vehicle path controller for reducing the maximum lateral deviation (Ymax) after an initial impact in a traffic accident. In previous research, a Quasi-Linear Optimal Controller (QLOC) was proposed and applied to a simple vehicle model with individually controlled brake actuators. QLOC uses non-linear optimal control theory to provide a semiexplicit approximation for optimal post-impact path control, and in principle can be applied to an arbitrary number of actuators. The current work extends and further validates the control method by analysing the effects of adding an active front axle steering actuator at different post-impact kinematics, as well as increasing the fidelity of the vehicle model in the closed-loop controlled system. The controller performance is compared with the results from open-loop numerical optimisation which uses the same vehicle model. The inherent robustness properties of the QLOC algorithm are demonstrated by its direct application to an independent high-fidelity multi-body vehicle model. Towards real-time implementation, the algorithm is further simplified so that the computational efficiency is enhanced, whereas the performance is shown not to be degraded

    Energy reduction by power loss minimisation through wheel torque allocation in electric vehicles: a simulation-based approach

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    As vehicles become increasingly electrified, electrical machines for propulsion can be divided into many sources making the vehicle highly over-actuated. For over-actuated vehicles, the allocation of a propulsive force is an underdetermined process with respect to both the number of wheels and electrical machines. Hence, the allocation can be made to favour particular attributes such as energy consumption. In this study, a vehicle equipped with four identical electric motors with a fixed transmission ratio connected through a half-shaft and a coupling to one wheel respectively is driven a 2-h-long city cycle in the vicinity of G\uf6teborg. Two different control allocation methods are presented to distribute torque momentaneously based on driver request while minimising power losses in electric motor and inverter as well as tyres. One method is a quadratic programming optimisation and the other is an offline exhaustive search method resulting in a look-up table based on requested torque and actual speed. The two methods are compared to other torque distribution strategies based on fixed distribution ratio and equal tyre-to-road friction utilisation. It was found that using the developed optimisation algorithms, a reduction of up to 3.9% in energy consumption can be obtained

    Design and development of a low temperature, inductance based high frequency ac susceptometer

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    We report on the development of an induction based low temperature high frequency ac susceptometer capable of measuring at frequencies up to 3.5 MHz and at temperatures between 2 K and 300 K. Careful balancing of the detection coils and calibration have allowed a sample magnetic moment resolution of 5×1010Am25\times10^{-10} Am^2 at 1 MHz. We will discuss the design and characterization of the susceptometer, and explain the calibration process. We also include some example measurements on the spin ice material CdEr2_2S4_4 and iron oxide based nanoparticles to illustrate functionality

    Reconstruction of Random Colourings

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    Reconstruction problems have been studied in a number of contexts including biology, information theory and and statistical physics. We consider the reconstruction problem for random kk-colourings on the Δ\Delta-ary tree for large kk. Bhatnagar et. al. showed non-reconstruction when Δ12klogko(klogk)\Delta \leq \frac12 k\log k - o(k\log k) and reconstruction when Δklogk+o(klogk)\Delta \geq k\log k + o(k\log k). We tighten this result and show non-reconstruction when Δk[logk+loglogk+1ln2o(1)]\Delta \leq k[\log k + \log \log k + 1 - \ln 2 -o(1)] and reconstruction when Δk[logk+loglogk+1+o(1)]\Delta \geq k[\log k + \log \log k + 1+o(1)].Comment: Added references, updated notatio

    Compendium in Vehicle Motion Engineering

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    This compendium is written for the course “MMF062 Vehicle Motion Engineering” at Chalmers University of Technology. The compendium covers more than included in that course; both in terms of subsystem designs and in terms of some teasers for more advanced studies of vehicle dynamics. Therefore, it is also useful for the more advanced courses, such as “TME102 Vehicle Modelling and Control”.The overall objective of the compendium is to educate engineers that understand and can contribute to development of good motion and energy functionality of vehicles. The compendium focuses on road vehicles, primarily passenger cars and commercial vehicles. Smaller road vehicles, such as bicycles and single-person cars, are only very briefly addressed. It can be mentioned that there exist a lot of ground-vehicle types not covered at all, such as: off-road/construction vehicles, tracked vehicles, horse wagons, hovercrafts, and railway vehicles.Functions are needed for requirement setting, design and verification. The overall order within the compendium is that models/methods/tools needed to understand each function are placed before the functions. Chapters 3-5 describes (complete vehicle) “functions”, organised after vehicle motion directions:\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 Chapter 3:\ua0Longitudinal\ua0dynamics\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 Chapter 4:\ua0Lateral\ua0dynamics\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 Chapter 5:\ua0Vertical\ua0dynamicsChapter 1 introduces automotive industry and the overall way of working there and defines required pre-knowledge from “product-generic” engineering, e.g. modelling of dynamic systems.Chapter 2 also describes the subsystems relevant for vehicle dynamics:• Wheels and Tyre\ua0• Suspension\ua0• Propulsion\ua0• Braking System\ua0• Steering System\ua0• Environment Sensing SystemThe compendium is released in a new version each year, around October, which is the version your read now. A "latest draft" is more frequently updated and often includes some more, sometimes unfinished, material: https://chalmersuniversity.box.com/s/6igaen1ugcjzuhjziuon08axxiy817f

    Spectroscopic and in vitro Investigations of Fe2+/alpha-Ketoglutarate-Dependent Enzymes Involved in Nucleic Acid Repair and Modification

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    The activation of molecular oxygen for the highly selective functionalization and repair of DNA and RNA nucleobases is achieved by alpha-ketoglutarate (alpha-KG)/iron-dependent dioxygenases. Of special interest are the human homologues AlkBH of Escherichia coli EcAlkB and ten-eleven translocation (TET) enzymes. These enzymes are involved in demethylation or dealkylation of DNA and RNA, although additional physiological functions are continuously being found. Given their importance, studying enzyme-substrate interactions, turnover and kinetic parameters is pivotal for the understanding of the mode of action of these enzymes. Diverse analytical methods, including X-ray crystallography, UV/Vis absorption, electron paramagnetic resonance (EPR), circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy have been employed to study the changes in the active site and the overall enzyme structure upon substrate, cofactor, and inhibitor addition. Several methods are now available to assess the activity of these enzymes. By discussing limitations and possibilities of these techniques for EcAlkB, AlkBH and TET we aim to give a comprehensive synopsis from a bioinorganic point-of-view, addressing researchers from different disciplines working in the highly interdisciplinary and rapidly evolving field of epigenetic processes and DNA/RNA repair and modification

    Evaluation of a Commercial Enzyme Linked Immunosorbent Assay (ELISA) for the Determination of the Neurotoxin BMAA in Surface Waters

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    The neurotoxin ß-N-methylamino-L-alanine (BMAA) is suspected to play a role in Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Because BMAA seems to be produced by cyanobacteria, surface waters are screened for BMAA. However, reliable analysis of BMAA requires specialized and expensive equipment. In 2012, a commercial enzyme-linked immunosorbent assay (ELISA) for determination of BMAA in surface waters was released. This kit could enable fast and relatively cheap screening of surface waters for BMAA. The objective of this study was to determine whether the BMAA ELISA kit was suitable for the determination of BMAA concentrations in surface waters. We hypothesised that the recovery of spiked samples was close to 100% and that the results of unspiked sample analysis were comparable between ELISA and liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. However, we found that recovery was higher than 100% in most spiked samples, highest determined recovery was over 400%. Furthermore, the ELISA gave a positive signal for nearly each tested sample while no BMAA could be detected by LC-MS/MS. We therefore conclude that in its current state, the kit is not suitable for screening surface waters for BMAA
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