Modellierung, Mehrfachregelung und optimale Steuerung eines leistungsverzweigten hybriden Antriebs

Der globale Klimawandel und die Endlichkeit konventionell eingesetzter Energieträger erfordern u.a. neue Antriebskonzepte in Kraftfahrzeugen. Ein vollkommener Wechsel zu klimaneutralen Energieträgern ist kurzfristig nicht möglich. Hybride Antriebe lassen sich hingegen schneller verbreiten und bieten nicht nur kurzfristig, sondern auch im Falle eines verbreiteten Einsatzes klimaneutraler Energieträger noch Einsparpotentiale. Grundsätzlich unterscheidet man zwischen seriellen, parallelen und leistungsverzweigten hybriden Antrieben. Aus systemtheoretischer Sicht weisen leistungsverzweigte Antriebsstränge die höchste Komplexität (und Ordnung) auf, entsprechendes gilt daher auch für deren Steuerung und Regelung. Insbesondere für die Stabilisierung des Antriebsstrangs im normalen Fahrbetrieb, aber auch für den Wiederstart der Verbrennungskraftmaschine und andere Schaltvorgänge ergeben sich anspruchsvollere Aufgabenstellungen als bei den anderen Varianten. In dieser Arbeit werden die erwähnten Aufgabenstellungen neben der Modellierung eines bestimmten leistungsverzweigten Antriebs eingehend behandelt. Oft weisen leistungsverzweigte Antriebsstränge (aus systemtheoretischer Perspektive) die gleiche Struktur auf wie der hier betrachtete Antriebsstrang. Die untersuchten Problemstellungen sind somit nicht nur für den betrachteten Antriebsstrang, sondern für eine ganze Klasse von Antriebssträngen gelöst.A research project dealing with hybrid drivetrains was treated at Technical University of Braunschweig in cooperation with Volkswagen AG. As a result of this project, a power splitting hybrid drivetrain to be driven in two modes with variable transmission ratio was developed. This thesis describes how to contol this drivetrain and how to derive the necessary mathematical descriptions of the systems to be controlled

Proteomic differences between native and tissue-engineered tendon and ligament

Tendons and ligaments (T/Ls) play key roles in the musculoskeletal system, but they are susceptible to traumatic or age‐related rupture, leading to severe morbidity as well as increased susceptibility to degenerative joint diseases such as osteoarthritis. Tissue engineering represents an attractive therapeutic approach to treating T/L injury but it is hampered by our poor understanding of the defining characteristics of the two tissues. The present study aimed to determine differences in the proteomic profile between native T/Ls and tissue engineered (TE) T/L constructs. The canine long digital extensor tendon and anterior cruciate ligament were analyzed along with 3D TE fibrin‐based constructs created from their cells. Native tendon and ligament differed in their content of key structural proteins, with the ligament being more abundant in fibrocartilaginous proteins. 3D T/L TE constructs contained less extracellular matrix (ECM) proteins and had a greater proportion of cellular‐associated proteins than native tissue, corresponding to their low collagen and high DNA content. Constructs were able to recapitulate native T/L tissue characteristics particularly with regard to ECM proteins. However, 3D T/L TE constructs had similar ECM and cellular protein compositions indicating that cell source may not be an important factor for T/L tissue engineering

Early Growth Response Genes Increases Rapidly After Mechanical Overloading and Unloading in Tendon Constructs

Tendon cells exist in a dense extracellular matrix and mechanical loading is important for the strength development of this matrix. We therefore use a three-dimensional (3D) culture system for tendon formation in vitro. The objectives of this study were to elucidate the temporal expression of tendon-related genes during the formation of artificial tendons in vitro and to investigate if early growth response-1 (EGR1), EGR2, FOS, and cyclooxygenase-1 and -2 (PTGS1 and PTGS2) are sensitive to mechanical loading. First, we studied messenger RNA (mRNA) levels of several tendon-related genes during formation of tendon constructs. Second, we studied the mRNA levels of, for example, EGR1 and EGR2 after different degrees of loading; dynamic physiologic-range loading (2.5% strain), dynamic overloading (approximately 10% strain), or tension release. The gene expression for tendon-related genes (i.e., EGR2, MKX, TNMD, COL3A1) increased with time after seeding into this 3D model. EGR1, EGR2, FOS, PTGS1, and PTGS2 did not respond to physiologic-range loading. But overloading (and tension release) lead to elevated levels of EGR1 and EGR2 (p amp;lt;= 0.006). FOS and PTGS2 were increased after overloading (both p amp;lt; 0.007) but not after tension release (p = 0.06 and 0.08). In conclusion, the expression of tendon-related genes increases during the formation of artificial tendons in vitro, including EGR2. Furthermore, the gene expression of EGR1 and EGR2 in human tendon cells appear to be sensitive to overloading and unloading but did not respond to the single episode of physiologic-range loading. These findings could be helpful for the understanding of tendon tensional homeostasis. (c) 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop ResFunding Agencies|Lundbeck FoundationLundbeckfonden [R198-2015-207]; Nordea Foundation (Center of Healthy Aging) [NF-007IOC]; IOC Sports Medicine Copenhagen; Danish Medical Research CouncilDanish Medical Research Council [0602-02960B]; Swedish Society for Medical Research; Lions Research Foundation; Magnus Bergvall Foundation [2015-01169, 2016-01811]; Swedish Research Council for Sport Science [P2017-0109, D2017-0021]; Swedish Fund for Research without Animal Experiments</p

Tenocyte contraction induces crimp formation in tendon-like tissue

Abstract Tendons are composed of longitudinally aligned collagen fibrils arranged in bundles with an undulating pattern, called crimp. The crimp structure is established during embryonic development and plays a vital role in the mechanical behaviour of tendon, acting as a shock-absorber during loading. However, the mechanism of crimp formation is unknown, partly because of the difficulties of studying tendon development in vivo. Here, we used a 3D cell culture system in which embryonic tendon fibroblasts synthesise a tendonlike construct comprised of collagen fibrils arranged in parallel bundles. Investigations using polarised light microscopy, scanning electron microscopy and fluorescence microscopy showed that tendon constructs contained a regular pattern of wavy collagen fibrils. Tensile testing indicated that this superstructure was a form of embryonic crimp producing a characteristic toe region in the stress-strain curves. Furthermore, contraction of tendon fibroblasts was the critical factor in the buckling of collagen fibrils during the formation of the crimp structure. Using these biological data, a finite element model was built that mimics the contraction of the tendon The results show that the contraction of the fibroblasts is a sufficient mechanical impulse to build a planar wavy pattern. Furthermore, the value of crimp wavelength was determined by the mechanical properties of the collagen fibrils and inter-fibrillar matrix. Increasing fibril stiffness combined with constant matrix stiffness led to an increase in crimp wavelength. The data suggest a novel mechanism of crimp formation, and the finite element model indicates the minimum requirements to generate a crimp structure in embryonic tendon

Early Growth Response Genes Increases Rapidly After Mechanical Overloading and Unloading in Tendon Constructs

Tendon cells exist in a dense extracellular matrix and mechanical loading is important for the strength development of this matrix. We therefore use a three-dimensional (3D) culture system for tendon formation in vitro. The objectives of this study were to elucidate the temporal expression of tendon-related genes during the formation of artificial tendons in vitro and to investigate if early growth response-1 (EGR1), EGR2, FOS, and cyclooxygenase-1 and -2 (PTGS1 and PTGS2) are sensitive to mechanical loading. First, we studied messenger RNA (mRNA) levels of several tendon-related genes during formation of tendon constructs. Second, we studied the mRNA levels of, for example, EGR1 and EGR2 after different degrees of loading; dynamic physiologic-range loading (2.5% strain), dynamic overloading (approximately 10% strain), or tension release. The gene expression for tendon-related genes (i.e., EGR2, MKX, TNMD, COL3A1) increased with time after seeding into this 3D model. EGR1, EGR2, FOS, PTGS1, and PTGS2 did not respond to physiologic-range loading. But overloading (and tension release) lead to elevated levels of EGR1 and EGR2 (p amp;lt;= 0.006). FOS and PTGS2 were increased after overloading (both p amp;lt; 0.007) but not after tension release (p = 0.06 and 0.08). In conclusion, the expression of tendon-related genes increases during the formation of artificial tendons in vitro, including EGR2. Furthermore, the gene expression of EGR1 and EGR2 in human tendon cells appear to be sensitive to overloading and unloading but did not respond to the single episode of physiologic-range loading. These findings could be helpful for the understanding of tendon tensional homeostasis. (c) 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop ResFunding Agencies|Lundbeck FoundationLundbeckfonden [R198-2015-207]; Nordea Foundation (Center of Healthy Aging) [NF-007IOC]; IOC Sports Medicine Copenhagen; Danish Medical Research CouncilDanish Medical Research Council [0602-02960B]; Swedish Society for Medical Research; Lions Research Foundation; Magnus Bergvall Foundation [2015-01169, 2016-01811]; Swedish Research Council for Sport Science [P2017-0109, D2017-0021]; Swedish Fund for Research without Animal Experiments</p