Integrated Servo-mechanical Design of High Performance Mechanical Systems

Ph.DDOCTOR OF PHILOSOPH

Mixed H2/H∞ control for infinite dimensional systems

The class of infinite dimensional systems often occurs when dealing with distributed parameter models consisting of partial differential equations. Although forming a comprehensive description, they mainly become manageable by finite dimensional approximations which likely neglect important effects, but underlies a certain structure. In contrast to common techniques for controlling infinite dimensional systems, this work focuses on using robust control methods. Thus, the uncertainty structure that occurs due to the discretization shall be taken into account particularly. Additionally, optimal performance measures can be included into the design process. The mixed H2/H∞ control approach handles the inclusion of disturbances and inaccuracies while guaranteeing specified energy or magnitude bounds. In order to include various of these system requirements, multi-objective robust control techniques based on the linear matrix inequality framework are utilized. This offers great flexibility concerning the formulation of the control task and results in convex optimization problems which can be solved numerically efficient by semi-definite programming. A flexible robot arm structure serves as the major application example during this work. The model discretization leads to an LTI system of specified order with an uncertainty model which is obtained by considering the concrete approximation impact and frequency domain tests. A structural analysis of the system model relates the neglected dynamics to a robust characterization. For the objective selection, stability shall be ensured under all expected circumstances while the aspects of optimal H2 performance, passive behavior and optimal measurement output selection are included. The undesirable spillover effect is thoroughly investigated and thus avoided.Tesi

Polarizable Particles and their Two-Dimensional Arrays: Advances in Small Antenna and Metasurface Technologies.

Metamaterials are subwavelength-structured materials designed to exhibit tailored electromagnetic properties. Metamaterials have allowed extreme control over constituent material parameters (i.e. permittivity, permeability, and chirality), which has enabled a myriad of counterintuitive physical phenomena. However, metamaterials typically suffer from high losses, difficulties in fabrication, and are bulky. This has led to the development of metasurfaces, which are the two dimensional equivalent of metamaterials. Metasurfaces can impart abrupt discontinuities on electromagnetic wavefronts, allowing electromagnetic fields to be tailored across subwavelength length scales. The building blocks of metasurfaces are subwavelength textured, polarizable particles. Near resonance, these particles support strong currents, which makes them excellent small antennas. In this thesis, a circuit model is developed that can model an arbitrary small antenna based on its frequency dependent polarizability. In addition, a direct transfer patterning process is developed that allows metallic patterns to be printed onto arbitrarily contoured substrates. This work will find immediate applications in a number of emerging technologies resulting from the rapid expansion of the mobile electronics industry. Next, extreme control of the polarization and profile of a wavefront is demonstrated using two-dimensional arrays of polarizable particles (i.e. metasurfaces). A new class of metasurfaces, referred to as metamaterial Huygens' surfaces, is shown to have a significantly improved efficiency over the state of the art. Metamaterial Huygens' surfaces utilize polarizable particles that exhibit both an electric and magnetic response, which allows for reflectionless wavefront control. Next, it is shown that simply cascading patterned metallic sheets can also provide high transmission and complete phase control. To demonstrate the design methodology, several different metasurfaces are developed that deflect incident Gaussian beams to a stipulated angle or convert an incident Gaussian beam into a vector Bessel beam. Further, utilizing sheets with anisotropic patterns provides additional magneto-electric coupling, which enables complete control of a wavefront (i.e. amplitude, phase, and polarization control). The experimental verification at frequencies ranging from microwaves to optics highlights the versatility of this work.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111395/1/carlpfei_1.pd

Flexible adaptation of iterative learning control with applications to synthetic bone graft manufacturing

Additive manufacturing processes are powerful tools; they are capable of fabricating structures without expensive structure specific tooling -- therefore structure designs can efficiently change from run-to-run -- and they can integrate multiple distinct materials into a single structure. This work investigates one such additive manufacturing process, micro-Robotic Deposition ($\mu$RD), and its utility in fabricating advanced architecture synthetic bone grafts. These bone grafts, also known as synthetic bone scaffolds, are highly porous three-dimensional structures that provide a matrix to support the natural process of bone remodeling. Ideally, the synthetic scaffold will stimulate complete bone healing in a skeletal defect site and also resorb with time so that only natural tissue remains. The objective of this research is to develop methods to integrate different regions with different porous microstructures into a single scaffold; there is evidence that scaffolds with designed regions of specific microstructures can be used to elicit a strong and directed bone ingrowth response that improves bone ingrowth rate and quality. The key contribution of this work is the development of a control algorithm that precisely places different build materials in specified locations, thereby the fabrication of advanced architecture scaffolds is feasible. Under previous control methods, designs were relegated to be composed of a single material. The control algorithm developed in this work is an adaptation of Iterative Learning Control (ILC), a control method that is typically best suited for mass manufacturing applications. This adaptation reorients the ILC framework such that it is more amenable to additive manufacturing systems, such as $\mu$RD. Control efficacy is demonstrated by the fabrication of advanced architecture scaffolds. Scaffolds with contoured forms, multiple domains with distinct porous microstructures, and hollow cavities are feasible when the developed controller is used in conjunction with a novel manufacturing workflow in which scaffolds are filled within patterned molds that support overhanging features. An additional application demonstrates controller performance on the robot positioning problem; this work has implications for additive manufacturing in general

Active control of the wake from a rectangular-sectioned body

This work of thesis is part of a wider research project with the aim of developing an aerodynamic active device for drag reduction of ground vehicles. The system, previously studied on a bullet-shaped body by Qubain (2009) and Oxlade (2013), is applied to a bluff body that idealises a long vehicle, such as an articulated lorry or a coach. The model, tested in the Honda wind tunnel of the Department of Aeronautics at Imperial College, is equipped with a synthetic jet, or zero net-mass-flux actuator, composed of a cavity, a plate with a slot, and an oscillating diaphragm, placed at the rear end of the body. The effects produced by the actuator are studied by monitoring the base pressure on the model, and by measuring the aerodynamic forces and the moments acting on the body. During the experiments, performed at a constant ReH=UH/ν=4.1x10^5, a parametric study of the response of the mean base pressure, forces and moments to changes in the forcing parameters (frequency and amplitude), and slot width is performed. The unforced wake is characterised by two main structures: the bubble-pumping mode, with Strouhal number StH≈0.08, and the vortex shedding, with StH≈0.17 and StH≈0.20 on the vertical and horizontal plane, respectively. These structures, still visible in the forced wake at low forcing amplitudes, are almost completely suppressed when the forcing amplitude is increased. The suppression of the structures in the wake corresponds to a decrease in the integrated energy of the wake itself, associated to base pressure recovery and drag reduction. The optimal values achieved corresponds to 27.3% gain in base pressure and -13.1% reduction of drag. The higher sensitivity to changes in forcing amplitude rather than in frequency displayed by the system confirms the existence of a plateau of optimal base pressure recovery/drag reduction at frequencies around 5 times the characteristic shear layer frequency.Open Acces

Fourth High Alpha Conference, volume 2

The goal of the Fourth High Alpha Conference, held at the NASA Dryden Flight Research Center on July 12-14, 1994, was to focus on the flight validation of high angle of attack technologies and provide an in-depth review of the latest high angle of attack activities. Areas that were covered include high angle of attack aerodynamics, propulsion and inlet dynamics, thrust vectoring, control laws and handling qualities, and tactical utility

Automatic Control with Experiments

Everybody has been a part of a control system at some time. Some examples of this are when driving a car, balancing a broomstick on a hand, walking or standing up without falling, taking a glass to drink water, and so on. These control systems, however,arenotautomaticcontrolsystems,asapersonisrequiredtoperformarole in it. To explain this idea, in this section some more technical examples of control systems are described in which a person performs a rol

Volume 2 – Conference: Wednesday, March 9

10. Internationales Fluidtechnisches Kolloquium:Group 1 | 2: Novel System Structures Group 3 | 5: Pumps Group 4: Thermal Behaviour Group 6: Industrial Hydraulic

Functional characterization of the Saccharomyces cerevisiae chromatin remodeler INO80

Knowing the explicit locations of nucleosomes in a genome is a pre-requisite for understanding the regulation of genes. Predominantly at regulatory active promoter sites, regular spaced arrays phased at reference points shape the chromatin landscape. In eukaryotic cells ATP-dependent chromatin remodeler align nucleosomes at reference points and are pivotal in the formation of the stereotyped promoter pattern. Chromatin remodeler of the ISWI, CHD, SWI/SNF and INO80 family convert energy derived from ATP hydrolysis to operate on their nucleosomal substrates to accomplish nucleosome spacing, eviction and editing reactions. Recent structural elucidations provided mechanistic insights into how chromatin remodelers engage their nucleosomal substrates (Eustermann et al., 2018, Aramayo et al., 2018, Willhoft et al., 2018, Ayala et al., 2018, Farnung et al., 2017, Wagner et al., 2020, Yan et al., 2019, He et al., 2020, Han et al., 2020) and brought about a unifying DNA wave mechanism underpinning ATP-dependent DNA translocation by chromatin remodeling complexes (Yan and Chen, 2020). Understanding how phased arrays of equally spaced nucleosomes are generated by chromatin remodelers represents an ultimate long-term goal in chromatin biology. What remains unclear is the underlying mechanism that directs nucleosome positioning by chromatin remodelers in absolute terms. How do ATP-dependent chromatin remodelers generate phased arrays of regularly spaced nucleosomes? How are the distances between nucleosomes and phasing sites and between adjacent nucleosomes set? Is DNA shape read-out part of nucleosome positioning driven by chromatin remodelers? Do remodelers have intrinsic ruler-like elements that set spacing and phasing distances? The aim of this thesis was to delineate whether, and if so, what type of genomic information is read by a remodeler in the stereotypic placement of nucleosomes at physiological sites, and how the remodeler activities fit into the unifying framework of ATP-dependent DNA translocation mechanism of chromatin remodelers. To gain an insight into nucleosome positioning driven by Saccharomyces cerevisiae (S.c.) ATP-dependent chromatin remodelers, a combination of a minimalistic genome-wide in vitro reconstitution system, biochemical analysis, high-resolution structures and structure-guided mutagenesis of the S.c. INO80 model system was applied. Findings of this work would have an impact on the mechanistic understanding of nucleosome positioning driven by ATP dependent chromatin remodelers based on the ruler concept that has been described earlier for the ISW1a chromatin remodeler (Yamada et al., 2011). The ISW1a, Chd1 and ISW2 remodelers demonstrated “clamping” activity and used ruler elements to set 1 Abstract distances with a defined linker length (21-26 bp at all densities, 12-13bp at all densities, 54-58 bp at low/medium densities, respectively). Mutagenesis of the INO80 model system identified and tuned the INO80 ruler element, which is comprised of the Ino80_HSA domain of the ARP module, the NHP10 module and Ino80 N-terminal residues. Regularly spaced symmetrical arrays were generated at the Reb1 reference point sites as well as at BamHI-introduced dsDNA break sites. Nucleosome positioning on the genomic sequences of S. c., Schizosaccharomyces pombe (S.p.) as well as Escherichia coli (E.coli) showed no significant differences. Mutagenesis of residues located within the Ino80_HSA domain established a causal link between nucleosome positioning by INO80 and DNA shape read-out by the INO80_HSA domain. The spacing and phasing distances generated by ATP-dependent chromatin remodelers point towards a remodeler-intrinsic ruler activity that is independent of underlying DNA sequences and can be sensitive to nucleosome density. This study measured linker lengths set by remodeler-intrinsic ruler-like functionalities in absolute terms, which will be instrumental to dissect contributions from individual remodelers in nucleosome positioning in vivo. This provides the starting point to understand how remodeler-driven nucleosome dynamics direct stable steady-state nucleosome positions relative to DNA bound factors, DNA ends and DNA sequence elements. Sequence-dependent DNA shape features have been mainly associated with binding of transcription factors as well as general regulatory factors and more static DNA binding events. This study augments the general description of nucleosome positioning sequences for chromatin remodelers by establishing nucleosome positioning motifs based on DNA shape analysis. This study provides an intriguing framework to implement DNA shape read-out in the tracking mechanism of DNA-translocating machineries