Large angle reorientation manoeuvre of spacecraft using robust backstepping control

The nonlinear control design problem for large angle reorientation manoeuvre of spacecraft has a proper structure for the direct application of backstepping design as its dynamics and kinematics are naturally in a cascade form. In this paper, the robustness of the backstepping control against the uncertainties in the moment of inertia matrix is investigated and a sufficient condition for the robust stability is derived. Numerical simulations show the validity of the condition

Design optimisation of electromagnetic devices using continuum design sensitivity analysis combined with commercial EM software

This paper deals with two types of optimisation problems: optimised source distribution and the shape optimum design, using Continuum Design Sensitivity Analysis (CDSA) in combination with standard electromagnetic (EM) software. Fast convergence and compatibility with existing EM software are the distinctive features of the proposed implementation. In order to verify the advantages and also to facilitate understanding of the method itself, two design optimisation problems have been tested using both 2D and 3D models: the first is a MRI design problem related to finding an optimal permanent magnet distribution and the second is a pole shape design problem to reduce the cogging torque in a BLDC

The implications of the use of composite materials in electromagnetic device topology and shape optimization

The use of soft magnetic composites (SMCs) provides electromagnetic device designers with serious challenges. While such materials have the potential of allowing novel 3-D topologies to be used, as well as providing major advantages in recycling at the end of the lifetime of the device, little or no design experience exists in this area. This paper proposes the use of sensitivity based topology optimization as a methodology for assisting designers in this task

Design Optimisation of Electromagnetic Devices Using Continuum Design Sensitivity Analysis Combined with Commercial EM Software

This paper deals with two kinds of optimisation problems, relevant to the optimised source distribution and the shape optimum design, using Continuum Design Sensitivity Analysis (CDSA) in combination with standard electromagnetic (EM) software. Fast convergence and compatibility with existing EM software are the distinctive features of the proposed implementation. In order to verify the advantages and also to facilitate understanding of the method itself, two design optimisation problems have been tested: one is an MRI design problem related to finding an optimal permanent magnet distribution and the other is a pole shape design problem of a BLDC motor for reducing cogging torque, using both 2D and 3D models

A Novel Scheme for Material Updating in Source Distribution Optimization of Magnetic Devices using Sensitivity Analysis

A novel material updating scheme, which does not require intermediate states of a material used, is presented for source distribution optimization problems. A mutation factor to determine a degree of topological change in the next design stage on the basis of a current layout accelerates the convergence of an objective function. Easy implementation and fast convergence of the scheme are verified using two MRI design problems where current and permanent magnet distributions have been optimized, respectively

Impact of energy-transfer-upconversion on the performance of hybrid Er:YAG lasers

Using a hybrid fiber-bulk laser scheme based on Er:YAG, we have achieved ~60 W and ~30 W of continuous-wave output at 1645nm and 1617nm respectively, and Q-switched pulse energies up to ~30 mJ (limited by coating damage). Investigation of various factors influencing laser performance has revealed that energy-transfer-upconversion can have a very detrimental impact on efficiency, even in continuous-wave mode of operation. In this paper we report on the results of this study, discuss various measures for reducing energy-transfer-upconversion and its effect on laser performance, and consider the prospects for further increase in output power and pulse energy

Robust optimization utilizing the second-order design sensitivity information

This paper presents an effective methodology for robust optimization of electromagnetic devices. To achieve the goal, the method improves the robustness of the minimum of the objective function chosen as a design solution by minimizing the second-order sensitivity information, called a gradient index (GI) and defined by a function of gradients of performance functions with respect to uncertain variables. The constraint feasibility is also enhanced by adding a GI corresponding to the constraint value. The distinctive feature of the method is that it requires neither statistical information on design variables nor calculation of the performance reliability during the robust optimization process. The validity of the proposed method is tested with the TEAM Workshop Problem 2

First demonstration of single trench fiber for delocalization of higher order modes

We demonstrate an ytterbium-doped single-trench fiber ensuring a high losses ratio (~1000) and low power fraction (~0.7) between the higher-order-modes and fundamental-mode with excellent bend robustness and 85% laser efficiency at a wavelength of 1040nm

Transfer or delivery of micro light-emitting diodes for light-emitting diode displays

As the next-generation display technology, microscale light-emitting diode (mu-LED) displays have attracted significant attention recently. For applying mu-LEDs as direct emissive pixels in everyday display applications, many chips in a relatively small-sized wafer must be relocated and distributed quickly over a wide screen area via so-called transfer technology. After a brief review of current conventional transfer technologies for placing mu-LEDs on a wide screen, for perspective, a new and versatile delivery technique for mu-LEDs is presented, in which an LED chip is converted to a ball shape in order to facilitate handling and processing of mu-LEDs for practical applications. Plausible procedures including the formation, arrangement, and removal of the plastic ball are discussed to envision potential impacts of the technology. (c) 2019 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).11Ysciescopu