Nominal Mode Research Articles

Design and performance of Soft Gamma-ray Detector onboard the Hitomi (ASTRO-H) satellite

Hitomi (ASTRO-H) was the sixth Japanese x-ray satellite that carried instruments with exquisite energy resolution of <7 eV and broad energy coverage of 0.3 to 600 keV. The Soft Gamma-ray Detector (SGD) was the Hitomi instrument that observed the highest energy band (60 to 600 keV). The SGD design achieves a low background level by combining active shields and Compton cameras where Compton kinematics is utilized to reject backgrounds coming from outside of the field of view. A compact and highly efficient Compton camera is realized using a combination of silicon and cadmium telluride semiconductor sensors with a good energy resolution. Compton kinematics also carries information for gamma-ray polarization, making the SGD an excellent polarimeter. Following several years of development, the satellite was successfully launched on February 17, 2016. After proper functionality of the SGD components were verified, the nominal observation mode was initiated on March 24, 2016. The SGD observed the Crab Nebula for approximately two hours before the spacecraft ceased to function on March 26, 2016. We present concepts of the SGD design followed by detailed description of the instrument and its performance measured on ground and in orbit.

THE EFFECT OF DIFFERENT OPTIONS OF BLADES MAIN ROTOR ON THE X-SHAPED TAIL ROTOR OF THE MI-171 LL

This paper describes the effect of different rotor blades on the X-shaped tail rotor of the Mi-171 LL, observed conducting flight tests. The tests were carried out on the same helicopter in the similar atmospheric conditions. The objective of the tests was the comparison of flight performance of two sets of rotor blades of the helicopter Mi-171 LL. However, materials test revealed a difference in the angles of the tail rotor at different MRs with the same takeoff weight. The authors are grateful to I.G. Peskov, S.R. Zamula and A.I. Orlov for assistance in carrying out this work and the preparation of this article. Noted that the helicopter takeoff weight when hovering out of ground effect in ISA with blades from polymer composite materials (PCM) exceeds the takeoff weight of the helicopter with the serial blades in the nominal mode of the engine operation at ~ 750kg, in the takeoff mode at ~ 700kg. Knowing the altitude and climatic characteristics of the engine, the obtained dependence allows to determine the balancing value of j рв on hovering at different combinations of pressure altitude and outside air temperature for a given speed of the main rotor (MR). It follows from the work that when the same value N пр (95/n нвпр ) 3 or Nfact the balancing values of j рв for the helicopter with the main rotor blades from the PCM is less than for the helicopters with serial blades by 0.5…0.9 ° . The difference in the angles of the tail rotor increases with growing of N епр (95/n нвпр ) 3 (N fact ). Perhaps this is caused by different induction effect of the main rotor on the tail rotor to the MR from PCM and the serial ones. As follows from the materials, the thrust of the main rotor with blades from PCM with the same engine power is more in comparison with the serial blades. Consequently inductive speeds of the main rotor are more and the angles of the tail rotor are less. It can be assumed that a large induced velocity of the main rotor increases the thrust of X-shaped tail rotor.

18-Pulse Transformer Rectifier Unit with an Amorphous Magnetic Core for Aircraft

This paper deals with a transformer-rectifier unit with a magnetic core made of amorphous steel. Transformers with various types of amorphous alloys have been compared. The most optimal amorphous alloy to use in a transformer is determined. The simulation of the electromagnetic and thermal processes occurring in transformers with a magnetic core made of amorphous steel was carried out, the amplitude and shape of the voltage and current were determined and the maximum temperature in nominal operating mode was defined. The dependencies of the specific losses in the studied samples of amorphous steel on the frequency of magnetization reversal, magnetic flux density and temperature were obtained. An experimental layout of a transformer rectifier unit with a magnetic core made of amorphous steel, loaded onto an 18-pulse rectifier with a power of 10.5 kVA and operating at a frequency of 400-800 Hz with a voltage of 115/27 V was designed and manufactured. An experimental study was carried out on the developed layout to verify the obtained data. The experimental studies confirmed the correctness of the chosen design methodology and of the design scheme of the transformer. It is important to note that the thermal loads detected on the transformer during its testing are within the permissible values.

Optimization of Powerful Two-stage Screw Centrifugal Pump

The article presents a refining method for a two-stage screw centrifugal pump by the joint usage of mathematical optimization software IOSO, meshing complex NUMECA and CFD software ANSYS CFX. The pump main parameters: high-pressure stage rotor speed was 13300 rpm; low-pressure rotor speed was 3617 rpm by gearbox; inlet total pressure was 0.4 MPa; outlet mass flow was 132.6 kg/s at the nominal mode. This article describes the process of simplifying the calculation model for the optimization. The parameters of camber lines of the low-pressure impeller, transition duct, and high-pressure impeller blades for two sections (hub and shroud) were chosen as optimization parameters. The blades of low-pressure impeller, transition duct and high-pressure impeller have changed during optimization. The optimization goal was the increase of the pump efficiency with preservation or slight increase in the pressure head. The efficiency was increased by 3%.

A Diagnosis Study on a Train Passenger Access System using Petri Net Models

In this paper, we conduct a diagnosis analysis of the passenger access system, while considering a high level abstraction perspective that allows for adapting discrete event models to represent the system behavior. Firstly, we establish Petri net behavioral models for the global system functions, including the nominal operating mode and various faulty behaviors. Then, based on the established Petri net models, a diagnoser-based approach is brought into play to investigate the diagnosability of the system regarding the different predetermined classes of failures.

Model-Based Monitoring of a Train Passenger Access System

The passenger access system (PAS) is a complex mechatronic train onboard module with high reliability and safety requirements. This module fulfills one of the dozen main onboard functions onboard train. Consequently, any related fault occurrence may have a serious impact on the safety and availability of the whole train operation. In this context, developing effective automated monitoring and diagnostic techniques for the PAS, as early as from the design phase of the system, becomes an essential and challenging task. In this paper, we carry out a monitoring study on this system, while considering a sufficiently high-level abstraction perspective that allows for adapting discrete event models representing the behavior of the system. First, we establish a Petri net behavioral model that includes the nominal operating mode as well as various faulty behaviors. Then, based on the established Petri net models, a fault detection approach is used to investigate the diagnosability property and synthesize the diagnosers regarding different predetermined classes of failures. Finally, we show how the outputs of the diagnosability analysis can help make efficient design choices that allow for improving the safety of the whole system.

An industrial security system for human-robot coexistence

PurposeThe installation of industrial robots requires security barriers, a costly, time-consuming exercise. Collaborative robots may offer a solution; however, these systems only comply with safety standards if operating at reduced speeds. The purpose of this paper is to describe the development and implementation of a novel security system that allows human–robot coexistence while permitting the robot to execute much of its task at nominal speed.Design/methodology/approachThe security system is defined by three modes: a nominal mode, a coexistence mode and a gravity compensation mode. Mode transition is triggered by three lasers, two of which are mechanically linked to the robot. These scanners create a dynamic envelope around the robot and allow the detection of operator presence or environmental changes. To avoid velocity discontinuities between transitions, the authors propose a novel time scaling method.FindingsThe paper describes the system’s mechanical, software and control architecture. The system is demonstrated experimentally on a collaborative robot and is compared with the performance of a state-of-art security system. Both a qualitative and quantitative analysis of the new system is carried out.Practical implicationsThe mode transition method is easily implemented, requires little computing power and leaves the trajectories unchanged. As velocity discontinuities are avoided, motor wear is reduced. The execution time is substantially less than a commercial alternative. These advantages can lead to economic benefits in high-volume manufacturing environments.Originality/valueThis paper proposes a novel system that is based on industrial material but can generate dynamic safety zones for a collaborative robot.

Reduction of idling losses of eighteen-pulse transformer rectifier unit for aerospace application

This paper considers a method of reducing idling losses with the use of amorphous steel for a magnetic core for an eighteen-pulse transformer rectifier unit for the aerospace application. Numerical calculations of transformer rectifier units with various types of amorphous alloys were carried out to determine the mass and overall dimensions and idling losses. To determine the shape, amplitude and harmonic composition of the eighteen-pulse rectifier, an imitation simulation of a three-to-nine-phase rectification system was carried out. In order to determine the maximum temperatures with a nominal mode, a computer simulation of the thermal fields of the transformer rectifier unit was carried out. To verify the numerical calculations, simulation and computer simulations, experimental studies were carried out on the developed demonstration layout.

Self-consistent Maxwell-Bloch model of quantum-dot photonic-crystal-cavity lasers

We present a powerful computational approach to simulate the threshold behavior of photonic-crystal quantum-dot (QD) lasers. Using a finite-difference time-domain (FDTD) technique, Maxwell-Bloch equations representing a system of thousands of statistically independent and randomly positioned two-level emitters are solved numerically. Phenomenological pure dephasing and incoherent pumping is added to the optical Bloch equations to allow for a dynamical lasing regime, but the cavity-mediated radiative dynamics and gain coupling of each QD dipole (artificial atom) is contained self-consistently within the model. These Maxwell-Bloch equations are implemented by using Lumerical's flexible material plug-in tool, which allows a user to define additional equations of motion for the nonlinear polarization. We implement the gain ensemble within triangular-lattice photonic-crystal cavities of various length $N$ (where $N$ refers to the number of missing holes), and investigate the cavity mode characteristics and the threshold regime as a function of cavity length. We develop effective two-dimensional model simulations which are derived after studying the full three-dimensional passive material structures by matching the cavity quality factors and resonance properties. We also demonstrate how to obtain the correct point-dipole radiative decay rate from Fermi's golden rule, which is captured naturally by the FDTD method. Our numerical simulations predict that the pump threshold plateaus around cavity lengths greater than $N=9$, which we identify as a consequence of the complex spatial dynamics and gain coupling from the inhomogeneous QD ensemble. This behavior is not expected from simple rate-equation analysis commonly adopted in the literature, but is in qualitative agreement with recent experiments. Single-mode to multimode lasing is also observed, depending on the spectral peak frequency of the QD ensemble. Using a statistical modal analysis of the average decay rates, we also show how the average radiative decay rate decreases as a function of cavity size. In addition, we investigate the role of structural disorder on both the passive cavity and active lasers, where the latter show a general increase in the pump threshold for cavity lengths greater than $N=7$, and a reduction in the nominal cavity mode volume for increasing amounts of disorder.

ANALYSIS OF THE OPERATION PECULIARITIES OF THE SUPERCONDUCTING INDUCTIVE CURRENT LIMITER WITH ADDITIONAL SUPERCONDUCTING SCREEN

Purpose. The inductances of magnetic system of a current limiter for the nominal operating mode were determined. The aspects of functioning and a design of a superconducting short-circuit current limiter of inductive type with a superconductive main and additional screens, and superconductive winding, which are placed in a general cryostat on a ferromagnetic core, which ensures an improvement of magnetic field dissipation and in energy efficiency are observed. Methodology. The analysis of distribution of magnetic field of the short-circuit current limiter of inductive type with superconducting high-temperature coil and superconducting main and additional screens, using mathematical modeling by the finite element method in math software package FEMM for different modes of operation is carried out. Results. The calculations of magnetic field dissipation in operational modes are carried out. Originality. The investigations aimed to analyze the influence of distribution of the magnetic field in inductive short-circuit current limiter with superconducting additional screen on its operation modes. First calculation of the distribution of magnetic fields in different modes of operation for the short-circuit current limiter in the area between high-temperature superconducting screens. Practical value. The advantage of additional screen of superconducting short-circuit current limiter is to improve screening from dissipation of the magnetic fields of the magnetic system and reducing the power losses at nominal mode. Using the proposed methodology will identify options acceptable to the current limiter mode of operation.

Evaluation of the Performance of Telecommunication Systems by Approach of Hybrid Stochastic Automata Combined With Neuro-Fuzzy Networks

This paper presents a functional and dysfunctional behavioral study of a telecommunication system, with the aim to evaluate the performance of its constituent units. It is question of taking advantage offered by artificial intelligence in order to evaluate by modeling and simulation in system reliability. The methodological approach consists in combining ANFIS neuro-fuzzy networks with hybrid stochastic automata. The Neuro-Fuzzy ANFIS networks provide a prediction for the passage from nominal mode to degraded mode, by controlling the occurrence of malfunctions at transient levels. This allows to anticipate the occurrence of events degrading system performance, such as failures and disturbances. The objective is to maintain the system in nominal operating mode and prevent its tipping in degraded mode. The results are implanted around a demonstrator based on Scilab, and implemented on Matlab / Simulink.

SELECTION OF RATIONAL PARAMETERS OF THE NOMINAL MODE ELECTRIC TRAINS WITH ASYNCHRONOUS TRACTION DRIVE

Purpose. Parameters of the nominal mode are related to the most important performance indicators of traction means, therefore, the problems of choosing their optimal values always inevitably arise when forming technical requirements for a new rolling stock. The paper describes the features of solving the above-mentioned problems for electric trains with an asynchronous traction drive in the case of two-zone and three-zone frequency control of power. Methodology. Power of nominal mode of the rolling stock should be chosen in such a way that it would be possible to realize a predetermined travel time along in the section or the movement speed. On that basis, and also taking into account the fact that the important operational characteristics of electric trains include the acceleration value during the start-up and acceleration at the design speed, we will formulate the problem of determining the nominal power. In the task for a given range of traction, it is necessary to find such a value of the nominal mode power and the corresponding force value to ensure the ability to carry out transportations with the given level of average speed with minimal energy consumption for traction. At the same time, it is necessary to fulfill the following conditions: a) the speed of the electric train on the section does not exceed the established limits; b) it is possible to realize the given values of accelerations. A more detailed consideration of the problem shows that in real conditions, when the starting acceleration and the mass of the train are given, the problem of determining electric train power is practically reduced to determining the optimal value of the nominal mode speed. Findings. The task of choosing the optimal values of the nominal mode speed is solved by determining the electric power consumption with the variation of the possible values of starting speed. Therefore, only those values that ensure the implementation of the given starting and residual accelerations should be taken into account. The work shows that the traction force value increases with the design speed increase and other equal conditions, if the starting speed is increased. Originality. Authors developed the methodology for determining the optimal values of the nominal mode parameters of electric trains with an asynchronous traction drive, with two-zone and three-zone frequency power regulation. Practical value. The above mentioned methodology can be the basis when forming technical requirements for new rolling stock for Ukraine’s railways.

Investigation of the combustion process in a tractor diesel 11 powered by an ethanol-fuel emulsion

The work is devoted to the use of ethanol-fuel emulsion as an alternative energy carrier in a tractor diesel 4Ch11,0/12,5. At the same time, the maximum allowable concentration of ethyl alcohol in the emulsion for this diesel is justified, amounting to 25 % of the total amount of fuel and providing sufficient conditions for the organization of a stable combustion process with no misfiring. Thus, according to the results of studies of the physicochemical properties of alcohol-fuel emulsions of various compositions, their stability and the initial tests of the engine, an emulsion of the following composition was accepted as optimal for a tractor diesel 4Ch11,0/12,5: ethyl alcohol 25 %, succinimide C-5A - 0,5 %, water - 7 %, diesel fuel - 67,5 %. The article describes the results of experimental studies on the effect of ethanol-fuel emulsion to the indicator parameters, the characteristics of the combustion process and heat diesel tractor. 4Ch11.0/12.5. In order to determine and optimize the main parameters of the diesel engine while working on the ethanol-fuel emulsion, its bench tests were carried out, including the entire set of adjusting, loading and speed characteristics. Experimental studies of the working process of the tractor diesel engine 4Ch11,0/12,5 when working with ethanol fuel emulsion have determined the values of the combustion process parameters and heat release characteristics at the nominal operating mode of the diesel engine: the maximum averaged temperature increases by 14,6 % and amounts to 2510 K; the maximum combustion pressure is increased by 9,9 % and is 8,9 MPa; the rigidity of the combustion process is increased by 71,2 % and is 1,01 MPa / deg; the ignition delay angle increases by 24,4 % and is 28,0°; the rate of active heat release increases by 68,4 % and amounts to 0,160.

Estimation and Attitude Control in CONASAT's Nominal Operation Mode: An Approach for SDRE Filter and PID Control

CubeSat attracted interest of international community with numerous studies being developed in some universities, schools or even space enthusiastic. Miniaturization of components and use of conventional electronics reduced costs with space projects, that previously restricted access to space to only a few nations at costs of several million dollars. So, governments and space agencies, especially in developing nations, has begun to invest in small satellite projects, because now they can have space missions at low cost. Thus, the National Institute for Space Research (INPE), in Brazil, has planning some CubeSat missions as an academic tool to spread the space technology across the country to universities and researches. One of the missions in development is the Nanosatellite Constellation for Environmental Data Collection (CONASAT). This project intends to launch at least two small satellites to replace the SCD1 and SCD2 satellites of the Brazilian's environmental data collection system. The main objective of this paper is to propose state estimation technique, known as State-Dependent Riccati Equation (SDRE), together with a PID controller based on attitude error given by the Euler angle and axis for nominal mode attitude control of CONASAT. Simulations were performed using an open computational tool for attitude and orbit simulation.

Development of ion thruster IT-500

A high-power ion thruster IT-500 was designed, manufactured and tested at Keldysh Research Center within a transport-power module project. This module is being designed to perform near-Earth space and interplanetary transport missions. In its nominal operation mode, IT-500 provides thrust in the range from 375 to 750 mN at specific impulse of 70 000 m/s and thrust efficiency of 0.75. Due to a high cost of the experimental testing of a large thruster, the emphasis was placed on the numerical optimization of the thruster design. The thruster completed performance tests and a 300 h wear test. The output characteristics of the thruster, obtained during the tests, confirmed the correctness of the provisional numerical optimization. IT-500 design, performance, and validation of the design approaches are discussed in this paper.

Performance Analysis of TanDEM-X Quad-Polarization Products in Pursuit Monostatic Mode

Since 2010, the two twin synthetic aperture radar (SAR) satellites TerraSAR-X and TanDEM-X have been acquiring high-resolution images to generate a global Earth's digital elevation model (DEM). Both satellites have been flying in a controlled close orbit formation, acquiring data in the nominal bistatic stripmap single-polarization mode. Once the acquisition of the dataset for the generation of the DEM has been completed, the flexibility offered by both SAR instruments in terms of interferometric, imaging, and polarization modes has been further exploited to demonstrate the different capabilities of the TanDEM-X experimental modes. By activating the dual-receive antenna mode, full polarimetric data can be acquired. For the first time, it has been possible to systematically command quad-polarization acquisitions in a dedicated TanDEM-X mission science phase, started in October 2014. In this paper, we present a first performance analysis and quality assessment of such quad-polarization products. The SAR image resolution and the noise equivalent sigma zero have been evaluated to show the quality of the focused SAR products. The influence of different instrument parameters on the SAR and interferometric performance, such as chirp bandwidth, pulse repetition frequency, or block adaptive quantization, has been investigated as well. For the evaluation of the interferometric performance, key parameters such as coherence and interferometric phase error have been analyzed. In this paper, the obtained results are presented and recommendations are given for the optimization in the commanding of TanDEM-X quad-polarization acquisitions.

The ITASAT CubeSat Development and Design

Because they are inexpensive platforms for satellites, CubeSats have become a low-cost way for universities and even developing countries to have access to space technology. This paper presents the ITASAT design, particularly the Attitude Determination and Control Subsystem, the Onboard Software, and the Assembly,Integration and Testing program. The ITASAT is a 6U CubeSat nano-satellite in development at the Instituto Tecnologico de Aeronautica, in Sao Jose dos Campos, Brazil. The platform and its subsystems will be provided by industry while the payloads are being designed and developed by the principal investigators. The ITASAT Attitude Determination and Control Subsystem will rely on a 3-axis magnetometer, 6 analog cosine sun sensors, 3-axis MEMS gyroscopes, 3 magnetic torque coils, and 3 reaction wheels. The Attitude Determination and Control Subsystem operating modes, control laws, and embedded software are under the responsibility of the Instituto Tecnologico de Aeronautica. A Kalman filter shall be employed to estimate the quaternion attitude and gyroscope biases from sensor measurements. The Attitude Determination and Control Subsystem operating modes are the nominal mode, with geocentric pointing attitude control and the stabilization mode, in which only the satellite angular velocity is controlled. The nominal mode will be split into 2 sub-modes: reaction wheel control plus magnetic wheel desaturation and 3-axis magnetic attitude control. Simulation results have shown that the attitude can be controlled with 1-degree accuracy in nominal mode with the reaction wheels, but these errors grow as much as 20 degrees or higher with the 3-axis magnetic control.

Data‐driven fault diagnosis and robust control: Application to PEM fuel cell systems

SummaryA data‐driven methodology that includes the unfalsified control concept in the framework of fault diagnosis and isolation (FDI) and fault‐tolerant control (FTC) is presented. The selection of the appropriate controller from a bank of controllers in a switching supervisory control setting is performed by using an adequate FDI outcome. By combining simultaneous online performance assessment of multiple controllers with the fault diagnosis decision from structured hypothesis tests, a diagnosis statement regarding what controller is most suitable to deal with the current (nominal or faulty) mode of the plant is obtained. Switching strategies that use the diagnosis statement are also proposed. This approach is applied to a nonlinear experimentally validated model of the breathing system of a polymer electrolyte membrane fuel cell. The results show the effectiveness of this FDI–fault‐tolerant control data‐driven methodology. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Dimensional variation tolerant mode converter/multiplexer fabricated in SOI technology for two-mode transmission at 1550 nm.

The use of an integrated asymmetrical directional coupler for two-mode transmission at 1550 nm is analyzed. The design is based on silicon-on-insulator (SOI) technology and permits mode conversion and mode multiplexing/demultiplexing. In the nominal design, mode conversion and mode (de)multiplexing are achieved with 97% efficiency and a 23.4 dB crosstalk level in the 1540-1560 nm band using a 0.1 μm gap. The dimension tolerance of the SOI process has been taken into account in the selection of the optimum design, and the coupling efficiency would remain above 82.3% (corresponding to 0.8 dB excess loss) with 3σ accuracy. A 90% efficiency has been experimentally obtained.

Experimental verification of the European 1 MW, 170 GHz industrial CW prototype gyrotron for ITER

The EU 1MW, 170GHz gyrotron with hollow cylindrical cavity have been designed within the European GYrotron Consortium (EGYC) in collaboration with the industrial partner Thales Electron Devices (TED) and under the coordination of Fusion for Energy (F4E). In the frame of the EU program, the short-pulse (SP) version of this tube was designed and manufactured by KIT in collaboration with TED. The experimental verification of the SP gyrotron prototype was successfully completed in 2015. The achieved experimental results show a very stable gyrotron operation with RF output power above 1MW at good cavity interaction efficiency around 35%. The gyrotron was operated up to 10ms pulse length; the nominal cavity mode TE32,9 has been excited at the frequency 170.1GHz in agreement with the corresponding ITER specification. The Gaussian mode content of the output RF beam was about 98% and the total level of internal stray radiation was in the range of 2–3%. The manufacturing of the first industrial continuous-wave (CW) prototype gyrotron, based on the SP gyrotron design, was completed in November 2015 at TED. The tube was delivered to KIT and the experimental verification started in February 2016. Operation of the gyrotron with ms pulse duration resulted in stable excitation of the nominal mode at 170.22GHz for a wide range of operating parameters and with a level of stray radiation comparable with the SP version. The maximum RF power achieved up to now in short-pulse operation at a level of 1MW. The measured Gaussian mode content of the RF beam is 97%. Currently, further preparation for the CW operation of the gyrotron is in progress.