Closed-loop Test System Research Articles

Design of Improved Ground Closed-loop Test System Based on Variable-stability Flight Control Computer

With the development of civil aviation, ground simulation test has gradually become a key link in the transformation of basic theory to engineering application. By forming a closed-loop link between the variable stability aircraft (VSA) dynamics model and the aircraft rudder surface, sensors, etc., the variable-stability ground closed-loop test system can simulate the aircraft flight state and response characteristics in the ground environment. However, the current ground test system suffers from a wide range of signals, complex signal simulation methods, and low system integration. In this study, an improved modular ground closed-loop test system for VSA is designed from three aspects: signal acquisition and simulation of airborne equipment, parameter monitoring and data processing, and fault simulation subsystem, which improves its compatibility and integrates with the software hardware of the variable-stability flight control computer and other air-borne equipment. After the system interconnection test, the generalized ground closed-loop test system designed in this study can replace the original system more efficiently, and its signal connection has inheritability, and provides a design method reference for other related researches of the variable-stability flight control computer.

Visualization of R134a cavitation flow in a rectangle Venturi tube and determination of thermal effects with cavity length and thickness

In order to study R134a cavitation behavior in a rectangle Venturi tube, high-speed photography combined with pressure, flow rate, and temperature measurements are performed to visualize the cavitation process and determine the cavity thickness and length through the tube in a closed-loop test system. The experimental results indicated that incipient cavitation of R134a is observed at the entrance of the tube throat when the cavitation number is below 2.50, regardless of the inlet temperature and pressure. The normalized cavity length is correlated with the cavitation number, and a critical cavitation number of 1.766 is defined to connect two linear functions. The throat and tail cavity thickness can be fitted as a cubic polynomial function with the cavitation number, and a transition cavitation number of 2.00 divides the growth rate of the thickness with the decrease of the cavitation number into fast and slow-growing parts. The temperature drop measured at the throat of the Venturi tube can be fitted to a cubic polynomial function about the cavitation number. Under the same cavitation number, the temperature drop decreases with the increase of the flow temperature. The B-factor can be fitted as a cavitation number quadratic polynomial function and a linear function of the tail cavity thickness. The transition cavitation number is defined by the transition point of the growth rate of the above function. The empirical correlation of B-factor is modified based on the throat and tail cavity thickness, and the cavitation thermal effect of R134a is accurately predicted. Combined with the inception cavitation number, the transition cavitation number, and the critical cavitation number, the shape of the cavity is divided into four regions: inception cavitation, attached cavitation, supercavitation, and fusion cavitation. The fast Fourier transformation analysis shows that the cavitation flow of R134a gradually changes from periodic flow to fully developed unsteady flow with the decrease of cavitation number.

Novel Voltage-Mode PID Controller Using a Single CCTA and All Grounded Passive Components

A compact voltage-mode proportional-integral-derivative (PID) controller based on the utilization of a single current conveyor transconductance amplifier (CCTA) is presented in this paper. The presented active PID controller is made up of a single CCTA, and four truly grounded passive components, i.e. two resistors, and two capacitors. The design consideration of the controller parameters has been examined. Besides, the crucial sensitivity performances of the controller parameters for ideal and non-ideal conditions have also been discussed. An application on the closed-loop test system is demonstrated to validate the practicability of the proposed PID controller circuit. To confirm the theoretical behavior, the proposed circuit is simulated with the PSPICE program using TSMC 0.35-um CMOS process technology. Experimental test results based on commercially available CFOA AD844 and OTA CA3080 integrated circuits are also provided to demonstrate the practicality of the proposed circuit.

Experimental research on the mechanical properties of steel fiber recycled aggregate concrete subjected to true triaxial compression

This paper presents an experimental research on the triaxial behavior of 270 steel fiber recycled aggregate concrete (SFRAC) specimens under true triaxial compression (σ1≠σ2≠σ3). By using a servo-hydraulic closed loop testing system, triaxial loading experiments were conducted considering three variables - the volume fraction of steel fiber (Vf), the replacement ratio of recycled coarse aggregate (RAR), and the stress ratio (α). The influences of these parameters on the failure modes, the stress–strain curves and the peak triaxial strength are analyzed. The experimental results indicated: (i) the stress ratio had the most significant effect on the failure mode of SFRAC specimens, where four modes were observed; (ii) the peak triaxial strength of specimens was sensitive to Vf, and a value between 0.6% and 1.2% was found to be optimum; (iii) the minimum stress ratio σ1/σ3 and the second stress ratio σ2/σ3 exhibited opposite effects on the peak triaxial strength of specimens, while RAR showed the least effect. Finally, a three-parameter failure criterion for SFRAC under true triaxial compression was proposed. The experimental results will provide SFRAC triaxial mechanical behavior for future engineering design and applications.

Study on the Adjustment of the Network Interface for the Station Domain Protection Device Based on RTDS

With continual development of smart grid construction, digital substation devices based on the specification IEC 61850, such as substation-area backup protection, have been widely applied. According to the “Technical requirements for the substation-area backup protection control device of the new generation of intelligent substation”, this paper put forward the debugging scheme of all digital network interface based on RTDS. Through the introduction of the RTDS software and hardware platform of the whole process building and commissioning, and by constructing substation simulation model and configuring GTNET-GSE card and GTNET-SV card, a closed-loop test system of substation-area backup protection device is completed, also this process development verification interface debugging method and configuration files have a certain practical value. The simulation of substation typical fault conditions and device data receiving processing mechanism can effectively meet the state grid enterprises standard Q/GDW11053-2013 for protection device test project requirements, and this test can significantly improve the smart substation integrated debugging efficiency.

The influence of software timing error on measurement accuracy of data acquisition

The application of high-speed real-time data acquisition is becoming increasingly wide spread in industrial field, and its measurement accuracy is also increasing. The closed-loop test system of sine wave signal is constructed by the RIGOL’s DG1022 dual-channel signal source, DS1102C oscilloscope and PCI7489 multifunctional data acquisition card. Three kinds of timing methods, such as Visual Basics (VB) Timer control, multimedia timer function timing and query performance frequency function timing method, were carried out a series of comparative experiments. This paper analyzes the correlation characteristics of the measured voltage peak data, which includes mean value, variance, standard deviation, range, mutation system, deviation, kurtosis and so on, and then finds out the influence rules of software timing error on data acquisition and measurement accuracy. In the high-speed data acquisition, the repeatability error can be reduced from 84.22% to 0.62%, which provides scientific basis and reference for selecting software timing method in different test environment.

Pyrogen retention: Comparison of the novel medium cut-off (MCO) membrane with other dialyser membranes

Haemodialysis effectively removes small solutes and smaller-sized middle molecules from the blood; however, the clearance of larger middle molecules, which have been associated with negative effects, is poor. The novel medium cut-off (MCO) dialysis membrane has larger pore sizes and a more open structure than other high-flux membranes, providing improved removal of larger middle molecules while retaining albumin. However, larger pore sizes may potentially increase permeability to pyrogens, including endotoxins and other bacterial contaminants, that could be present in the dialysis fluid. In this study, we tested the capacity of low-flux, high-flux, MCO and high cut-off dialyser membranes with different pore sizes to prevent pyrogens crossing from dialysate to the blood side in a closed-loop test system, differentiating among lipopolysaccharides, peptidoglycans and bacterial DNA using a toll-like receptor assay. Even though the bacterial contamination levels in our test system exceeded the acceptable pyrogen dose for standard dialysis fluid, levels of lipopolysaccharides, peptidoglycans and bacterial DNA in the blood-side samples were too low to identify potential differences in pyrogen permeability among the membranes. Our results suggest that MCO membranes are suitable for haemodialysis using ISO standard dialysis fluid quality, and retain endotoxins at a similar level as other membranes.

Fatigue Damage Characteristics Considering the Difference of Tensile-Compression Modulus for Asphalt Mixture

Abstract In order to reveal the difference and correlation of tensile modulus, compressive modulus, and flexural modulus, the four-point bending fatigue test is used on two kinds of asphalt mixtures—rock asphalt modified asphalt mixture and styrene butadiene styrene block copolymer modified asphalt mixture, were conducted using closed-loop test system. The fatigue damage variable was defined by the modulus attenuation based on the theory of damage mechanics, and the modulus attenuation equation was deduced. Under the same conditions, the initial value and the critical value of the tensile modulus were less than those of the compressive modulus, but the critical damage value and the attenuation slope of the tensile modulus were larger than those of the compressive modulus. The attenuation models of the tensile and compressive modulus of the asphalt mixture during the bending fatigue test were established. Based on the fatigue test results, a new concept of design and analysis was developed, in which the corresponding modulus and its evolution law is chosen according to its actual stress state at each point of asphalt pavement. The results indicate that under the bending fatigue stress state, there exists great differences between the attenuation law of the modulus of tension and compression for asphalt mixture and that the attenuation rate of tensile modulus is greater than that of compressive. Therefore, the tensile zone results in greater damage; the pavement structure of the tensile zone is damaged, which should be given more attention.

Electromagnetic flow rate measurement in molten tin circulating in a closed-loop test system

Flow rate measurement in molten metals at elevated temperatures is still a challenging task in metallurgie application. Due to the opaqueness and chemical aggressiveness of such melts, non-contact and non-invasive electromagnetic methods are of special interest. In order to develop and to test such methods under controllable laboratory conditions, during the last years at TU Ilmenau we have built up and instrumented the test facility TINTELO (tin test loop). TINTELO is a closed loop facility made of stainless steel in which molten tin at a temperature up to 350°C circulates in the horizontal plane. The flow is driven by an electromagnetic pump based on rotating permanent magnets. The rotation frequency of the pump can be fixed at up to 60 Hz providing a mass flow rate of 17.5 kg/s which corresponds to a Reynolds number of Re = 2·105. TINTELO is instrumented with both a Lorentz force flowmeter and a wall potential flowmeter. The Lorentz force flowmeter measures the force which the electrical conducting moving molten tin exerts on a system of permanent magnets arranged outside of the loop. This force is the counter force to the well-known braking Lorentz force that is proportional to the melt flow rate. Moreover, the wall potential flowmeter records the electric potential difference between two electrodes inserted in the conducting wall of the loop. This potential difference, induced by the moving melt when interacting with an externally applied magnetic field, is proportional to melt velocity. In this paper we present the design and the instrumentation of TINTELO, the calibration methods for the used flowmeters and first results of the flow rate test measurements.

Development of NPP digital I&C system closed-loop online test system based on signal transmission array

With the development of process control technology, the digital Instrumentation and Control (I&C) system has been gradually adopted in the latest Nuclear Power Plants (NPPs). Accordingly, the digital I&C system test has become a key step during the NPP design phase. To effectively reflect the integrated performance, including the hardware, software, and interaction of the digital I&C system, it is necessary to adopt NPP operating data to drive the I&C system under test. NPP operating data can be obtained by a Full-Scope Simulator (FSS) merged into the test system. However, it is difficult to perform real-time conversion between the operating data in the memory of the FSS and the electrical signals in the I&C system. For this purpose, a closed-loop test system based on the Signal Transmission Array (STA)—a special signal generating and receiving device for communication between the FSS and I&C systems in real time—has been presented in this work. The initial development of this test system has been accomplished and is being used for China Lead-based Research Reactor (CLEAR-I) digital I&C system. The results show that the test system based on the STA can trace variations of the operation data of the NPP and electrical signals of the digital I&C system and is able to reveal the control performance and failure characteristics.

DURABILITY TESTS: statistical analysIs for variable amplitude loads

The reduced time available for product evolution has forced original equipment manufacturers and their suppliers to develop new components and subsystems more rapidly, while taking into consideration the reliability of the final product in terms of its durability. Although durability is nowadays improved through virtual testing, it is mandatory to perform experimental tests for the final release of a product. The complexity of this kind of testing has increased. In the early 20th century, evaluations began to represent a real life time history with standardized load–time histories. This coincided with the introduction of the closed-loop test system to reproduce more realistic time histories. Most tier-1 suppliers perform such testing at their own development centers or at consultant test facilities; however, design engineers and product management need to understand the requirements of the testing and be able to interpret the results to understand how to improve a mechanical component. Most papers published on durability give experimental results for constant-amplitude loads and analytical predictions. However, information on tests with time histories and statistical analysis is very often missing. The present paper reviews the main aspects of durability tests for variable-amplitude loads, including the main statistical analysis conducted to reproduce damage to vehicles traveling on roads and proving grounds in the laboratory.

Design and Implementation of Delay-Dependent Wide-Area Damping Control for Stability Enhancement of Power Systems

In this paper, the hardware and software design and implementation are proposed for the wide-area damping control (WADC) strategies. First, the hardware-in-the-loop (HIL) real-time (RT) simulation system based on the RT-Lab is established as the closed-loop test platform for the WADC applied in multi-machine interconnected power system. The hardware, which contains the microcontroller, the peripheral analog to digital converter, and the digital to analog converter, are developed based on the AVR 32-bit development board. Three WADC algorithms, i.e., the phase-compensation, the delay-dependent state-feedback, and the dynamic output-feedback method, are introduced. Then, the software design of the above algorithms is proposed and the bilinear transform method is employed to get the discrete-time model of the controllers. The flowchart of each algorithm is designed for the implementation in the environment of hardware. The designed WADC is embedded in a real-time power system. Finally, case studies are carried out based on the HIL real-time simulation system. The proposed control concept and WADC design methods are validated by considering the big/small disturbance and the signal time-varying delay. The effectiveness of the proposed HIL closed-loop test system is also confirmed.

Mechanical properties of concrete to cyclic uniaxial tensile loading using variable waveforms

The mechanical properties of concrete under cyclic tensile loading using square waveform, sine waveform and ramp waveform are studied. The experiments are performed on a closed-loop electro-hydraulic servo-controlled material testing system (MTS). The axial strain, dissipated energy per loading cycle, the damage evolution law and deformation modulus are mainly studied. The results show that the three-stage evolution law of axial strain and damage variable of concrete under ramp waveform and sine waveform are more obvious than those under the square waveform. The dissipated energy changes at different stages of fatigue life. At the beginning and end of the fatigue life, the rate of dissipated energy is higher than that at the medium stage of the fatigue time, which is attributed to the formation of cracks. The evolution of deformation modulus of concrete subjected to cyclic tensile loading using three loading waveforms also shows three stages: fast increase in the damage—increase at a slow constant rate—and accelerated increase in damage until failure.

The new technology and on-orbit validity for GNC demonstration subsystem of CRRS

Guidance, navigation and control (GNC) demonstration subsystem is one of the three GNC subsystems of CRRS (Circumlunar Return and Reentry Spacecraft). It includes three new products, which are central control unit, micro star sensor and dustproof equipment for star sensor. And GNC demonstration subsystem is the partial products of GNC subsystem for land-ascent assembly spacecraft in the following task. To meet the demands of weight and functions in the third phase of China Lunar Exploration Program, central control unit was integrated designed based on SoPC technology to reduce the weight, and multi-layers protection was designed to fit the space radiation environment. Micro star sensor utilized aspherical Optical System and high speed processing circuit to obtain less weight. Based on micro step Motor, dustproof equipment for star sensor realized better architecture and damper design, not only satisfied the function requirement but also achieved the optimization of weight. In order to make on-orbit validity more forcefully and credibly using the CRRS, an on-orbit validity method based on Virtual-satellite control system was designed. This method presented an on-orbit and closed-loop test system for the above mentioned new products, without using actuator and real spacecraft. This paper mainly introduces the key technology of new products and the on-orbit validity method for GNC demonstration subsystem. Moreover, this paper makes the positive conclusion for new products according to the on-orbit validity results.

A Closed-Loop Test System for Network Performance of Smart Substation

The key support technology of smart substation testing technology is analyzed, the concrete application of smart substation is combined with the traditional network testing, and the function of real-time network packet analysis is introduced, which has make the process of smart substation layer network test form a closed loop system, extend and improve the system of smart substation performance test. And links to the reality, to the transformer substation switchboard network storm suppression function, the time delay, lost projects and so on the frame rate to carry on the statistics, the contrast has confirmed this plan feasibility and the validity.

Real Time Closed-loop Test Rig for Decentralized Control of Smart Distribution Networks

Electric power grids are moving towards Smart Grids and many new energy sources and loads are being integrated into distribution networks requiring the network to become more active and smart. The distribution networks have not been designed to cope with new constraints set up by the new energy sources and complex loads and will result in a number of adverse impacts. There is a considerable need for developing new algorithmic solutions for decentralised control within distribution networks and validating them at laboratory level before they can be successfully applied in the power grid. This research work addresses the development of a real time test rig which provides a decentralised control environment in distribution networks, onto which data management and network control functions are able to be implemented in a closed loop fashion, to observe their performance. This work also describes the development of a substation network controller; a platform that provides a closed loop test system for research, development, testing and validation of real time distribution network management and control functions.

Development of an in-cell SPME method to determine the chemical resistance of polymeric membranes to permeation by organic solvents

A stainless steel cell with an in-cell solid-phase microextraction (SPME) sampling device is proposed to investigate the permeation of dichloromethane, 1,2-dichloroethane, and benzene through a high-density polyethylene (HDPE) membrane. The advantage of using SPME as a direct sampling device in the collection chamber is that it is a simple and sensitive means to monitor the concentrations of organic compounds in the collection medium for a closed-loop test system. Compared with the permeation results for an ASTM F739 cell, the standardized breakthrough times were shorter and the permeability coefficients were greater using the alternative cell. Although the optimum SPME sampling parameters should be obtained in advance, the in-cell SPME method can be an appropriate approach to determine the resistance of polymeric membranes to permeation by organic solvents.

The effect of repeated loadings on the stress relaxation properties of 2.25Cr–1Mo steel at 550 °C and the influence on the Feltham ‘ a’ and ‘ b’ parameters

This paper describes studies undertaken to evaluate the stress relaxation behaviour of 2.25Cr–1Mo steel, a material used extensively in high temperature steam components. Repeated stress relaxation loadings were conducted on normalised and tempered 2.25Cr–1Mo steel at 550 °C, under constant strain, in a closed loop testing system. Detailed analysis of stress relaxation curves is presented. Application of the data to the Feltham equation for subsequent use in life assessment procedures is discussed and analysed.

The Effect of Injection Molding Process Parameters on the Tensile Properties of Short Glass Fiber-Reinforced PBT

This study investigates the influence of various injection molding process parameters and fiber amount on the tensile properties of short fiber-reinforced polybutylene terephthalate (PBT). The parameters that govern injection molding process are filling time, melt temperature, mold temperature, and packing pressure. The tensile properties of neat PBT, 15 wt%, and 30 wt% short fiber-reinforced PBT are obtained using a computerized closed-loop servohydraulic testing system. The frozen core morphology is observed by scanning electron microscopy (SEM), which can define the layer thickness. The observation can explain the influence of fiber orientation on the tensile properties. The fracture surfaces are also observed by SEM to understand the fracture mechanisms of different fiber orientations. It is found that the addition of short glass fibers can significantly strengthen neat PBT. The strength depends on the thickness of the layer where fibers are oriented in the loading direction. The layer thickness is strongly affected by the injection molding parameters and pin gate locations. Also, the fracture mechanisms of fiber pullout and across-matrix crack dominate the failure process in the layer where fibers are parallel to the direction of applied load. However, the failure of fiber–matrix interface dominates the fracture mechanism of the layer where fibers are mostly perpendicular to the applied load.

Development of a nondestructive compliance test for resilient denture liners.

Resilient denture liners are prescribed for patients who cannot adjust to hard-based dentures because of a thin mucosa or severe alveolar ridge resorption. A nondestructive test to evaluate compliance of new soft liner materials will be useful in clinical trials. The purpose of this study was to evaluate a nondestructive compliance testing technique designed to characterize long-term, silicone-based resilient denture liner materials. Samples of thicknesses of 1.1, 2.2, 3.3, and 4.4 mm of 2 materials (MPDS-SL [Lai Laboratories, Inc, Burnsville, MN] and Molloplast-B [Buffalo Dental, New York, NY]) were assessed for compliance using a closed-loop servohydraulic testing system, applying a 3 lb force following a squarewave pattern; force and position values were recorded using a storage oscilloscope. The oscilloscope values were analyzed using computer software to determine compliance values. The effect of material thickness was examined by testing wedges of the 2 materials. The testing technique used showed that differing thicknesses had significantly different compliance values (p <.0001). In the materials used to evaluate the technique, MPDS-SL behaved more elastically than did Molloplast-B (p <.0001). Material thicknesses beyond 2.2 mm did not increase compliance, although MPDS-SL had a steeper thickness-compliance curve than Molloplast-B. The method used to test compliance proved to be sufficiently sensitive to distinguish between 2 materials and between varying thicknesses. The sensitivity and nondestructive nature of this test show its suitability for clinical evaluation of resilient denture liners.