Reliability Analysis on Repairable System with Dual Input Closed-Loop Feedback Link Considering Shutdown Correlation Based on Goal Oriented Methodology

Goal oriented( GO) methodology is a kind of success oriented system reliability analysis method and has been used widely.The repairable system with dual input closed-loop feedback link( DICLFL) considering shutdown correlation didn't make reliability analysis accurately based on existing GO methodology. So, a reliability analysis method used to deal with DICLFL considering shutdown correlation is provided based on GO methodology.Firstly, a new operator, which is used to describe DICLFL considering shutdown correlation,whose number is 1,is created and named as Type 9C operator. And then,the formulas of type 9C operator are derived based on Markov process theory. Finally,the new method presented in this paper is adopted to conduct the reliability analysis of an electro-hydraulic servo speed control system. The analysis result is compared with those of Monte Carlo simulation and fault tree analysis( FTA). The comparison results show that this new reliability analysis method based on GO methodology is feasible and meaningful for reliability analysis of repairable systems with DICLFL considering shutdown correlation.Meantime,it will be useful for more other applications.

Reliability Analysis of Repairable System with Multiple Closed-Loop Feedbacks Based on GO Method

In order to solve the problem of reliability modeling and the analysis of complex systems with multiple closed-loop feedbacks,a new reliability analysis method for repairable systems with multiple closed-loop feedbacks is proposed based on the goal-oriented(GO)methodology.Firstly,the basic theories and advantages of GO method are introduced.Secondly,a type-24B multiple closed-loop feedback structure operator is proposed through GO method with its operation formula given,which expands the types of GO method operators and the application scope of their reliability analysis.Finally,taking a certain type of diesel engine fuel supply system an example,the quantitative and qualitative analysis is carried out through GO method,Monte Carlo simulation as well as FTA respectively.The availability results verify the availability of the proposed type-24B operator in the reliability analysis of multiple closed-loop feedback systems.The qualitative analysis results indicate the accuracy and usability of the GO method as a qualitative analysis method.

A new adaptive bending method using closed loop feedback control

As the competition from companies in low cost countries increases,the need for more automated production which reduces labour cost while improving product quality is required.A new rotary compression bending set-up with automated closed-loop feedback control is thus being developed.By transferring in-process measurement data into an algorithm for predicting springback and bend angle prior to the unloading sequence,the dimensional accuracy is improved.This work focuses on the development of this steering model.Since the method used does not increase cycle time,it is attractive for high-volume industrial applications.More than 150 bending tests of AA6060 extrusions were conducted to determine the capability of the technology.The results show that by activating the automated closed-loop feedback system,the dimensional accuracy of the bent parts is more than three times better than that obtained by traditional compression bending.Since the steering model permits the direct use of additional process data,such as instant wall thickness and cross sectional distortions,it is believed that extension of the measurement capabilities would improve the accuracy of the methodology even further.

Closed-loop transmit diversity systems with hybrid antenna selection

The paper investigates closed-loop transmit diversity （CLTD） systems with antenna selection technique. The expected received signal-noise-ratio （RxSNR） of the proposed systems is analyzed and compared with CLTD systems. An algorithm is proposed for determining the number of increased transmit antennas in terms of a reduced RF chains without performance degradation. Since a feedback channel is bandwidth-limited, we present a method of quantizing transmit-weight vectors. Simulation results demonstrate advantage of the proposed systems with full and quantized feedback information. Quantized feedback has less effect on the proposed systems than CLTD systems.

Quadrature error and offset error suppression circuitry for silicon micro-gyroscope

The reasons for inducing quadrature error and offset error are analyzed and the expressions of quadrature error and offset error are induced. The open-loop system analysis indicates that, in order to avoid the appearance of harmonic peaks, the frequency difference δf between drive mode and sense mode must be less than 1/（2Qy）. In order to eliminate the effects of the quadrature error and the offset error, as well as the inherent non- linearity in the capacitance-type sensors, a closed-loop feedback control circuit with quadrature correction is designed. The experimental results indicate that the quadrature error and offset error are corrected. By comparing with open-loop detection, the closed-loop feedback control circuit with quadrature correction decreases the non-linearity of the scale factor from 16. 02% to 0. 35 %, widens the maximum rate capability from ± 270 （°）/s to ± 370 （°）/s and increases the stability of zero bias from 155. 2 （°）/h to 60. 6 （°）/h.

A combined modulated feedback and temperature compensation approach to improve bias drift of a closed-loop MEMS capacitive accelerometer

The bias drift of a micro-electro-mechanical systems （MEMS） accelerometer suffers from the l/f noise and the tem- perature effect. For massive applications, the bias drift urgently needs to be improved. Conventional methods often cannot ad- dress the l/f noise and temperature effect in one architecture. In this paper, a combined approach on closed-loop architecture modification is proposed to minimize the bias drift. The modulated feedback approach is used to isolate the l/f noise that exists in the conventional direct feedback approach. Then a common mode signal is created and added into the closed loop on the basis of modulated feedback architecture, to compensate for the temperature drift. With the combined approach, the bias instability is improved to less than 13 μg, and the drift of the Allan variance result is reduced to 17 μg at 100 s of the integration time. The temperature coefficient is reduced from 4.68 to 0.1 mg/℃. The combined approach could be useful for many other closed-loop accelerometers.

Analysis of thermal-mechanical coupled characteristics of vehicle twin-tube shock absorber

A comprehensive model that included mechanical dynamics of the shock absorber coupled with its thermal properties was proposed innovatively.Moreover a thermal-mechanical coupled model which reflected the closed-loop positive feedback system was established by using MATLAB/SIMULINK,and some curves of shock absorber temperature rising characteristic were obtained by simulation ＆computation under several operating modes and different parameters conditions.Research results show that：shock absorber design parameters,external excitations,and thermo-physical properties parameter,such as oil density have effect on the shock absorber temperature rising characteristic.However other thermo-physical properties parameters,such as oil specific heat,cylinder density,cylinder specific heat,and cylinder thermal conductivity,have no effect on it.The results may be used for studying reliability design of the shock absorber.

Simple Closed-Loop Method to Compensate Interference Asymmetry in Time-Division Duplex MIMO-OFDM Systems

In wireless communications systems with time-division duplex (TDD) deployment, channel reciprocity and symmetric interference between transmitter and receiver sides are two widely-adopted assumptions for the design of optimal adaptation transmission mode. However, in practice, there is an undesirable but non-negligible effect, namely the asymmetric interference, that makes the assumptions no longer valid. In this paper, a simple closed-loop feedback method of compensating interference asymmetry in TDD multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system is proposed. The system makes the estimated interference at transmit-side be able to track the instantaneous receive-side interference dynamically. The proposed method maintains constant frame error rate (FER) by adopting adaptive modulation coding (AMC) and power loading. The final simulations have verified the effectiveness of the new method.

Closed-loop flow control of an ultra-compact serpentine inlet based on nondimensional model

Ultra-compact serpentine inlet faces serve inlet-engine compatibility issues due to flow distortion.To ensure inlet-engine compatibility over a wide range of Mach number,novel active flow control techniques with the ability of being opened or adjusted as needed draw many attentions in recent years.In this paper,a feedback control system was developed based on the method of microjet blowing.The proposed system includes a pressure adjusting valve to adjust the control effort,a dynamic pressure sensor to sense the inlet distortion intensity,a signal processing instrument to calculate the Root-Mean-Squared(RMS)pressure,and a controller to implement feedback control.To achieve high quality closed-loop controls at dynamic conditions,a novel nondimensional feedback method was developed.The advantage of this nondimensional method was validated at both off-design and arbitrarily changing Mach number conditions.With a sectional PI control law,the RMS control error reduced more than 56%at arbitrary changing conditions.Works in this paper also showed that the dynamics of this nondimensional system can be simplified as a stable second-order overdamped system.

A feedback control mechanism for adaptive SLO maintenance in dynamic service level management

With the increasing scale of information technology(IT)service system,traditional thresholdbased static service level management(SLM)solution appears to be inadequate to meet current increasingly management requirement of SLM.Due to the stochastic service request rate,the random inherent failure and load surge of IT devices during service operating stage of large scaled IT system,service level objective(SLO)maintenance issue has become a realistic and important issue in dynamic SLM.This paper proposes a closed-loop feedback control mechanism to adaptively maintain SLO that service provider(SP)guaranteed at service operation stage.The mechanism can automatically tune the capacity of IT infrastructure according to service performance dispersion and reduce SLO violations.Considering that the tuning operations also affect service performance,fuzzy control is applied to alleviate the negative effect caused by tuning operations.In the dynamic SLM system that is applied with this mechanism compared with the traditional threshold-based solution,it is proved that the amount of SLO violations obviously decreases,the reliability of the service system increases relatively,and the resource utilization of IT infrastructure is optimized.

Design and Experiments of Model-free Compound Controller of Flight Simulator

A model-flee compound controller design method is proposed to achieve the wide frequency bandwidth requirement of flight simulators. The method based on quantitative feedback theory, acquires system uncertainty under different working conditions through closed-loop identification with power spectrum estimation. Then in controller designing, it makes a trade, off between the strict requirements for magnitude-frequency characteristics and those for phase-frequency characteristics of flight simulators, by converting the indices of magnitude-frequency characteristics of flight simulators into quantitative feedback theory-based tracking specification bounds and using feedforward controller to attain the required phase-flequency characteristics. Simulation and experimental results indicate that, when used to design inner flame controller of flight simulator, the proposed method can fulfill the requirements for wide frequency bandwidth indices. Compared with other controller design methods, it has the property of model-free and transparency.

A naive optimization method for multi-line systems with alternative machines

The scheduling of parallel machines and the optimization of multi-line systems are two hotspots in the field of complex manufacturing systems.When the two problems are considered simultaneously,the resulting problem is much more complex than either of them.Obtaining sufficient training data for conventional data-based optimization approaches is difficult because of the high diversity of system structures.Consequently,optimization of multi-line systems with alternative machines requires a simple mechanism and must be minimally dependent on historical data.To define a general multi-line system with alternative machines,this study introduces the capability vector and matrix and the distribution vector and matrix.A naive optimization method is proposed in accordance with classic feedback control theory,and its key approaches are introduced.When a reasonable target value is provided,the proposed method can realize closed-loop optimization to the selected objective performance.Case studies are performed on a real 5/6-inch semiconductor wafer manufacturing facility and a simulated multi-line system constructed on the basis of the MiniFAB model.Results show that the proposed method can effectively and efficiently optimize various objective performance.The method demonstrates a potential for utilization in multi-objective optimization.