Developing a method to detect internal leakage in hydraulic cylinder, which is used for Electro‐Hydrostatic Actuators (EHA), is important to prevent serious malfunctions for aircrafts. At present, ...the internal leakage in an EHA cannot be accurately detected only using operational data. This paper proposed a convolutional neural networks (CNN) based method to detect internal leakage in hydraulic cylinder according to the relationship between operational state parameters of EHA and leakage in the hydraulic cylinder. A method was presented to align multi‐source signals with different forms by using the motor current as a benchmark. Because the number of monitoring signals are relatively small, a feedforward neural network (FFNN) based data augment method is proposed to increase parameters of input data set. A general method on how to detect internal leakage by combining signals alignment, data augmentation and multiscale residual CNN was proposed. The experimental results show that the proposed method can be used to accurately detect internal leakage in a hydraulic cylinder operating under non‐stationary load and velocity conditions, and the detection accuracy reached 99.8%.
A method was proposed to detect internal leakage in hydraulic cylinder depending on control signals by combining proposed multi‐source signals alignment, data augmentation based on feedforward neural network and multiscale residual convolutional neural networks. The experimental results show the detection accuracy reached 99.8% even when hydraulic cylinder operating under non‐stationary load and velocity conditions.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
•EEMD and HT approaches are adopt for the internal leakage detection.•EMD and DWT based methods are applied on the same pressure signals.•The developed scheme owns the best performance among three ...approaches.
This paper investigates the detection of the internal leakage in the hydraulic inlet guide vane (IGV) system at the gas turbine compressor. Based on methods of ensemble empirical mode decomposition (EEMD) and Hilbert transform (HT), we propose the internal leakage detection method. Firstly, EEMD is applied to decompose the pressure signal at chamber A of the cylinder into intrinsic mode functions (IMFs). Secondly, the instantaneous amplitude of the first IMF (IMF1) is obtained through HT. Finally, the mean of IMF1 instantaneous amplitude at a time period is adopted for the detection of the internal leakage fault and its levels. After setting the proper number of ensemble size and threshold value of the white noise amplitude to reduce the root mean-squared deviation for the multi-mode distribution of the IMFs, the developed method can identify the internal leakage in the IGV cylinder during experiments under the time-varying cylinder position and load at a built hydraulic IGV emulator. The empirical mode decomposition (EMD) and discrete wavelet transform (DWT) based methods are applied on the same pressure signals, respectively. The results show that the developed scheme owns the best performance comparing with the EMD and DWT based approaches in our case.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Valve internal leakage is easily found because of various defects resulting from environmental factors and load fluctuation. The timely detection of valve internal leakage is of great significance to ...the safe operation of pipelines. As an effective means for detecting valve internal leakage, the acoustic emission technique is characterized by nonintrusive and strong anti-interference ability, which can realize the in situ monitoring of the valve running status in real time. In this paper, acoustic emission signals from an internal leaking valve were obtained experimentally. Then, the dimensionality reduction technology based on factor analysis was introduced to the processing of valve internal leakage detection data. Next, the wavelet decomposition was carried out to decompose the sample feature set into four subsets. Finally, the decomposed sample feature sets were inputted into the error backpropagation (BP) neural network quantitative model, respectively. The optimized results show that the predicted internal leakage rate by the wavelet-BP neural network model has good precision with an error of less than 10%. The wavelet-BP neural network model can realize the analysis of the valve internal leakage rate quantitatively and has good robustness, which provides technical support and guarantees the safe operation of natural gas pipeline valves.
This paper proposes a fault estimation and fault-tolerant control strategy with two observers for a pump-controlled electro-hydraulic system (PCEHS) under the presence of internal leakage faults and ...an external loading force. The mathematical model of the PCEHS is dedicatedly derived in the state-space form for developing control methodology. Two different observers are developed in which an extended state observer is applied to estimate the internal leakage flow rate, and a disturbance observer is used to deal with the external loading force. Then, the proposed control is designed based on the backstepping sliding mode technique in which estimated information from the observers is taken into consideration to guarantee the working performance of the system. With the proposed methodology, the robustness and stability of the controlled system are theoretically analyzed and proven by the Lyapunov theorem. Comparative simulation results are given to demonstrate the effectiveness of the proposed methodology through different testing conditions.
This paper proposes an improved robust position controller for the electro-hydraulic actuator system using the varying boundary layered sliding mode control scheme. The proposed scheme has the ...ability to improve the position tracking performance of the actuator in the presence of friction and internal leakage. The former is represented using the LuGre model while later is modelled as a turbulent flow. To evaluate the effectiveness of the proposed method, MATLAB simulations are carried out under friction and leakage effects. Its performance is compared with the conventional PID and fuzzy PID (FPID) methods. Finally, an experimental rig that comprises of a single-rod and double acting hydraulic cylinder is set up to validate the proposed idea. The software development is carried out in the DSpace 1104 environment using a TMS320F240 digital signal processor. The superiority of the proposed method over the PID and FPID in terms of tracking position is highlighted by simulation and experimental results.
An energy and exergy analysis of the condensate pump from the marine steam propulsion system during the condensate leakage between pump stages is presented in this paper. Measurements from the steam ...propulsion system during exploitation were necessary for collecting all the data for the condensate pump analysis. Due to condensate leakage inside the pump casing, the producer specified condensate pressures at the pump outlet could not be obtained during the exploitation. Low condensate pressure at the pump inlet and condensate temperature slightly above the atmospheric significantly influences the pump exergy analysis. Increase in pump load resulted in an increase of pump energy and exergy losses and efficiencies. In the observed load range during the leakage, pump energy losses are between 19.88 kW and 24.78 kW, while pump energy efficiencies are between 11.12 % and 41.54 %. Pump exergy losses are slightly higher, while exergy efficiencies are slightly lower when compared to energy losses and efficiencies. During normal operation, without leakage, the pump energy efficiencies are from 5 % to 20 % higher in comparison with pump operation when the leakage occurs.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In order to fully predict the performance of variable displacement vane oil pump (VDVP) during concept design phase， one-dimensional simulation software AMESim is used to model the centralised ...parameters of VDVP. Several important performance indexes of VDVP are predicted, including the flow, pressure, torque and initial variable point, it is proved by the bench test that the simulation results have a good correlation with the test results. In addition, the effect of leakage on volumetric efficiency is studied, external leakage is smaller than internal leakage, and the higher the temperature, the larger the leakage. The force characteristics of VDVP are studied. Under extreme conditions, the maximum pressure of the internal chamber is about 15.9 bar, and the maximum forces of the stator and rotor are 1920 and 1653 N, respectively. The effect of temperature on the frictional power is studied. Under low-temperature conditions, the viscous frictional power is much greater than the dry frictional power, while the high temperature is the opposite.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Internal leakage in the hydraulic actuators is concerned in this article, which is caused by seal damage, resulting in the limited performance of the system. To study the issue, this article proposes ...a method based on time–frequency analysis for the detection in hydraulic actuators. First, the pressure signal after filtering of the actuator in one side is collected when the control valve is affected by sinusoidal-like inputs. Second, the time–frequency image of pressure signal in a period at different leakage levels is obtained after continuous wavelet transform. Third is the sum of pixels in the time–frequency image. It is shown that the feature pattern is established by the sum of pixels in the time–frequency image that internal leakage and its severity could be detected effectively. The proposed method required two baselines and premeasured the pressure signal at 11 leakage levels. Once the sum of pixels in the time–frequency image values, obtained from the time–frequency image by continuous wavelet transform based on wavelet Cmor1-1 in subsequent offline tests, are greater than the first baseline, a leakage alarm is triggered. Furthermore, a severe leakage alarm is triggered when the value is greater than the second baseline. Experimental tests show the accuracy of the proposed scheme at different mother wavelets, and it is done without knowing the model of actuator or leakage.
As interest in safety and performance of power plants becomes more serious and wide-ranging, the significance of research on turbine cycles has attracted more attention. This paper particularly ...focuses on thermal performance analysis under the conditions of internal leakages inside closed-type feedwater heaters (FWHs) and their diagnosis to identify the locations and to quantify leak rates. Internal leakage is regarded as flow movement through the isolated path but remaining inside the system boundary of a turbine cycle. For instance, leakages through the cracked tubes, tube-sheets, or pass partition plates in a FWH are internal leakages. Internal leakages impact not only plant efficiency, but also direct costs and/or even plant safety associated with the appropriate repairs. Some types of internal leakages are usually critical to get the parts fixed and back in a timely manner. The FWHs installed in a Korean standard nuclear power plant were investigated in this study. Three technical steps have been, then, conducted: (1) the detailed modeling of FWHs covering the leakage from tubes, tube-sheets, or pass partition plates using the simulation model, (2) thermal performance analysis under various leakage conditions, and (3) the development of a diagnosis model using a feed-forward neural network, which is the correlation between thermal performance indices and leakage conditions. Since the operational characteristics of FWHs are coupled with one another and/or with other neighbor components such as turbines or condensers, recognizing internal leakages is difficult with only an analytical model and instrumentation at the inlet and outlet of tube- and shell-sides. The proposed neural network-based correlation was successfully validated for test cases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Aim: Welding is one of the most common occupations associated with occupational lung disease and is often associated with respiratory symptoms because inhalation is a common way of exposure with ...welding fume in welders. The aim of this study was to investigate the efficiency and Total Internal Leakage (TIL) valve fabric respiration protection mask made in Iran against different metals in the welding fume. Methods: To determine the efficiency of the mask, the concentration of pollutants in the air outside the mask and the concentration of pollutants in the air inside the mask were measured simultaneously. NIOSH 7302 method was used to sample the air inside and outside of the masks. The elements Al, Cu, Fe, Mn, Ti, and Zn in the welding fume were analyzed. Results: The efficiency of the mask against titanium and iron metals is higher than other metals. The average efficiency of the respiratory mask is 75.46% and the TIL rate is 23.42%. Conclusion: The mask absorbs different metals of welding fumes with different efficiencies. Improving the efficiency of the mask body to create a suitable fit that eliminates or minimizes the leakage caused by the seal is a priority.
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