The cylinder block/valve plate interface is one of the most critical frictional interfaces of the swashplate-type axial piston pump. However, the poor lubrication interface caused rapid wear and high ...friction loss in an elastohydrodynamic lubrication system, decreasing the pump lifetime. Wear resistant bronze coatings were fabricated on 38CrMoAl substrate by Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD), respectively. Ball-on-disc wear tests were performed to comparatively investigate the wear behaviors of the coatings and bulk ductile iron samples. It can be found that the PVD-bronze coating exhibited better wear resistance than the other two samples. This enhanced wear resistance was attributed to the unique composite microstructure and desired mechanical strength, which could resist to mechanical shear and spallation, decreasing friction loss. The appropriate hardness of (1.33 ± 0.07) GPa could be beneficial for enhancing its wear resistance. The PVD-bronze coating possessed a much lower and stable coefficient of friction (about 0.1) and wear rate (about 6000 μm3·N−1·m−1) under the loading forces of about 100 N after 20 min. The wear mechanism was the abrasive wear.
Aviation hydraulic pump is one of the key components in aircraft hydraulic system, therefore, high-precision fault diagnosis is essential to improve the reliability and performance of hydraulic pump. ...A novel multi-source information fusion fault diagnosis method is proposed based on the Dempster–Shafer (D–S) evidence theory, which utilizes the three-level signals from pump level, hydraulic power system level and hydraulic actuation system level. The feature vectors of these three levels are extracted as three bodies of evidences (BOEs) and the fuzzy membership function is employed to construct the basic probability assignments (BPAs) of three BOEs. In order to solve the issue of combining the conflicting evidences, the D–S evidence theory based on the new evidence similarity distance is developed to combine the obtained BPAs. Finally, the making-decision rules are given to diagnose the faults. The diagnosis results validate that the proposed method not only can increase significantly the belief level of supporting the diagnosis target, but also has the ability to diagnose fault of pump correctly even if a sensor is faulty.
•A new electro-hydraulic servo pitch system is proposed for wind turbine.•An adaptive robust integral sliding mode pitch angle controller.•A projection adaptive law is designed.•Comparative ...experiments have been performed.
A new electro-hydraulic servo pitch system is proposed to enhance pitch angle control performances and hence to smooth generator power fluctuations for wind turbines. The pitch system mainly consists of a variable-speed hydraulic pump, a hydraulic motor and a pitch gear set. The hydraulic pump is employed to directly regulate the direction and rotational speed of the hydraulic motor that achieves the final pitch angle control through the gear set. An adaptive robust integral sliding mode pitch angle controller and a projection type adaptation law are synthesized to accurately track the desired pitch angle trajectory and compensate for model uncertainties and uncertain disturbances. The proposed controller and the adaptation law have their achievable performances in practice. Comparative results verify that the proposed pitch angle controller, together with the adaptation scheme, gives improved performances for the accurate pitch angle tracking and generator power control regardless of various uncertainties and disturbances.
As the number of agricultural workers is decreasing, there are a lot of demands on the robotics automation of agricultural tasks, including the automation of repacking and shipping in vegetable ...factories. A soft robot hand is suitable for such tasks because of its less damaging to vegetables and adaptability to variety in size and weight of vegetables. However, most of soft robotic hands are actuated by the air pressure, and the output force is not sufficient for heavy vegetables that are often dealt with in a vegetable factory. To solve this problem, we developed a prototype of a hydraulic soft robot hand in our previous research. Selecting an oil as the hydraulic source, the prototype was actuated by a compact built-in pump, we showed that the prototype could hold 2 or
cabbage with
pressure control. In this paper, we develop a compact water pump that can generate maximum
, and update the prototype selecting the water as the hydraulic source. We experimentally show that the soft hand can grasp and hold a cabbages, assuming a real situation in a vegetable factory.
Scales of IAMMA are adaptively determined by morphological features of signal, thus fault features of a hydraulic pump fault signal presented in multi-scales can be adaptively demodulated. In some ...coefficient range, IAMMA outperforms AMMA in demodulation ability based on the same SE, and it is less susceptible to noises than AMMA. The best performance of IAMMA with triangle SE is stronger than that of IAMMA with plat and semi-circle SE when they demodulate the same fault signal of hydraulic pump. Compared with traditional demodulation methods of HT and TKEO, IAMMA is adaptive and has stronger demodulation ability. An evaluation method based on kurtosis, power and standard deviation is proposed, by which some PFs which are rich in fault features can be selected as data source.
•IAMMA is free of selecting scales, and scales are adaptively determined by morphological features of signal, and the fault features of the hydraulic pump fault signals presented in multi-scales can be adaptively demodulated.•In some coefficient range, IAMMA outperforms AMMA in demodulation ability based on the same SE, and it is much less susceptible to the noises than AMMA.•The best performance of IAMMA with triangle SE is stronger than those of IAMMA with plat and semi-circle SE when they demodulate the same fault signal of hydraulic pump.•Compared with traditional demodulation methods of HT and TKEO, IAMMA is adaptive and has stronger demodulation ability.•An evaluation method based on kurtosis, power and standard deviation is proposed. By the method, some PFs which are rich in fault features can be selected as data source.
•the intergradation of distance-based similarity and spatial direction similarity to modify the AAKR method;•the first multi-source fusion of vibration and return oil flow by the MAAKR for HI ...construction;•the use of a hybrid model comprised of B-spline regression and particle filter for RUL prediction;•the monotonicity-constrained particle filtering for updating model parameters monotonically.
Accurate and scientific pump remaining useful life (RUL) prediction is vital to ensure the reliability and safety of hydraulic pumps. However, this is a challenging work due to the insufficient degradation data and the complex degradation mechanism of hydraulic pumps. A novel RUL prediction method is proposed in this paper to address this issue. Firstly, the Auto-Associative Kernel Regression (AAKR) is modified by integrating distance similarity and spatial direction similarity. The modified AAKR (MAAKR) is applied in the multi-source fusion of vibration and return oil flow to provide sufficient degradation data. Then the fused health indicator (HI) is modeled by the degree 3B-spline with monotonicity constraints. Moreover, this paper proposes a monotonicity-constrained particle filtering (MCPF) approach to update the random coefficients of the model monotonously. Thus, the monotonic degradation process of hydraulic pumps can be well described and predicted. The RUL can be predicted indirectly by the time when the predicted data reaches the failure threshold. Two run-to-failure cases of pumps verify the performance of the proposed RUL prediction approach. The experimental results demonstrate that the multi-source fusion based on MAAKR can significantly improve the prediction performance of degradation features. The proposed MCPF can give an accurate RUL value and scientific RUL confidence intervals. The comparison results indicate better performance of the MCPF than several other state-of-the-art approaches.
•A FBG temperature sensor with rapid response and anti-vibration is proposed.•The analysis and verification of this sensor temperature response.•The analysis and verification of this sensor ...anti-vibration performance.•The use of fiber Bragg grating intensity demodulation with high precision.•The application of this sensor in the motor of hydraulic pump.
This paper fabricated a fiber Bragg grating (FBG) temperature sensor with rapid response and excellent anti-vibration performance. The lightweight and miniaturization of the sensor provided favorable conditions for its application in mechatronic components. Specifically, the Invar capillary with an ultra-low thermal expansion coefficient was selected to package the FBG, which avoided the separation possibility between capillary and FBG under sharp temperature differences. It implied a wide temperature measurement range of the sensor. Nanometer copper suspension filled the tiny gap between capillary and FBG. Its good thermal conductivity brought a fast response speed close to the bare FBG. In addition, the jitter of FBG in the capillary was significantly reduced thanks to the nanometer copper suspension occupying its motion space. This sensor realized the reliability, rapidity and stability together. The FBG temperature sensor was applied to the temperature monitoring of small-size motor for hydraulic pump and achieved ideal results.
•Structure establishing of EHP.•System modeling and simulating.•Experiments on prototype.
Electro-hydraulic pumps (EHP) possess the advantages of integrated structure and high working efficiency, ...which thereby attract widespread attention. For the purpose of airborne deployment, an axial piston pump based EHP is established in this work. The modeling of the EHP is carried out in detail considering its structure and working principle via AMESim. Specifically, the model is performed on the basis of three aspects, which are electromagnetic driving, mechanical transmission and fluid dynamic. The computational simulation is conducted based on the modeling. Further, the prototype is designed and machined for working performance evaluation. The properties under different configurations of the EHP are investigated by experiments. Experimental results indicate that the proposed EHP provides a decent working performance in line with the modeling and simulating. The effectiveness of the EHP is verified and the scheme for further improvement is presented.
