Research on Fault Diagnosis of Hydraulic System of Fast Erecting Device Based on Fuzzy Neural Network

In order to improve the fault diagnosis effectiveness of hydraulic system in erecting devices, the fuzzy neural neural network is applied to carry out fault diagnosis of hydraulic system. Firstly, the main faults of hydraulic system of erecting mechanism are summarized. The main faults of hydraulic system of erecting devices concludes abnormal noise, high temperature of hydraulic oil of hydraulic system, leakage of hydraulic system, low operating speed of hydraulic system, and the characteristics of different faults are analyzed. Secondly, basic theory of fuzzy neural network is studied, and the framework of fuzzy neural network is designed. The inputting layer, fuzzy layer, fuzzy relation layer, relationship layer after fuzzy operation and outputting layer of fuzzy neural network are designed, and the corresponding mathematical models are confirmed. The analysis procedure of fuzzy neural network is established. Thirdly, simulation analysis is carried out for a hydraulic system in erecting device, the BP neural network reaches convergence after 600 times iterations, and the fuzzy neural network reaches convergence after 400 times iterations, fuzzy neural network can obtain higher accuracy than BP neural network, and running time of fuzzy neural network is less than that of BP neural network, therefore, simulation results show that the fuzzy neural network can effectively improve the fault diagnosis efficiency and precision. Therefore, the fuzzy neural network is reliable for fault diagnosis of hydraulic system in erecting devices, which has higher fault diagnosis effect, which can provide the theory basis for healthy detection of hydraulic system in erecting devices.

Investigation on the Effect of Impeller Design Parameters on Performance of a Low Specific Speed Centrifugal Pump Using Taguchi Optimization Method

In order to investigate the effect of blade design on pump performance, a CFD analysis was carried out, and the results were compared with experimental performance data of a low specific speed radial pump, which presents a good agreement. After model verification, the effect of impeller geometrical parameters includes blade outlet angle, wrap angle, and width at the exit, was investigated on the pump’s performance. Moreover, these parameters were chosen on three levels using an L9 orthogonal standard array of the Taguchi optimization method. The efficient levels of variables were calculated using the analysis of variance (ANOVA) method. The results revealed that impeller width at exit and blade outlet angle is the most effective pump shaft power and efficiency parameters. To minimize power, the optimal levels are the outlet angle of 27∘∘, wrap angle of 150∘∘, and width at the exit of 9 mm. Further, an outlet angle of 23∘∘, a wrap angle of 155∘∘, and a width at the exit of 9 mm lead to maximum pump efficiency. According to the validation simulations, an increase of 2.4% inefficiency and a minimum power of 3.9KW were achieved. The Overall Evaluation Criteria (OEC) technique revealed that considering 23∘∘, 160∘∘, and 9 mm for outlet angle, wrap angle, and width at the exit, minimum shaft power, and maximum pump efficiency will be achieved. ANOVA introduced width at the exit as the most governing parameter of pump performance characteristics.

Optimisation of a Pump-Controlled Hydraulic System using Digital Displacement Pumps

When electrifying working machines, energy-efficient operation is key to maximise the use of the limited capacity of on-board batteries. Previous research indicate high energy savings by means of component and system design. In contrast, this paper focuses on how to maximise energy efficiency by means of both design and control optimisation. Simulation-based optimisation and dynamic programming are used to find the optimal electric motor speed trajectory and component sizes for a scooptram machine equipped with pump control, enabled by digital displacement pumps with dynamic flow sharing. The results show that a hardware configuration and control strategy that enable low pump speed minimise drag losses from parasitic components, partly facilitated by the relatively high and operation point-independent efficiencies of the pumps and electric motor. 5–10% cycle energy reductions are indicated, where the higher figure was obtained for simultaneous design and control optimisation. For other, more hydraulic-intense applications, such as excavators, greater reductions could be expected.

Adaptive Identification and Application of Flow Mapping and Inverse Flow Mapping for Electrohydraulic Valves

Good estimation of flow mapping (FM) and inverse flow mapping (IFM) for electrohydraulic valves are important in automation of fluid power system. The purpose of this paper is to propose adaptive identification methods based on LSM, BPNN, RBFNN, GRNN, LSSVM and RLSM to estimate the uncertain structure and parameters in flow mapping and inverse flow mapping for electrohydraulic valves. In order to reduce the complexity and improve the identification performance, model structures derived from new algorithm are introduced. The above identification methods are applied to map the flow characteristic of an electrohydraulic valve. With the help of novel simulation architecture via OPC UA, the accuracy and efficiency of these algorithms could be verified. Some issues like invertibility of flow mapping are discussed. At last, places and suggestions to apply these methods are made.

Extended Analysis of a Valve-Controlled System with Multi-Chamber Actuator

This paper outlines an extended analysis on how multi-chamber actuators can improve the efficiency of valve-controlled systems. Resistive control is a major source of energy losses in valve-controlled systems that share the same pump to drive multiple loads. By combining different chambers, the load on multi-chamber actuators can be transformed into different pressure and flow rate levels. This allows the adaptation of its load to the loads on other actuators. This can lead to a reduction of resistive control energy losses that occur between pump and actuators when driven simultaneously. As a case study to highlight how the system efficiency can be improved, a load sensing system with a conventional and a multi-chamber actuator is analysed. The equations that describe the system steady state behaviour are presented to evaluate the effect of the load transformations on the system efficiency. A disadvantage of such architecture is the fact that load transformations result in different actuator speeds. To reduce this effect, a compensation factor for the command signal to the proportional valve is presented. The highlight from this paper is the potential for efficiency improvement enabled by the adoption of multi-chamber actuators in a valve-controlled architecture. Further research is required for the selection of number of chambers and their areas since they directly affect the system efficiency.

Heat Transfer Model of Pneumatic End-Position Cylinder Cushioning

In this paper a thermal model of a pneumatic cylinder with an integrated pneumatic end cushioning is presented. Being a part of a multidomain model presented in former research, this model is needed to simulate and analyse the thermodynamic processes in the pneumatic end cushioning and to elaborate a novel design strategy for damping systems with a higher capability on kinetic energy absorption and robust performance under fluctuating operating conditions. For this purpose, a proper heat exchange model is inevitable to calculate the pressure in the cushioning volume and consequently the deceleration of the load. An approach of splitting the complex geometry of cylinder into simple geometries, such as plain or cylindrical surfaces, is used in this study for a fast computation of convective heat flow rates. To validate this approach, the simulation results were compared with the measurements, carried out at different supply pressures, piston speeds and end cushioning throttle openings. The model will be used further for sensitivity analysis and robust optimisation of the cushioning system design.

Direct Actuation of Large Sized Valves by a Hydraulically Relieved Electromechanical Actuation System

Extensive actuation forces and strokes are required for the actuation of large sized valves normally implemented in high power hydraulic systems. A hydraulically piloted operation is, for now, the most suitable solution and state of the art. However, there are some applications where electromechanical valve actuation systems are at advantage against common pilot operation systems. In this contribution it is analyzed in which cases the application of electro-mechanical actuators can be of advantage and why displacement-controlled systems may be one of these applications. A novel electromechanical valve actuation system for large sized 4/3-way directional control valves for the use in displacement-controlled systems is presented. This new actuation system is characterized by a hydraulic relief of the centering springs. Therefore, the springs are only active in safety-critical conditions, such as a power outage. Since the actuator is not working against the spring force during every displacement, the necessary actuation force is reduced drastically. Thus, common electromechanical actuators can be used. In case of a power outage, the spring relief is deactivated causing the stored energy to center the spool in its neutral position. The performance of the novel actuation system is examined through measurements conducted on a manufactured demonstrator for valves of nominal size 25 with a flow rate of up to 600 l/min.

Pulsation Simulation and Energy Consumption Analysis of Series Pump Valve Cooperative Control Hydraulic System

In order to reduce the pulsation and the energy consumption of the hydraulic system, the series pump and valve cooperative control hydraulic system is designed, and the pulsation simulation and energy consumption analysis of it is carried out. Firstly, the working principle of series pump valve co control system is studied. Secondly, the mathematical model of series pump valve cooperation control system is established. And then the Controller of series pump valve cooperation control system is designed. Finally, the simulation analysis of the proposed hydraulic system is carried out, and results show that the proposed system has high stability and low energy consumption.

Study on Dynamic Characteristics of Negative Flow Control Variable Axial Piston Pump for Hydraulic Excavator

Hydraulic excavator is important mechanical equipment in engineering construction, which is widely used in mining enterprises, construction industry, etc. Variable axial piston pump is the main power component of hydraulic excavator. The negative flow control variable axial piston pump is deduced and the mathematical model is established. The dynamic simulation model of negative flow control variable axial piston pump is built by using SIMULINK in MATLAB software, and the simulation analysis is carried out. The influence of the main parameters of negative flow control mechanism on the dynamic characteristics of negative flow control variable axial piston pump is obtained, which provides a reference for the parameter design of negative flow control mechanism.

Influence of Air Dissolved in Hydraulic Oil on Cavitation Erosion

This article gives experimentally evidence that cavitation erosion in hydraulic components like valves and pumps is caused by vapour cavitation not gas or pseudo cavitation. In fact, the free air content which is released by vapour and gas cavitation reduces the erosion significantly. In order to clearly separate the different cavitation types, a test rig with a specially designed reservoir with integrated degassing capability is presented. As flow geometry a valve model with realistic dimensions and under realistic operating conditions was used, which ensures very high transferability of the results to the reality of hydraulic components in practical applications and typical operating conditions. A total of 4 five-hour long tests are performed and analysed. The quantification of the cavitation erosion is determined by the mass loss of the copper samples. The experimental results show a 4.4–5.1 times higher mass loss in tests with air-free oil compared to tests with air-saturated or oversaturated hydraulic oil. The experimental fact that air-free hydraulic oil causes significantly more cavitation erosion than normal (saturated) hydraulic oil, and its implications are discussed. The conclusion can be drawn, that further developments of hydraulic components and systems towards the use of air-free oil or increasing power densities will be disproportionately challenged by cavitation erosion.