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The enormous throttling losses are the crucial reason for the low energy efficiency of non-road mobile machinery. To achieve energy saving, a parallel electro-hydraulic hybrid drivetrain that combines an electric-hydraulic energy recovery system with a valve-controlled system is proposed. With a parallel electric-hydraulic energy recovery system, both the energy lost caused by load imbalances and overrunning loads can be recovered and reutilized. To achieve satisfactory operation performance and minimize energy consumption, a rule-based energy management strategy is implemented for real-time control. Several experiments are conducted to verify the feasibility and energy-saving features of the proposed scheme. Additionally, taking a 37-ton hydraulic excavator as an example, a co-simulation platform is established to demonstrate its working characteristics under various conditions. Compared with the hydraulic excavator without energy recovery, throttling losses and energy consumption of the proposed system are reduced by 60%-75% and 24%-27%. Moreover, the proposed system integrates the energy-saving pressure compensator, and the response lag between the heavy-load actuator and light-load actuator is shortened by 47% during multi-actuator motion, effectively improving coordination and maneuverability.

In the process of frequent start-stop actions of the slewing platform in existing electric shovels, there is a substantial waste of kinetic energy. Furthermore, the installed power of the drive motor is often configured according to the maximum load, which makes it frequently operate in a low-efficiency region further exacerbating energy losses. To address these issues, this paper proposes an electro-hydraulic active-passive hybrid drive system for the shovel’s slewing system. The aim of this system is to efficiently store and utilize the kinetic energy generated by the shovel’s slewing system, reduce the installed power of the system’s drive motor, and consequently enhance the overall energy efficiency. To achieve high-efficiency energy recovery during the swing process of the slewing system, the proposed system introduces an additional hydraulic pump/motor and hydraulic accumulator. The pump/motor is situated at the original drive motor’s drive shaft. It serves to recover kinetic energy during the deceleration of the shovel’s slewing system and assists the motor in driving the load during the acceleration. This approach not only allows efficient storage of kinetic energy but also significantly reduces the installed power of the drive motor. The paper begins by analyzing the operational principles of the proposed electric-hydraulic active-passive hybrid drive slewing system of electric shovel. Subsequently, a test platform was constructed using a 36-ton excavator to preliminarily validate the proposed system feasibility. Experimental results indicate that, compared with the original system, the peck power and decrease energy consumption of the swing motor can be reduced by 28% and 49% respectively. Ultimately, an electromechanical-hydraulic coupling model was established for the electric-hydraulic active-passive hybrid drive electric shovel’s slewing system. Simulation results reveal that, compared with the original system, the peak power and energy consumption of the slewing motor can be reduced by 300 kW and 59%, respectively. The proposed system offers a significant improvement in the efficient storage of kinetic energy in large inertia slewing platforms.

The rotary motion field of heavy equipment is a large energy-consuming field, characterized by frequent cyclical start-stop, significant load inertia, and braking energy is usually dissipated as thermal energy, for energy regeneration, no good solution has been found. This paper proposes a new energy-regenerative hybrid drive (ERHD) system and defines three operating modes. Taking the reversible rolling mill’s roll as load, and taking the energy consumption of electric motor (EM) and peak power as evaluation indexes, the influence law of key component parameters on the driving characteristics of the system is studied. Simulation models for the pure electric motor drive (PEMD) system and ERHD system were established by AMESim, along with a rule-based energy management strategy (EMS). The results show that the hydraulic pump/motor displacement has the greatest influence on braking time, peak power, and energy consumption. Under the optimal parameters, the proposed ERHD system can reduce the peak power of EM by 45.75% and energy consumption by 48.33% compared with the PEMD system. Starting and braking times were reduced by 44.54% and 1.21%, respectively. Based on the test results, the ERHD system reduces start-up time by 22.70% and peak power by 23.72%. The proposed system will significantly contribute to developing the rotary motion field of heavy equipment in terms of energy efficiency, low carbon and green.

Abstract Mining shovel is a crucial piece of equipment for high-efficiency production in open-pit mining and stands as one of the largest energy consumption sources in mining. However, substantial energy waste occurs during the descent of the hoisting system or the deceleration of the slewing platform. To reduce the energy loss, an innovative hydraulic-electric hybrid drive system is proposed, in which a hydraulic pump/motor connected with an accumulator is added to assist the electric motor to drive the hoisting system or slewing platform, recycling kinetic and potential energy. The utilization of the kinetic and potential energy reduces the energy loss and installed power of the mining shovel. Meanwhile, the reliability of the mining shovel pure electric drive system also can be increased. In this paper, the hydraulic-electric hybrid driving principle is introduced, a small-scale testbed is set up to verify the feasibility of the system, and a co-simulation model of the proposed system is established to clarify the system operation and energy characteristics. The test and simulation results show that, by adopting the proposed system, compared with the traditional purely electric driving system, the peak power and energy consumption of the hoisting electric motor are reduced by 36.7% and 29.7%, respectively. Similarly, the slewing electric motor experiences a significant decrease in peak power by 86.9% and a reduction in energy consumption by 59.4%. The proposed system expands the application area of the hydraulic electric hybrid drive system and provides a reference for its application in oversized and super heavy equipment.

In the existing electric excavators, the energy efficiency of the hydraulic system is less than 30% due to a large amount of throttling loss and waste of potential energy. In order to improve excavator energy efficiency, an electric excavator scheme using a hydraulic-electric dual-power drive boom system is proposed. A linear actuator, including electro-mechanical unit and hydraulic unit, was adopted in the boom system. The boom velocity is controlled by the electro-mechanical unit instead of hydraulic valve to reduce throttling loss. The non-rod chamber of the linear actuator is connected to a hydraulic accumulator to reutilize boom gravitational potential energy. In addition, when the boom and other devices are operated together, the throttling loss caused by load difference of multi-actuators can be reduced because the linear actuator can compensate for the pump pressure. The working principle, control strategy, and characteristics of the proposed electric excavator were analyzed through theory and experiments. The results show that the proposed system can reduce throttling loss and efficiently reutilize the boom gravitational potential energy. During boom lifting and lowering process, the reutilization rate of the boom gravitational potential energy is 67.6%, and the energy consumption is reduced by 66.1%. During land levelling process, the throttling loss of the electric excavator is reduced by 49.6% and the energy consumption is reduced by 38.1%. The research results will provide new methods for the electrification of construction machinery.

A novel lignocellulosic aerogel, MT-LCA, was successfully prepared from MT by undergoing partial dissolution in an ionic liquid, coagulation in water, freezing in liquid nitrogen, and subsequent freeze-drying. The MT-LCA preserves its original honeycomb-like porous structure, and the newly formed micropores contribute to increased porosity and specific surface area. FT-IR analysis reveals that MT, after dissolution and coagulation, experiences no chemical reactions. However, a change in the crystalline structure of cellulose is observed, transitioning from cellulose I to cellulose II. Both MT and MT-LCA demonstrate a quasi-second-order kinetic process during methylene blue adsorption, indicative of chemical adsorption. The Langmuir model proves to be more appropriate for characterizing the methylene blue adsorption process. Both adsorbents exhibit monolayer adsorption, and their effective adsorption sites are uniformly distributed. The higher porosity, nanoscale micropores, and larger pore size in MT-LCA enhance its capillary force, providing efficient directional transport performance. Consequently, the prepared MT-LCA displays exceptional compressive performance and efficient directional transport capabilities, making it well-suited for applications requiring high compressive performance and selective directional transport.

Abstract With the widespread application of the computer and microelectronic technology in the industry, digitization becomes the inevitable developing trend of the hydraulic technology. Digitization of the hydraulic components is critical in the digital hydraulic technology. High-speed on-off valves (HSVs) which convert a train of input pulses into the fast and accurate switching between the on and off states belong to widely used basic digital hydraulic elements. In some ways, the characteristics of the HSVs determine the performance of the digital hydraulic systems. This paper discusses the development of HSVs and their applications. First, the HSVs with innovative structures which is classified into direct drive valves and pilot operated valves are discussed, with the emphasis on their performance. Then, an overview of HSVs with intelligent materials is presented with considering of the switching frequency and flow capacity. Finally, the applications of the HSVs are reviewed, including digital hydraulic components with the integration of the HSVs and digital hydraulic systems controlled by the HSVs.

In order to realize the high energy efficiency and high performance motion control of the lifting device of construction machinery, this paper proposes an electro-hydraulic compound driving system that can regenerate the potential energy. In this new system, the high-power density combination of hydraulic cylinder with accumulator is used to balance the self-weight of the lifting device and recycle the gravitational potential energy directly. The green electro-mechanical actuator with high energy efficiency and control performance is used to control the motion of the lifting device. In addition, control valves are added to dynamically adjust the pressure of the two chambers of the hydraulic cylinder and increase the stiffness of the hydraulic system, which can restrain the impact of acceleration and deceleration of large inertia lifting device and rapid charging and discharging of accumulator on electro-mechanical actuator. Finally, a typical construction machinery excavator is structurally modified to build a test platform. The test results show that, under the same working conditions, the proposed electro-hydraulic compound driving system can further reduce energy consumption by 31% and reduce peak power by 15% than that of the high energy efficiency three-chamber hydraulic cylinder driving system with potential energy regeneration. The boom runs smoothly, and the velocity overshoot and fluctuation time are significantly reduced, realizing high performance driving of the lifting device with low energy consumption. The research results also have broad application prospects in missile erection devices, cranes, presses, and other equipment.

Abstract The tribological properties of cylinder block/valve plate is an important consideration in the design of axial piston pump. The effect of materials and heat treatment on friction and wear properties has been studied in depth. Engineering experiences show that the speed and load also affect the tribological properties, but these have not been systematically analyzed. The purpose of this paper is to evaluate the tribological properties of the commonly used materials (CuPb15Sn5 and 38CrMoAl/42CrMo) for cylinder block/valve plate with different heat treatment and contact pressure at different speed. During the test, tribometer is used to simulate the contact pattern between the valve plate/cylinder block in axial piston pump, the friction coefficient, wear rate and surface topography are analyzed to evaluate the tribological properties of different types of friction samples at different speed. Results indicate that: (1) contact surface of the samples at 1800 r/min is more prone to adhesive wear than those at 500 r/min; (2) in the terms of wear resistance, quench-tempered and nitrided 38CrMoAl (38CrMoAl QTN for short) is better than quench-tempered and nitrided 42CrMo, although they are all commonly used materials in the axial piston pump; (3) 2.5 MPa is the critical contact pressure of the interface between valve plate made of 38CrMoAl QTN and cylinder block made of CuPb15Sn5 on the tribometer, which implies the pressure bearing area at the bottom of the cylinder block should be carefully designed; (4) the valve plate/cylinder block made of 38CrMoAl QTN/CuPb15Sn5 exhibits good tribological properties in a real axial piston pump. This research is useful for the failure analysis and structural optimization design of the valve plates/cylinder block.

Fused deposition modeling (FDM) processed Poly-ether-ether-ketone (PEEK) materials are widely used in aerospace, automobile, biomedical, and electronics industries and other industries due to their excellent mechanical properties, thermal properties, chemical resistance, wear resistance, and biocompatibility, etc. However, the manufacture of PEEK materials and parts utilizing the FDM process faces the challenge of fine-tuning a list of process parameters and heat treatment conditions to reach the best-suiting mechanical properties and microstructures. It is non-trivial to make the selection only according to theoretical analysis while counting on a vast number of experiments is the general situation. Therefore, in this paper, the extrusion rate, filling angle, and printing orientation are investigated to adjust the mechanical properties of 3D-printed PEEK parts; then, a variety of heat treatment conditions were applied to tune the crystallinity and strength. The results show that the best mechanical performance is achieved at 1.0 times the extrusion rate, varied angle cross-fillings with ±10° intervals, and vertical printing. Horizontal printing performs better with reduced warpage. Additionally, both crystallinity and mechanical properties are significantly improved after heat treatment, and the best state is achieved after holding at 300 °C for 2 h. The resulting tensile strength is close to 80% of the strength of injection-molded PEEK parts.

There are the problems of low flow control accuracy, small flow control difficulty, and limited flow range in the traditional pressure-compensation flow-control valve. For this, a method of continuous control pressure drop $\Delta p_{\mathrm {rated}}$ to control flow-control valve flow is proposed. And the precise control of small flow is realized by reducing the pressure drop $\Delta p_{\mathrm {rated}}$ . In the research, the flow-control valve with controllable pressure compensation capability (FVCP) was designed firstly and theoretically analyzed. Then the sub-model model of PPRV and traditional flow-control valve were established and verified through experiments respectively. Finally, the accurate co-simulation model of the FVCP was established. The continuous control characteristics of pressure drop $\Delta p_{\mathrm {rated}}$ , the flow characteristics of FVCP, and the influence of different parameters $d_{2}$ were studied. The research results demonstrate that, compared with the traditional flow-control valve, the designed FVCP can adjust the compensation pressure difference in the range of 0.3 ~ 1.7 MPa in real-time. And the flow rate can be altered within the range of 44% ~ 100% of the rated flow. The diameter $d_{2}$ of the console shoulder has almost no effect on the compensator operating characteristics.

Generally, during the accelerating process of construction machinery large inertia hydraulic swing system, a lot of kinetic energy is accumulated, and it will be eventually dissipated through the relief valve orifice during the decelerating process, which results in serious energy waste and large overflow loss. In order to solve this problem, a new dual source hydraulic motor with non-uniform flow distribution is proposed, which can drive high-frequency swing mechanism efficiently. The new dual source hydraulic motor has two groups of oil inlet and outlet, corresponding to two groups of different displacement. The two groups of inlet and outlet are respectively connected with the energy recovery unit and the main driving unit. During the starting process, the energy recovery unit assists the main driving unit to drive the swing mechanism together, so that the main drive unit output torque and overflow loss are reduced; during the braking process, the energy recovery unit recovers the braking energy. Finally, the integrated control of braking energy direct recovery and utilization is realized. In the research, the 38 t hydraulic excavator is taken as the research object. Firstly, the multi-body dynamics electro-hydraulic simulation model of the dual source integrated driving hydraulic excavator swing system is established, and the accuracy of the model is verified by experiments. Then the effects of the accumulator working pressure and the dual source hydraulic motor displacement ratio on the working performance of the system were simulated. The simulation results show that with the displacement ratio increasing, the accelerating time, the maximum angular velocity and decelerating time increase. Compared with the original system, when the displacement ratio $\alpha $ is 0.6, the comprehensive performance of the system is the best, and the hydraulic pump output energy is reduced by 48.6% and 46.6% respectively in the process of full load and no-load operation.

Abstract The current research mainly focuses on the flow control for the two-stage proportional valve with hydraulic position feedback which is named as Valvistor valve. Essentially, the Valvistor valve is a proportional throttle valve and the flow fluctuates with the change of load pressure. The flow fluctuation severely restricts the application of the Valvistor valve. In this paper, a novel flow control method the Valvistor valve is provided to suppress the flow fluctuation and develop a high performance proportional flow valve. The mathematical model of this valve is established and linearized. Fuzzy proportional-integral-derivative (PID) controller is adopted in the closed-loop flow control system. The feedback is obtained by the flow inference with back-propagation neural network (BPNN) based on the spool displacement in the pilot stage and the pressure differential across the main orifice. The results show that inference with BPNN can obtain the flow data fast and accurately. With the flow control method, the flow can keep at the set point when the pressure differential across the main orifice changes. The flow control method is effective and the Valvistor valve changes from proportional throttle valve to proportional flow valve. For the developed proportional flow valve, the settling time of the flow is very short when the load pressure changes abruptly. The performances of hysteresis, linearity and bandwidth are in a high range. The linear mathematical model can be verified and the assumptions in the system modeling is reasonable.

Abstract The spherical valve plate/cylinder block pair has the advantages of strong overturning resistance and large bearing area. However, the configurations of the unloading and pre-boosting triangular grooves on the spherical valve plate are different from those in the planar valve plate, resulting in special cavitation phenomenon on the spherical port plate pair. In order to study cavitation characteristics of spherical port plate pair, a dynamic CFD model of the piston pump including turbulence model, cavitation model and fluid compressibility is established. A detailed UDF compilation scheme is provided for modelling of the micron-sized spherical oil film mesh, which makes up for the lack of research on the meshing of the spherical oil film. In this paper, using CFD simulation tools, from the perspectives of pressure field, velocity field and gas volume fraction change, a detailed analysis of the transient evolution of the submerged cavitation jet in a axial piston pump with spherical valve plate is carried out. The study indicates the movement direction of the cavitation cloud cluster through the cloud image and the velocity vector direction of the observation point. The sharp decrease of velocity and gas volume fraction indicates the collapse phenomenon of bubbles on the part wall surface. These discoveries verify the special erosion effect in case of the spherical valve plate/cylinder block pair. The submerged cavitation jet generated by the unloading triangular grooves distributed on the spherical valve plate not only cause denudation of the inner wall surface of the valve plate, but also cause strong impact and denudation on the lower surface of the cylinder body. Finally, the direction of the unloading triangular groove was modified to extend the distance between it and the wall surface which can effectively alleviate the erosion effect.

Abstract Mobile machinery energy efficiency and emission pollution are the national and worldwide issues. This paper contributes in solving these problems by applying a speed variable power source. Unfortunately, almost all of the speed variable systems have the dynamic response problem when the motor starts with full load or heavy load. To address this problem, a hydraulic accumulator is used to balance the load of the power source for assisting starting of the motor and a matching method combined with speed and displacement control of the pump is proposed to improve the energy efficiency and dynamic performance simultaneously under different working conditions. Also, the power source/valve combined control strategy of an independent metering system is designed to realize flow matching of the whole system. Firstly, a test system is established to study the dynamic performance and energy efficiency of the speed variable power source with an auxiliary accumulator. Working performance and energy consumption of the power source under different rotating speeds and different loads are studied. And then, the hydraulic excavator test rig with the proposed system is constructed. Furthermore, the working performance of the excavator with the speed-fixed and speed-variable strategy are studied comparatively. Results show that, compared with fixed-speed strategy, the electric power consumption during the idle period and partial load condition can be reduced about 2.05 kW and 1.37 kW. The energy efficiency of speed variable power source is about 40%‒71%, which is higher than that of the fixed-speed power source by 3%–10%.

Abstract Due to the influence of material characteristics and winding power, single output electromagnet has limited ability to improve the dynamic characteristic of electro-hydraulic valve. Therefore, an electromechanical converter with double push rods is proposed in this paper, which can simultaneously output two electromagnetic forces, can push or pull the valve core and sleeve according to the current direction and realize rapid operation of load. According to the electromagnetic principle and the magnetic circuit analysis method, the mathematical model and equivalent circuit of the electromechanical converter with double push rods are established. Through the finite element simulation model of the electromechanical converter with double push rods with the same magnetization directions, the changing rules of its magnetic field distribution and force–displacement behaviors are studied and analyzed. According to the analysis results, the electromagnetic mechanical parameters and mechanical structure of the electromechanical converter with double push rods are determined, and the prototype is made. The test platform for the push-pull characteristics of the electromechanical converter with double push rods is built, and its static and dynamic characteristics are tested and analyzed. The results show that the thrust and pull output characteristics of the internal and external push rods are basically consistent with the simulation output, and proportional to the current density of the coil; the push-pull hysteresis of internal and external push rods output force is less than 5%; and the dynamic time response characteristics of the displacement and force are obtained. The hysteresis effect of output force is improved effectively through the H bridge drive control circuit modulated by PWM. Compared with the displacement response of a single-winding electromagnet with a similar volume, it can effectively improve the dynamic displacement response. Follow-up work will further optimize the structure of the electromechanical converter and test the corresponding pilot valve. The research results provide a new theory for improving the output characteristics of electro-hydraulic pilot valve and have an extremely high engineering application value and broad application prospect.

Nowadays, the hydraulic pump driven by the diesel engine is widely used as the power unit for mobile machines, which consumes a large amount of fuel and cause high emissions. One solution is to use the electric driving mode. In this paper, the energy consumption characteristics of 4 electro-hydraulic power units, which are a fixed speed motor or a variable speed motor to drive a fixed displacement hydraulic pump or a variable displacement hydraulic pump, are compared and analyzed respectively. The results show that the power unit which a variable displacement hydraulic pump is driven by a variable speed asynchronous motor has the highest cost-performance ratio. However, due to the limitation of the battery peak current, the dynamic response of the power unit is slow. To solve this problem, a new power unit is proposed which add an accumulator to the hydraulic pump outlet to recover the power unit braking kinetic energy. The high-pressure oil stored in the accumulator can be absorbed into the hydraulic pump inlet to improve the power unit starting and braking performance and energy efficiency. The starting and braking characteristics of the power unit with and without the accumulator are compared experimentally. The results show that, if the power unit is driven by the motor alone, the power unit response is slow, and the load pressure has a significant influence on the response time. After adding the accumulator to the hydraulic pump, the power unit starting and braking time could be shortened significantly, and the starting power demand is also reduced. The proposed power unit is further used to drive a hydraulic excavator. Under the same working conditions and operating characteristics, energy consumption can be reduced by 28.5% compared with using the variable displacement hydraulic pump alone.

Excavators are widely used in construction, mining, and other projects. However, there are certain environments, such as chemical substance leakage and conflagration sites, which are not suitable for on-site operation. In such situations, the necessity for automatic control and position control is considerably high and it is the development trend of the excavators. In this paper, a position control strategy combined with velocity feedforward is proposed for the excavator boom to achieve position and velocity control simultaneously. Moreover, an independent metering system is introduced to reduce throttling loss. In this work, the controller is designed with two modes-velocity control and position control-based on the difference between the target and real displacements. When the target position is given, if the difference is sufficiently large, the system operates in the velocity control mode. In this mode, the velocity feedforward signal is generated as a designed type to control the cylinder velocity, and the desired trajectory can be obtained by integrating the generated velocity. In order to account for the velocity error and realize trajectory tracking, displacement control is employed to compensate for the velocity feedforward control. During this process, the valve can be fully open to reduce throttling loss. When the boom approaches the target position, the system operates in the position control mode. With this strategy, position control and velocity control can be achieved simultaneously, fast positioning and low energy consumption are also realized. In order to verify the feasibility of the foregoing strategy, a test rig is installed on a 6-t excavator. The test results show that the boom can move smoothly to the target position along the desired trajectory and achieve fast positioning. The investigation can provide some reference for the automatic operation of mobile machinery.

Hydraulic systems are widely used in industry due to their small size-to-power ratios and their ability to produce very large linear force and torque. In traditional hydraulic systems, a variable pump driven by an electric motor is often used as power source. In these systems, the electro-hydraulic power source always operates at its rated speed, causing lots of noise and low energy consumption, especially in no-load and light-load conditions. These problems can be solved by changing the speed of the electric motor according to the load state of the electro-hydraulic power source. In order to improve the energy efficiency of the electro-hydraulic power source and realize pressure and flow control on the basis of low cost, this paper presents the power-source structure of a variable-displacement pressure-compensated pump driven by a variable-speed electric motor; this controls the flow by adjusting the electric motor speed and controls the pressure with the variable-displacement pressure-compensated pump. However, for the variable-speed system, the starting of the electric motor with a load is relatively slow; this makes it difficult to meet the demand of flow control, and will also have a great impact on the power grid. To address these problems, a hydraulic accumulator is introduced to the inlet port of the hydraulic pump to assist in starting the pump. This method can realize the combined control of pressure, flow and power, and has high energy efficiency. This research uses experiments to verify the feasibility of the scheme, and the results show that the starting periods of the power source can be shortened from 2.8 s to 0.7 s when the load pressure is about 18 MPa. Furthermore, regarding maintaining pressure without flow outputs, the energy consumption of the designed power source can be reduced by almost 30% compared with a pure variable-displacement power source.

For electro-hydraulic system of large flow and overloading, established position and pressure closed-loop control in accordance with the conventional hydraulic servo system theory that system control algorithm is complicated and difficult to implement. This article presents a method which gives priority to position closed-loop control and establishes the corresponding relation between pressure of hydraulic cylinder and load by collecting the pressure signal from rear cavity and rod cavity of hydraulic cylinder; meanwhile, applied position-pressure conversion formula will turn dynamic pressure signal into position signal and compensate the transformed position signal to the master position closed loop of the electro-hydraulic servo system which could achieve the position-pressure master-slave control. The simulation results show that the control method is correct, effective, and feasible. The results indicate that the method can achieve online converting between position and pressure which are different variables and improve the response speed and control precision of the system.

For the traditional reciprocating pumping unit, it generally starts at the bottom dead point with full load and is accelerated when starting and decelerated when stopping, which not only requires great energy from the motor but also impact on the output torque of motor. In order to tackle the above problems, we propose an energy-saving smooth reversing pumping system, which could store the energy in deceleration by making use of springs, and the stored energy could be reused in acceleration after reversion. This novel system targets to make the motor starting with light load, which could reduce the fluctuation in motor torque, decrease the starting time. In this article, a dynamic model and an efficiency model are established to compute the polished rod load dynamometer card and efficiency of the pumping unit. It is shown that the installed springs could help to reduce the impact on the system when reversing, and significantly decrease the energy consumption. In addition, we set up the real pumping system with load test system to verify the effectiveness of the model establishment. Through the experiment, the proposed pumping system could save energy up to 9.204% as compared to the traditional reciprocating pumping system.

Compared with the strong background noise, the energy entropy of early fault signals of bearings are weak under actual working conditions. Therefore, extracting the bearings’ early fault features has always been a major difficulty in fault diagnosis of rotating machinery. Based on the above problems, the masking method is introduced into the Local Mean Decomposition (LMD) decomposition process, and a weak fault extraction method based on LMD and mask signal (MS) is proposed. Due to the mode mixing of the product function (PF) components decomposed by LMD in the noisy background, it is difficult to distinguish the authenticity of the fault frequency. Therefore, the MS method is introduced to deal with the PF components that are decomposed by the LMD and have strong correlation with the original signal, so as to suppress the modal aliasing phenomenon and extract the fault frequencies. In this paper, the actual fault signal of the rolling bearing is analyzed. By combining the MS method with the LMD method, the fault signal mixed with the noise is processed. The kurtosis value at the fault frequency is increased by eight-fold, and the signal-to-noise ratio (SNR) is increased by 19.1%. The fault signal is successfully extracted by the proposed composite method.

The variable displacement pump control system has greater energy-saving advantages and application prospects than the valve control system. However, the variable displacement pump control of differential cylinder is not concurrent with the existing technologies. The asymmetric pump-controlled cylinder is, therefore, used to balance the unequal volume flow through a single rod cylinder in closed-circuit system. This is considered to be an effective method. Nevertheless, the asymmetric axial piston pump (AAPP) is a constant displacement pump. In this study, variable-displacement asymmetric axial piston pump (VAPP) is investigated according to the same principle used in investigating AAPP. This study, therefore, aims at investigating the characteristics of VAPP. The variable-displacement output of VAPP is implemented by controlling the swash plate angle with angle feedback control circuit, which is composed of a servo proportional valve and an angular displacement sensor. The angular displacement sensor is connected to the swash plate. The simulation model of VAPP, which is set up through the ITI-SimulationX simulation platform, is used to predict VAPP’s characteristics. The purpose of implementing the experiment is to verify the theoretical results. Both the simulation and the experiment results demonstrated that the swash plate angle is controlled by a variable mechanism; when the swash plate angle increases, the flow of Port B and Port T increases while the response speed of Port B and Port T also accelerates. When the swash plate angle is constant, the flow of Port B and Port T increases along with the increase of pump speed, although the pressure-response speed of Port B is faster than that of Port T. Consequently, the flow pulsation of Port B and Port T tends to decrease gradually along with the increase of pump speed. When the pressure loaded on Port B equals to that of Port T, the flow ripple cycle of Port B is longer than that of Port T, whereas the peak flow of Port B is higher than that of Port T. Since the flow ripple of Port T is bigger than that of Port B, Port T should be connected to the low pressure sides or the oil tank so that it does not affect VAPP’s performance. Further, to avoid the backflow of VAPP from Port T to Port B, Port T cannot be loaded alone, and the loading pressure of Port T also cannot exceed that of Port B.

Abstract Background In addition to single-locus (main) effects of disease variants, there is a growing consensus that gene-gene and gene-environment interactions may play important roles in disease etiology. However, for the very large numbers of genetic markers currently in use, it has proven difficult to develop suitable and efficient approaches for detecting effects other than main effects due to single variants. Results We developed a method for jointly detecting disease-causing single-locus effects and gene-gene interactions. Our method is based on finding differences of genotype pattern frequencies between case and control individuals. Those single-nucleotide polymorphism markers with largest single-locus association test statistics are included in a pattern. For a logistic regression model comprising three disease variants exerting main and epistatic interaction effects, we demonstrate that our method is vastly superior to the traditional approach of looking for single-locus effects. In addition, our method is suitable for estimating the number of disease variants in a dataset. We successfully apply our approach to data on Parkinson Disease and heroin addiction. Conclusion Our approach is suitable and powerful for detecting disease susceptibility variants with potentially small main effects and strong interaction effects. It can be applied to large numbers of genetic markers.