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One of the most promising areas for improving the energy efficiency of machines is the use of energy recovery from its source. The study aims to develop a basic hydraulic scheme of the clamping mechanism of the sowing section, which would allow to recovery of the energy of the oscillatory movement of the sowing section relative to the sowing frame. The paper considers the scheme of using hydraulic loading of sowing sections using a single-acting hydraulic cylinder. To collect the energy of the sowing section of the seeder, it is proposed to install a hydraulic motor in the existing hydraulic loading circuit to convert the hydraulic energy of the system into the mechanical energy of rotation of its output shaft and a system of check valves to redirect the working fluid in the system and ensure that the hydraulic motor shaft rotates in one specified direction. The input parameters of this system are unevenness of the soil, design features of the sowing section of the seeder, and forward speed of the seeder. The influence of the main parameters of the hydraulic cylinder, hydraulic accumulator and hydraulic motor of the system on the rotational speed and torque on the hydraulic motor shaft is investigated. The research shows that under certain external conditions, when modelling the system in the MATLAB Simulink software, the forced reciprocating motion of the hydraulic cylinder piston is converted into the rotational motion of the hydraulic motor output shaft, which, under certain system parameters under study, can rotate at a speed of 6-86 rpm, developing a theoretical torque of up to 22 N∙m. The size of the hydraulic cylinder piston has the greatest influence on the output characteristics of the system. The hydraulic accumulator provides smoothing of pulsations, the magnitude of which, like the total pressure in the system, depends on the pressure of its pre-charging. The results of this study can be applied in agriculture to optimise energy use during the sowing process by developing efficient energy recovery systems for sowing machines, which will reduce fuel consumption and negative environmental impact

It is possible to use low-potential wind energy for the efficient operation of a wind power plant and for increasing the Annual Energy Production for guaranteed power supply to facilities in remote rural areas with a shortage of wind power. Currently in the development of large wind power plants worldwide hydraulic transmission is used to increase reliability and reduce the cost. However, the efficiency of such systems is lower than the efficiency of systems with a mechanical transmission (gearbox). But in regions with a shortage of wind power, wind power plants with a gearbox are not effective, and a hydraulic transmission could provide an increase in the Annual Energy Production of small wind power plants. Proposed is a small multi-unit wind-driven power plant with a hydraulic drive and an accumulator for power supply to remote facilities in rural areas. Methods for calculating the parameters and modes of operation of a multi-unit wind-driven power plant have been developed. The operation of a multi-unit wind-driven power plant was studied in the range of wind speeds of 4–14 m/s. The results of the theoretical analysis of the operation of the multi-unit wind-driven power plant are presented in the form of torque, rotational speed, power and flow rate diagrams. The results showed that the sum of flow rates of several pumps in the hydraulic system can provide the required constant flow rate of the hydraulic motor in a wide range of wind speeds. Thus, even at low wind speeds of 3–4 m/s on a typical day for a region with an average periodic wind speed of 4.3 m/s the total daily flow shortage is 75.2 L/min, while the total daily surplus is 180 L/min. The above calculation methods allow for a comparative analysis of the parameters, as well as the selection of design for the multi-unit wind-driven power plant being developed. The use of a hydraulic system with a hydraulic accumulator and several wind-receiving devices of different parameters, connected in parallel, significantly increases the efficiency of a small wind-driven power plant in a region with low-potential wind energy. In this case, the efficiency of the electric generator of a wind-driven power plant will always be maximum, since a constant rotational speed of the generator shaft is maintained and optimal generator modes are provided. [ABSTRACT FROM AUTHOR]

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To improve the efficiency and stability of an eccentric rotating wave energy converter (ERWEC), the adaptive hydraulic power-take-off (PTO) system with an accumulator is designed and developed. Experiments are performed to analyze the effects of trigger pressure, delay time, and open state duration on average output power and power fluctuation index. The results show that the effects of those three control parameters of accumulator on output power are strongly coupled. The experimental examples are designed based on the optimal Latin hypercube sampling (OLHS) method, and the nonparameterized agent models of control parameters to output power indices are established based on the Gaussian process regression (GPR) method. With the help of sensitivity analysis, it is found that the coupled effect of delay time and open state duration on the power fluctuation index is greater than that on the average output power. Furthermore, the optimal combination of control parameters is obtained by non-dominated sorting genetic algorithm-III (NSGA-III), which improves the amount and stability of output power from a hydraulic PTO system. This paper is of important significance for parameter setting of hydraulic PTO systems with an accumulator for wave energy converter, and provides the basis for the real-time adjustment of control parameters under complex sea conditions. [ABSTRACT FROM AUTHOR]

Experimental regulating parameters of the non-stationary expansion of air inside a bladder-type hydraulic accumulator, working with the simple short pipeline, are presented in the paper. The technique of continuous online monitoring of changes in time of volume and absolute air pressure inside the hydraulic accumulator during the discharge process has been improved. Three series of experimental studies of transient gas processes inside the accumulator at different values of the average volume flow rate are made. Tendencies of change of the integral parameters of the hydraulic accumulator are obtained and analyzed depending on the serial number of the discharge cycle. A general dependence of dimensionless storage volume Kreg on the polytropic index n in series # 1–3, approximated by single power-law dependence, is obtained. The systematic changes of integral parameters in each subsequent discharge cycle can be explained by the non-stationary transient thermodynamic processes in air inside the accumulator until the thermodynamic equilibrium with the ambient air parameters is reached.

Instead of using position sensor, a position measurement and output feedback tracking method is proposed based on pressure sensor for a class of hydraulic servo system. First, the desired accumulator pressure is calculated and obtained in an open-loop way according to the desired cylinder position. Then, the position tracking task can be indirectly realized by achieving the pressure control. As a result, only one pressure sensor is required instead of position sensor, which is different from almost all the traditional output feedback position controller of hydraulic system. For the closed-loop pressure tracking, a desired compensation method and an auxiliary variable-based state observer are integrated to form the nonlinear controller. The theoretical and numerical simulation results demonstrate that the presented controller can attain satisfactory pressure tracking performance. [ABSTRACT FROM AUTHOR]

In order to address the problems of low energy storage capacity and short battery life in electric vehicles, in this paper, a new electromechanical-hydraulic power coupling drive system is proposed, and an electromechanical-hydraulic power coupling electric vehicle is proposed based on this system. The system realizes the mutual conversion between mechanical energy, hydraulic energy, and electric energy through the electromechanical–hydraulic coupler. This paper describes the structural characteristics and working principles of the system and analyzes the different working modes during the driving of the vehicle. We established a mathematical model of the hydraulic accumulator and the hydraulic pump and motor. Based on the vehicle dynamics model, an AME Sim vehicle model was built and the vehicle, and the relevant hydraulic parameters were set in combination with the actual situation. The braking energy recovery and release process was jointly simulated by AME Sim and Simulink. The simulation results show that the hydraulic accumulator size of the accumulator volume can influence the maximum working pressure of the accumulator and the SOC of the vehicle battery, and it is verified that 35 L is the best capacity. This study has an important reference value for matching electromechanical–hydraulic coupling parameters of electric vehicles. [ABSTRACT FROM AUTHOR]

Positive displacement pumps are widely employed for their characteristics, but the pulsating flow they produce is a major and well-known drawback. To reduce the flow ripple produced by the pump, which in turn generates a pressure ripple, many methods have been investigated, from optimising the pump geometrical features to the introduction of active and passive systems to the delivery side. A passive system that has demonstrated to be particularly effective is the in-line bladder-type hydraulic pulsation suppressor. This device, consisting of a bladder gas-charged accumulator with a singular geometry, has been the subject of several studies. This paper describes a model based on the lumped parameter method for simulating and predicting the reduction effect on the pressure ripple achieved by the hydraulic suppressor. To validate the model, an experimental study was conducted, which confirmed the good potential of the model proposed thanks to the good agreement between the modelling results and empirical data.

As a typical energy storage in hydraulic hybrid powertrain, the hydraulic accumulator has high power density but low energy density. There are some efforts in improving the energy density of hydraulic energy storage to achieve balanced performance. Therefore in this study an electric-hydrostatic energy storage system is proposed to replace hydraulic accumulator in a hydraulic hybrid wheel loader. Through active control of proposed energy storage, constant system pressure is possible to provide good vehicle drivability. A rule-based energy management strategy without estimating final drive power is proposed. The vehicle performance and fuel consumption with different constant system pressures are studied. Results show the vehicle fuel consumption is reduced by 5.9% with constant system pressure reduced from 33 to 27 MPa. The energy density and power density of proposed energy storage are calculated, showing a much higher energy density and slightly lower power density than gas-charged accumulator. [ABSTRACT FROM AUTHOR]

Telescopic handler is combined of truck crane and forklift. Equipped with different accessories, the telescopic handler can achieve fork loading, lifting and other operations. Large amount of energy is needed to maintain lifting and lowering in large range with high frequency of the working device of telescopic handler. There is no energy recycling device for the working device that leads to the large dissipating of gravitational potential energy. In order to recycle the wasted energy, a three-chamber hydraulic cylinder boom system (TCCBS) is proposed. In this paper, the recycling principle is described. Then the energy consumption characteristics are analyzed. Further, the mode of TCCBS of telescopic handler is established and analyzed. Compared with the double chamber cylinder boom system (DCCBS), the single-action time of the boom is reduced 4.15 s. The velocity shock decrease from 0.12 m/s to 0.02 m/s at the beginning of the boom lowering process. The peak pressure decreased from 24 MPa to 21 MPa and the average pressure decreased from 17 MPa to 13 MPa during boom lifting process. The potential energy recycling of the working device is 139 kJ, which accounts for about 47.1 % of total potential energy. The cumulative output energy of TCCBS is 311 kJ, which is 92 kJ less than the DCCBS. The comprehensive energy saving efficiency is 22.3 %. The results show that the TCCBS can realize the potential energy recycling. [ABSTRACT FROM AUTHOR]

To improve the efficiency and stability of an eccentric rotating wave energy converter (ERWEC), the adaptive hydraulic power-take-off (PTO) system with an accumulator is designed and developed. Experiments are performed to analyze the effects of trigger pressure, delay time, and open state duration on average output power and power fluctuation index. The results show that the effects of those three control parameters of accumulator on output power are strongly coupled. The experimental examples are designed based on the optimal Latin hypercube sampling (OLHS) method, and the nonparameterized agent models of control parameters to output power indices are established based on the Gaussian process regression (GPR) method. With the help of sensitivity analysis, it is found that the coupled effect of delay time and open state duration on the power fluctuation index is greater than that on the average output power. Furthermore, the optimal combination of control parameters is obtained by non-dominated sorting genetic algorithm-III (NSGA-III), which improves the amount and stability of output power from a hydraulic PTO system. This paper is of important significance for parameter setting of hydraulic PTO systems with an accumulator for wave energy converter, and provides the basis for the real-time adjustment of control parameters under complex sea conditions.

Abstract In this paper, a novel fuzzy Proportion Integration Differentiation (PID) controller is proposed to extract the optimal energy from wind for a hydraulic offshore wind turbine. Firstly, in order to calculate the theoretical power, an adaptive neuro‐fuzzy inference system (ANFIS) is designed for wind speed evaluation, in which the input parameters include rotor speed, rotor torque, and pitch angle, and the output parameter is the estimated wind speed. Then, the optimal power coefficient is achieved by controlling the hydraulic pump torque to tracking the optimal rotor speed, and a fuzzy PID is designed to adjust the pump displacement and to obtain the optimal hydraulic pump torque. Furthermore, aiming to meet the various output power demand, a hydraulic accumulator is utilized for storing the excess energy, and a PID controller is designed for distributing the hydraulic energy between the accumulator and the Pelton turbine. Finally, the performance of proposed controls system are confirmed by two case simulations on a 5 MW hydraulic offshore wind turbine. The simulation results show that, compared with the conventional control methods (fuzzy logical and PID controller) used in electro‐hydraulic servo system, the fuzzy PID controller can provide the better tracking effect with a faster speed and a minimal steady‐state oscillation. Moreover, with the use of a hydraulic accumulator, all the power fluctuations from the wind speed disturbances are damped out and the output power become controllable.

According to the hydraulic accumulators used by explosion-proof vehicles in underground coal mines at present, the accumulators or pipelines are often removed with pressure during maintenance, resulting in high pressure oil gushing out, which is easy to form production safety accidents. In this paper, based on the characteristics of the explosion-proof vehicle engine work and the request of Coal Mine Safety Regulation, a set of accumulator automatic unloading device is designed. By detecting the oil pressure of engine, the oil pressure in the accumulator is automatically established or released to ensure that the oil pressure in the accumulator is automatically unloaded when the vehicle shuts down, avoiding the hidden danger of accidents caused by the operation with pressure. Through actual installation and test, it is proved that the automatic unloading system has small leakage, short unloading time and reliability.

Traditional excavators driven by diesel engine have poor emissions and low energy efficiency. Pure electric driven excavators have high cost and limited endurance. Therefore, at present, hybrid power train system is an ideal candidate for excavators to realize energy-saving and emission reduction. In this paper, a novel series hybrid hydraulic excavator based on electro-hydraulic composite energy storage, which provides the average power of the system through the diesel engine, and the battery and accumulator are used as the intermediate energy storage devitalize the output current of the battery, and improve the service life of the battery, is proposed. Advantages of high energy density of battery and high power density of hydraulic accumulator are synthetically utilized. A 7-ton crawler excavator is taken as the research object, according to typical load spectrum, through analysis method and modeling method, and using dynamic programming (DP) to optimize the parameters of the novel series power train system. The control strategy of the power system is further studied, and the AMESim and Simlink co-simulation models of the transmission system is established to verify the feasibility of the system. At last, the experimental platform is built. Experiments are conducted to verify the effectiveness of the power train system.

The relief valve overflowing energy loss is considered impossible to solve. This paper proposes a new type of proportional relief valve (PRV) with a hydraulic energy regeneration unit (HERU) connected to its outlet. The mathematical model of the proposed PRV is set up, and its stability is analyzed. A control strategy is put forward for designing the working modes which are based on the pressure of the hydraulic accumulator. The simulation model and the test rig, where a hydraulic accumulator is used as a HERU, are established to verify the effectiveness of the control strategy and energy savings of the proposed PRV. The results show that the system can switch among energy regeneration, energy release, and traditional modes according to the hydraulic accumulator pressure, indicating that the proposed control strategy works well. During the energy regeneration mode, the hydraulic accumulator is charged and the PRV inlet pressure decreases only slightly, indicating the HERU has little influence on the PRV working performance. During the energy release mode, the hydraulic accumulator is discharged and the PRV inlet pressure increases to its preset value. Both during the regeneration and release modes, the driving electric motor consumed less energy. Higher hydraulic accumulator pre-charging pressure can achieve higher energy regeneration efficiency, whereas lower hydraulic accumulator pre-charging pressure can regenerate more overflowing energy.

In order to address the intermittency of offshore renewable energy sources, a novel form of compressed air energy storage integrated within a tension leg platform is proposed. The energy storage concept involves a hydro-pneumatic accumulator. The objective of this study was to investigate the variation in the physical and hydrodynamic characteristics of a hypothetical full-scale prototype of the proposed system. The design was developed so as to analyse the effect on said characteristics of the tension leg platform diameter and the inner diameter of the umbilical connecting the floating and seabed-mounted compressed air chambers. Results indicate that better hydrodynamic behaviour was observed for smaller diameter tension leg platforms, whereby the resulting motion became more restrained. Moreover, the dynamic characteristics were observed to indicate marginal improvement for increasing inner diameters of the pneumatic umbilical. [ABSTRACT FROM AUTHOR]

In this paper, a novel fuzzy Proportion Integration Differentiation (PID) controller is proposed to extract the optimal energy from wind for a hydraulic offshore wind turbine. Firstly, in order to calculate the theoretical power, an adaptive neuro‐fuzzy inference system (ANFIS) is designed for wind speed evaluation, in which the input parameters include rotor speed, rotor torque, and pitch angle, and the output parameter is the estimated wind speed. Then, the optimal power coefficient is achieved by controlling the hydraulic pump torque to tracking the optimal rotor speed, and a fuzzy PID is designed to adjust the pump displacement and to obtain the optimal hydraulic pump torque. Furthermore, aiming to meet the various output power demand, a hydraulic accumulator is utilized for storing the excess energy, and a PID controller is designed for distributing the hydraulic energy between the accumulator and the Pelton turbine. Finally, the performance of proposed controls system are confirmed by two case simulations on a 5 MW hydraulic offshore wind turbine. The simulation results show that, compared with the conventional control methods (fuzzy logical and PID controller) used in electro‐hydraulic servo system, the fuzzy PID controller can provide the better tracking effect with a faster speed and a minimal steady‐state oscillation. Moreover, with the use of a hydraulic accumulator, all the power fluctuations from the wind speed disturbances are damped out and the output power become controllable. [ABSTRACT FROM AUTHOR]

A method of diagnosing fuel systems with direct injection by means of producing a pressure oscillation in a hydraulic accumulator is presented. Having obtained a signal from pressure sensor it is possible to register a pressure drop at the moment of injection. If the system has a malfunction, then the pressure drop will be higher.

The paper gives an analysis of implementation of hydropneumatic accumulators that provide significant reduce of energy consumption work processes and increase performance of mining machines, in particular cone crushers. A method that allows passing a body that is not to be crushed through a crushing chamber of a cone crusher with hydraulic cylinders and hydropneumatic accumulators is given. The system that presses crushing bowl to a frame is described. A system of hydraulic unloading from non-crushing bodies and blockages is presented. A basic hydraulic scheme of pressing system is proposed. The paper gives a description of mechanism that creates work pressure inside hydropneumatic accumulator. Parameters of hydraulic cylinders and hydraulic accumulators are determined. The crushing force is set by dimensions of hydraulic cylinders and pressure of work fluid in hydropneumatic accumulator. When a non-breaking body enters a crushing chamber a movable cone moves an armor of a bowl with support and control rings and associated elements. An example of calculation is given. Calculations are necessary to design a new hydraulic unit that control discharge slot of a cone crusher. A method for determination of geometric parameters of crushing chamber when passing a non-crushing body is given. Calculation of power parameters of hydraulic system of a cone crusher including hydraulic cylinders and hydropneumatic accumulators is proposed. The method can be applied in design departments of mining and industrial enterprises while design of cone crushers. A proposed hydraulic scheme with throttle installation will reduce speed of fluid flow when unloading a hydraulic accumulator. That will reduce impact of accumulator piston and foaming of liquid in a tank.

One of the problems in the analysis of the dynamics performance of off-road vehicles is the effect of the accuracy of the hydro-pneumatic suspension model. However, the accuracy of the model for the polytropic process of nitrogen in the gas-charged hydraulic accumulator is one of the key factors, which affects the accuracy of the model for the hydro-pneumatic suspension systems. The traditional approach based on the energy equation and the Benedict-Webb-Rubin equations deduces the well-known thermal time constant model. However, researchers indicate that the thermal time constant varies with the change in the accumulator size and operating cases. Other researchers attempt to modify the polytropic exponent to model the real gas behavior, but the hysteresis loop representing the energy losses in a cycle can’t be described because the polytropic exponent is treated as a constant value. In this paper, an attempt was made to describe the hysteresis loop by adopting a variable polytropic exponent. On the accumulator rig, some tests excited by the sinusoidal displacement with four different amplitudes and frequencies respectively were carried out. The plots of the gas pressures versus the gas volume ratio and the gas volume rate respectively were made according to the experimental data from the accumulator test by using the Matlab software. A comprehensive analysis of experimental data showed that the relationship between the gas pressure and both the volume compression ratio and the volume compression rate were very close. To analyze the relationship between the polytropic exponent and the two parameters respectively, the formula of the polytropic exponent was deduced based on the ideal gas approach and polytropic processes. By substituting the experimental data from the accumulator test into the formula, the plots of the polytropic exponent versus the two parameters respectively were also made. The plots illustrated that the polytropic exponent was closely proportional to the two parameters, respectively. Based on the analysis, a novel method was proposed to build a polytropic exponent model with the two parameters to describe the real gas behavior. In order to verify the correctness and the accuracy of the proposed polytropic exponent model, the two coefficients in the model were identified by using the experimental data from the previous accumulators test, and the coefficient of the volume compression ratio in the model (k1) was 2.4 for the test accumulator, and the coefficient of the volume compression rate (k2) was 1.5. Moreover, substituting the values of the two parameters, which were determined by the different operating cases, into the proposed polytropic exponent model with the two identified coefficients gave a comparison with these experimental data. Furthermore, a co-simulation model, which was based on the polytropic exponential model, for six hydro-pneumatic suspension systems was built to check the application of the polytropic exponent model in the hydro-pneumatic suspension systems of the overall vehicle. And a platform for the hydro-pneumatic suspension systems of the overall vehicle invented and designed by our laboratory, which was the first platform with the capability to test the comprehensive characteristics of multiple suspension systems, was used to test the rolling characteristics of the six hydro-pneumatic suspension systems. Several tests were carried out under the sinusoidal displacements with four different amplitudes and frequencies, respectively. The comparison of the co-simulation results and experimental data showed that the average discrepancy was equal to 5.12% and the maximum discrepancy was less than 10.9%. Therefore, a good correlation was achieved. It further demonstrated that the proposed polytropic exponent model can describe the behavior of the real nitrogen in the accumulator. But the proposed model should be further verified by using more experimental data from much higher frequency tests, and the influence of dissipated energy on the two coefficients in the proposed model should be explored. [ABSTRACT FROM AUTHOR]

The method of diagnosing the fuel systems with direct injection by means of the creating pressure oscillations in the hydraulic accumulator is offered in the article. Getting a signal from pressure sensor, it is possible to record a pressure drop at the moment of fuel insection. If there is a malfunction in the system, then pressure dropping will be higher.

Energy regeneration systems are a key factor for improving energy efficiency in electrohydraulic machinery. This paper is focused on the study of electric energy storage systems (EESS) and hydraulic energy storage systems (HESS) for energy regeneration applications. Two test benches were designed and implemented to compare the performance of the systems under similar operating conditions. The electrical system was configured with a set of ultracapacitors, and the hydraulic system used a hydraulic accumulator. Both systems were designed to have the same energy storage capacity. Charge and discharge cycle experiments were performed for the two systems in order to compare their power density, energy density, cost, and efficiency. According to the experimentally obtained results, the power density in the hydraulic accumulator was 21.7% higher when compared with the ultracapacitors. Moreover, the cost/power ($/Watt) ratio in the hydraulic accumulator was 2.9 times smaller than a set of ultracapacitors of the same energy storage capacity. On the other hand, the energy density in the set of ultracapacitors was 9.4 times higher, and the cost/energy ($/kWh) ratio was 2.9 times smaller when compared with the hydraulic accumulator. Under the tested conditions, the estimated overall energy efficiency for the hydraulic accumulator was 87.7%, and the overall energy efficiency for the ultracapacitor was 78.7%.

To reduce the energy consumption and emissions of the hydraulic excavator, a two-level idle speed control system with a hydraulic accumulator for the construction machinery is proposed to reduce the energy consumption and improve the control performance of the actuator when the idle mode is cancelled. The structure and working principle are analyzed. The hydraulic accumulator (HA) is used to store the energy, which can provide backup pressured fluid when the idle mode is cancelled. Then, a method of how to set the pressure differential between the hydraulic accumulator and the load is proposed and the control law is discussed. The test rig is built. The experimental result shows that the idle speed can be switched among the first idle speed, the second idle speed and the normal speed automatically. Though the idle speed in the novel system can be reduced more than that in the conventional automatic idle speed control system (AISCS), the proposed system can still build the actuator pressure more quickly when the idle mode is cancelled. When compared to the system without the idle speed control, the energy saving of the proposed system is about 67%. The proposed two-level idle speed control system with a HA can achieve a high energy efficiency and a good control performance. [ABSTRACT FROM AUTHOR]

To reduce the energy consumption and emissions of a hydraulic excavator (HE), an electric motor (EM) is employed to replace the internal combustion engine (ICE) that powers the hydraulic pumps. Owing to the excellent control characteristics and high efficiency of the EM, a two-level idle speed control system with a hydraulic accumulator (HA) for a HE is proposed to reduce energy consumption and improve the control performance of the actuator when the idle speed control (ISC) is switched off. A mathematical model is established and key parameters are analyzed and optimized. A simulation is performed using AMESim, and a control strategy for the two-level idle speed control is developed by using a co-simulation between AMESim and Simulink. A test rig is built based on the optimized parameters and simulation results. Experimental results show that the EM speed can be automatically switched between the first idle speed, second idle speed, and normal operating speed. Although the idle speed of the EM in the novel ISC system can be reduced more than that in a conventional ISC system, the proposed ISC system can still build actuator pressure more quickly in a working mode when the ISC is switched off. Compared to a system without idle speed control, the energy saving of the proposed system is approximately 36.06%. The proposed two-level idle speed control system with a HA can achieve high energy efficiency and excellent control performance, and it can be also applied to engine-driven construction machinery. [ABSTRACT FROM AUTHOR]

The effects of the decay characteristics of a hydraulic accumulator on the responses of the hydrostatic drive system used in mining vehicles are studied in this article. The system considered for the analysis basically consists of a hydraulic pump, hydro-motor, accumulator and a loading circuit. The studies have been carried out with respect to two different sizes of accumulators. The system model has been made in MATLAB/Simulink® environment. The simulation test results are obtained with respect to the hydro-motor speeds and the system pressure at different resistive loads and capacities of the accumulator and they are verified with the experimental test data. Using the validated model, the parametric studies are also made on the speed responses of the hydrostatic drive for different precharge pressures of the accumulator and inertial load on the motor shaft. The studies made in this article may be useful for the selection of proper capacity of accumulators incorporated in the hydrostatic drive system in mining vehicles. [ABSTRACT FROM AUTHOR]

Considering the disadvantage of higher throttling loss for the open-circuit hydrostatic transmission at present, a novel gravitational potential energy regeneration system (GPERS) of the boom of hydraulic excavator, namely the closed-circuit GPERS, is proposed in this paper. The closed-circuit GPERS is based on a closed-circuit hydrostatic transmission and adopts a hydraulic accumulator as main energy storage element fabricated in novel configuration to recover the entire gravitational potential energy of the boom of hydraulic excavator. The matching parameter and control system design are carried out for the proposed system, and the system is modeled based on its physical attributes. Simulation and experiments are performed to validate the employed mathematical models, and then, the velocity and the pressure performance of system are analyzed. It is observed that the closed-circuit GPERS shows better velocity control of the boom and response characteristics. After that, the average working efficiency of the closed-circuit GPERS of boom is estimated under different load conditions. The results indicate that the proposed system is highly effective and that the average working efficiency in different load conditions varied from 60% to 68.2% for the experiment platform. [ABSTRACT FROM AUTHOR]