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In order to solve the problems of nonlinearity, uncertainty and coupling of multi-hydraulic cylinder group platform of a digging-anchor-support robot, as well as the lack of synchronization control accuracy of hydraulic synchronous motors, an improved Automatic Disturbance Rejection Controller-Improved Particle Swarm Optimization (ADRC-IPSO) position synchronization control method is proposed. The mathematical model of a multi-hydraulic cylinder group platform of a digging-anchor-support robot is established, the compression factor is used to replace the inertia weight, and the traditional Particle Swarm Optimization (PSO) algorithm is improved by using the genetic algorithm theory to improve the optimization range and convergence rate of the algorithm, and the parameters of the Active Disturbance Rejection Controller (ADRC) were adjusted online. The simulation results verify the effectiveness of the improved ADRC-IPSO control method. The experimental results show that, compared with the traditional ADRC, ADRC-PSO and PID controller, the improved ADRC-IPSO has better position tracking performance and shorter adjusting time, and its step signal synchronization error is controlled within 5.0 mm, and the adjusting time is less than 2.55 s, indicating that the designed controller has better synchronization control effect. [ABSTRACT FROM AUTHOR]

Due to a rapid decrease in fossil fuel resources and ever-growing carbon emissions, clean energy is urgently needed as a vital solution. In the past two decades, harvesting clean energy from ambient environment has attracted much attention. Flow induced vibration and energy harvesting performance of a cylinder with fins attached were investigated. Four configurations were studied: a plain cylinder, a cylinder with two windward fins, a cylinder with two leeward fins, and a cylinder with four fins. These four cylinders were tested in a water channel with a reduced velocity ranging between 2 and 25 and a Reynolds number ranging between 1500 and 11 400. It was found that the two-windward-fin cylinder underwent galloping, exhibiting much larger vibration amplitudes and a much broader operational velocity range, whereas the two-leeward-fin cylinder only underwent weak vortex-induced vibrations. By attaching both two windward and two leeward fins to the cylinder, a bi-directional flow-energy harvester was implemented, which outperformed the plain cylinder with much larger vibration amplitudes and a much broader velocity range. More importantly, due to the geometric symmetry, it is able to harvest flow energy from two opposite directions. A tuned-mass-damper system was then attached to the four-fin cylinder for the purpose of demonstration. Within the current flow speed range, the maximal voltage and power outputs are about 7.37 V and 1.81 μW, respectively, about 2.7 and 7.2 times the plain cylinder's peak values. The effects of flow incident angle and fin length were also studied. Numerical simulations were also conducted to provide a detailed information of flow and pressure to uncover the underlying physics. This bi-directional flow-energy harvester is a suitable candidate to operate at sites where the flow periodically switches its directions, such as in tidal flows. [ABSTRACT FROM AUTHOR]

Experimental results of tests to investigate the load‐bearing behavior of anchor channels embedded in concrete and subjected to loads in three‐dimensional (3D) interaction are presented. For testing, a variably adjustable rig is introduced in which arbitrary 3D loads are applied with just one hydraulic cylinder. Investigations focus on concrete failure. The test program includes variable load angles and anchor channels installed at the edges and at corner of concrete prisms. In both configurations a significant impact of the loading direction regarding the channel axis is found. Mathematically interaction is captured with trilinear and Lamè curves. Therein, the experimental findings are reflected by individual model parameters that yield the best fit in regression. For both configurations, an optimal prognosis model is derived which covers all 3D load situations in assured quality. Moreover, the tests prove the general suitability of the developed rig, which thus qualifies for application in other experimental settings. [ABSTRACT FROM AUTHOR]

Motion control of truck-mounted concrete pump booms is an important part of concrete construction work. The quality of the boom movement will affect the efficiency and safety of construction operations. To make the boom move quickly and steadily, its hydraulic control system needs to be improved. In this article, we firstly combine independent metering control (IMC) and active disturbance rejection control (ADRC). The hydraulic system that controls the boom is meliorated by replacing the traditional proportional directional spool valve with four cartridge flow control valves to realize IMC. Meanwhile, a fuzzy linear ADRC algorithm is proposed for a new IMC hydraulic system where ADRC is linearized and combined with fuzzy logic to achieve better motion control performance of boom sections. According to the results of experiments conducted using all six boom sections, compared with the PID control algorithm, the fuzzy linear active disturbance rejection control (FLADRC) proposed in this article can improve the stability and rapidity of valves controlled by hydraulic cylinders by 10.0% to 66.7% in different working conditions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article comprehensively investigates the thermal performance of a ternary hybrid nanofluid flowing in a permeable inclined cylinder/plate system. The study focuses on the effects of key constraints such as the inclined geometry, permeable medium, and heat source/sink on the thermal distribution features of the ternary nanofluid. The present work is motivated by the growing demand for energy-efficient cooling systems in various industrial and energy-related applications. A mathematical model is developed to describe the system's fluid flow and heat-transfer processes. The PDEs (partial differential equations) are transformed into ODEs (ordinary differential equations) with the aid of suitable similarity constraints and solved numerically using a combination of the RKF45 method and shooting technique. The study's findings give useful insights into the behavior of ternary nanofluids in permeable inclined cylinder/plate systems. Further, important engineering coefficients such as skin friction and Nusselt numbers are discussed. The results show that porous constraint will improve thermal distribution but declines velocity. The heat-source sink will improve the temperature profile. Plate geometry shows a dominant performance over cylinder geometry in the presence of solid volume fraction. The rate of heat distribution in the cylinder will increase from 2.08% to 2.32%, whereas in the plate it is about 5.19% to 10.83% as the porous medium rises from 0.1 to 0.5. [ABSTRACT FROM AUTHOR]

Hydraulic soil insertion device is a key component of orchard gas explosion subsoiling and fertilizing machine to realize rod fixed point soil insertion and gas fertilizer injection into soil. In order to explore the influence of the main working parameters and structural parameters on the depth and cylinder pressure of the hydraulic insertion device during the insertion process, the working parameters were optimized to ensure the insertion quality and efficiency. In this paper, force analysis was performed on the rod insertion process, and key parameter equation of soil insertion resistance was established. LS- DYNA finite element simulation software was applied to analyze the force variation of the rod during the insertion process. Box-Behnken test optimization design method and Design-Expert V8.0.6.1 software were used to carry out parameter optimization test of hydraulic insertion device. A multivariate quadratic polynomial regression equation was established by setting the engine revolution, insertion rod diameter and insertion time as independent variables, and the operation parameters of the hydraulic insertion device were optimized based on the relationship between the independent variables and the response values. The results showed that the regression equation model based on the response values of insertion depth and cylinder pressure had a good fitting degree. The engine revolution, rod diameter and insertion time all had significant effects on the increase of insertion depth and decrease of cylinder pressure, with interaction between the engine speed and insertion time with the insertion depth, and interaction between any two factors of engine revolution, rod diameter and insertion time with the cylinder pressure. The influences of the test factors on the insertion depth showed a descending order as engine speed, insertion time, and rod diameter. The influences of the test factors on the cylinder pressure showed a descending order as engine speed, rod diameter, and insertion time. Based on the results of insertion depth and cylinder pressure, the optimal combination of parameters was as follows: engine revolution of 1450 r/min; rod diameter of 32 mm; and the insertion time of 8 s. Under this optimal combination, the insertion depth of the hydraulic insertion device was 44.43 cm, and the cylinder pressure was 23.09 MPa. The experimental results showed that the optimal combination of parameters could meet the agronomic requirements of fast and deep insertion, thus providing a theoretical support for the improvement and optimization of hydraulic soil insertion device of gas explosion subsoiling and fertilizing machine. [ABSTRACT FROM AUTHOR]

With the advantages of large flow capacity and high pressure, the use of hydraulic driving piston compressors in hydrogen refueling stations is becoming the development trend. Understanding transient flow and heat transfer characteristic is the key issue for the design and application of hydrogen compressors. The transient model of the hydraulic driving piston compressor is constructed by dynamic mesh and the National Institute of Standards and Technology (NIST) real hydrogen model, which accurately predicts flow field and heat transfer. Moreover, the effect of piston reciprocating cycle frequency on hydrogen parameters variation and heat transfer characteristic is investigated. Adiabatic compression theory is commonly applied in the design of reciprocating compressors. The results show that due to the heat transfer, the exhaust temperature predicted by the adiabatic compression theory is 6.29 K higher than the actual value. This study provides beneficial references for the design optimization and reliable operation of hydraulic driving piston hydrogen compressors. • Hydrogen temperature inside cylinder is nonuniform during the compression stroke. • Exhaust temperature predicted by adiabatic compression theory is higher than actual value. • As reciprocating cycle frequency increases, maximum wall temperature decreases. [ABSTRACT FROM AUTHOR]

This study experimentally investigates the potential of using surface pattern fabrics for the cylinder noise and drag control in different Reynolds number ranges. The aerodynamic and aeroacoustic effects were evaluated through the noise and force measurements in an anechoic wind tunnel. It was observed that the noise and drag reductions take place simultaneously but in different Reynolds number ranges, corresponding to the cylinder flow in different flow regimes, e.g., sub-critical, critical, and supercritical flow regimes. Microphone arc array measurements reveal that the suppression of the Aeolian tone in the critical regime is the major cause of noise reductions, and the noise directivity gradually loses dipole features in the critical and supercritical flow regimes, which is probably related to the reduced lift fluctuation coefficient and the spanwise segment of the sound sources. Further hotwire wake survey revealed significant changes in flow dynamics, which explain the variations of noise and drag in different flow regimes. We have shown for the first time that fabric with different surface patterns can effectively reduce cylinder drag and noise in different Reynolds number ranges. Since the Reynolds number is a key factor that determines the flow state in practical engineering applications, e.g., cycling aerodynamics, this study suggests that optimal drag and noise reductions can be realized by employing the combinations of different surface pattern fabrics to account for the Reynolds number effects. [ABSTRACT FROM AUTHOR]

Significant advances have been made in prostheses with the aim of enhancing the quality of life for transfemoral amputees. While commercially available transfemoral prostheses mainly focus on the developing passive prostheses that act only as dampers, academic research is centered round powered prostheses that can provide net-positive knee torque. Although recent active-powered prostheses have made excellent progress in terms of weight and battery life, it remains unclear if these prostheses can be effectively used in everyday life. This study presents a rotary hybrid prosthesis based on the combination of a multifunctional rotary hydraulic cylinder that is designed to operate as a brake, clutch, and damper with a 100 W active motor system. This prosthesis enables long-term level ground walking while supplying active power as needed. The passive and active components of this hybrid prosthesis are designed such that they can be decoupled when operated independently, allowing for quick switching between passive and active modes in 50–100 ms. The study outlines the aims and procedures for the design of rotary hybrid prostheses, as well as the feasibility tests for each module and the amputee's clinical test on the developed knee prosthesis. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a new type of hydraulic system, the independent valve control system (IMCS) has higher flexibility compared with the traditional four-side slide valve control system. The independent metering control system (IMCS) is divided into four quadrant modes, based on the speed and load of the actuator. The traditional control methods always use a discrete control strategy to realize the switching between different modes based on mode recognition. However, the spool signals frequently switch, and the actuator operating pressure and speed are not stable when the IMCS is switched between different modes. To solve the above problems, this paper proposes a continuous control strategy for the IMCS. Based on the fuzzy control principle, the variable universe fuzzy controller (VUFC) was designed. The controller contains 49 fuzzy rules, and the output of the controller at any time is calculated by the weighted sum of several fuzzy rules. The VUFC divides the system into 49 rules, which are activated by multiple modes at any time to achieve a smooth transition between different modes. The VUFC was verified in a 37 ton excavator model and compared with the traditional independent metering meter-out (IM_MO) control strategy. The results showed that the VUFC significantly improved the frequent switching of the spool signals, and the running speed and pressure stability of the hydraulic cylinder were significantly improved. At the same time, the response speed of the hydraulic cylinder became faster at the start of the system. The VUFC can realize the continuous control of the IMCS and improve the operating performance of excavators. [ABSTRACT FROM AUTHOR]

Manual handling of hot and heavy workpiece in forging press industry increases the process time and causes safety risks to workers. To increase the productivity and optimise the use of manpower, manipulators are needed to be designed for supporting the workers handling the workpiece. Designing robots for such applications is challenging since the robot suffers from a heavy payload at the arm tip, and it operates at a high speed in a large workspace. This research addresses the design and implementation of a novel robot for handling workpiece for a given forging press cell. A novel robotic mechanism is designed with two key features: (i) the addition of parallel links in between serial links and (ii) the use of hydraulic actuators for driving robot's joints. The addition of parallel links and the use of hydraulic cylinders are to increase the structural rigidity. It is also to reduce the number of joint variables and restrict the end-effector moving parallel to the ground surface so that the robot grips and releases the workpiece in a more efficient and simplified manner. The effectiveness of the designed robot mechanism is demonstrated through functional tests, and experimental results are carried out on the implemented robot. [ABSTRACT FROM AUTHOR]

This work presents two versions of landing gear drives numerically simulated. We follow to obtain the right driving sequence of the legs and doors and the estimation of the landing gear deploy and retract time. Although the studies in this paper do not exhaust all the aspects concerning landing gear hydraulic system functioning, these are useful in the design phase of the aircraft hydraulic systems. Regarding the landing gear hydraulic system, we highlight one version of the drive stall phenomenon. When the hydraulic feeding pressure decreases, it is possible that the forces developed by the hydraulic cylinders are enough to retract completely the legs. The landing gear remains in an intermediate position, and the aircraft cannot accomplish its mission safely. For a second version, logic command functions are synthesized using Karnaugh diagrams, and after that, the numerical simulation is accomplished to validate the solution. We used the AMESim software to perform numerical simulations. [ABSTRACT FROM AUTHOR]

Hydrogen is being more and more widely deployed in various fields for its 'clean' character. For applications in automobiles where hydrogen has already been adopted for years, higher pressure means better mileage. To improve the pressure of the hydrogen compressor, a novel self-commutating liquid piston hydrogen compressor is proposed in the present study. A two-stage hydrogen booster is designed on both sides of the hydraulic cylinder piston, which is driven by a spool installed in the cylinder piston. The benefits of the novel hydrogen compressor are reducing the throttling loss and enhancing the response of the piston. Furthermore, the principle of the hydrogen compressor is illustrated, based on which a dynamic model is established while taking oil compressibility, leakage and flow force in the compression process into consideration. Moreover, system simulation model is established by applying the simulation software, verifying the feasibility and validity of the novel structure. Accordingly, the energy efficiency on the mechanical-hydraulic structure is improved. • By improving a piston pump structure, a novel self-commutating liquid piston hydrogen compressor is proposed. • This compressor can solve the problem of energy loss and shock during the commutation of liquid piston compression. • A dynamic mathematical model is carried out for the whole working process especially for the commutating process. • System simulation is performed for this compressor to demonstrate its low shock and high stability. [ABSTRACT FROM AUTHOR]

Bale density is one of the main performance indicators to measure the quality of baler operation. In this study, a real-time baler bale density monitoring system was designed for the problem of difficult real-time measurement of bale density on round balers. Firstly, a weighing calculation model for the rolling and sliding stage of the bale was established, and the dynamic characteristics during the contact between the bale and the inclined surface were analyzed based on ADAMS dynamics simulation. Then, a real-time monitoring system for the bale density based on the contact pressure of the inclined surface, attitude angle measurement and hydraulic monitoring of the cylinder was constructed, and the accuracy of the weighing model was confirmed. The system was used to observe and analyze the changes in the pitch angle of the carrier table and the oil pressure in the rod chamber of the backpack cylinder during the operation of the round baler. Finally, the monitoring system was calibrated and the dynamic calibration equations were obtained. The results show that the maximum error between the calculated value of the original weighing model and the actual weight was 3.63%, the maximum error of the calculated value of the weighing model corrected by the calibration equations was 3.40% and the measurement accuracy could be satisfied. The results show that the system was highly accurate and met the practical needs of bale weighing in the field. [ABSTRACT FROM AUTHOR]

Hydraulic integrated interconnected regenerative suspension (HIIRS) is a novel suspension system that can simultaneously harvest the vibration energy in the suspension and enhance the vehicle dynamics. The parameter sensitivity of the HIIRS system is analyzed and the significant parameters are optimized in this paper. Specifically, a half-vehicle model with the HIIRS is established. Based on the model, the parameter sensitivity of the hydraulic system is analyzed with three objectives, ride comfort, road holding, and average energy harvesting power. The parameters considered in this study are more abundant than those in previous related studies, including hydraulic cylinder inner diameter, hydraulic motor displacement, resistance, initial system pressure, and accumulator parameters. It turns out that the most sensitive parameters are the inner diameter of the hydraulic cylinder, the resistance, and the displacement of the hydraulic motor. To further study the performances that the HIIRS could present, both the single-objective optimization and the multi-objective optimization problems are solved and compared with the optimized traditional suspensions. The optimized HIIRS performs better in ride comfort and road holding than the optimized traditional suspension and anti-roll bar suspension. Different from the previous suspension optimization design, multi-objective optimization not only considers the traditional performance of the suspension but also incorporates the energy harvesting characteristics into the optimization objective. In the multi-objective optimization, a Pareto front is obtained, which shows that the ride comfort conflicts with the road holding and the energy harvesting power, while road holding and energy harvesting power did not conflict. The Pareto front shows that the optimized HIIRS is superior to the traditional suspension in ride comfort and road holding, and also harvests considerable energy. [ABSTRACT FROM AUTHOR]

Aiming at the problem of insufficient control accuracy of automatic disturbance rejection controller (ADRC) in valve-controlled hydraulic cylinder system, the ADRC is improved and applied to the electro-hydraulic servo system. To further reduce the influence of external disturbance and improve the anti-interference ability of the system, PD feedforward ADRC and error feedforward ADRC were designed based on the improved ADRC. The simulation and experimental results show that the anti-interference ability of error feedforward ADRC is stronger than PD feedforward ADRC and traditional ADRC, and can effectively improve the performance of the system, improve the response speed of the system, and greatly improve the anti-interference control accuracy of the system. [ABSTRACT FROM AUTHOR]

Given the influence of flow instability, parameter uncertainty, and unpredictable disturbances in electro-hydraulic lifting systems, high-precision position control for electro-hydraulic lifting systems is challenging to achieve. This study proposes an observer–sliding mode control strategy to improve the control accuracy of the tractor electro-hydraulic lifting system. Firstly, the principle of the electro-hydraulic hoisting system is analyzed. Secondly, a mathematical model of the electro-hydraulic hoisting system is established, and the electro-hydraulic hoisting system is reduced to design an observer to achieve a real-time evaluation of the unknown system state and disturbance. The observer and the sliding mode control are then integrated into a controller to improve system response. Theoretical analysis demonstrates that the controller ensures that the actuator can achieve the desired control effect even under disturbing effects. Finally, a joint AMESim–MATLAB simulation and conducting pilot studies are carried out to compare the observer–sliding mode control with PID (Proportion–Integral–Derivative) control and sliding mode control. At the same time, in the process of the simulation and test, the symmetric structure as the electro-hydraulic lifting system was used to build a ploughing depth simulation system (changes in the hydraulic cylinder thrust simulate changes in ploughing depth values). The results show that the proposed observer–sliding mode control strategy can achieve a better position and pressure tracking and parameter change robustness than PID control and sliding mode control. [ABSTRACT FROM AUTHOR]

Electro-hydraulic servo systems (EHSSs) are nonlinear and uncertain due to their inappropriate fluid levels, air temperature, friction, and leakage. The finite-time tracking control is difficult with the use of a proportional, integral, and derivative (PID) controller, which no longer provides adequate and achievable control performance over the whole operating range. This has led to the idea of an iterative learning controller (ILC). An intelligent and memory-based learning control approach that attempts to imitate the human way of thinking. The proposed ILC has an additional learning gain, learning filter, and robustness filter to enhance the finite-time tracking performance and stability improvement. This study is focused on the design of the ILC to regulate the servo spool valve of an EHSS, which in turn controls the displacement of a hydraulic cylinder. In simulation and experimentation, vital parameters such as overshoot and settling time in the varieties of tests, the ILC has shown better results when compared to conventional PID controllers. In step input tracking at different operating points over 0-250 mm, the ILC has 40% less overshoot and settles 12-15 s faster than the PID controller. In sinewave tracking and disturbance rejection, the PID controller performs better than the ILC in integral square error and integral absolute error as the error indices are not considered as the objective function in the design of the controller. During a robustness test, the ILC rejects the uncertainty, which evidences the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

In order to reduce the impact force of the legged hydraulic-robot when it is driving on the ground, a new method based on magnetorheological technology is proposed for damping control of hydraulic mechanical legs in this paper. Firstly, the structure of hydraulic-driven leg with magnetorheological fluid (MRF) damper is designed, and the magnetic field simulation analysis of MRF damper is carried out to verify the rationality of magnetic circuit. Then the effects of different damping ratios on the dynamic performance of valve-controlled cylinder system are analyzed by theoretical modeling. Further, the co-simulation modeling of MRF damper and valve-controlled cylinder is established based on AMESIM to analyze the vibration reduction effect under impact force. Finally, the experiments of the hydraulic system designed in this paper are carried out under step load and triangular-wave load to obtain the system output displacement and pressure under two kinds of loads. Compared with the results without MRF damper, it is found that the new method can reduce the increase of pressure impact by 82% and almost eliminate the pressure fluctuation in the high pressure chamber of hydraulic cylinder. [ABSTRACT FROM AUTHOR]

The article presents the results of experiments aimed at finding the displacement of a cylinder being part of a boom system, as recorded after initiating a rapid breaking process. The tests were performed on a special test stand which allows modifications of the control system architecture. The article presents a comparative analysis of three systems different with respect to their architecture and use of control valves. It discusses the test results and the influence of the architecture of a hydrostatic system on the accuracy of the resultant position of the working element. The article also describes the influence of external loads on the working movement accuracy of the tested systems. The results allow the author to relate the structure of a hydraulic system to the parameter of the obtained working movement accuracy with respect to the maximum values of pressures and dynamic forces. [ABSTRACT FROM AUTHOR]

In order to significantly improve the energy saving of the hydraulic system of large straw baler, an energy recovery system was designed. The working mode of baler hydraulic system was analyzed, and the energy loss in throttling and overflow stage was calculated according to the hydraulic control scheme of baling forming. The three-chamber hydraulic cylinder was directly connected with the accumulator to design the energy recovery circuit, therefore, the energy utilization of the system was effectively improved and the complexity of the hydraulic circuit was reduced. The system simulation model was built based on AMESim software to study the dynamic response characteristics of hydraulic cylinder and the change law of hydraulic pump energy consumption in a single baling forming cycle. The results show that under the action of the energy recovery system, the energy consumption of the hydraulic pump can be reduced by more than 60%, and the stroke of the three-chamber hydraulic cylinder can maintain high control accuracy and stability. In the pressure release stage of the accumulator, the average power of the hydraulic pump can be reduced by more than 75%. The energy saving effect and cost performance of the entire hydraulic system were significantly improved. The research provides a reference for improving the working life and stability of the hydraulic system of large straw baler. [ABSTRACT FROM AUTHOR]

The airflow exchange between the mine ventilation system and the surface atmosphere can influence ventilation effectiveness and emit more greenhouse gas from the mine for shallow cover mines. This airflow exchange also changes the airflow dynamics at the ventilation system, specially at the tailgate corner of the longwall. In this study, the fix-point traverse technique was employed to conduct a comprehensive survey at a coal mine longwall face and tailgate region. The air velocity, oxygen and carbon monoxide concentrations, barometric pressure, and temperature were measured and surveyed. Based on the survey data, the airflow pattern and gas concentration were analyzed at return air corner on the tailgate side. Based on the measurement and analyses, it was found that the airflow at the face can be broken into two compartments by the hydraulic cylinder. These two compartments can periodically exchange the air at the face. This can influence the abnormal gas concentration for the release of carbon monoxide from the gob attributed from coal spontaneous combustion. Also, our study provided detailed information for more understanding of airflow in working face and gob by simulation method in the future work. [ABSTRACT FROM AUTHOR]

In order to study the influences of feedback mechanism clearances on static errors and closed-loop stability of the hydraulic system of coal winning machine, the interaction mechanism of 4 kinematic pairs and their clearances in feedback processes was analyzed, and a digital hydraulic cylinder model with feedback mechanism clearances was established. By comparing the position relationship between negative inverse frequency curves of clearances and Nyquist curves of the linear parts, it is found that the clearances do not affect the stability of the system. Using the static analysis method, the static error expression caused by each clearances was derived, and the factors and laws affecting the static errors were revealed. The AMESim simulation model of digital hydraulic cylinder was established and simulated. Correctness of the theory and simulation analysis was verified by experiments. [ABSTRACT FROM AUTHOR]

Mechanical products are becoming more diversified with the continuous development of precision processing and materials technologies. The friction force generated by the O-ring seal in a hydraulic cylinder was once considered redundant. However, its utilization has recently been proposed. The hardness of the O-ring and the inner diameter of its groove directly affect the normal pressure between the O-ring and the inner wall of the cylinder, thereby affecting the friction behavior. In order to explore this friction behavior, a strain-based friction force measurement system is developed in this study, and the steady-state and dynamic friction values under different working conditions are studied and discussed in depth. This research on the friction behavior in the cylinder provides a theoretical basis for more convenient design and utilization of the friction force generated between the O-ring and the inner wall of the cylinder. [ABSTRACT FROM AUTHOR]

The effect of fluid properties on hydraulic cylinder rod seal stick‐slip friction was studied. Breakaway and stick‐slip forces were measured for three ISO VG 32 fluids with slipper, U‐cup, and Vee‐pack seals. Breakaway forces increased exponentially with dwell time. Stick‐slip friction produced audible low‐frequency noise. Differences in the stick‐slip behavior of the fluids were observed. Fast Fourier transform analysis of sound, force, and mechanical vibrations was conducted. Stick‐slip friction increased the amplitude of low‐frequency vibrations in all three domains. Micro stick‐slip movement was elucidated via motion amplification technology. These findings provide a basis for the development of fluids that improve the control and safety of hydraulic equipment. [ABSTRACT FROM AUTHOR]

To meet the demand for high-altitude fruit picking, a luffing mechanism system is designed and used to control the hydraulic cylinder. Combined with the performance index of the servo system, the fuzzy proportional–integral–differential (PID) is adaptive and strong, and the robustness of the picking robot is simulated. Using the MATLAB/Simulink module, the fuzzy PID controller model of the electro-hydraulic servo system for picking the robot arm is established. The simulation results show that the fuzzy PID controller model can effectively reduce the error and meet the requirements. Through the simulation of the picking robot arm, the results show that the fuzzy PID control method can not only improve the performance of the picking robot arm but also provide a reference value for future optimization control. [ABSTRACT FROM AUTHOR]

Achieving precise load detection for Intelligent Loaders is an important task, which directly affects the operation energy efficiency and the fatigue life analysis for the loader's working mechanism. The operation of the mechanism is regarded as a 3-DOF (degree of freedom) planar motion process coordinated with the vehicle body. Affected by complex dynamic coupling in motion, the existing dynamic models of the mechanism have the problem of insufficient accuracy, which is not conducive to the precise calculation of load. Taking the reverse six-linkage loader as the research object, an accurate dynamic model of the mechanism is established considering its cooperative motion with the vehicle body. Firstly, the kinematic description of the mechanism is given by the Rodriguez method. Then, to overcome the coupling effect caused by the cooperative motion, the sufficient inertia forces of the mechanism are established in joint space using the Lagrange method. Furthermore, to overcome the coupling effect caused by the complex structure, the Newton–Euler method is used to establish the force mapping relations between the joint space and the drive space by multi-body modeling. Finally, the dynamic model of the mechanism in drive space is obtained, and the specific mapping relations between the bucket force, the vehicle driving force, and the drive parameters are given. Compared with existing dynamic models in simulation, the analysis shows that the average and maximum absolute errors of the vehicle driving force calculated by the established model do not exceed 20% of the existing model errors, and the corresponding errors of the bucket force do not exceed 10% of the existing model errors, which proves that the motions of vehicle body and front-end mechanism, as well as the force of the tilt hydraulic cylinder, play important roles in improving the model accuracy. The established model is superior to existing models and is more suitable for cooperative motion with the vehicle body. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The steering gear system is part of the group of vital installations for a ship. Its role is to ensure course stability and, at the same time, to facilitate the changes of navigation direction. In this context, the technology for assembling the system is well-defined through rules, procedures, and work instructions. A steering system that is correctly assembled according to the instructions and execution drawings will lead to proper operation and, at the same time, the successful completion of applicable steering system tests. The applicable tests for steering systems are depending to the type and purpose of the vessel. However, SOLAS defines a series of general high-level tests that must be performed, and during these tests, the quality of the installation is to be demonstrated. The present work will develop both the subject of the steering gear installation, which directly influences the results of the tests. [ABSTRACT FROM AUTHOR]

During the operation of main pipelines, many defects occur in the body of the pipe and on its surface. The main method for eliminating such defects is cutting out the defective section and welding a new one in its place. The cutting process is complicated by the possible sharp displacement of the ends of the pipeline located on both sides of the cutting site, which is dangerous for the lives of workers and can lead to breakage of the cutting equipment. In addition, to weld a new section, it is necessary to center the ends of the pipeline until they reach the alignment position, for which heavy, difficult-to-transport pipelayers are used, which allow centering the ends of the pipeline only by lifting them. Ensuring the possibility of such centering often requires additional digging of the repaired pipeline. Moreover, due to the large dimensions of pipelayers, payment of permits for their transportation is required. In addition, before transportation, pipelayers require their disassembly and assembly before carrying out repair work, which entails additional time and labor costs. To solve the problems described in this article, a developed design of devices for fixing and centering the ends of the pipeline is proposed, which makes it possible to fix the ends of the pipeline from their sharp displacement, and also to center them before welding a new section. A mathematical model was developed to assess the centering forces, the resulting stresses in the pipeline wall and the reaction forces that arise in the hydraulic cylinders of devices when leaving the ends of the pipeline in their sharp displacement. The initial data for the developed model are the coefficients of the polynomial describing the position of the pipeline in the repair trench. To accurately assess the position of the pipeline, a method of its laser scanning is proposed, the result of which is a point cloud of the pipeline. As part of the study, a method was also developed for the obtaining of a polynomial equation describing the bending of its central axis from a pipeline point cloud. As a result of experimental studies, this method has demonstrated sufficient accuracy in determining the position of the pipeline in the repair trench. Thus, the developed repair method makes it possible to increase both the safety of the repair and the technological and economic efficiency of the process of replacing a defective section. [ABSTRACT FROM AUTHOR]

This paper presents the problem of natural vibration of a two-stage hydraulic cylinder subjected to Euler compression load. The considered hydraulic cylinder is freely supported at both of its ends. The linear vibration problem of the telescopic hydraulic cylinder is based on the kinetic stability criterion using Hamilton’s principle and the Bernoulli-Euler theory. The stiffness of the guide and sealing elements between successive stages of the hydraulic cylinder were considered in this paper. These stiffnesses were modelled using translational and rotational springs. The effects of cylinder wall thickness, piston rod diameter, and thickness of guiding and sealing elements on the natural vibration of the system were analysed. Results are presented in the form of characteristic curves on the plane load – natural frequency with different parameters characterizing the considered hydraulic cylinder. [ABSTRACT FROM AUTHOR]

To improve the stubble avoidance rate of no-till wheat seeders under the environment of corn stubble, the side-shift stubble avoidance system was developed in the present study based on deviation-perception fusion technology. Firstly, the amount of implement deviation compensation was accurately obtained by the information sensing system. Then, a fuzzy PID algorithm was proposed to optimize the performance of the control system. Finally, the simulation model of the control system was developed by Matlab/Simulink. The simulation results showed that the regulation time required for the system response curve to reach the steady state was 1.0 s, and the maximum overshoot was 8.2%. To verify the performance of the side-shift stubble avoidance system, an orthogonal test was conducted. The optimal combination of parameters was obtained, including the operation speed of 1.3 m/s, the hydraulic cylinder speed of 25 mm/s, and the straw mulch amount of 1.2 kg/m2. The field verification test was performed under the optimal parameters, showing the stubble avoidance rate was 90.6%, and the mean value of the sowing variation coefficient was 27.12%, which fully satisfied the requirements of stubble avoidance and sowing operation. [ABSTRACT FROM AUTHOR]

An excavator is an off-road vehicle or machine used for several types of construction activities. It has an attachment called a backhoe that is widely used for digging. While digging the earth's massive force works on bucket tips and may bring deformation in it. In this paper an attempt is made to quantify the value of the variables obtained while the all-attached backhoe is considered as a multibody, given in rotation to each joint and simulated in Ansys. The results obtained show that the deformation obtained is small at low rotation and large at high rotation rate. Comparison of the deformation, joint forces and velocity at each set of rotation has been tabulated in x, y and Z directions as well as the overall velocity, total joint force and deformation has also been calculated. This paper provides the base to study and design a multibody system which may undergo deformation so that the end effect may be obtained precisely as required in precision tools and machinery. [ABSTRACT FROM AUTHOR]

It is the first time that the full floating rubble bed leveling technology is adopted for the Dalian Bay Subsea Tunnel project. When the leveling ship is afloat, the stability of the hull is easily affected by tidal and wave conditions. The adjusting capability of hydraulic cylinders under different working conditions is tested in order to verify that the auto-adjusting hydraulic cylinder at the end of the riprapping pipe better compensates the influence of tides when the leveling ship is afloat and to solve the instability of the ship, so as to ensure that the leveling precision of crushed-stone foundation bed meets the construction requirements. According to the results of the test, it is verified that the adjusting capability of oil cylinder at the end of the riprapping pipe under the full floating conditions meets the need of construction, thus providing reference for similar projects. [ABSTRACT FROM AUTHOR]

A hydraulic remote control system (HRCS) of subsea equipment and devices equipped with long transmission pipelines was studied. Considering the influence of the long pipelines, a transient dynamic model of the HRCS was established, which includes a model of the transmission pipeline and the hydraulic cylinder. A modified instantaneous acceleration-based unsteady friction model was used to calculate the dissipation along the pipelines. The dynamic model was verified by comparing it with a previous water hammer experiment. Moreover, a land test of the HRCS of a deepwater safety valve was carried out. The response time of the hydraulic cylinder after the sudden upstream valve of the HRCS opened was numerically simulated and measured. The results show that both simulation and test have the same response time. The pressure difference at different positions of the pipeline indicates that a long pipeline plays a significant role in the system. The length of the pipeline affects the amplitude of the transient pressures and the response time. Then, a comprehensive sensitivity analysis of the pipe parameters was carried out. A phenomenon was discovered that the inner diameter and the rated working pressure have different effects on the response time for different pipe lengths. The dynamic response model in this paper is efficient and low-cost for secondary development and is attractive for the design and evaluation of the HRCS of subsea equipment and devices. [ABSTRACT FROM AUTHOR]