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In this paper, attention was focused on identifying the components of the amplitude-frequency spectrum of pressure pulsations in a hydraulic system in which an external low-frequency mechanical vibration was subjected to a proportional hydraulic directional control valve. It was observed that an operating machine or device equipped with hydraulic valves is a source of mechanical vibrations with a wide frequency spectrum. The influence of these vibrations on the pressure pulsation spectrum was analyzed, identifying the components resulting from the forcing of the directional control valve spool. In addition, it was noted that the pressure pulsation spectrum includes components resulting from the pulsation of the displacement pump output feeding the hydraulic system. A description of these spectrum components was also made and, using the solution superposition method, the components of the pressure pulsation spectrum over a wide frequency range were identified. [ABSTRACT FROM AUTHOR]

This article presents the methodology and process of the modeling, designing, and testing of a research station enabling the identification, tuning, and verification of Digital Twin (DT) in control systems in power hydraulics. The concept of the station is presented, the main part of which is a subsystem forcing a dynamic, variable load using a hydraulic actuator controlled by a proportional valve, together with data acquisition and processing systems and software. The load application subsystem can subject the tested power hydraulic system, usually consisting of an actuator with its own control system, to controlled dynamic loads, which allows for the determination of its characteristics and tuning of the DT. This article describes the electro-hydraulic elements used to adjust the position of the actuators and the designed hydraulic and electrical diagrams of the station. The process of identifying, modeling, and selecting a controller for a subsystem simulating an external load is presented. The test station is built and tested. The identification, modeling, and tuning of DTs, for example, actuators and controllers, are described. A satisfactory convergence of the simulation and modeling results with the operation of the real system is achieved, which allows the obtaining of a reliable DT for actuator control systems operating under variable load. [ABSTRACT FROM AUTHOR]

This study brings out the results of simulating the transient response regarding the angle of rotation of a crane when applying hydraulic automatic control system. The model is built based on the compatible selection and connection among the controller, proportional valve, hydraulic cylinder, angle sensor, and crane. This work involves establishing the differential equations, Laplace equations of the components in the model, and their relationships. Simulation diagrams of the system are constructed from these equations. The responses of two control methods, PID and fuzzy PID, are identified, in this manner providing results for comparison and selection of the best control method for the experimental model. The results of both control methods show satisfactory overshoot, response time, and steady-state error, meeting the requirements for designed response criteria. This research model contributes to supplementing and enriching the problems in the field of hydraulic automatic control. [ABSTRACT FROM AUTHOR]

The dynamics of a slide valve plunger of an upgraded spool and sleeve is considered. The minimum force for preloading the plunger with a screw is determined and its value is compared with the force required for a standard sleeve. The slide valve is numerically simulated. The dynamics of a spool plunger with an upgraded drive and sleeve is studied. [ABSTRACT FROM AUTHOR]

Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press 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.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) 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.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) 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 COVID-19 pandemic has revealed numerous global health system deficits, even in developed countries. The high cost and shortage of treatment, health care, and medical devices are the reasons. Aside from new mutations, the availability of respirators is an urgent concern, especially in developing countries. Even after the pandemic, respiratory diseases are among the most prevalent diseases. Researchers can help reduce treatment costs by offering scalable, open-source solutions that are manufacturable. Since March 2020, serious efforts have been made to reduce the problems caused by the lack of respirators at the lowest possible cost. In this research paper, a unique and integrated solution for a fully automatic ventilator is presented and described. The design considers the cost, speed of assembly, safety, ease of use, robustness, portability issues, and scalability to fit all requirements for emergency ventilation. Furthermore, the device was developed using turbine technology to generate air pressure. The work describes a low-cost alternative ventilator that uses a novel proportional-valve approach to control oxygen mixing process, control circuit, and control algorithm. The current software supports pressure mode controllers, and it can be upgraded to volume-mode or dual mode without any modifications in the hardware. In addition, the hardware, particularly the electronic circuit, has idle input/output ports for further development. Based on the evaluations of the developed ventilator using an artificial lung, the system exhibited acceptable accuracy regarding to the pressure, leak compensation, and oxygen concentration levels. The designated safety conditions have been met, and the safety alarms tripped according to any violations. Moreover, all design files are provided with clear instructions to rebuild the device, despite the complexity of electronics assembly. The system can be described as a development kit, which can shorten the time for researchers/manufacturers to develop a device equivalent to the expensive devices available in the market. [ABSTRACT FROM AUTHOR]

This article discusses the dynamic behavior of a spool plunger with a modernized drive. Modernization of the drive consists in replacing the electromagnet with a stepper motor with the transformation of rotational motion, — with the help of a screw pair, — into a rectilinear one. The contact between the ends of the screw and the plunger is provided by a spring. The value of the preliminary compression of the plunger to the end of the screw is assigned on the basis of guaranteed operation without loss of contact, due to which the plunger practically does not respond to disturbances and is devoid of an oscillatory component during the transient process. The mathematical model includes the influence of fluid friction and hydrodynamic force arising from pressure loss on the distributor 4 MPa. The study of the dynamics of the plunger consists in the accelerated retraction of the screw — which is in force contact with the end face of the spool — and the determination of the limit values of acceleration as a function of the preload force.

The optimization control and efficiency improvement of proton exchange membrane fuel cells (PEMFCs) are being paid more attention. Ejectors have been applied in PEMFC hydrogen recirculation subsystems due to the advantages of a simple structure and no power consumption. However, the hysteresis deviation of a proportional valve ejector is found in the loading and unloading processes such that the hysteresis phenomena can cause deviations in fuel cell control process and affect the power dynamic output stability of PEMFCs. This paper analyzes the causes and effects of proportional valve hysteresis phenomena through experiments and simulations. The results show that the resultant force of proportional valve armature is different in loading and unloading processes because of the hysteresis phenomena, and the maximum flow deviation is up to 0.42 g/s. The hysteresis phenomena of flow rate further cause a deviation of 68.7–89.3 kW in PEMFC power output. Finally, a control compensation model is proposed to effectively reduce the deviation. This study provides a reference for the control and optimization of PEMFC with ejector technology. [ABSTRACT FROM AUTHOR]

The interest in soft pneumatic actuators has been growing rapidly in robotics, owing to the contact adaptability with the material softness. However, these actuators are mostly controlled by rigid electronic pneumatic valves, which can hardly be integrated into the robot itself, limiting its mobility and adaptability. Recent advances in soft or electronics‐free valve designs provide the potential to achieve an integrated soft robotic system with reduced weight and rigidity. Nevertheless, the challenge in valve response remains open. To enable dynamic control of a soft pneumatic actuator (SPA), a fast‐response proportional valve is needed. Herein, the potential of Ecoflex‐based magnetorheological elastomer (MRE) membrane to create a proportional valve that can be used in the control of a soft robot made from the same silicone material is explored. Experimental characterization shows that the proposed MRE valve (30 mm × 30 mm × 15 mm, 30 grams) can hold pressure up to 41.3 kPa and regulate the airflow in an analog manner. The valve is used to perform closed‐loop proportional–integral–differential (PID) control with 50 Hz on a SPA and is able to control the pressure within the actuator chamber with a root‐mean‐square error of 0.05 kPa. [ABSTRACT FROM AUTHOR]

The interest in soft pneumatic actuators has been growing rapidly in robotics, owing to the contact adaptability with the material softness. However, these actuators are mostly controlled by rigid electronic pneumatic valves, which can hardly be integrated into the robot itself, limiting its mobility and adaptability. Recent advances in soft or electronics‐free valve designs provide the potential to achieve an integrated soft robotic system with reduced weight and rigidity. Nevertheless, the challenge in valve response remains open. To enable dynamic control of a soft pneumatic actuator (SPA), a fast‐response proportional valve is needed. Herein, the potential of Ecoflex‐based magnetorheological elastomer (MRE) membrane to create a proportional valve that can be used in the control of a soft robot made from the same silicone material is explored. Experimental characterization shows that the proposed MRE valve (30 mm × 30 mm × 15 mm, 30 grams) can hold pressure up to 41.3 kPa and regulate the airflow in an analog manner. The valve is used to perform closed‐loop proportional–integral–differential (PID) control with 50 Hz on a SPA and is able to control the pressure within the actuator chamber with a root‐mean‐square error of 0.05 kPa.

Due to a sharp change in the direction and velocity of the fluid flow in the hydraulic distributor, hydrodynamic forces arise. When positioning and holding the spool, the magnitude of the above forces determines the required control power. The aim of the article was to find an optimal constructive solution that would reduce the influence of hydrodynamic forces. In the article we have considered the theoretical foundations laid in the analytical solution of the problem of calculating the magnitude of the hydrodynamic force acting on the plunger of the spool. In addition, a numerical experiment was carried out using CAD Solidworks and the Flow Simulation application package and a comparison of the results obtained with the analytical solution of the problem. During the numerical experiment, it was found that by upgrading the spool sleeve, it is possible to reduce the value of the hydrodynamic force by 4.5 times, compared with the original design. At the same time, it was found that the modernization of the plunger does not further reduce the maximum hydrodynamic forces. The article highlights the economic benefits of reducing the required power to control the hydraulic distributor. The article may be of interest to both researchers whose research interests lie in the field of hydrodynamics, and manufacturers of hydraulics.

The piston cylinder system controlled by proportional valve has the problem of tedious manual tuning of PID parameters. In order to solve the problem of tuning the control parameters of the variable mechanism of the four-distribution axial piston motor, a parallel collaborative design method based on particle swarm optimization (PSO) was proposed. Firstly, the swashplate nclination of the four-port axial piston motor was controlled by PID closed-loop control composed of servo proportional valve and the angular displacement sensor fixedly connected with the swash plate, and changed the output shaft speed of the four-port axial piston motor. Then the Simulation X was used to model the variable displacement four-port axial piston motor and the valve-controlled variable mechanism. Finally, a parallel collaborative design method based on particle swami optimization algorithm was proposed to solve the control parameter tuning problem of variable mechanism of four-port axial piston motor without hydraulic simulation software platform, which could be used for automatic optimization and tuning of PID parameters to reduce control tracking error. The results show that compared with the system without optimizing the control parameters, after optimizing the control parameters, the overshoot of the swing angle of the motor swashplate is reduced by 21%, the peak pressure in the plunger cavity is reduced by 3.4 MPa, and the motor speed is stable, which provides a theoretical basis for the subsequent construction of the physical prototype of the variable displacement four-port axial piston motor. [ABSTRACT FROM AUTHOR]

Proportional valve was the core component of the large diesel engine piston pump. The performance of the spool valve affected the hydraulic operating system. For the influence of proportional valve orifice on flow characteristics, the flow characteristics of proportional valve with different port structures were analyzed by means of numerical simulation and experiment. Firstly, based on the Schnerr-Sauer cavitation model of two-phase flow in Fluent, the cavitation and flow characteristics of the valve under three different throttles were analyzed. Then, the proportional valve test rig was used to complete the flow test of the sample. Finally, the simulation results were compared with the experimental data. The comparison conclusion between simulation and experiment was obtained. The reliability of the simulation results was verified. The results show that the cavity volume of the proportional valve has no effect on the flow characteristics. The three throttles are fully open, and the flow of the valve is 9.56 L/min. The throttle shape of proportional valve affects the flow characteristic curve. The minimum flow coefficient of triangular valve port is 0.66. The flow coefficient of rectangular valve port is more than 0.7. The second-order rectangular valve port can control the flow linearly and accurately in low condition, and respond quickly in high condition. The second-order rectangular valve port is more suitable for large diesel engine piston pump. [ABSTRACT FROM AUTHOR]

For analyzing ejector's performance in the system, an ejector for a 10 kW polymer electrolyte membrane fuel cell (PEMFC) system was first designed, manufactured, and a 10 kW PEMFC system bench was built up. A proportional valve and PI pressure feedback control method were adopted to control the hydrogen supply and anode inlet pressure. During the test, performances between dead-ended anode (DEA) mode and ejector mode were compared. Ejector's performances in the system, i.e., volume flow recirculated ratio, difference pressure, dynamic responses of primary pressure, anode inlet pressure, and recirculated gas flow rate during the purge process and current variation condition, were investigated. The results show that pressure adjustment is accurate, continuous, and fast using the proportional valve and PI pressure feedback control method. The hydrogen consumption rate in the ejector mode can reduce from 5% to 10% compared with the rate in the DEA mode except for the stack current 5 A and 10 A conditions. For better water removal out of the anode channel in ejector mode, the maximum stack power increases from 5.11 kW (DEA mode) to 9.56 kW (ejector mode). Anode pressure surge caused by the purge valve switching enhances the ejector's recirculated performance significantly. • An ejector for a 10 kW PEMFC system is designed, manufactured and evaluated. • The stack in ejector's mode shows a better performance than that in DEA mode. • Hydrogen recirculation can reduce the hydrogen consumption. • The proportional valve with the PI pressure feedback method can accurately control the anode inlet pressure. • Anode pressure surge can enhance ejector's recirculated performance. [ABSTRACT FROM AUTHOR]

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.

An electro-hydraulic elevator is a new type of enhanced elevators that are used in low-rise buildings that do not exceed more than three floors. In this paper, an electro-hydraulic servo system for controlling the speed of a hydraulic elevator prototype by using a proportional valve and PID controller was investigated theoretically and experimentally. A three floors elevator prototype model with 76cm height was built including hydraulics components and electrical components. The elevator system is fully automated using the Arduino UNO board based Data Acquisition (DAQ) system. LabVIEW software is used to control the hydraulic elevator system through L298 DC drive via the DAQ board. The best PID gains was obtained experimentally. The elevator system prototype could be emplimented for educational purposes; such as learning the undergraduate students in the Electromechanical Engineering Department in the University of Technology how to structuring the electro-hydraulic elevator as well as the appropriate control strategy.

This article proposes to utilize linear-quadratic tracking (LQT) control to reduce the air brake system response time and vehicle stopping distance, and hence, to significantly improve the system performance of a commercial vehicle air brake system equipped with electro-pneumatic proportional valve actuators. The nonlinear dynamic model of the air brake system, consisting of a control actuator (a proportional valve) and braking actuator (the brake chamber), is developed and linearized using the q-Markov COVariance Equivalent Realization (q-Markov Cover) method in our early work. Based on the linearized dynamic model, an infinite horizon LQT controller is designed along with Kalman state estimation at each linearized operational condition. To apply the LQT control law over a wide operational range to track the target pressure, the designed controller was interpolated between the neighboring controllers to have a control law cover the entire operational range. To validate this control law, the control scheme is implemented into a dSPACE unit and validated through bench tests under different supply and reference pressures. The LQT control performance is also compared with the PID (proportional-integral-derivative) one. The bench test results confirm the effectiveness of the proposed control scheme.

The optimization control and efficiency improvement of proton exchange membrane fuel cells (PEMFCs) are being paid more attention. Ejectors have been applied in PEMFC hydrogen recirculation subsystems due to the advantages of a simple structure and no power consumption. However, the hysteresis deviation of a proportional valve ejector is found in the loading and unloading processes such that the hysteresis phenomena can cause deviations in fuel cell control process and affect the power dynamic output stability of PEMFCs. This paper analyzes the causes and effects of proportional valve hysteresis phenomena through experiments and simulations. The results show that the resultant force of proportional valve armature is different in loading and unloading processes because of the hysteresis phenomena, and the maximum flow deviation is up to 0.42 g/s. The hysteresis phenomena of flow rate further cause a deviation of 68.7–89.3 kW in PEMFC power output. Finally, a control compensation model is proposed to effectively reduce the deviation. This study provides a reference for the control and optimization of PEMFC with ejector technology.

Soft pneumatic actuators (SPAs) are commonly used in various applications because of their structural compliance, low cost, ease of manufacture, high adaptability, and safe human-robot interaction. The traditional approach for achieving proportional control of soft pneumatic robots requires the use of industrial proportional valves or syringe drivers, which are not only rigid and bulky but also hard to be integrated into the body of soft robots. In our previous research, we developed a Magnetorheological elastomer (MRE)-based soft valve that showed advantages for controlling SPAs due to its compliance, compactness, robustness, and compatibility for continuous pressure modulation. Modern soft robots with multiple chambers require more MRE valves onboard for their control. However, merely packing more MRE valves for soft robots can cause problems like magnetic interference, flow rate deviation, and overheating. Therefore, in this study, we proposed a two-dimensional MRE valve array design to solve issues of magnetic interference and overheating when expanding from a single MRE proportional valve into an integrated array. The magnetic interference and the overheating problem were investigated through multiphysics simulation, bringing the optimal choice of valve spacing (1.2 times the single valve diameter), magnetic coil pole arrangement (same pole), and the cooling system design (internal cooling chamber with flowing water). Physical experiments showed that our MRE valve array maintained its original flowrate performance with low magnetic interference (0.89 mT) and low coil temperature (under 73.9°C for 5 min).

The presented work was directed to develop the dynamic performance of an electro-hydraulic proportional system (EHPS). A mathematical model of the EHPS is presented using electro- hydraulic proportional valve (EHPV) by Matlab-Simulink, which facilitates the simulation of the hydraulic behavior inside the main control unit. Experimental work is done and the closed loop system is designed using the linear variable displacement transducer sensor (LVDT). The controller of the system is an Arduino uno, which is considered as a processor of the system. The model is validated by the experimental system. The study also presents a real time tracking control method, based on pulse width modulation, by controlling the speed of the actuator to achieve the position tracking with minimum error and low transient time, by applying the constant input signal 50 mm the transient time was 0.9 seconds and the error 1.8 %. [ABSTRACT FROM AUTHOR]

The presented work was directed to develop the dynamic performance of an electro-hydraulic proportional system (EHPS). A mathematical model of the EHPS is presented using electro- hydraulic proportional valve (EHPV) by Matlab-Simulink, which facilitates the simulation of the hydraulic behavior inside the main control unit. Experimental work is done and the closed loop system is designed using the linear variable displacement transducer sensor (LVDT). The controller of the system is an Arduino uno, which is considered as a processor of the system. The model is validated by the experimental system. The study also presents a real time tracking control method, based on pulse width modulation, by controlling the speed of the actuator to achieve the position tracking with minimum error and low transient time, by applying the constant input signal 50mm the transient time was 0.9 seconds and the error 1.8%.

The present research concentrates on the performance improvement of a two-stage proportional valve with internal hydraulic position feedback which is named as the Valvistor valve. In this paper, the performance constraint of this valve is identified and a novel electronic closed-loop control strategy with an integral-separation fuzzy proportional-integral-derivative controller is proposed to improve the valve performance, including the static characteristics and the dynamic characteristics. The results show that in the Valvistor valve, the comparison point and the feedback loop for the internal hydraulic position feedback is only in the main stage, while the input is in the pilot stage. This leads to the poor performance of this valve. The control strategy is very effective and the performance of the Valvistor valve is improved. With the control strategy, the error of the poppet displacement is reduced from 4.9% to 2.1% by adjusting the spool displacement in the pilot stage in real-time and the flow error is reduced from 5.3% to 2.3%. The dead zone of the poppet displacement and the flow is eliminated. The hysteresis is reduced from 5.3% to 2.6% and the linearity is improved. The overshoot is reduced from 0.06 to 0.02 mm and the settling time is reduced from 0.5 to 0.2 s. Moreover, the bandwidth is increased from 8 to 16 Hz. [ABSTRACT FROM AUTHOR]

A clean and healthy environment must be an increasing priority. Different kinds of hydraulic fluids are in use nowadays. Unfortunately, the majority of them are harmful. The use of tap water as a hydraulicpressure medium is one of the possible solutions. This study presents the research and development of different hydraulics components. Every research of a new water-hydraulic component starts with basic tribological investigations of different material pairs and their surfaces. Then follows the design and calculations of the hydraulics characteristics, the production of a prototype and its experimental investigations. The following water-hydraulic components, i.e., proportional control valve, hydraulic cylinder, piston pump, hydraulic accumulator, check valve and hydraulic motor, will be presented.

Ensuring uniform motion of hydraulic actuators is one of the most demanding tasks in the field of Hydraulic Drive Technology. Various, more or less demanding and precise, mechanical-hydraulic or electro-hydraulic solutions are used depending on the accuracy requirements of uniform motion. In addition to more precise uniform motion, the electro-hydraulic solutions also enable compensation and elimination of many inequalities. The paper deals with the issue of ensuring quality uniform motion of hydraulic rotary actuators. To ensure high rotation accuracy, proportional valves are used as cost-effective, continuously operating electrohydraulic valves. At the forefront of the discussion is the influence of different valve characteristics on the uniform rotation, with differences arising from faults in valve manufacturing, valve assembly, or due to different valve degradation. Based on a detailed mathematical model of the system and simulations based on real measured different characteristics of the valves used, the effects of these differences are shown and control methods to eliminate them. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

Actuators of constant speed operation in hydraulic power systems are highly required in many applications such as steel sheet rolling and pressing operations. To achieve this, a variable pump and/or control valve may be used to control the actuator speed in different operating conditions. A mathematical model of the selected hydraulic system and its components has been carried out using SIMULINK to study its static and dynamic characteristics. A direct comparison between the mathematical model results and experimental results of the same hydraulic system published by the author has been introduced. For the experimental and the mathematical models, a linear and nonlinear PID control algorithm has been applied for pump speed control and proportional directional control valve in the presence of system disturbance, herein is an external leakage, to maintain the actuator velocity constant either by controlling the pump speed or the proportional directional control valve with achieving the minimum error. The nonlinear control PID showed a better system response than the PID controller and reduced the error hence improved the system response. It has been shown that the proportional valve control is better than the pump speed control for different external leakage, 5–10%, with an error of the order 3% from the setting velocity. [ABSTRACT FROM AUTHOR]

This paper presents a control-oriented LPV (Linear Parameter-Varying) model for commercial vehicle air brake systems, where a pneumatic valve actuator is used to control the brake chamber pressure. To improve the brake system response time and reduce the vehicle stopping distance, the traditional treadle valves used in the air brake system are replaced by electro-pneumatic valves. Also, to develop the model-based brake control strategy, a nonlinear mathematical model is developed based on Newton's second law, fluid dynamics of the orifice, force balance of spool, and solenoid dynamic characteristics. The brake chamber dynamics is also considered during the charging and discharging processes. The developed nonlinear model is calibrated based on both valve actuator geometry and test bench experimental results. It is proposed to model the nonlinear system in the LPV form so that gain-scheduling controllers can be developed. To obtain the LPV model, system identification is conducted using the calibrated nonlinear model to obtain a set of linearized models under different brake chamber pressure levels, and the resulting identified linear models are assembled to form the LPV model with brake chamber pressure as the varying parameters. A linear infinite-horizon continuous-time LQR (Linear Quadratic Regulator) controller was designed for the braking system based on the developed LPV model with the fixed parameter to demonstrate the effectiveness of the developed LPV model. [ABSTRACT FROM AUTHOR]

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications 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.)

A novel full circumferential reluctance maglev coupling (FCRMC) is proposed in this paper, which not only meets the requirements of force transmission and valve position feedback of two-dimensional (2D) valve but also has the advantages of closed-loop magnetic circuit and high magnetic energy utilization rate. To investigate the torque-displacement characteristic of FCRMC, a detailed analytical model based on the equivalent magnetic circuit method is formulated, which considers the leakage flux effect, edge effect, and magnetic permeability nonlinearity. The effects of the inclination angle, width, air gap, and number of teeth on the torque are explored by the analytical model, and appropriate structural parameters are selected to design and manufacture the prototype. A dedicated test bench is built and the static/dynamic characteristics of FCRMC are tested. The experimental results show that the FCRMC prototype has a step velocity of 20.8 × 10−3 mm/ms, a torque-volume ratio of 8.47 × 10−3 N m/cm3, a torque-permanent magnets(PMs) volume ratio of 0.050 N m/cm3, and a step velocity-PMs volume ratio of 2.63 × 10−3 mm/ms·cm3. Finally, to verify the feasibility of the FCRMC in real work situations, the FCRMC is applied to a 2D electro-hydraulic proportional flow valve. The experimental results show that, at 15 MPa, the no-load flow of the valve is 82.4L/min, with a hysteresis of 3.8 %, a step velocity of 17.5 × 10−3 mm/ms, and amplitude and phase frequency widths of 22.4 Hz and 26.5 Hz. • The highlights of this paper are as follows: since rare earth permanent magnet is a non-renewable strategic resource, the study on rare earth permanent magnet effective utilization of maglev coupling is substantially important. Therefore, a novel FCRMC for 2D valves is proposed, which not only meets the requirements of force transmission and valve position feedback of 2D valves but also has the advantages of closed-loop magnetic circuit and high magnetic energy utilization rate. [ABSTRACT FROM AUTHOR]

Aiming at the problem that the dynamic and static characteristics of the main spool of pilot electro-hydraulic proportional valve are quite different in the process of left and right motion,the asymmetric characteristics of the left and right dead zones of the pilot spool of electro-hydraulic proportional valve caused by machining and assembly tolerances were studied. An overall mathematical model of proportional valve with pilot asymmetric dead zone was established, the influence of the asymmetric dead zone of the pilot valve on the dynamic and static characteristics of the main spool was analyzed in the mathematical model,an asymmetric control strategy based on the asymmetric dead zone of the pilot valve and a variable gain dead zone compensation algorithm were proposed, that is, different dead zone parameters and controller parameters were set in the forward and reverse directions of the pilot valve. The control strategy was evaluated on the proportional valve test bench. The results indicate thatthe main valve spool overshoot is reduced by 80% , the steady-state error is reduced by 60% , the response time is reduced by 50% , etc. The dynamic and static characteristics of the main spool are significantly improved. [ABSTRACT FROM AUTHOR]

Pneumatic systems are used in a wide range of industrial robotic and automation systems due to their interesting properties. However, air compressibility, friction, and the other nonlinear characteristics of a servo pneumatic system are difficulties, which contribute to use modern controllers. Conventional linear controllers face steady-state error and uncertainty. Nonlinear modeling with model-based control is a good choice to deal with this problem. In this paper, behavior equation of flow and pressure, friction, and other nonlinear factors are studied. Afterward to reach precise position tracking and low steady error, sliding mode control is proposed. In this way, measurement of pressures and other states of system is required. To reduce the cost of using pressure sensor, observation of pressure with nonlinear high gain observer is suggested. It was seen that the new proposed approach solved the observability problem of servo pneumatic systems. Pressure signal of each sides of cylinder are observed simultaneously by measurement of piston position. Finally, stability of designed controller is studied in the presence of observed states. Experimental results validate the advantage of using designed controller-observer instead of conventional proportional–integral–derivative controller with different input signals in the presence of high friction actuator. [ABSTRACT FROM AUTHOR]

Pneumatic soft actuator is a crucial component of soft robot. This paper proposes several pneumatic control schemes implemented with proportional and PWM-solenoid valves to achieve optimal control for pneumatic soft actuators adapted to different soft robots, such as soft gripper and soft humanoid hand. The schemes include: proportional valve; 3/2-way PWM-solenoid valve; 2/2-way PWM-solenoid valve. The control framework of these schemes contains human–machine interface in upper computer and control algorithm in lower computer. Sinusoidal and multi-step signals are served as reference input to draw a comparison of pressure tracking precision, steady-state accuracy and responsibility of these proposed schemes. The experimental results show that the scheme of proportional valve is more excellent than those of the PWM-solenoid valves, and the scheme of 3/2-way is superior to that of 2/2-way with regard to PWM-solenoid valve. Considering the cost, the scheme of 3/2-way PWM-solenoid valve is the most suitable choice for the system with multi-channel soft actuators. Therefore, the research achievement of this paper is providing a valuable suggestion on balancing the performance and cost for different soft robotic system applications. [ABSTRACT FROM AUTHOR]

This paper presents a control-oriented LPV (Linear Parameter-Varying) model for commercial vehicle air brake systems, where a pneumatic valve actuator is used to control the brake chamber pressure. To improve the brake system response time and reduce the vehicle stopping distance, the traditional treadle valves used in the air brake system are replaced by electro-pneumatic valves. Also, to develop the model-based brake control strategy, a nonlinear mathematical model is developed based on Newton’s second law, fluid dynamics of the orifice, force balance of spool, and solenoid dynamic characteristics. The brake chamber dynamics is also considered during the charging and discharging processes. The developed nonlinear model is calibrated based on both valve actuator geometry and test bench experimental results. It is proposed to model the nonlinear system in the LPV form so that gain-scheduling controllers can be developed. To obtain the LPV model, system identification is conducted using the calibrated nonlinear model to obtain a set of linearized models under different brake chamber pressure levels, and the resulting identified linear models are assembled to form the LPV model with brake chamber pressure as the varying parameters. A linear infinite-horizon continuous-time LQR (Linear Quadratic Regulator) controller was designed for the braking system based on the developed LPV model with the fixed parameter to demonstrate the effectiveness of the developed LPV model.