Flexible Valve Research Articles

Millimeter-scale soft capsules for sampling liquids in fluid-filled confined spaces.

Sampling liquids in small and confined spaces to retrieve chemicals and microbiomes could enable minimally invasive monitoring human physiological conditions for understanding disease development and allowing early screening. However, existing tools are either invasive or too large for sampling liquids in tortuous and narrow spaces. Here we report a fundamental liquid sampling mechanism that enables millimeter-scale soft capsules for sampling liquids in confined spaces. The miniature capsule is enabled by flexible magnetic valves and superabsorbent polymer, fully wirelessly controlled for on-demand fluid sampling. A group of miniature capsules could navigate in fluid-filled and confined spaces safely using a rolling locomotion. The integration of on-demand triggering, sampling, and sealing mechanism and the agile group locomotion allows us to demonstrate precise control of the soft capsules, navigating and sampling body fluids in a phantom and animal organ ex vivo, guided by ultrasound and x-ray medical imaging. The proposed mechanism and wirelessly controlled devices spur the next-generation technologies for minimally invasive disease diagnosis.

Wirelessly Actuated Microfluidic Pump and Valve for Controlled Liquid Delivery in Dental Implants.

Enabling minimally invasive and precise control of liquid release in dental implants is crucial for therapeutic functions such as delivering antibiotics to prevent biofilm formation, infusing stem cells to promote osseointegration, and administering other biomedicines. However, achieving controllable liquid cargo release in dental implants remains challenging due to the lack of wireless and miniaturized fluidic control mechanisms. Here wireless miniature pumps and valves that allow remote activation of liquid cargo delivery in dental implants, actuated and controlled by external magnetic fields (<65 mT), are reported. A magnet-screw mechanism in a fluidic channel to function as a piston pump, alongside a flexible magnetic valve designed to open and close the fluidic channel, is proposed. The mechanisms are showcased by storing and releasing of liquid up to 52µL in a dental implant. The liquid cargos are delivered directly to the implant-bone interface, a region traditionally difficult to access. On-demand liquid delivery is further showed by a metal implant inside both dental phantoms and porcine jawbones. The mechanisms are promising for controllable liquid release after implant placement with minimal invasion, paving the way for implantable devices that enable long-term and targeted delivery of therapeutic agents in various bioengineering applications.

Gas exchange optimization in aircraft engines using sustainable aviation fuel: A design of experiment and genetic algorithm approach

The poppet valves two-stroke (PV2S) aircraft engine fueled with sustainable aviation fuel is a promising option for general aviation and unmanned aerial vehicle propulsion due to its high power-to-weight ratio, uniform torque output, and flexible valve timings. However, its high-altitude gas exchange performance remains unexplored, presenting new opportunities for optimization through artificial intelligence (AI) technology. This study uses validated 1D + 3D models to evaluate the high-altitude gas exchange performance of PV2S aircraft engines. The valve timings of the PV2S engine exhibit considerable flexibility, thus the Latin hypercube design of experiments (DoE) methodology is employed to fit a response surface model. A genetic algorithm (GA) is applied to iteratively optimize valve timings for varying altitudes. The optimization process reveals that increasing the intake duration while decreasing the exhaust duration and valve overlap angles can significantly enhance high-altitude gas exchange performance. The optimal valve overlap angle emerged as 93 °CA at sea level and 82 °CA at 4000 m altitude. The effects of operating parameters, including engine speed, load, and exhaust back pressure, on the gas exchange process at varying altitudes are further investigated. The higher engine speed increases trapping efficiency but decreases the delivery ratio and charging efficiency at various altitudes. This effect is especially pronounced at elevated altitudes. The increase in exhaust back pressure will significantly reduce the delivery ratio and increase the trapping efficiency. This study demonstrates that integrating DoE with AI algorithms can enhance the high-altitude performance of aircraft engines, serving as a valuable reference for further optimization efforts.

The development of direct 3-dimensional printing of patient-specific mitral valve in soft material for simulation and procedural planning

ObjectivesReplicating 3-dimensional prints of patient-specific mitral valves in soft materials is a cumbersome and time-consuming process. The aim of this study was to develop a method for a direct 3-dimensional printing of patient-specific mitral valves in soft material for simulation-based training and procedural planning. MethodsA process was developed based on data acquisition using 3-dimensional transesophageal echocardiography Cartesian Digital Imaging and Communication of Medicine format, image processing using software (Vesalius3D, Blender, Meshlab, Atum3D Operation Station), and 3-dimensional printing using digital light processing, an additive manufacturing process based on photopolymer resins. Experiments involved adjustment of 3 variables: curing times, model thinness, and lattice structuring during the printing process. Printed models were evaluated for suitability in physical simulation by an experienced mitral valve surgeon. ResultsDirect 3-dimensional printing of a patient's mitral valve in soft material was completed within a range of 1.5 to 4.5 hours. Prints with postcuring times of 5, 7, 10, and 15 minutes resulted in increased stiffness. The mitral valves with 2.0-mm and 2.4-mm thinner leaflets felt more flexible without tear of the sutures through the material. The addition of lattice structures made the prints more compliant and better supported suturing. ConclusionsDirect 3-dimensional printing of a realistic and flexible patient-specific mitral valve was achieved within a few hours. A combination of thinner leaflets, reduced curing time, and lattice structures enabled the creation of a realistic patient-specific mitral valve in soft material for physical simulation.

Environmental test and evaluation technology of control and protection device for flexible DC converter valve

Environmental suitability is particularly important for the safe and reliable operation of the product. The environmental test and evaluation method are studied to target the reliability requirements for the control and protection device of the flexible DC converter valve. According to the characteristics of the secondary board card of the control and protection device, a study is carried out on the mechanism of salt spray corrosion, and specific methods for implementing and evaluating the salt spray test are proposed. Using this method, a salt spray test is conducted on a secondary board card of a relay control and protection device under the finalization of the design. The test results show that this method can effectively reveal the salt spray corrosion weakness of the product. Besides, salt spray test results are also evaluated according to the corrosion conditions of the product after the test. The application of environmental test and evaluation technology of the control and protection device of the flexible DC converter valve has a significant meaning in improving the reliability of relevant products.

Fault Diagnosis Method of Flexible Converter Valve Equipment Based on Ensemble Empirical Mode Decomposition and Temporal Convolutional Networks

The flexible converter valve is a crucial component of the flexible transmission system, and its proper functioning is directly related to the power system's reliability. This study proposes a method for diagnosing faults in flexible converter valve equipment based on ensemble empirical mode decomposition and temporal convolutional networks. The method involves measuring voltage signal data in the power submodule of the flexible converter valve, decomposing and reconstructing the voltage signal using ensemble empirical mode decomposition to extract frequency variation patterns and fault features. Subsequently, a temporal convolutional network is introduced, and a device fault diagnosis model is constructed by learning the evolution law of voltage signals in time series. The experimental results demonstrate that the proposed method has high fault diagnosis accuracy and robustness with an average F1-score of 89.58% and an average area under the curve (AUC) of 94.38%, which are higher than other methods by at least 1.39% and 1.03%.

A fault diagnosis method for flexible converter valve equipment based on DSC-BIGRU-MA

Introduction: Precise fault diagnosis is crucial for enhancing the reliability and lifespan of the flexible converter valve equipment. To address this issue, depthwise separable convolution, bidirectional gate recurrent unit, and multi-head attention module (DSC-BiGRU-MAM) based fault diagnosis approach is proposed.Methods: By DSC and BiGRU operation, the model can capture the correlation between local features and temporal information when processing sequence data, thereby enhancing the representation ability and predictive performance of the model for complex sequential data. In addition, by incorporating a multi-head attention module, the proposed method dynamically learns important information from different time intervals and channels. The proposed MAM continuously stimulates fault features in both time and channel dimensions during training, while suppressing fault independent expressions. As a result, it has made an important contribution to improving the performance of the fault diagnosis model.Results and Discussion: Experimental results demonstrate that the proposed method achieves higher accuracy compared to existing methods, with an average accuracy of 95.45%, average precision of 88.67%, and average recall of 89.03%. Additionally, the proposed method has a moderate number of model parameters (17,626) and training time (935 s). Results indicate that the proposed method accurately diagnoses faults in flexible converter valve equipment, especially in real-world situations with noise overlapping signals.

A Novel Piezoelectric Energy Harvester for Earcanal Dynamic Motion Exploitation Using a Bistable Resonator Cycled by Coupled Hydraulic Valves Made of Collapsed Flexible Tubes.

Scavenging energy from the earcanal's dynamic motion during jaw movements may be a practical way to enhance the battery autonomy of hearing aids. The main challenge is optimizing the amount of energy extracted while working with soft human tissues and the earcanal's restricted volume. This paper proposes a new energy harvester concept: a liquid-filled earplug which transfers energy outside the earcanal to a generator. The latter is composed of a hydraulic amplifier, two hydraulic cylinders that actuate a bistable resonator to raise the source frequency while driving an amplified piezoelectric transducer to generate electricity. The cycling of the resonator is achieved using two innovative flexible hydraulic valves based on the buckling of flexible tubes. A multiphysics-coupled model is established to determine the system operation requirements and to evaluate its theoretical performances. This model exhibits a theoretical energy conversion efficiency of 85%. The electromechanical performance of the resonator coupled to the piezoelectric transducer and the hydraulic behavior of the valves are experimentally investigated. The global model was updated using the experimental data to improve its predictability toward further optimization of the design. Moreover, the energy losses are identified to enhance the entire proposed design and improve the experimental energy conversion efficiency to 26%.

Iterative Learning for Laboratory Electro-Hydraulic Fully Flexible Valve Actuation System Transient Control

&lt;div&gt;Fully flexible valve actuation (FFVA) is a key enabling technology of internal engine combustion research and development. Two laboratory electro-hydraulic FFVA systems have been developed and implemented in R&amp;amp;D test cells. These FFVA systems were designed using repetitive control (RC), which is based on internal model principle (IMP), for constant engine speed operation. With the engine operating in a steady-state condition, the valve profile input is periodic. This can be accommodated by a repetitive controller, which provides the function of flexible control to step changes in valve lift, valve opening duration, and cam phase angle position.&lt;/div&gt; &lt;div&gt;During engine speed transients, as the valve reference trajectory becomes aperiodic in the time domain, the controllers based on the linear time invariant (LTI) IMP, such as RC, are no longer applicable. Engine speed transient control is a desired function to engine research and other similar applications, such as motor control. Several investigations are reported with limited results because of the assumption of IMP and periodic input.&lt;/div&gt; &lt;div&gt;This article presents the control design and verification of the iterative learning control (ILC) algorithm for the laboratory electro-hydraulic FFVA system. This algorithm tracks valve lift profiles under steady-state and transient operation. A dynamic model of the plant was obtained from experimental data to design and verify the effectiveness and robustness of this approach. The simple structure of the ILC in implementation and low cost in computation are crucial benefits to recommend the ILC. It is not an IMP-based approach, and its structure does not depend on the system input. Therefore, it has higher robustness to perturbation and modeling errors than other control methods for repetitive valve lift profile tracking tasks.&lt;/div&gt;

A Topology and Control Method for Operational Testing of ±800 kV/8 GW Flexible DC Transmission Modular Multilevel Converter Valve

A Topology and Control Method for Operational Testing of ±800 kV/8 GW Flexible DC Transmission Modular Multilevel Converter Valve

A Deep Learning-Based Fault Diagnosis Method for Flexible Converter Valve Equipment

A Deep Learning-Based Fault Diagnosis Method for Flexible Converter Valve Equipment

Flow Analysis and Structural Optimization of Double-Chamber Parallel Flexible Valve Micropumps

In the current study, a two-dimensional numerical study is carried out to investigate the performance of a novel Double-Chamber Parallel Flexible Valve micropump, which utilized the electrowetting-on-dielectrics (EWOD) effect to drive the microfluid flow. By observing the flow fields, the internal circulations are seen on both the left and right sides of the pump. The generation of the backflow is discussed as well by tracking the movement of the vortices. Only slight flow fluctuations are seen in the micropump. Based on the simulation results, the structural parameters including the width of the inlet and the outlet, the width of the pumping channel and the diverging angle in the micropump are analyzed, and the influence of these parameters on the pumping volume and the maximum pressure are discussed. Eventually, a group of optimal parameter combinations is given according to the simulation results to extend the operating potential of the micropump.

Refined Modeling and Dynamic Characteristics of Self-excited Vibration in the Main Inlet Valve of Pumped Storage Power Stations

Self-excited vibration of the main inlet valve poses a great threat to the safe operation of the pumped storage power system, thereby making an indirect hazardous effect on the frequency stability of the power grid. In order to avoid self-excited vibration, this paper focuses on the refined modeling and dynamic characteristics of self-excited vibration. Firstly, the flexible valve model is introduced and the refined pumped storage power system modeling considering self-excited vibration is established. The constructed model is then validated by comparing it with field data in the frequency domain. Secondly, the sensitivity of self-excited vibration to system parameters is investigated by using the modified Morris method. Once the sensitive parameters are found, the effect law of these parameters on the dynamic characteristics of self-excited vibration is studied in depth. Finally, engineering advice is proposed. The result indicates that the self-excited vibration is most sensitive to the length of the diversion pipe, valve clearance of the main inlet valve, and water hammer velocity. Moreover, it is verified by simulation that shorter upstream pipe length, lower water hammer velocity and smaller valve clearance help to restrain the amplitude and deterioration rate of self-excited vibration.

Analysis of the Seismic Performance of ±500 kV Flexible DC Converter Valves

The converter valve is the core equipment of flexible DC transmission, but it has been severely damaged in previous earthquakes. Therefore, the seismic performance of its structure has a significant impact on the safety and reliability of power transmission. To study the seismic performance of ±500 kV flexible DC converter valves and identify weak links in the supporting valve tower, this article first established a refined finite-element model of a valve tower based on its physical structure; then modal analysis on the valve tower was conducted; finally, time-domain analysis of the valve tower under three seismic excitations, namely Wenchuan, EI Centro, and artificial, was conducted, and the equivalent stress and directional displacement cloud maps of the key parts of the valve tower were obtained. The research results indicate that the dynamic characteristics of the valve tower are relatively complex, with low fundamental frequency and diverse natural vibration modes. Under earthquake action, the predominant frequency of EI Centro waves is close to the fundamental frequency of the valve tower, which is prone to resonance and causes significant damage to the valve structure. The improved design of the valve tower meets the seismic strength requirements of level 8 seismic intensity.

Mechanical Behavior of Crimping Composite Post Insulator: Experimental and Simulation Study

The composite post insulator composed of a large diameter mandrel and flange pressed by a one-time integral pultrusion has high strength and good toughness and is widely used in the existing flexible converter valve. For constructing the finite element model of the crimped post insulator, most of the flange surface and the mandrel surface are directly connected, making the simulation model’s stiffness deviate from the actual model and the model distortion. Based on this, this study proposes a new finite element simplified model of crimped composite post insulator based on multi-point constraints (MPC), which accurately simulates the crimping area of mandrel and flange in engineering practice. It verifies the model’s reliability through static tests and characteristic vibration tests. The results show that the difference between the finite element simulation and the test results is within 5%. The finite element modeling method based on MPC local constraints is very reliable in applying crimped composite post insulators. Based on the proposed model, the influence of flange height and thickness on the mechanical properties of composite post insulators is further explored. The results show that the influence of flange height on mechanical properties can be ignored when the height of the insulator stiffener (non-press common area) is constant. Within the allowable thickness range of the flange crimping process, the increase in flange thickness will significantly reduce the maximum bending stress of the insulator and increase its safety margin. It provides a good design idea for the design of crimping composite insulators.

Loss analysis of a novel compound electromagnetic linear actuator under different operating modes and working conditions

As an important actuator component, the electromagnetic linear actuator has a significant impact on the performance of fully flexible variable valve trains. Aiming at the shortcomings of the conventional moving coil electromagnetic linear actuator (MCELA) with low force density and insufficient end-passive self-holding ability, a novel compound electromagnetic linear actuator (CELA) integrating the advantages of MCELA and the moving iron electromagnetic linear actuator (MIELA) was proposed in this work. The CELA has two operating modes, including single drive mode and cooperative drive mode, and its loss variation is different from that of the single MCELA or MIELA. Firstly, the current and displacement curves under different operating modes were obtained through experiments, which were then used as the excitation source to quantitatively analyze the copper and iron losses under different working conditions by means of 3D finite element simulation. The loss distribution and ratio of CELA under typical operating conditions were discussed in detail. The effects of stroke and valve opening duration on CELA losses were analyzed. The results show that there are significant differences in the loss variation rules between the two operating modes, the losses increase as the working stroke increases in single drive mode. In the cooperative drive mode, the losses are much greater than in the single drive mode, with the losses decreasing in the initial stage and then increasing as the stroke increases. None of the valve opening durations had a significant effect on losses. This study provides a reference for loss studies of other novel electromagnetic linear actuators.

Flexible and Efficient Control Blocks

Korean off-highway manufacturer Hyundai Construction Equipment is standardising the working hydraulics of wheel loaders, excavators and forklifts with the help of Bosch Rexroth’s flexible RS valve platform

Added value of thermodynamic white-box data for HCCI combustion prediction

Homogeneous charge compression ignition (HCCI) is a promising combustion process to reducing both greenhouse gas and pollutant emissions in the transportation sector. The combustion starts when the thermodynamic state of the cylinder charge reaches the auto-ignition properties of the fuel, which is challenging to model. In addition, the strong cyclic coupling due to required exhaust gas recirculation leads to a significant dependence on the combustion of the previous cycle.This work focuses on identifying accurate models to predict the combustion process for potential use in an MPC. In this work HCCI is achieved using negative valve overlap (NVO) on a fully flexible valve train. The fluctuating composition and temperature of the cylinder charge is not directly measurable and not taken into account in state of the art approaches. It is assumed that it has a decisive influence on the start of combustion. Hence, in this work, the thermodynamic state is modeled by a detailed physical white-box model, which is used as an additional input for the combustion prediction. To investigate the added value of the thermodynamic state data, an Artificial neural network (ANN) is trained to predict combustion both with and without the thermodynamic state data from the white-box model. The root-mean-square error of the ANN including thermodynamic data is reduced by 12.7%. Thus, by adding the thermodynamic white-box data, the HCCI combustion prediction can be significantly improved.

Design and analysis of Double-cavity micropump of flexible valve

Piezoelectric micropump and surface tension micropump are generally favored in industrial applications, but these two micropumps have obvious defects through industrial practice. Due to the presence of a piezoelectric oscillator, it is difficult to reduce the volume by optimization further, and the oscillator will be damaged to a certain extent after use for a long time. Based on electric wetting on dielectric (EWOD), a new, efficient EWOD-driven flexible valve micropump is designed using EWOD and flexible valves to replace the conical tube, and a dual microchannel structure is proposed to reduce flow fluctuations at the outlet. The working principle of the EWOD flexible valve micro-pump is deeply discussed. The micropump design is optimized by the finite element method, and its performance is analyzed. The numerical analysis results show that: (1) When the flexible valve structure is adopted, the micropump outlet flow increases significantly. (2) When using the double microchannel, the outlet flow fluctuation of the micropump is significantly reduced. (3) Using the structure of the double microchannel, the micropump has two internal rings, and the direction of the inner ring is related to the direction of the vibration droplet. The EWOD micropump structure is designed to solve the reflux phenomenon in the current micropump pumping process

Piezoelectric pump with flexible venous valves for active cell transmission

Piezoelectric pump with flexible venous valves for active cell transmission