•A digital twin-based scheme for EP valve degradation prediction is proposed.•A high-fidelity digital twin model with parameter-updating ability is developed for degradation status assessment.•A ...novel degradation model with adaptive forgetting factors is developed to improve the prediction performance.•Accelerated degradation tests and offline brake tests are conducted to validate the effectiveness of the proposed methodology.
The train electro-pneumatic (EP) valve is a crucial driving component in the electronically-controlled pneumatic (ECP) brake system and directly affects the reliability of brake equipment. The degradation prediction of the EP valve can help to ensure the safe and reliable operation of the ECP brake system and enable predictive maintenance-based decision-making. Yet, degradation prediction of the EP valve faces several challenges such as insufficient fault data and complex physics. This paper proposes a degradation prediction scheme based on a high-fidelity digital twin (DT) model with parameter-updating ability, consisting of the EP valve model and the degradation model of the direct-current resistance (DCR). The electromagnetic part and the pneumatic part were constructed to accurately simulate the dynamic response of the EP valve. Moreover, a novel degradation model with adaptive forgetting factors is developed to regularly update the EP valve model. This approach can improve prediction accuracy and continuously track the latest degradation trend through the information interaction between virtual simulations and actual experiments. The effectiveness of the proposed scheme was demonstrated in a case study through the accelerated degradation tests and brake test-rig experiments.
In manufacturing automation, there is a strong need for highly integrated intelligent components and subsystems. In this context, a novel two-stage pneumatic piezoelectric-actuated valve has recently ...been developed. It covers a wide range of pneumatic products and functions in one compact component and enables flexible and adaptive plant operation. The valve consists of four poppet main-stage valves that are driven by piezoelectrically actuated pre-stage valves and includes pressure sensors as well as a powerful computational unit. This work presents the systematic development of a model-based position control algorithm including modeling, identification, and controller design. The control concept comprises a hysteresis compensation based on the Prandtl–Ishlinskii operator theory, a flatness-based feedforward controller, and a PI feedback controller with appropriate anti-windup measures. Measurement results from a test bench demonstrate the performance of the proposed concept.
•The paper analyzes the flapper-nozzle type pneumatic valve with two ports in the frequency domain.•The valve is a part of the pneumatically driven parallel robot platform.•The system is observed as ...a parallel connection between the fixed orifice, the nozzle and the chamber.•The describing function is reduced to the unit gain and does not depend on the amplitude of the input signal.•The system becomes linear and is described only by means of the frequency response.
This paper addresses the mass flow rate characteristic of a pneumatic valve set in the frequency domain. The valve set consists of a flapper-nozzle type valve and a constant isothermal volume chamber. It represents a part of the control system of the pneumatic parallel robot platform. Different flow regimes are analyzed because of air compressibility. The nonlinearity originating from the mass flow rate characteristic is approximated by the sinusoidal input describing function. Analytical determination of the describing function in a general case is not possible. However, the equivalent nonlinearity and the corresponding Hammerstein model can be introduced for a certain flow regime. In that case, the describing function of nonlinearity can be determined analytically. Amplitude and frequency responses show that the nonlinearity becomes more prominent at smaller frequencies and higher amplitudes of the exogenous signal. Analytical results show good agreement with the experimental results.
Assays toward single‐cell analysis have attracted the attention in biological and biomedical researches to reveal cellular mechanisms as well as heterogeneity. Yet nowadays microfluidic devices for ...single‐cell analysis have several drawbacks: some would cause cell damage due to the hydraulic forces directly acting on cells, while others could not implement biological assays since they could not immobilize cells while manipulating the reagents at the same time. In this work, we presented a two‐layer pneumatic valve‐based platform to implement cell immobilization and treatment on‐chip simultaneously, and cells after treatment could be collected non‐destructively for further analysis. Target cells could be encapsulated in sodium alginate droplets which solidified into hydrogel when reacted with Ca2+. The size of hydrogel beads could be precisely controlled by modulating flow rates of continuous/disperse phases. While regulating fluid resistance between the main channel and passages by the integrated pneumatic valves, on‐chip capture and release of hydrogel beads was implemented. As a proof of concept for on‐chip single‐cell treatments, we showed cellular live/dead staining based on our devices. This method would have potential in single cell manipulation for biochemical cellular assays.
Typically, the actual volume of the residual limb changes over time. This causes the prosthesis to not fit, and then pain and skin disease. In this study, a prosthetic socket was developed to ...compensate for the volume change of the residual limb. Using an inflatable air bladder, the proposed socket monitors the pressure in the socket and keeps the pressure distribution uniform and constant while walking. The socket has three air bladders on anterior and posterior tibia areas, a latching type 3-way pneumatic valve and a portable control device. In the paper, the mechanical properties of the air bladder were investigated, and the electromagnetic analysis was performed to design the pneumatic valve. The controller is based on a hysteresis control algorithm with a closed loop, which keeps the pressure in the socket close to the initial set point over a long period of time. In experiments, the proposed prosthesis was tested through the gait simulator that can imitate a human's gait cycle. The active volume compensation of the socket was successfully verified during repetitive gait cycle using the weight loads of 50, 70, and 90 kg and the residual limb model with a variety of volumes. It was confirmed that the pressure of the residual limb recovered to the initial state through the active control. The pressure inside the socket had a steady state error of less than 0.75% even if the volume of the residual limb was changed from -7% to +7%.
This paper deals with the compensation of nonlinearities in dynamical systems using Nonlinear polynomial AutoRegressive models with eXogenous inputs (NARX) identified from data. The compensation ...approach is formulated for static and dynamical contexts for the general case and is also adapted for systems with hysteresis. Both simulated and experimental results are presented to illustrate the method. In the experimental case, the proposed method is compared to other approaches and was found to be competitive. This method yielded a maximum tracking error of
3.9
%
while the corresponding value for the uncompensated system was
21.0
%
. Furthermore, the presented technique typically results in compensation signals with lower energy requirements. The results also show that the proposed methodology can provide compensation signals that practically linearize the systems using simple nonlinear models with very few terms.
Pneumatic cylinders have advantages of light weight, low heat generation, and low cost, making them potentially suit- able for coarse motion stages in large positioning systems. However, the ...high-precision and high-speed positioning with the pneumatic driving system has many challenges. One challenge is the dead zone, which is one of the nonlinear characteristics. The conventional dead zone compensation method using the inverse model of the valve cannot cope with the dead zone variation caused by temperature and pressure fluctuation. Furthermore, the effect of nonlinearity is strong at small flow rates near the dead zone, making flow control difficult. To solve these problems, we proposed a twin-drive system using two valves, which can control the sum and difference of mass flow rates (total flow rate and leakage). By setting the leakage of the mass flow rate, the system can be driven at an operating point with high linearity, which enables precise flow control. The interference between the two valves was decoupled by the Hadamard matrix. The experimental results show that the mass flow rate difference follows the reference value without being affected by the dead zone compared to the conventional method.
The pneumatic seat suspension is one of the most important, and in some situations, one of the key components of the vibration protection system for the human operator of the vehicle. At the present ...stage of scientific and technical activities of most developers, great emphasis is placed on controlled seat suspension systems, as the most promising systems. This article analyzes the methods of controlling the elastic damping characteristics of the air suspension of a vehicle seat. Ten different and fairly well-known methods of changing the shape and parameters of elastic damping characteristics due to electro-pneumatic valves, throttles, motors, additional cavities, auxiliary mechanisms and other actuators were considered, the advantages, application limits and disadvantages of each method were analyzed. Based on the results of the performed analytical procedure, as well as the recommendations known in the scientific and technical literature on improving the vibration-protective properties of suspension systems, the authors proposed and developed a new method for controlling the elastic-damping characteristic, which is implemented in the proposed technical solution for the air suspension of a vehicle seat. The method differs in the thing that it implements a cyclic controlled exchange of the working fluid between the cavities of the pneumatic elastic element and the additional volume of the receiver on the compression and rebound strokes, forming an almost symmetric elastic damping characteristic, and partial recuperation of vibrational energy by a pneumatic drive, presented in the form of a rotary type pneumatic motor. In addition, the method does not require an unregulated hydraulic shock absorber, while still having the advantage of improved vibration-proof properties of the air suspension of a vehicle seat over a wide range of operating influences.
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