Pneumatic Pressure Control Research Articles

Development and validation of a novel system that combines a new masticatory simulator and analysis method for modeling the human gummy candy masticatory process.

During mastication, food undergoes state and texture changes influenced by various mechanical properties, including compression and fracturing of the molar teeth, mixing with saliva, and oral temperature. Prior studies have explored mastication simulators, however, no studies have assessed the forces and duration applied to the molars by the food during bolus formation. In this study, we developed a novel system that integrates a masticatory simulator and analysis method to evaluate mechanical properties. We developed ORAL-MAPS which is equipped with 6-axis force sensor, pneumatic pressure control mechanism, vertical movement, molar-like module, artificial saliva injection unit, and temperature control apparatus. A gap exists between the upper and lower unit at the closest point, allowing the sensor to measure vertical upward force and duration from food, while compressed air provides constant downward pressure. We hypothesized a correlation between the total integrated muscle activity ratio obtained from the human masseter muscle electromyography (iEMG). We compared the normalized impulse obtained from ORAL-MAPS with the normalized total iEMG obtained from human studies with four different types of gummy candies. As a result, the normalized total impulse of gummy candies A, B, C, and D were 1.00 ± 0.00, 1.29 ± 0.06, 0.95 ± 0.00, and 0.39 ± 0.0, respectively. The normalized total iEMG of the same gummy candies were 1.00 ± 0.00, 1.23 ± 0.15, 0.98 ± 0.09, and 0.45 ± 0.07, respectively. Thus, no significant difference was observed between the normalized total impulse obtained in vitro and the normalized total iEMG values for masticating the gummy candies B, C, and D (p > .05).

METHOD DEVELOPMENT AND VALIDATION OF DIMETHYL SULPHATE CONTENT IN ESOMEPRAZOLE MAGNESIUM DRUG SUBSTANCE BY GC-MS

Dimethyl sulfate is universally used as an alkylating, sulfating and sulfonating agent in organic synthesis; hence it is one of the probable impurities during the synthesis of the esomeprazole magnesium. As per ICH M7, it is genotoxic and mutagenic, so it needs to be controlled as per the acceptable intake of dimethyl sulfate and daily sample dosage. This method validation can be achieved by the hyphenated technique of gas chromatography with mass spectroscopy, which is used to develop the dimethyl sulfate impurity in esomeprazole magnesium drug substance containing salt. The method is achieved with a DB-1 column with electron impact ionization source in sim mode ion under electronic pneumatic pressure control and deliberate oven ramp programming temperature was used. A dissolved, extracted and auto-injection sample was implemented for sample introduction in a splitless mode. Dichloromethane and 2N NaOH was used as a diluent. The calibration curve showed good linearity over the 1.69 to 8.40 ppm (limit: 5.56 ppm) and its correlation coefficient was >0.999. A limit of detection 0.50 ppm and limit of quantitation 1.69 ppm was achieved when the samples were prepared at 50 mg/mL. While recovery proved to be 106.8 to 113.5%, hence it signified the matrix effect.

Pneumatic pressure control based on improved NMPC and its application to aeroengine surge simulation

In the semi-physical simulation of aeroengines, using the pneumatic pressure servo control technology to provide realistic pneumatic excitation to the sensors and electronic controller can improve the confidence of the simulation and reduce the test cost and risk. However, the existing methods could not satisfy the precise simulation of large-amplitude and high-frequency pulsating pressure during aeroengine surge. In this paper, a pneumatic pressure control system with asymmetric groups of the High-Speed on–off Valve (HSV) is designed, and an Improved Nonlinear Model Predictive Control (INMPC) method is proposed. First, the volumetric flow characteristics of HSV are tested and analyzed with Pulse Width Modulation (PWM) signal input. Then, a simplified HSV model with the volume flow characteristic correction is developed. Based on these, an integrated model for the whole system is further established and used as the prediction model in INMPC. To improve the computational speed of the rolling optimization process, the mapping scheme from control signal to PWM duty cycle of HSVs and the objective function with exterior penalty function are designed. Finally, the random step, sinusoidal and real engine surge data are set as the reference pressure in multiple comparative experiments to verify the effectiveness of the pressure tracking system.

Design and experiment of the pneumatic pressure control device for no-till planter

Design and experiment of the pneumatic pressure control device for no-till planter

Pneumatic Pressure Control Using on‐off Valves with Pulse Width Modulation

AbstractServomotor‐controlled valves are widely used in industry for pressure control of pneumatic systems. However, as a first stage, they can cause significant hysteresis that can result in loss of pressure or flow control accuracy at the second stage level. To reduce this effect and improve accuracy, a possible solution relies on the use of on‐off switching valves controlled by Pulse Width Modulation (PWM). This approach is studied, firstly by analytically determining how the PWM parameters have to be tuned according to the on‐off valve characteristics, secondly by ensuring that these characteristics provide the desired behavior of the system, and finally by experimentally verifying whether the PWM control can successfully reduce hysteresis, without decreasing the application range.

A More Precise Modeling Method for Pneumatic Cabin Pressure Control System considering the Ambient Environmental Impacts

Pneumatic cabin pressure control system (PCPCS), with its exceptional electromagnetic compatibility, is expected to become the major equipment on a high-performance airplane again in the future. Although the PCPCS has been mature for a long time, the broad popularization of the digital cabin pressure control system (DCPCS) has left the PCPCS in the cold for decades. This makes the PCPCS unable to meet the severe cabin pressure regulation requirements of high-speed aircraft today. For this purpose, a more precise PCPCS modeling method is proposed. Through this method, the relation between different parts in the PCPCS can be accurately characterized. Moreover, the impact of the ambient environment on the PCPCS is taken into consideration. This method can be used to accurately analyze the PCPCS under maneuvering flight. And it also assists in the verification of the system improvements of dynamic performance in the future. Simulation results show that the aircraft acceleration disturbs the PCPCS slightly, and the cabin air inflow fluctuation has a significant impact on the cabin air pressure.

Pneumatic System Capable of Supplying Programmable Pressure States for Soft Robots

Pneumatic soft robots are of great interest in varieties of potential applications due to their unique capabilities compared with rigid structures. As a part of the soft robotic system, the pneumatic system plays a very important role as all motion performance is ultimately related to the pressure control in air chambers. With the increasing flexibility and complexity of robotic tasks, diverse pneumatic robots driven by positive, negative, or even hybrid pressure are developed, and this comes with higher requirements of pneumatic system and air pressure control precision. In this study, we aim to propose a simplified pneumatic design capable of generating programmable pressure states ranging from negative to positive pressure in each air branch. Based on the design concept and system configuration, special inflation and deflation strategies and closed-loop feedback control strategy are proposed to achieve precise pressure control. Then, a prototype of the pneumatic system with six independent air supply branches is designed and fabricated. Experimental results show that the pneumatic system can achieve a wide range of pressure from -59 to 112 kPa. The speed of inflation and deflation is controllable. Finally, we demonstrate three robotic applications and design the related algorithms to verify the feasibility and practicability of the pneumatic system. Our proposed pneumatic design can satisfy the pressure control requirements of a variety of soft robots driven by both positive and negative pressure. It can be used as a universal pneumatic platform, which is inspiring for actuation and control in the soft robotic field.

Development of a Soft Pneumatic Actuator System Based on Flexible Force Sensor for Lower Limb Compression Therapy

The use of a soft pneumatic actuator (SPA) in compression therapy to enhance blood circulation shows potential because of its unique proactive bio-mechanical force delivery mode and wide range of pneumatic pressure control. This work presented new insights into the model-experiment method using mathematical simulation and flexible force sensor array (FFSA) to explore the bio-mechanical force delivery mechanism of a newly developed SPA and offer accurate pressure for lower limb compression therapy. Multichambered bladders were incorporated in the SPA system as key components to exert pressure on the lower limb, and the FFSA visualized the skin pressure on a software interface. Pressure signals were transiently collected by differential sensors and FFSA using the data acquisition unit and then transmitted to a computer software via Bluetooth module to build the interface pressure feedback and control subsystem. According to the interface pressure variation, the SPA system could automatically adjust the air pressure in bladders to generate suitable bio-mechanical force for compression therapy. Results revealed that the sensors-based SPA system could generate rhythmic (intermittent) bio-mechanical force, which could be transformed by FFSA and visualized in a morphological interface pressure mapping from quantitative and qualitative perspectives. This study provided an evidence-based technical guidance for a new SPA system design which could delivered controllable and precise dynamic pressure to affect the lower limb during compression therapy.

A programmable and self-adaptive dynamic pressure delivery and feedback system for efficient intermittent pneumatic compression therapy

Controlled dynamic pressure delivery is essential for efficiently promoting hemodynamics of the lower extremities in pneumatic compression therapy. Pressure dosage control is challenging because of diverse influencing factors, such as irregular interface contact geometries, different stiffnesses of body tissues and pressure materials, and customized pressure recipes and individual patient demands. To address these challenges, a programmable and self-adaptive dynamic pressure delivery and feedback system for enhanced compression therapy were developed in this study. This system comprised a soft pneumatic actuator (SPA) unit in a stocking laminated with multi-bladder, a programmable pressure control unit for pneumatic and interface pressure control, matrix soft sensors for real-time interface pressure detection, and differential pressure sensors for pneumatic pressure monitoring as well as connective accessories (air tubes and valves). A fluid–structure interaction model was developed to analyse the interaction between the bladder and lower limb by considering essential factors (bladder and soft tissue stiffness, contact area, and bladder-lower limb interface characteristics). An improved proportional–integral–derivative controller was designed to regulate dynamic interface pressure and personalized pneumatic compression treatment. Dedicated software was developed to monitor, process, and display the tested pressure data. In vitro and in vivo experiments were performed to validate the developed system. This study integrated theoretical and experimental approaches to a novel solution for customized dynamic pressure therapy. The findings enhanced our understanding of the working mechanisms and characteristics of the SPA–lower limb system. Moreover, the results serve as a foundation for the design and innovation of advanced programmable units for efficient compression treatment in various applications in healthcare, medicine, and rehabilitation.

A proposed soft pneumatic actuator control based on angle estimation from data-driven model.

This article proposes a bending angle controller for soft pneumatic actuators, which could be implemented in soft robotic rehabilitation gloves to assist patients with hand impairment, such as stroke survivors. A data-driven model is used to estimate the angle as pneumatic pressure is applied to the actuator. Furthermore, a finite element model was used to manually optimize the dimensions of the actuator. An embedded flex sensor, which together with a custom testing rig, was used to gather input data for the data-driven model. This rig contains a pneumatic pressure control circuit as well as a camera for image acquisition. Collected data were fed into a linear regression model to predict the data-driven model. Experiments were carried out to validate model's accuracy as well as modified proportional-integral-derivative controller angle controller performance. The latter controller is designed to mitigate the non-linear response of solenoid valves at different pressures of the actuator. The data-driven model along with the used controller allows more accurate estimation and quicker response.

Asymmetric Fuzzy Control of a Positive and Negative Pneumatic Pressure Servo System

The pneumatic pressure control systems have been used in some fields. However, the researches on pneumatic pressure control mainly focus on constant pressure regulation. Poor dynamic characteristics and strong nonlinearity of such systems limit its application in the field of pressure tracking control. In order to meet the demand of generating dynamic pressure signal in the application of the hardware-in-the-loop simulation of aerospace engineering, a positive and negative pneumatic pressure servo system is provided to implement dynamic adjustment of sealed chamber pressure. A mathematical model is established with simulation and experiment being implemented afterwards to discuss the characteristics of the system, which shows serious asymmetry in the process of charging and discharging. Based on the analysis of the system dynamics, a fuzzy proportional integral derivative (PID) controller with asymmetric fuzzy compensator is proposed. Different from conventional adjusting mechanisms employing the error and change in error of the controlled variable as input parameters, the current chamber pressure and charging or discharging state are chosen as inputs of the compensator, which improves adaptability. To verify the effectiveness and performance of the proposed controller, the comparison experiments tracking sinusoidal and square wave commands are conducted. Experimental results show that the proposed controller can obtain better dynamic performance and relatively consistent control performance across the scope of work (2–140 kPa). The research proposes a fuzzy control method to overcome asymmetry and enhance adaptability for the positive and negative pneumatic pressure servo system.

Guiding mechanism design and precision pressure control in composites filament winding system

During the composite winding process, pressure fluctuation will affect the density and homogeneity of the products and will make the interfacial strength disaccord with the fiber volume fraction. In order to improve the guiding precision and stability of the winding pressure, the bearing guide is replaced by the rolling guide in designing the pressure guiding mechanism, and parametric model of the guiding mechanism is established based on dynamics experiment of the joint surfaces. By analyzing the modal and harmonic response, the corresponding measures for improvement are proposed. Experimental results show that the designed guiding mechanism based on the rolling guide has high precision and perfect stability. Additionally, roundness error and installation error of the mandrel can cause the winding pressure to fluctuate and the gas compressibility, nonlinear flow, dead zone, cylinder friction, measurement noise and other nonlinear disturbances have significant impact on the pneumatic pressure control system. Considering the above circumstance, an adaptive fuzzy proportional–integral–derivative (PID) controller based on the grey prediction is proposed. By predicting the output pressure, trend of the pressure signal can be reflected accurately, which provides a reliable basis for the decision-making of the fuzzy PID controller. Simultaneously, two separate fuzzy inference systems are employed to adjust the step length of the predictive control and the scale factor of the step self-tuning algorithm. Simulation and experimental results show that the fuzzy PID controller based on grey prediction has shorter settling time, smaller overshoot and error, stronger robustness and interference immunity. The designed guiding mechanism and control algorithm have effectively improved the precision and stability of the pressure control system for the composite materials winding formation.

Design of a Pneumatic Flow Rate Control Microvalve Driven by a Stepper-Motor

A pneumatic microvalve which can be used in pneumatic pressure control for lab-on-a-chip applications is presented in this paper. In order to realize a feedback control and miniaturization, a micro stepper-motor is selected to control the opening of the microvalve. After introducing the structure and working principle of the pneumatic microvalve driven by a stepper-motor, the static flow rate simulation of pneumatic stepper-motor microvalve is processed in the condition of different opening sizes of the microvalve and pressure difference over the valve. The stepper-motor microvalve is fabricated and corresponding control circuit is designed. Experiments on static and dynamic characteristics of the microvalve are carried out. Good agreement has been shown between the simulation and experimental results.

WEARABLE HAPTIC DISPLAY FOR IMMERSIVE VIRTUAL ENVIRONMENT

Recently a number of immersive displays that project virtual environment on large-sized screens have been developed. In applications of virtual reality technology for such large immersiveenvironments, it is important to develop some haptic display that gives a real feedback sensation such as forceor tactile to users from the virtual environment. Especially, it is necessary to develop small, light and safety actuators for the wearable haptic display. In this paper, the haptic display system using pneumatics for theimmersive virtual environment is proposed and developed. The system consists of a tactile and a force reflecting type wearable haptic displays using pneumatic pressure control. Experiments for grasping virtual objects in the virtual environment are performed by the wearable haptic displays using pneumatic actuators. It is experimentally verified that the performance of the haptic display system is effective to touch and grasp the virtual objects.

A Study on Development of an Asymmetric Flow Control Pneumatic Valve

A new type of an asymmetric electro-pneumatic servo valve which is used as a hardware compensation of the system to make fast the response speeds is developed and studied. To develop a very high speed system, such as pneumatic force control system for a spot welding machine an asymmetric servo valve which downstream port width is two times of the upstream one is expected as a hardware direct compensation to compensate the system and to equalize the response speeds. The asymmetric electro-pneumatic newly designed servovalve was investigated here to provide asymmetric control flows as an important component in the pneumatic pressure control system for achieving high speed control. This paper describes the characteristics of this asymmetric valve, and we assured the effectiveness of this valve by the experiment.

力平衡型ノズルフラッパ式電空圧力変換器空気圧回路の特性解析 第二報 圧力流量特性の理論解析

This paper centers on the theoretical analyses of the pressure versus the flow characteristics of a force -balance nozzle-flapper type pneumatic pressure control proportional valve. The influence of the flow force and effective area of the diaphragm, regarding the pressure versus the flow characteristics, have be studied. Especially, the effects of the radii of the corner rounding of the disk and casing wall have been researched. It has been clarified that the main reason for a pressure decrease in the valve characteristics is due to the change in the effective diaphragm area according to the displacement of the supply valve, and that the flow force may have a slight effect on the characteristics at the time the valve setting pressure is low.

力平衡型ノズルフラッパ式電空圧力変換器空気圧回路の特性解析 第一報 ノズルフラッパ間隙対出力圧特性

Many kinds of nozzle-flapper type pneumatic pressure control proportional valves are in use. This paper describes the results of experiments and theoretical analyses regarding the characteristics of the valve pneumatic circuit. It was found that the characteristics of the output pressure versus the nozzle flapper clearance has a switching point as a relay. As it has a direct relation with valve linearity, this phenomenon has been studied experimentally and theoretically for various valve parameters. A way for choosing the optimum nozzle-flapper clearance is suggested from the results presented in this paper.

Static characteristics of a pneumatic pressure control proportional valve with nozzle-flapper mechanism

The paper is concerned with experiments and simulations of the static characteristics of the valve which is a force balance type pneumatic pressure control proportional valve with a nozzle flapper mechanism. It is recognized that the input-output characteristics of the valve has excellent linearity and the characteristics of output pressure versus nozzle flapper clearance look like those of a relay. The effects of the valve parameters on the valve pressure-load flow characteristics are discussed here also. According to the results of the simulations, it is confirmed that the fluid force influencing on the supply valve should be considered.

Optimal control of active air suspension.

It is important to improve both the ride quality and the driving stability of vehicles. However, with conventional passive suspensions, these two requirements can rarely be simultaneously satisfied. In this paper, an active air suspension is constructed using a pneumatic cylinder and two electro pneumatic proportional pressure control valves, which has the advantage of inherent buffer function due to the air compressibility. However, an electro pneumatic control valve involves a considerable delay time which deteriorates the vibration control performance. To cope with this problem, the control valve delay is formulated as an input time delay in the discrete-time state equation, for which an optimal regulator with a state observer is designed. Through experiments, the applicability of this optimal control method for the active air suspension can be confirmed.

弾性変形を利用した空圧ダイリップ駆動機構の開発

In the laminating process, automatic profile control of extruded film thickness in crossdirection is required for better productivity and product uniformity. The thickness profile is determined by the gap pattern of the die-lip heated at 350°C. Conventionally the correction of the gap is made by manual adjustment of the individual die bolts equipped in the side of the die. In this paper, a new method, which utilizes the mechanical elastic deformation of the lip by a pneumatic pressure control, is proposed with its construction and characteristic. Two bellows, which pressure is controlled with electro-pneumatic converter, are constructed in each zone of the die as actuators. As a result, the resolution of deformation 1.0 μm and the response time 0.4 s are obtained in heated condition. Additionally, a decoupling method for the model is proposed, in order to compensate the interactive deformation characteristic which is caused by continuum construction of the lip. Consequently, decoupling accuracy of 1% per full span and 0.6-1.0 μm resolution of deformation are obtained.