Pneumatic Mode Research Articles

SMA Wire Use in Hybrid Twisting and Bending/Extending Soft Fiber-Reinforced Actuators

Soft fiber-reinforced actuators have demonstrated significant potential across various robotics applications. However, the actuation motion in these actuators is typically limited to a single type of motion behavior, such as bending, extending, and twisting. Additionally, a combination of bending with twisting and extending with twisting can occur in fiber-reinforced actuators. This paper presents two novel hybrid actuators in which shape memory alloy (SMA) wires are used as reinforcement for pneumatic actuation, and upon electrical activation, they create a twisting motion. As a result, the hybrid soft SMA-reinforced actuators can select between twisting and bending, as well as twisting and extending. In pneumatic mode, a bending angle of 40° and a longitudinal strain of 20% were achieved for the bending/twisting and extending/twisting actuators, respectively. When the SMA wires are electrically activated by the Joule effect, the actuators achieved more than 90% of the maximum twisting angle (24°) in almost 2 s. Passive recovery, facilitated by the elastic response of the soft chamber, took approximately 10 s. The double-helical reinforcement by SMA wires not only enables twisting in both directions but also serves as an active recovery mechanism to more rapidly return the finger to the initial position (within 2 s). The resulting pneumatic–electric-driven soft actuators enhance dexterity and versatility, making them suitable for applications in walking robots, in-pipe crawling robots, and in-hand manipulation.

Design and characterization of a pneumatic micro glass beads matrix sensor for soil water potential threshold control in irrigation management

Soil moisture porous matrix sensors may be good alternatives to tensiometers for measuring soil–water matric potential (SMP) for irrigation scheduling based on soil–water status approaches. The objective of this paper is to present and evaluate a new porous matrix sensor (IGstat) for detecting specific SMP thresholds for possible application in irrigation scheduling regulated by the SMP threshold concept. The IGstat sensor uses a non-sintered, glass bead microspheres (microGB) core and an outer ceramic cup, having larger air bubbling pressure (BP), to establish hydraulic contact with the soil. Pneumatic, optical, or electrical properties of the microGB porous medium can be then measured to infer the SMP. This paper describes and evaluates the performance of IGstat sensors for SMP threshold detection, using the pneumatic mode with a small air flow applied and air pressure monitored in the sensor tubing. Five IGstat sensors were built with different microGB diameters (15–125 µm) having air BP varying from 6 to 40 kPa. A power function was fitted to the data, which can be used to select microGB diameters to build IGstat sensors of required air BP. The experimental setup proposed to determine the sensor BP by incremental air injection provided air BP values in good agreement with those observed in a soil evaporation experiment (average relative error of 7.6%). The sensor responses in soil, with a small air pressure applied to them, showed a sharp pressure decreases when the SMP approached the sensor air BP, decreasing to about zero for SMP equal to the sensor air BP. The proposed sensors and approach showed potential for irrigation scheduling.

Hybrid Pneumatic-Hydraulic Actuator with Adaptable Stiffness

This work presents a method to control the stiffness of a hybrid actuator. The resulting stiffness is required to meet the conditions of real life applications, such as human prosthetics, human-robot interaction, and delicate robot interaction. The hybrid actuator is basically a pneumatic-hydraulic muscle, which can operate simultaneously in both pneumatic and hydraulic modes. The main challenge in this work is to manage the switching between pneumatic and hydraulic modes. In pneumatic mode when a load is applied to the actuator, air in the tank is allowed to compress resulting in muscle extension. While in hydraulic mode, the fluid is pressurized and the resultant system stiffness is higher. In both cases, the McKibben muscle is full with hydraulic fluid. It has been shown that the performance of the actuator is mostly the same in terms of response and bandwidth in both modes of operation. The use of different types of controllers to improve the system performance is investigated. It is found that the parallel configuration combined with PID controller is the best solution for achieving the required muscle performance.

Clinical Application of Neurally Adjusted Ventilatory Assist in Neonates with Respiratory Distress: A Systematic Review

Context: Neurally adjusted ventilatory assist (NAVA) is a novel mode of ventilation that coordinates the mechanical ventilator and the patient via electrical impulses of the diaphragm. Using these impulses as neural triggers, the patient’s respiration synchronizes with the ventilator. Ventilation with NAVA has successfully been performed in adults with various lung diseases but the application of NAVA in neonates is a novel issue. Objectives: The aim of this review study was to emphasize the NAVA as a new way of neonatal ventilatory support and the importance of ventilator-neonate synchrony in neonatal intensive care units. Study Selection: Several studies have evaluated NAVA in the neonatal period but we described here the cardinal studies. Therefore, we included studies performing NAVA in the neonatal and pediatric population. Results: The review of 10 studies showed that asynchrony was less frequent when using NAVA than when using the pneumatic modes of ventilation. Most of the studies observed a reduction in peak inspiratory pressure (PIP) and FIO2 with NAVA. A reduction in mean airway pressure and work of breathing and an improvement in gas exchange were also observed in some of the studies. Conclusions: We concluded that according to recent studies, the NAVA should be administered in neonates for better synchronization with ventilator and improving the gas exchange and outcomes.

Analysis of Poiseuille Flow Property in Two-Dimensional Mi-cro Channels of Microfluidic Pneumatic Micro-Valve

In this paper, the control mechanism and mathematical description of the microfluidic flow in the microfluidic process of the PDMS membrane type pneumatic micro-valve were studied. The velocity and pressure variation law of the velocity field inside micro valve was analyzed by numerical simulation method. The influence of the two kinds of inlet drive modes on the working effect and the pressure flow characteristics of the pneumatic micro-valve was studied. The structure of the elastic solid valve diaphragm under the dual action of the airway and the liquid channel was analyzed. Deformation and stress distribution. The results show that the gas flow in the gas flow channel under the diaphragm by the vacuum part of the role of the formation of a suction gas vortex, pressure-driven mode was easier under the diaphragm to produce a strong gas vortex, resulting in internal and external pressure to promote diaphragm cut-off liquid channel; In the pressure pneumatic mode, the stress at both ends of the diaphragm was smaller, the membrane was not easy to tear failure.

Experimental study of a pneumatic engine with heat supply to improve the overall performance

As an environmental friendly technology, hybrid pneumatic concept regenerating the engine braking energy to boost the engine performance for better fuel economy and lower engine emissions attracts ever increasingly attentions in automotive industry. However, the pneumatic operational mode of the engine suffers from low energy efficiency, which requires more research efforts. This study presents an optimisation method for the pneumatic mode of hybrid pneumatic engine by supplying heat during the expansion process of compressed air. A pneumatic prototype engine has been designed, constructed and used to simulate the working process of the engine during pneumatic mode. Hot water has been used as the heat source to heat up the engine cylinder wall in order to study the effects of using heat supply on the performance of the pneumatic engine. The results show that the power and torque of the pneumatic prototype engine under the heat source temperate at 90 °C and 1 MPa intake pressure are both increased. The maximum power output of the HPE obtained is around 1.5 kW, which is 22% higher than that of the HPE without heat supply. Under the engine rotational speed at 400 r/min, the torque produced from the HPE is about 29 N·m, which is 7% improvement than that without heating supply. The maximum energy efficiency of the HPE can be improved from 27% to 35%, when the cylinder wall is heated by 90 °C water and the intake pressure is set at 1 MPa. Moreover, the effects of hot water temperature have also been investigated and in total twenty-one testing points have been conducted under the engine intake pressure set at 1 MPa. The maximum power output from the HPE under water temperature at 70 °C and 90 °C can respectively be as high as 1.4 kW and 1.5 kW, which is about 14% and 22% improvement compared with the HPE without heat supply.

Variable stiffness Mckibben muscles with hydraulic and pneumatic operating modes

McKibben muscles have been shown to have improved stiffness characteristics when operating hydraulically. However when operating pneumatically, they are compliant and so have potential for safer physical human–robot interaction. This paper presents a method for rapidly switching between pneumatic and hydraulic modes of operation without the need to remove all hydraulic fluid from the actuator. A compliant and potentially safe pneumatic mode is demonstrated and compared with a much stiffer hydraulic mode. The paper also explores a combined pneumatic/hydraulic mode of operation which allows both the position of the joint and the speed at which it reacts to a disturbance force to be controlled.

Fuel consumption evaluation of an optimized new hybrid pneumatic–combustion vehicle engine on several driving cycles

In this paper, we describe an optimization followed by a fuel-saving evaluation of a new concept of a hybrid pneumatic–combustion engine that can be obtained by modifying a conventional internal combustion engine without developing a new cylinder head. Until now, most studies on the pneumatic hybridization of internal combustion engines have dealt with a two-stroke pure pneumatic mode. The few concept studies that have dealt with a hybrid pneumatic–combustion four-stroke mode required a supplementary valve to be added to charge compressed air in the combustion chamber. This heavy modification cannot be carried out by simply adjusting an existing internal combustion engine because a new cylinder head should be developed. It is therefore not logical to suggest this concept as an option in vehicle powertrains to reduce fuel consumption. Moreover, those studies focus on spark-ignition engines; there are reasons to think that their concepts might not work adequately for diesel engines. Our concept is capable of making a diesel engine operate under two-stroke pneumatic motor modes, two-stroke pneumatic pump modes and four-stroke hybrid modes, without requiring an additional valve in the combustion chamber. This fact constitutes our study’s strength and innovation. The evaluation of our concept is based on ideal thermodynamic cycle modeling. The optimized valve actuation timings for all modes lead to generic maps that are independent of the engine size. The fuel economy is calculated based on the new European driving cycle and on the assessment and reliability of transport emission models and inventory system urban and rural cycles.

A new hybrid pneumatic combustion engine to improve fuel consumption of wind–Diesel power system for non-interconnected areas

This paper presents an evaluation of an optimized Hybrid Pneumatic-Combustion Engine (HPCE) concept that permits reducing fuel consumption for electricity production in non-interconnected remote areas, originally equipped with hybrid Wind–Diesel System (WDS). Up to now, most of the studies on the pneumatic hybridization of Internal Combustion Engines (ICE) have dealt with two-stroke pure pneumatic mode. The few studies that have dealt with hybrid pneumatic-combustion four-stroke mode require adding a supplementary valve to charge compressed air in the combustion chamber. This modification means that a new cylinder head should be fabricated. Moreover, those studies focus on spark ignition engines and are not yet validated for Diesel engines. Present HPCE is capable of making a Diesel engine operate under two-stroke pneumatic motor mode, two-stroke pneumatic pump mode and four-stroke hybrid mode, without needing an additional valve in the combustion chamber. This fact constitutes this study’s strength and innovation. The evaluation of the concept is based on ideal thermodynamic cycle modeling. The optimized valve actuation timings for all modes lead to generic maps that are independent of the engine size. The fuel economy is calculated for a known site during a whole year, function of the air storage volume and the wind power penetration rate.

Convective Heat Transfer in a Pneumatic Hybrid Engine

Several previous studies have proven that pneumatic hybridization of an internal combustion engine is a technically viable and cost-efficient alternative to electric hybridization. Because the heat transfer process remains a first order factor while the engine operates in a motored or pneumatic mode without combustion, an accurate instantaneous heat transfer model is required in order to predict the in-cylinder pressure. This study shows that the original Woschni model is not suitable for describing the shape of the measured instantaneous heat flux versus crank angle while the engine operates in a motored pneumatic mode, because of the extinction of tumble motion near Top Dead Center (TDC). A modified form of the Woschni model is therefore proposed here that better describes the instantaneous heat flux during compression and expansion strokes, applicable to pneumatic and motored with fuel cut-off modes. First, the new constant parameter model is identified from experimental measurements performed in various motored mode conditions. Next, the pneumatic supercharged mode without combustion (ignition not performed) is investigated with the new model using the same identification values as for the motored mode. This study shows that the modified model remains fully applicable to the supercharged mode, despite of a certainly modified in-cylinder aerodynamic structure created by the opening of the charging valve under a high pressure ratio.

Pneumatic-Combustion Hybrid Engine: A Study of the Effect of the Valvetrain Sophistication on Pneumatic Modes

Although internal combustion engines display high overall maximum global efficiencies, this potential cannot be fully exploited in automotive applications: in real conditions, the average engine load (and thus efficiency) is quite low and the kinetic energy during a braking phase is lost. This work presents a hybrid pneumatic-combustion engine and the associated thermodynamic cycles, which is able to store and recover energy in the form of compressed air. The study focuses on the two major pneumatic modes: pneumatic pump mode and pneumatic motor mode. For each of them, three valvetrain technologies are considered: 4-stroke mode, 4-stroke mode with one camshaft disengaged, and 2-stroke fully variable.The concept can be adapted to SI or CI engines. In any case the valvetrain technology is the key to best fuel economy. A kinematic model of the charging valve’s actuator is introduced, and implemented in a quasi dimensional model of the pneumatic-combustion hybrid engine. Simulation results are presented for each pneumatic mode, for each valvetrain technology, in order to determine the best valve train configuration, and to show the impact of the kinematic valve actuator on the performance of the engine The tradeoffs between valvetrain sophistication and fuel economy will be presented for each case.

Evaluation of column performance in constant pressure and constant flow capillary gas chromatography

It has been demonstrated that there is no significant difference between the maximum peak capacity and analysis time at the same peak capacity in constant pressure (isobaric) and constant flow (isorheic) modes of temperature programmed GC. In view of that, the choice between the two pneumatic modes should be based on considerations other than the speed-separation performance of the column.

The pneumatic foundation of political theology in Voegelin

This article situates the foundation of Voegelin's political theology in the differentiation between noetic and pneumatic modes of human consciousness. The author establishes that Voegelin envisions the reconstructive science of politics as a political theology, amplifies Voegelin's ontology of human consciousness, then further delineates the specific difference Voegelin develops between the noetic and pneumatic differentiations of consciousness. He then identifies how Voegelin construes the critical implications of the pneumatic differentiation of consciousness for political theology in the fourth part. In light of this essential Voegelinian principle, the author concludes by amplifying some ramifications of Voegelin's political theology for the renewal of sustainable political communities.