Pneumatic Force Research Articles

Periodic Flows in Microfluidics.

Microfluidics, the science and technology of manipulating fluids in microscale channels, offers numerous advantages, such as low energy consumption, compact device size, precise control, fast reaction, and enhanced portability. These benefits have led to applications in biomedical assays, disease diagnostics, drug discovery, neuroscience, and so on. Fluid flow within microfluidic channels is typically in the laminar flow region, which is characterized by low Reynolds numbers but brings the challenge of efficient mixing of fluids. Periodic flows are time-dependent fluid flows, featuring repetitive patterns that can significantly improve fluid mixing and extend the effective length of microchannels for submicron and nanoparticle manipulation. Besides, periodic flow is crucial in organ-on-a-chip (OoC) for accurately modeling physiological processes, advancing disease understanding, drug development, and personalized medicine. Various techniques for generating periodic flows have been reported, including syringe pumps, peristalsis, and actuation based on electric, magnetic, acoustic, mechanical, pneumatic, and fluidic forces, yet comprehensive reviews on this topic remain limited. This paper aims to provide a comprehensive review of periodic flows in microfluidics, from fundamental mechanisms to generation techniques and applications. The challenges and future perspectives are also discussed to exploit the potential of periodic flows in microfluidics.

Biological Fate Tracking of Nitric Oxide-Propelled Microneedle Delivery System Using an Aggregation-Caused Quenching Probe.

Nanoparticle-loaded dissolving microneedles (DMNs) have attracted increasing attention due to their ability to provide high drug loading, adjustable drug release behavior, and enhanced therapeutic efficiency. However, such delivery systems still face unsatisfied drug delivery efficiency due to insufficient driving force to promote nanoparticle penetration and the lack of in vivo fate studies to guide formulation design. Herein, an aggregation-caused quenching (ACQ) probe (P4) was encapsulated in l-arginine (l-Arg)-based nanomicelles, which was further formulated into nitric oxide (NO)-propelled nanomicelle-integrated DMNs (P4/l-Arg NMs@DMNs) to investigate their biological fate. The P4 probe could emit intense fluorescence signals in intact nanomicelles, while quenching with the dissociation of nanomicelles, providing a "distinguishable" method for tracking the fate of nanomicelles at a different status. l-Arg was demonstrated to self-generate NO under the tumor microenvironment with excessive reactive oxygen species (ROS), providing a pneumatic force to promote the penetration of nanomicelles in both three-dimensional (3D)-cultured tumor cells and melanoma-bearing mice. Compared with passive microneedles (P4 NMs@DMNs) without a NO propellant, the P4/l-Arg NMs@DMNs possessed a good NO production performance and higher nanoparticle penetration capacity. In conclusion, this study offered an ACQ probe-based biological fate tracking approach to demonstrate the potential of NO-propelled nanoparticle-loaded DMNs in penetration enhancement for topical tumor therapy.

Ultra-high-precision pneumatic force servo system based on a novel improved particle swarm optimization algorithm integrating Gaussian mutation and fuzzy theory

In this study, an ultra-high-precision pneumatic force servo system (UPFSS) is proposed. On the one hand, a novel air-floating pneumatic cylinder (AFPC) with an air-floating piston capable of independent air supply and exhaust is developed for this system, and its special flow channel design allows the air-floating piston to be suspended in the cylinder without being constrained by the pressure in the chambers. The friction force of the AFPC is less than 0.0049 N. On the other hand, a leakage chamber is constructed to simulate the clearance between the air-floating piston and the cylinder wall, and a fuzzy proportional integral (FPI)-based pressure control system (PCS) is designed for the simulated leakage chamber. Furthermore, a novel particle swarm optimization algorithm integrating Gaussian mutation and fuzzy theory (IGF-PSO) is presented. After testing, the IGF-PSO algorithm is found to have outstanding optimization performance. Then, the parameters of the FPI controller are optimized through the IGFPSO algorithm. Experimental comparisons reveal that the steady-state error achieved by the parameter-optimized pressure controller in response to the leakage condition is about 38 % smaller than that achieved by the pressure controller with parameters obtained using the trial-and-error method. Finally, the UPFSS is tested by using the optimized PCS to supply compressed air to the chamber of the AFPC. The results show that the UPFSS achieves a steady-state error of no more than 0.0279 N in the continuous step response within the range of 240 N.

Enhancing resource utilization: A novel method for effective separation of residual film and impurities in cotton fields

This study addresses the challenge of incomplete separation of mechanically recovered residual films and impurities in cotton fields, examining their impact on resource utilization and environmental pollution. It introduces an innovative screening method that combines pneumatic force and mechanical vibration for processing crushed film residue mixtures. A double-action screening device integrating pneumatic force and a key-type vibrating screen was developed. The working characteristics of this device were analyzed to explore the dynamic characteristics and kinematic laws of the materials using theoretical analysis methods. This led to the revelation of the screening laws of residual films and impurities. Screening tests were conducted using the Central Composite Design method, considering factors such as fan outlet, fan speed, vibration frequency of the screen, and feeding amount, with the impurity-rate-in-film (Q) and film-content-in-impurity (W) as evaluation indexes. The significant influence of each factor on the indexes was determined, regression models between the test factors and indexes were established, and the effect laws of key parameters and their significant interaction terms on the indexes were interpreted. The optimal combination of working parameters for the screening device was identified through multivariable optimization methods. Validation tests under this optimal parameters combination showed that the impurity-rate-in-film was 3.08% and the film-content-in-impurity was 1.94%, with average errors between the test values and the predicted values of 3.36% and 5.98%, respectively, demonstrating the effectiveness of the proposed method. This research provides a novel method and technical reference for achieving effective separation of residual film and impurities, thereby enhancing resource utilization.

Adaptive control of pneumatic end-effector polishing force based on dual extended state observer

Adaptive control of pneumatic end-effector polishing force based on dual extended state observer

Research of the FLC + PID switching control strategy based on real-time error for the pneumatic polishing force regulating system

This paper designs an active pneumatic polishing force control system and investigates its control strategy. A straightforward method based on the experiments is proposed for identifying and modeling the pneumatic system and a convenient and effective control strategy based on real-time error is proposed for pneumatic polishing force regulating. Corresponding function between the input duty cycles and the output force values is created based on the experiment data tested by the system. Then the pneumatic force regulating system is modeled by the corresponding function. Base on the results of simulations and experiments, a FLC (Fuzzy Logic Control) + PID (Proportion-Integration-Differentiation) switching control strategy is designed with a switching mechanism to choose different control algorithm based on real-time error which can take the advantages of both PID and FLC. The FLC + PID switching controller can eliminate the steady state errors occurring in FLC controller and achieve the same accuracy as the PID controller but with a faster response speed. The approach effectively stabilizes the polishing force, resulting in polishing force errors that are distributed within ± 1 N. The mean errors are less than 0.2 N and the absolute mean errors hover around 0.3 N. The pneumatic polishing force control system regulated by the FLC + PID switching control exhibits effectiveness, stability, high control precision and fast response speed, and satisfies the force control requirements of polishing process.

A comparison of the effects of mediolateral surface and foot placement perturbations on balance control and response strategies during walking

BackgroundBalance perturbation studies during walking have improved our understanding of balance control in various destabilizing conditions. However, it is unknown to what extent balance recovery strategies can be generalized across different types of mediolateral balance perturbations. Research questionDo similar mediolateral perturbations (foot placement versus surface translation) have similar effects on balance control and corresponding balance response strategies? MethodsKinetic and kinematic data were previously collected during two separate studies, each with 15 young, healthy participants walking on an instrumented treadmill. In both studies, medial and lateral balance perturbations were applied at 80% of the gait cycle either by a treadmill surface translation or a pneumatic force applied to the swing foot. Differences in balance control (frontal plane whole body angular momentum) and balance response strategies (hip abduction moment, ankle inversion moment, center of pressure excursion and frontal plane trunk moment) between perturbed and unperturbed gait cycles were evaluated using statistical parametric mapping. ResultsBalance disruptions after foot placement perturbations were larger and sustained longer compared to surface translations. Changes in joint moment responses were also larger for the foot placement perturbations compared to the surface translation perturbations. Lateral hip, ankle, and trunk strategies were used to maintain balance after medial foot placement perturbations, while a trunk strategy was primarily used after surface translations. SignificanceSurface and foot placement perturbations influence balance control and corresponding response strategies differently. These results can help inform the development of perturbation-based balance training interventions aimed at reducing fall risk in clinical populations.

Soft Coiled Pneumatic Actuator with Integrated Length-Sensing Function for Feedback Control

SPIRA Coil actuators are formed from thin sheets of PET plastic laminated into a coil shape that unfurls like a “party horn” when inflated, while many soft actuators require large pressures to create only modest strains, SPIRA Coils can easily be designed and fabricated to extend over dramatic distances with relatively low working pressures. Internal metalized PET strips separate in the extended portion of the actuator, creating an electrical circuit with a resistance that corresponds to the actuator length. This paper presents and experimentally validates easy-to-use design models for the actuators’ self-retracting spring stiffness, its pneumatic extension force, and its internal length-sensing electrical resistance. Testing of the self-sensing capabilities demonstrates that the embedded sensor can be used to determine the actuator length with virtually no hysteresis. Feedback control with the resistance-based sensing resulted in length-control errors within 5% of the extended actuator length (i.e., 3 cm of 60 cm).

Training Induced Improvement on Human Perception of the Force Feedback Provided by A Soft Robotic Glove.

Creating haptic interface by glove-based wearable robotic system has become an increasingly interested topic in the area of human robotic interaction. Many force feedback gloves are constructed based on soft actuators. However, the recent development of haptic and force feedback technology mainly focused on the advancement of the actuating components and mechanism, and innovation of the force feedback rendering algorithms. It seems that another important part of this human-robot-interaction loop, i.e. the human factors, were understudied. Here, this study focused on the learning effect in haptic perception. We designed a pneumatic muscle-based force feedback robotic glove which can provide customized force feedback to the dorsal surface of each finger. An experiment was carried out with a specifically training procedure and evaluation on the force feedback perceptions. The results show that practice-induced improvement can be achieved by this training, allowing people have a better perception of the force feedback provided by this glove.

Adaptive friction compensation control of robotic pneumatic end-effector based on LuGre model

PurposeConsidering the response lag and viscous slip oscillation of the system caused by cylinder piston friction during automatic polishing of aero-engine blades by a robotic pneumatic end-effector, the purpose of this study is to propose a constant force control method with adaptive friction compensation.Design/methodology/approachFirst, the mathematical model of the pneumatic end-effector is established based on the continuous LuGre model, and the static parameters of the LuGre model are identified to verify the necessity of friction compensation. Second, aiming at the problems of difficult identification of dynamic parameters and unmeasurable internal states in the LuGre model, the parameter adaptive law and friction state observer are designed to estimate these parameters online. Finally, an adaptive friction compensation backstepping controller is designed to improve the response speed and polishing force control accuracy of the system.FindingsSimulation and experimental results show that, compared with proportion integration differentiation, extended state observer-based active disturbance rejection controller and integral sliding mode controller, the proposed method can quickly and effectively suppress the polishing force fluctuation caused by nonlinear friction and significantly improve the blade quality.Originality/valueThe pneumatic force control method combining backstepping control with the friction adaptive compensation based on LuGre friction model is studied, which effectively suppresses the fluctuation of normal polishing force.

Aircraft landing gear system with magnetorheological shock strut: Performance evaluation via drop test

This work presents a magnetorheological (MR) damper applicable to the landing gear system in the aircraft. The proposed MR landing gear (MRLG) is modeled as a two degrees of freedom (2-DOF) system for the drop performance evaluation. A mathematical model of the governing equations is then formulated considering a flow path whose pressure depends on the major and minor losses. The flow path of MR fluid is composed of annular orifice and bypass as the required damping force for compression and extension is much different, and relief valve operates in conformity with the motion direction of the piston rod. An entry region is added to guarantee precise controllability of the field-dependent damping force. In addition, the magnetic intensity and total loss coefficient are estimated using magnetic analysis and computational fluid dynamics tools, respectively. It is demonstrated from the drop test based on the Federal Aviation Regulation (FAR) Part 23 that the shock struct efficiency (SSE) of the proposed MRLG can be increased from 42% at zero current to 84% at 1 A, and the agreement between simulation and experimental results is excellent showing similar pneumatic force, strut force, and jerk behavior which validates the accuracy of the proposed model.

Damping transformation modeling on wheel suspension using pneumatic cylinder thrust force as a substitute for vehicle weight

This study aims to produce a vertical dynamic load transformation model, FDV of medium weight vehicles that burden the road structure, the form of suspension work characteristics on vehicle wheels that experience disturbances and vertical loading, and the relationship between vehicle vertical dynamic loads and road structure strength, FA0 in the form of a dimensionless parameter. The experiment was carried out at the Pneumatic and Hydraulics Laboratory of the State Polytechnic of Ujung Pandang using pneumatic actuators as a substitute for vehicle weight. The dynamic load fluctuation of the medium weight category vehicle is equivalent to a pressurized air setting from 1 bar to 6 bar which puts a direct load on the suspension system on the vehicle’s wheels. The deviation, Y (cm) that occurs when there is compression on the Spring and Shock Absorber can be measured using a distance sensor, while the vertical dynamic load, FDV which burdens the road surface using a Load Cell. The data were analyzed using the vehicle dynamic load equation with pressure variable, P2 (bar), spring constant, k2 and damping fluid coefficient, c. A mathematical study of the vibration characteristics of the vehicle suspension was obtained using the Mat Lab program. The results showed that the vibration characteristics of the vehicle body experienced an overshot at a deviation of Y is 0.534 m for 0.131 seconds. The role of the shock absorber in the suspension mechanism can reduce 26.43 % of the vertical dynamic load FDV (N), and in the time interval, t is 3 seconds with acceleration deviation, is 0.25 m/s2 begins to feel comfortable. The relationship between vehicle dynamic load, FDV and road structure strength, FA0 is 0.0178. The data from the comparative analysis is then recommended as a consideration for road construction planners to determine the strength and service life of the road.

Selection of Robotic Machining Parameters with Pneumatic Feed Force Progression

The subject matter of the above paper presents part of the research carried out as part of the robotization of the manufacturing processes of aircraft engine components. The paper concerns robotic deburring of the V2500 diffuser’s sharp edges. The diffuser is a precision casting characterized by a slight variation in the geometry of the workpiece depending on the accuracy of the casting molds and the phenomenon of shrinkage during solidification. Due to the small degree of deburring and thus low cutting forces, robotic machining with the FDB150 tool was used. This tool is characterized by compliance with adjustable force, which enables machining of workpieces with a randomly changing shape. The authors of the paper propose a procedure for carrying out work allowing for the selection of suboptimal process parameters. In the analyzed case, these parameters are the speed of movement of the characteristic point of the tool (TCP) and the tool/workpiece contact force. The proposed procedure for determining the parameters of the force and speed of movement allowed for indicating a set of parameters ensuring the performance of the product in accordance with the requirements defined in the documentation. The proposed solution is of an engineering nature and is not a classic search for the extreme of a function from the point of view of the adopted criteria (quality indicators). Its advantage is simplicity, which is very important from the point of view of an industrial application.

An improved rational Bezier model for pneumatic constant force control device of robotic polishing with hysteretic nonlinearity

The pneumatic constant force control device has been widely used in robot deburring, sanding, polishing, and other fields due to its good flexibility, simple control, and low cost. The force control accuracy of the pneumatic constant force system could be greatly affected by its nonlinear hysteresis characteristics in the process from the cylinder input to the force output at the end of the device. A rational Bezier-based state fitting method (BSFM) has been presented for calibrating the inherent nonlinearity of the low-cost pneumatic constant force system. Compared with the most widely used PSFM, which is a polynomial-based state fitting method, the BSFM could calibrate the strong inherent nonlinearity of the system more smoothly with the lower ordered model and in a continuous form rather than the piecewise form of the PSFM. The BSFM could maintain a balance between simplicity and precision. Through a series of comparative experiments with different contact forces and feed rates, the proposed method has smaller force overshoot and when active force control is turned on, the force variation is greatly reduced to less than 2 N. The average roughness of the workpiece reached 0.4 µm after polishing.

Numerical investigation on the performance of internal flow and atomization in the recessed gas-centered swirl coaxial injectors

Recessed gas-centered swirl coaxial (GCSC) injector has been widely applied in the liquid rocket engine (LRE), and its internal flow and atomization have a significant impact on the combustion downstream. The oxygen (gas)-kerosene (liquid) two-phase flow in the recessed chamber of GCSC injectors under the conditions of back pressure of 17 MPa is numerically simulated by the volume-of-fluid (VOF) method. The liquid film, atomization and gas-liquid two-phase flow fields are obtained for liquid flow with or without swirling. The atomization of liquid kerosene does not have typical atomization characteristic of a swirling injector but accomplishes in the recessed chamber by action of pneumatic force. The swirling flow in the outer injector is helpful to achieve higher gas-to-liquid axial momentum ratio for good atomization performance and smaller injector size as well as lower gas-to-liquid momentum ratio for longer liquid-film length and more steady mass flowrate. The droplet sizes of the spray, the length of liquid film and the sizes of GCSC injectors decrease with increase of the gas-to-liquid (axial) momentum ratio, while the liquid mass flowrate in the outer injector becomes much unstable due to a recirculation flow adjacent to the exit of outer injector. Therefore, it is found that increasing the gas-to-liquid (axial) momentum ratio has two contradictory effects on improving atomization performance and promoting combustion instability. To balance these contradiction influences, the corresponding limits of the gas-to-liquid (axial) momentum ratio for well-working GCSC injectors are defined in this paper. The lower and upper limits of the gas-to-liquid momentum ratio are 7.6 and 14, and the gas-to-liquid axial momentum ratio corresponds to 17.6 and 31. In actual engineering project, the gas-to-liquid (axial) momentum ratios of the GCSC injector investigated in this paper is 9 (20). It indicates that the limits proposed in this paper are reasonable.

Algorithm for numerical calculation of nonlinear lenticular membrane-pneumatic systems by iterative method of parameter increments taking into account the aftereffect of air pressure

Objective. The purpose of this study is to create a static calculation algorithm to determine the maximum bearing capacity of a lenticular membrane-pneumatic system for covering large spans under the action of external force loads.Method. A numerical study of a large-span membranepneumatic structure was carried out by the step method of incrementing parameters using the finite element method and the Euler-Cauchy numerical procedure of the third order of accuracy at the step.Result. The authors have developed a technique for computer static calculation of geometrically and physically nonlinear lenticular membrane-pneumatic systems of coatings for large span structures by the iterative method of parameter increments with the phased application of the finite element method in the form of the displacement method, the universal equation of gas state and the improved Euler-Cauchy numerical procedure of the third order of accuracy.Conclusion. Ignoring the aftereffect in the calculations means the imbalance of the system due to unbalanced pneumatic forces calculated with an error of 11.2% and affecting, as the calculations showed, in the amount of approximately 7% percent on the increment of excess air pressure in the lens.

Pneumatic cylinder speed and force control using controlled pulsating flow

An application for accurate and low-cost force and velocity control of a pneumatic actuator, which can be used in any pneumatic circuit, is described in this paper. Control of a pneumatic cylinder is proposed via a pulsating flow technique. The technique uses on/off solenoid coils in the direction control valves in lieu of expensive servo controllers, such as proportional directional control valves. Pulsating air frequencies of 1.5, 3, and 4.5 Hz are applied by the designed circuit to investigate inlet constant pressures ranging from 1.72 to 5.17 × 105 Pa. The speed and force of a pneumatic cylinder rod are controlled using the generated pulsating flow and the results show success of idea of ​​controlling the speed and force of the pneumatic cylinder rod using the pulse flow technique. Empirical correlations suitable for later use in automatic control circuits are derived and are shown to exhibit an accuracy of up to ∼ 90–95.5% in predicting output force and velocity. It is also used to select the required frequency to obtain the speed and force required for the cylinder. To validate the pneumatic cylinder speed and force control using pulse flow technique, simulations are carried out using the Automation Studio program. The results show an improvement in control of the pneumatic cylinder mechanical performance and demonstrate that improvements are a function of the frequency of compressed air source pulses and pressure. An empirical correlation is also derived for predicting the cylinder rod speed and force at any source pressure and pulse frequency.

Study on the dynamic characteristics of stable formation of single droplet in gas-liquid co-flow device

The dynamic characteristics of the stable formation of a single droplet in a gas-liquid co-flow device are studied experimentally. The scaling laws of the dimensionless necking radius R of a droplet with dimensionless remaining time τ for different parameters are analyzed, and the reasons for the transformation between these scaling laws are discussed. The results show that the change in the main pressure has little effect on the scaling law. In the earlier necking, R follows a 1/5 power law with respect to τ. In the later collapse, a 2/3 power law is matched. When the auxiliary pressure changes, the pneumatic shear force has a large impact on the earlier necking, causing the scaling law to change, but only a slight effect on the later collapse. Simultaneously, the droplet size and jet limit length decrease significantly with an increase in auxiliary pressure. The results are of great significance for revealing the mechanism of droplet formation and reducing droplet formation size in gas-liquid co-flow devices and provide a theoretical reference for further study of stable droplet formation.

Heave Compensation Dynamics for Offshore Drilling Operation

In this study, dynamic response analysis of a heave compensation system for offshore drilling operations was conducted based on multibody dynamics. The efficiency of the heave compensation system was computed using simulation techniques and virtually confirmed before being applied to drilling operations. The heave compensation system was installed on a semi-submersible and comprises several interconnected bodies with various joints. Therefore, a dynamics kernel based on multibody dynamics was developed to perform dynamic response analysis. The recursive Newton–Euler formulation was adopted to construct the equations of motion for the multibody system. Functions of the developed dynamics kernel were verified by comparing them with those from other studies. Hydrostatic force, linearized hydrodynamic force, and pneumatic and hydraulic control forces were considered the external forces acting on the platform of the semi-submersible rig and the heave compensation system. The dynamic simulation was performed for the heave compensation system of the semi-submersible rig for drilling operations up to 3600 m water depth. From the results of the simulation, the efficiency of the heave compensation system was evaluated to be approximately 96.7%.

Design and Testing of a Pneumatic Oscillating Chinese Wolfberry Harvester

A pneumatic oscillating Chinese wolfberry harvester was designed to improve the efficiency of manual harvesting and minimize fruit damage by mechanical harvesting. The shedding model of Chinese wolfberry under pneumatic forces was established based on kinetic analysis, and the flow field characteristics were investigated using computational fluid dynamics (CFD). The position and shape of the fan outlet were determined by comparing the effects of a linear reduction outlet and a Laval reduction outlet on the outlet airflow rate. The size of the oscillating mechanism was optimized with nonlinear constraints to achieve uniform oscillation of the airflow. A three-factor, three-level orthogonal test was conducted on the NingQi 7 wolfberry variety. The flow rate at the outlet, the oscillation frequency, and the outlet distance were the test factors, and the net harvesting rate of ripe fruits, the harvesting rate of green fruits, and the damage rate of ripe fruits were the test indices. The results showed that the net harvesting rate of ripe fruits was 85.21% at an outlet distance of 10 cm, an outlet flow rate of 70 m·s−1, and an oscillation frequency of 2 Hz. This study provides references for the design of pneumatic harvesters for Chinese wolfberry.