Pneumatic Vibration Research Articles

The effect of various high-frequency powerful vibration (HFPV) types on fouling control of hollow fiber membrane elements in a small pilot-scale SMBR system

During the last decade in Europe, membrane bioreactor (MBR) systems have been proven to be a very efficient technique for municipal and industrial wastewater treatment (WWT). The most obvious appeal of the MBR technology is that it produces a stable and excellent effluent quality and eliminates the need for good sludge settleability, as it is one of the basic requirements in conventional WWT plants. Due to both the compact footprint and the great potential for automation, MBR plants ensure precise control of the sludge residence time and the mixed liquor suspended solids, which are basic operating parameters. The above results in: (a) the reduction of the required reactor size, (b) the promotion of the evolution of specific nitrifying bacteria, and finally, (c) the production of less sludge. However, the effluent rate of MBRs is limited, mainly because of the membrane fouling effect. Membrane fouling is probably the most critical problem of the submerged membrane bioreactors (SMBRs), and the applied techniques to avoid this problem have as a drawback the high energy that is needed and finally the production of chemical wastes. A lot of lab studies have been published concerning the impact of mechanical action on the removal of foulants from the membranes (e.g. vibration, buck-pulse, and ultrasound). The scope of this study is to examine the feasibility of high-frequency powerful vibration (HFPV) technique, as an alternative cleaning method, applied on fouled membrane elements in a continuous operated small pilot-scale SMBR unit, treating a novel synthetic wastewater (SWW). In this work, the implementation of various HFPV types (using commercial pneumatic vibrators) on identical, parallel hollow fiber (HF) fouled membranes, showed the following: (a) a repetitive pattern for transmembrane pressure and flux values vs. time; (b) the ability to select the proper vibration type according to the fouling extend on membranes; (c) the efficiency of this technique on membrane cleaning, in a membrane module system. After HFPV implementation, this system tends to have similar behavior with that of using new membrane modules. The HFPV technique seems to be very promising with respect to energy savings, compared to conventional air cleaning systems in SMBRs because it contributes to a low air-scouring operation due to the periodic and proper HFPV implementation. Moreover, this technique copes with the handling of membrane fouling in SMBRs units, using continuous MBR operating mode.

Study on a novel pneumatic stratified vibration sorting method of waste plastic films

Waste plastic films introduce serious pollution and need to be separated and collected for recycling. Aiming at highly efficient sorting of waste plastic films, a kind of novel pneumatic stratified vibration sorting method of waste plastic films is proposed combining with the characteristics of pneumatic sorting and linear reciprocating vibration mechanism. The kinematic model of waste plastic films on the vibrating bed is established to study the kinematic characteristics of waste plastic films in the separating process. The effects of the directional angle of the vibration, the inclined angle of the vibration bed, the crank, the air speed, the critical rotational speed of the motor, and motion parameters on sliding trajectories of waste plastic films on the stratified vibration bed have been analyzed. Then, the optimum process parameters are determined. Based on the analyses, the prototype has been designed. The virtual prototype is created and simulated by software ADAMS. The results have verified the theoretical analyses. It shows the introduced pneumatic stratified vibration sorting method has a higher efficiency than conventionally compound sorting methods.

Test–Retest Reliability and Concurrent Validity of an fMRI-Compatible Pneumatic Vibrator to Stimulate Muscle Proprioceptors.

Processing proprioceptive information in the brain is essential for optimal postural control and can be studied with proprioceptive stimulation, provided by muscle vibration, during functional magnetic resonance imaging (fMRI). Classic electromagnetic muscle vibrators, however, cannot be used in the high-strength magnetic field of the fMRI scanner. Pneumatic vibrators offer an fMRI-compatible alternative. However, whether these devices produce reliable and valid proprioceptive stimuli has not been investigated, although this is essential for these devices to be used in longitudinal research. Test–retest reliability and concurrent validity of the postural response to muscle vibration, provided by custom-made fMRI-compatible pneumatic vibrators, were assessed in a repeated-measures design. Mean center of pressure (CoP) displacements during, respectively, ankle muscle and back muscle vibration (45–60 Hz, 0.5 mm) provided by an electromagnetic and a pneumatic vibrator were measured in ten young healthy subjects. The test was repeated on the same day and again within one week. Intraclass correlation coefficients (ICC) were calculated to assess (a) intra- and interday reliability of the postural responses to, respectively, pneumatic and electromagnetic vibration, and (b) concurrent validity of the response to pneumatic compared to electromagnetic vibration. Test–retest reliability of mean CoP displacements during pneumatic vibration was good to excellent (ICCs = 0.64–0.90) and resembled that of responses to electromagnetic vibration (ICCs = 0.64–0.94). Concurrent validity of the postural effect of pneumatic vibration was good to excellent (ICCs = 0.63–0.95). In conclusion, the proposed fMRI-compatible pneumatic vibrator can be used with confidence to stimulate muscle spindles during fMRI to study central processing of proprioception.

Design of a Miniaturized Pneumatic Vibration Isolator With High-Static-Low-Dynamic Stiffness

In the ultraprecision vibration isolation systems, it is desirable for the isolator to have a larger load bearing capacity and a broader isolation bandwidth simultaneously. Generally, pneumatic spring can bear large load and achieve relatively low natural frequency by enlarging its chamber volume. However, the oversized isolator is inconvenient to use and might cause instability. To reduce the size, a miniaturized pneumatic vibration isolator (MPVI) with high-static-low-dynamic stiffness (HSLDS) is developed in this paper. The volume of proposed isolator is minimized by a compact structure design that combines two magnetic rings in parallel with the pneumatic spring. The two magnetic rings are arranged in the repulsive configuration and can be mounted into the chamber to provide the negative stiffness. Then dynamic model of the developed MPVI is built and the isolation performances are analyzed. Finally, experiments on the isolator with and without the magnetic rings are conducted. The final experimental results are consistent with the dynamical model and verify the effectiveness of the developed vibration isolator.

Membrane fouling control using high-frequency power vibration, in an SMBR pilot system—preliminary studies

Membrane bioreactors (MBRs) in wastewater treatment have gained significant popularity recently, especially due to reclamation needs. Submerged membrane bioreactors (SMBRs) are considered to be an extremely successful method for this purpose. However, membrane fouling is one of the most critical problems of the SMBR systems, and the used techniques to avoid this problem have the disadvantage of the high energy needed. The objective of this study was to introduce an alternative cleaning technique of submerged membranes, with reduced energy consumption. A lot of lab studies have been published concerning the impact of mechanical action in the removal of foulants from the membranes (e.g. vibration, buck-pulse, and ultrasound). In this preliminary study, the feasibility of high frequency power (or powerful) vibration (HFPV), as cleaning technique, on fouled membrane modules, in a small pilot-scale SMBR system, treating a novel synthetic wastewater was examined. This pilot-scale system comprised from small copies of commercialized filter modules working under low aeration mode, in order to study the membrane fouling in a relatively short time period. Two new membrane filter modules (hollow fiber (HF) and flat sheet (FS)) consisting of three filter elements each, were used in the SMBR unit. After working the unit for a long time period, where trans-membrane pressure (TMP) exceeded the specified values or where membrane fouling blocking phenomena were observed, various time-period HFPV schemes were applied on the filter modules, via two different in power commercial pneumatic vibrators. These vibration schemes give distinct vibration characteristics (frequency, displacement, acceleration, etc.) to the membrane modules and their effectiveness on filter fouling was monitored continuously via TMP and flux values vs. time, without interrupting the operating mode of the whole SMBR system. After a continuous working period of 19 d with HF filter module, where TMP values reaches the upper set point of 200 mbar, different HFPV schemes were implemented within a day. This results a considerably lower TMP values (to 100 mbar), while flux was recovered to initial values and the system after that, behaved similarly with that of having new filter modules in terms of TMP and flux values. Medium HFPV schemes were subsequently applied for about two-day period, giving a conservation of TMP values at previous levels. Similar promising results were obtained using various time-period HFPV schemes on FS membrane filter module. The above results confirm a clear influence of the HFPV technique on reducing the severe membrane fouling at first and then preserving the good membrane operating conditions. HFPV technique seems to be very promising with respect to energy savings, compared to conventional air cleaning systems in SMBRs because it contributes to a low air-scouring operation due to the periodic application of vibration. Additionally, this technique copes with the problem of membranes fouling in real time, by applying HFPV schemes without interrupting SMBRs operation mode.

913 3自由度空気圧パラレルリンク型アクティブ吸振器付き全方向移動ロボットによる球面振子の制振搬送制御(ロボティクス・メカトロニクスVI+情報・知能・精密機器)

913 3自由度空気圧パラレルリンク型アクティブ吸振器付き全方向移動ロボットによる球面振子の制振搬送制御(ロボティクス・メカトロニクスVI+情報・知能・精密機器)

Effect of External Excitation on Dynamic Characteristics of Vibro-Isolating Table

Performance of optical table with pneumatic vibration isolators is analyzed within 2–50 Hz frequency range. Specific vibrational excitation platform with a vibrator of the frequency range of 1–50 Hz in one of three directions were tested.The following pneumatic vibration isolator dynamic parameters were identified:transmissibility of vertical oscillation characteristics at 50 Hz frequency range;resonant frequency (vertical direction);damping efficiency at 5 Hz to 10 Hz for excitation frequencies.

Generic vibration criteria–based dual-chamber pneumatic spring vibration isolation table design

Dual-chamber pneumatic spring vibration isolation tables are commonly used as the base of precision equipment to isolate vibrations from the floor. During the design of dual-chamber pneumatic spring vibration isolation table, transmissibility is often taken as the performance measure, which does not represent the precision requirements directly and could not be adapted to different floor vibration conditions. In this article, a new performance measure is developed to obtain an optimum isolation performance during the design of a dual-chamber pneumatic spring vibration isolation table. Based on the generic vibration criteria, the weighted root-mean-square velocity of platform vibration in one-third octave bands resulting from the floor excitations is used as the new measure. The platform vibration is predicted by establishing a model of dual-chamber pneumatic spring vibration isolation table, which consists of a platform and four dual-chamber pneumatic springs. The model disturbance inputs are actual random floor excitations (7.98 µm/s, vibration criteria-C level), which are obtained by vibration acquisition test in a typical laboratory. The genetic algorithm is applied to solve this nonlinear optimization problem. The maximum weighted root-mean-square velocity of platform with the optimum design isolation table decreases to 2.35 µm/s, which provides a vibration criteria-E level environment.

Active pneumatic vibration isolation system using negative stiffness structures for a vehicle seat

Abstract In this paper, an active pneumatic vibration isolation system using negative stiffness structures (NSS) for a vehicle seat in low excitation frequencies is proposed, which is named as an active system with NSS. Here, the negative stiffness structures (NSS) are used to minimize the vibratory attraction of a vehicle seat. Owing to the time-varying and nonlinear behavior of the proposed system, it is not easy to build an accurate dynamic for model-based controller design. Thus, an adaptive intelligent backstepping controller (AIBC) is designed to manage the system operation for high-isolation effectiveness. In addition, an auxiliary control effort is also introduced to eliminate the effect of the unpredictable perturbations. Moreover, a radial basis function neural network (RBFNN) model is utilized to estimate the optimal gain of the auxiliary control effort. Final control input and the adaptive law for updating coefficients of the approximate series can be obtained step by step using a suitable Lyapunov function. Afterward, the isolation performance of the proposed system is assessed experimentally. In addition, the effectiveness of the designed controller for the proposed system is also compared with that of the traditional backstepping controller (BC). The experimental results show that the isolation effectiveness of the proposed system is better than that of the active system without NSS. Furthermore, the undesirable chattering phenomenon in control effort is quite reduced by the estimation mechanism. Finally, some concluding remarks are given at the end of the paper.

Static and dynamic stability of pneumatic vibration isolators and systems of isolators

Abstract Pneumatic vibration isolation is the most widespread effective method for creating vibration-free environments that are vital for precise experiments and manufacturing operations in optoelectronics, life sciences, microelectronics, nanotechnology and other areas. The modeling and design principles of a dual-chamber pneumatic vibration isolator, basically established a few decades ago, continue to attract attention of researchers. On the other hand, behavior of systems of such isolators was never explained in the literature in sufficient detail. This paper covers a range of questions essential for understanding the mechanics of pneumatic isolation systems from both design and application perspectives. The theory and a model of a single standalone isolator are presented in concise form necessary for subsequent analysis. Then the dynamics of a system of isolators supporting a payload is considered with main attention directed to two aspects of their behavior: first, the static stability of payloads with high positions of the center of gravity; second, dynamic stability of the feedback system formed by mechanical leveling valves. The direct method of calculating the maximum stable position of the center of gravity is presented and illustrated by three-dimensional stability domains; analytic formulas are given that delineate these domains. A numerical method for feedback stability analysis of self-leveling valve systems is given, and the results are compared with the analytical estimates for a single isolator. The relation between the static and dynamic phenomena is discussed.

Note: High frequency vibration rejection using a linear shaft actuator-based image stabilizing device via vestibulo-ocular reflex adaptation control method

In mobile robotics, obtaining stable image of a mounted camera is crucial for operating a mobile system to complete given tasks. This note presents the development of a high-speed image stabilizing device using linear shaft actuator, and a new image stabilization method inspired by human gaze stabilization process known as vestibulo-ocular reflex (VOR). In the proposed control, the reference is adaptively adjusted by the VOR adaptation control to reject residual vibration of a camera as the VOR gain converges to optimal state. Through experiments on a pneumatic vibrator, it will be shown that the proposed system is capable of stabilizing 10 Hz platform vibration, which shows potential applicability of the device to a high-speed mobile robot.

Active suppression of pneumatic vibration isolators using adaptive sliding controller with self-tuning fuzzy compensation

This paper develops intelligent control schemes for a diaphragm-type pneumatic vibration isolation system. The active-control schemes are applied to the pneumatic isolator to enhance isolation performances in the low-frequency range where passive techniques usually have difficulties in remaining effective, especially at the resonance frequency. The functional approximation technique (FAT) is integrated with a sliding-mode control (SMC) design to capture unknown system dynamics and release the requirement of mathematical modeling. To deal with approximation error and system dynamics variation, an adaptive fuzzy sliding-mode controller (AFSMC) is employed as a compensator of the FAT-based SMC. Lyapunov stability theory is used not only to ensure the closed-loop stability, but also to formulate the updating laws for weighting coefficients of expansion basis and fuzzy tuning parameters. To validate the proposed method, a composite control scheme using pressure and velocity measurements as feedback signals is implemented. Experimental explorations indicate that isolation performances obtained using the proposed FAT-based sliding control augmented with AFSMC compensation (FA + AFSMC) are evidently better than those of the traditional proportional integral-derivative control and solely AFSMC scheme.

Active Pneumatic Vibration Control by Using Pressure and Velocity Measurements and Adaptive Fuzzy Sliding-Mode Controller

This paper presents an intelligent control strategy to overcome nonlinear and time-varying characteristics of a diaphragm-type pneumatic vibration isolator (PVI) system. By combining an adaptive rule with fuzzy and sliding-mode control, the method has online learning ability when it faces the system's nonlinear and time-varying behaviors during an active vibration control process. Since the proposed scheme has a simple structure, it is easy to implement. To validate the proposed scheme, a composite control which adopts both chamber pressure and payload velocity as feedback signal is implemented. During experimental investigations, sinusoidal excitation at resonance and random-like signal are input on a floor base to simulate ground vibration. Performances obtained from the proposed scheme are compared with those obtained from passive system and PID scheme to illustrate the effectiveness of the proposed intelligent control.

Dynamics and stability of pneumatically isolated systems

Pneumatic vibration isolation is the most widespread effective method for creating vibration-free environments that are vital for precise experiments and manufacturing operations in optoelectronics, life sciences, microelectronics, nanotechnology, and other areas. The modeling and design principles of a dual-chamber pneumatic vibration isolator continue to attract attention of researchers. On the other hand, behavior of systems of such isolators was never explained in the literature in sufficient detail. After a brief summary of the theory and a model of a single standalone isolator, the dynamics of a system of isolators supporting a payload is considered with main attention directed to three aspects of their behavior: first, the static stability of payloads with high positions of the center of gravity; second, role of gravity terms in the vibration transmissibility; third, the dynamic stability of the feedback system formed by mechanical leveling valves. The direct method of calculating the maximum stable position of the center of gravity is presented and illustrated by three-dimensional stability domains. A numerical method for feedback stability analysis of self-leveling valve systems is provided, and the results are compared with the analytical estimates for a single isolator. The relation between the static and dynamic phenomena is discussed.

3-D endoscope using a single CCD camera and pneumatic vibration mechanism

During endoscopic surgical procedures, surgeons must manipulate an endoscope inside the body cavity to observe a surgical area while estimating the distance between that area and the surgical instruments by reference to a monitor on which the movement and size of the surgical instruments are displayed in 2-D endoscopic images. Therefore, there is a risk of the endoscope or instruments physically damaging body tissues. To overcome this problem, we developed a Ø5-mm, 3-D endoscope using a single 1/10-inch CCD camera and pneumatic vibration mechanism. The 3-D endoscope proposed in this paper consists of an outer and inner sleeve, a 1/10-inch CCD camera attached to its distal end, and a pneumatic vibration mechanism attached to its proximal end. This endoscope can acquire left and right endoscopic images for stereovision in synchrony with the periodical motion generated by the vibration mechanism. We measured the displacement at the proximal and distal end of the 3-D endoscope simultaneously, and evaluated the feasibility of its use in vivo. The displacement at the distal end of the endoscope to which the CCD camera is attached was approximately ±0.25 mm. The timing when the displacement of the CCD camera was at maximal amplitude coincided with the timing when the displacement of its proximal end was at maximal amplitude. In the in vivo experiment, this 3-D endoscope can provide clear 3-D images of the surgical area. The developed 3-D endoscope that uses a single CCD camera and pneumatic vibration mechanism can successfully visualize internal organs inside the body even though the CCD camera is moved by the vibration. Therefore, the risk of damage to fragile body tissues can be significantly decreased.

Liver stiffness measured by magnetic resonance elastography as a risk factor for hepatocellular carcinoma: a preliminary case–control study

To examine if liver stiffness measured by magnetic resonance elastography (MRE) is a risk factor for hepatocellular carcinoma (HCC) in patients with chronic liver disease. By reviewing the records of magnetic resonance (MR) examinations performed at our institution, we selected 301 patients with chronic liver disease who did not have a previous medical history of HCC. All patients underwent MRE and gadoxetic acid-enhanced MR imaging. HCC was identified on MR images in 66 of the 301 patients, who were matched to controls from the remaining patients without HCC according to age. MRE images were obtained by visualising elastic waves generated in the liver by pneumatic vibration transferred via a cylindrical passive driver. Risk factors of HCC development were determined by the odds ratio with logistic regression analysis; gender and liver stiffness by MRE and serum levels of aspartate transferase, alanine transferase, alpha-fetoprotein, and protein induced by vitamin K absence-II. Multivariate analysis revealed that only liver stiffness by MRE was a significant risk factor for HCC with an odds ratio (95 % confidence interval) of 1.38 (1.05-1.84). Liver stiffness measured by MRE is an independent risk factor for HCC in patients with chronic liver disease.

Reduced elbow extension torque during vibrations

Impact sports and vibration platforms trigger vibrations within soft tissues and the skeleton. Although the long-term effects of vibrations on the body have been studied extensively, the acute effects of vibrations are little understood. This study determined the influence of acute vibrations at different frequencies and elbow angles on maximal isometric elbow extension torque and muscle activity. Vibrations were generated by a pneumatic vibrator attached to the lever of a dynamometer, and were applied on the forearm of 15 healthy female subjects. The subjects were instructed to push maximally against the lever at three different elbow angles, while extension torque and muscle activity were quantified and compared between vibration and non-vibration (control) conditions. A change in vibration frequency had no significant effects on torque and muscle activity although vibrations in general decreased the maximal extension torque relative to the control by 1.8% (±5.7%, p>0.05), 7.4% (±7.9%, p<0.01), and 5.0% (±8.2%, p<0.01) at elbow angles of 60°, 90°, and 120°, respectively. Electromyographic activity increased significantly between ∼30% and 40% in both triceps and biceps with vibrations. It is speculated that a similar increase in muscle activity between agonist and antagonist, in combination with an unequal increase in muscle moment arms about the elbow joint, limit the maximal extension torque during exposure to vibrations. This study showed that maximal extension torque decreased during vibration exposure while muscle activity increased and suggests that vibrations may be counterproductive during activities requiring maximal strength but potentially beneficial for strength training.

Effect of mechanical stimuli on live cells in a pneumatically driven cell trap

A pneumatically driven cell trap device with individually controllable vibrators was fabricated and the effect of mechanical stimuli on a trapped live cell was examined. The device consisted of two polydimethylsiloxane (PDMS) layers that formed pneumatic vibrators and a trap chamber connected to a fluid channel for introducing the cell. When the vibrators were supplied with compressed air, the flexible diaphragms in the vibrators were deformed and exerted pressure on the fluid film in the trap chamber. If a cell was present in the trap chamber, drag force generated by the fluid flow affected the cell. By using a symmetrical arrangement of four vibrators, the cell could be manipulated and trapped in region at the center of the four vibrators. In order to verify this working principle, the ability of the device to trap solid particles and live cells was tested. Intracellular calcium levels were measured to investigate the influence of mechanical stimuli produced via the fluid film, which was induced by pneumatic actuation, on a single cell within the trap chamber. Once the vibrators were actuated, the intracellular calcium level of the cell at rest increased rapidly as it responded to the external mechanical stimulation induced by deformation of the vibrator. When considering the typical increases in calcium induced by shear stress, the measured peak value was very small. As the duration of trapping was prolonged, the calcium levels decreased. The calcium level was comparable to that of a cell at rest, with some fluctuations. In short, the influence of mechanical stimuli on a live cell induced by the pneumatic cell trap appeared to be negligible during trapping.

Systematic design of a magneto-rheological fluid embedded pneumatic vibration isolator subject to practical constraints

A systematic design of a magneto-rheological fluid embedded pneumatic vibration isolator (MrEPI) considering practical constraints and optimal performance is proposed. The design procedure basically consists of three steps, i.e. system level design, component level design and practical realization. The system level design involves synthesizing appropriate non-dimensional system parameters of pneumatic spring and MR damper elements based on parameter sensitivity analysis considering requirements for compact and efficient hardware utilization. The component level design involves optimal design of the MR valve by minimizing an objective function in terms of non-dimensional geometric, material and excitation parameters, and guaranteeing required performance in the worst cases. Then practical realization involves determining actual plant parameters from the non-dimensional analysis in system and component level designs with the considerations of practical requirements/constraints. To verify the effectiveness of this optimization procedure, the semi-active vibration control performance of the optimized MrEPI subject to harmonic disturbances is evaluated, which shows good isolation performance in all tested cases. This study actually provides a systematic method for the optimal analysis and design of all those nonlinear vibration isolators consisting of pneumatic spring and MR damper elements. This is achieved firstly by developing effective sensitivity analysis of dominant design parameters upon the adjustable stiffness and damping capacity irrespective of bulky or small system mass configuration and subsequently via a systematic realization design with the consideration of practical constraints in applications.

Study on Performance and Optimal Design of Pneumatic Vibrator of Repetitive Shock Machine on Cold Soak Temperature

Pneumatic vibrator,which produces excitation signals,is one of the most important part of repetitive shock machine.In low temperature condition,pneumatic vibrator cannot work as usual.In order to solve this problem,firstly the failure mechanism is studied by theory model.Then the structure of the pneumatic vibrator is ameliorated by the ways of choosing appropriate stuff and dimensions of the cylinder,and minishing the gap in temperature between the inside and outside of the cylinder.The method of controlling temperature is brought forward according to the model.Finally a pneumatic vibrator of cold temperature is made,whose durability of repetitive shock and uniformity and efficiency of calefaction is tested in low temperature conditions,and whose response characteristic of excitation on the roof is tested in low and room temperature condition,respectively.The results show that the working capability in low temperature condition of the newly designed vibrator is much better than that of the primary one,and that it can work normally and continuously in low temperature condition,and that the response characteristics of excitation in low and room temperature condition are accordant,which validates the availability of the new pneumatic vibrator in practice.