Pressure Feedback Research Articles

Closed-Loop Fault Diagnosis of SDR Using Gap Metric, PCA, and Kalman’s Principle

The measurement of the pressure in the gas generator (GG) plays a decisive role in the closed-loop regulation of the gas flow in a solid ducted rocket ramjet (SDR). Therefore, the fault detection and isolation (FDI) of the pressure sensors is particularly significant. Especially in the GG with double pressure feedback, there are issues such as less available data and sensor fault transmission, which make the FDI more difficult. In this paper, for the GG with double pressure feedback, firstly, the “Consistency Index” was constructed based on the principal component analysis (PCA) algorithm, which made it easier to evaluate the consistency of the measured values. Secondly, based on Kalman’s principle, the redundancy information of the system was used to estimate the pressure in the GG. Finally, the gap metric between the measured pressure and the estimated pressure was employed to characterize the health of the sensors. Compared with the MWPCA algorithm, it was shown that our proposed algorithm was more accurate in fault diagnosis and could avoid the problem of missing alarm when two sensors had consistent faults, which would provide strong support for the safe operation of the SDR and could further promote its application in long-endurance aircrafts.

Transient analysis of a noise suppression method with aerating techniques in capillary tubes

Flow-induced noise is closely related to the flow characteristics through an adiabatic capillary tube and a transition pipe, most existing methods for suppressing flow-induced noise are passive. An aerating technique is proposed based on the pressure feedback in the transition pipe to actively suppress flowinduced noise. The 3-D simulations of flashing are presented by performing the Schnerr-Sauer cavitation model coupling with the mixture model. For the turbulence model, the large eddy simulation approach is used. With the installation of aerating module, the pressure fluctuation in the transition pipe is weakened significantly, and the phenomenon of bubble collapse is suppressed. Numerical results illustrate that the transient pressure of the monitoring points downstream of the capillary outlet oscillates seriously due to the bubble bursting. The shedding process of the bubble group is observed according to the vaporliquid interface in the transition pipe. In addition, the oscillations of monitored transient pressure are suppressed with the application of aerating module. Then the noise source can be partially reduced actively in essence. This paper is devoted to understanding the two-phase flow characteristics of refrigerants in a transition pipe and presents a practical method to suppress noise near the capillary outlet.

The Utility of Synthetic Reflexes and Haptic Feedback for Upper-Limb Prostheses in a Dexterous Task Without Direct Vision.

Individuals who use myoelectric upper-limb prostheses often rely heavily on vision to complete their daily activities. They thus struggle in situations where vision is overloaded, such as multitasking, or unavailable, such as poor lighting conditions. Able-bodied individuals can easily accomplish such tasks due to tactile reflexes and haptic sensation guiding their upper-limb motor coordination. Based on these principles, we developed and tested two novel prosthesis systems that incorporate autonomous controllers and provide the user with touch-location feedback through either vibration or distributed pressure. These capabilities were made possible by installing a custom contact-location sensor on the fingers of a commercial prosthetic hand, along with a custom pressure sensor on the thumb. We compared the performance of the two systems against a standard myoelectric prosthesis and a myoelectric prosthesis with only autonomous controllers in a difficult reach-to-pick-and-place task conducted without direct vision. Results from 40 able-bodied participants in this between-subjects study indicated that vibrotactile feedback combined with synthetic reflexes proved significantly more advantageous than the standard prosthesis in several of the task milestones. In addition, vibrotactile feedback and synthetic reflexes improved grasp placement compared to only synthetic reflexes or pressure feedback combined with synthetic reflexes. These results indicate that autonomous controllers and haptic feedback together facilitate success in dexterous tasks without vision, and that the type of haptic display matters.

Cylinder Pressure Feedback Control for Ideal Thermodynamic Cycle Tracking: Towards Self-learning Engines

To meet increasingly strict future greenhouse gas and pollutant emission targets, development time and costs of heavy-duty internal combustion engines will reach unacceptable levels. This is mainly due to increased system complexity and need to guarantee robust performance under a wide range of real-world conditions. Cylinder Pressure Based Control is a major contributor to achieve these goals in advanced, highly-efficient engine concepts. Current Cylinder Pressure Based Control approaches use combustion and air-path parameters as feedback signals. These signals are not directly linked to engine efficiency; therefore, compensation for changing ambient conditions, engine ageing or differences in fuel qualities is a non-trivial problem. Contrary to other methods, the method presented in this paper aims to realise an idealised thermodynamic cycle by directly control of the entire cylinder pressure curve. From measured in-cylinder pressure, a new set of feedback signals is derived using principle component decomposition. With these signals, optimal fuel path settings are determined. The potential of this method is demonstrated for a dual fuel Reactivity Controlled Compression Ignition (RCCI) engine, which combines very high efficiency and ultra low nitrogen oxides and particle matter emission. For the studied RCCI engine, it is shown that the newly proposed optimisation method gave the same optimal fuel path settings as existing methods. This is an important step towards self-learning engines.

Simulation Study on Variable Pressure Margin Energy Recovery of Electric Loader Actuator

The conventional electric loader uses a motor instead of an engine, which aligns with the current energy-saving and emission-reduction trend. However, the motor’s speed control performance and overload capacity are under-utilized, and the actuator suffers from the potential energy waste problem of the boom arm. This study proposes a variable pressure margin energy recovery system for the electric loader actuator. It uses a combination of a permanent magnet synchronous motor (PMSM) and a quantitative pump. It can achieve variable pressure margin control and energy recovery through the pressure feedback closed-loop control. AMESim is used to build the simulation model based on the system control strategy, actuator, supercapacitor, and PMSM mathematical mode. Under typical working conditions, the simulation study is conducted on a 50-type wheel loader to obtain cylinder displacement, system energy recovery, and energy-saving performance. The simulation results show that the system is feasible and can effectively reduce energy consumption. Its energy recovery efficiency is 65.4%. The PMSM energy supply is reduced by 28.6% with the variable pressure margin control. It has high energy-saving performance, and the energy-saving efficiency is 38.5%. It provides a reference for research on energy-saving systems for electric construction machinery.

Elucidating the oscillation instability of sessile drops triggered by surface acoustic waves

Surface acoustic waves (SAWs) are used in droplet microfluidics for operations on sessile droplets, such as internal mixing, directional motion, or nebulization. An unsolved problem has been to understand how high frequency (MegaHz) SAWs can counterintuitively cause low frequency (10-500 Hz) oscillations on the drop free surface, which is known to enhance drop mobility. Using simultaneous measurements of the free-surface dynamics and internal acoustic pressure, we find that the drop oscillation instability results from coupling between an intracavity acoustic mode excited by the SAW, and an inertia-capillary surface eigenmode, through amplitude modulation and delayed radiation pressure feedback.

Fluid Injection System for X-ray Tomography Experiments

Due to recent developments on synchrotron sources, time-resolved experiments are favored by fourth-generation machines. In particular, X-ray tomography beamlines can now perform complete experiments in less than one second. MOGNO, the nano and microtomography beamline at Sirius, is designed for in situ and operando experiments. The first designed and tested environmental cell is a complete injection system for porous media materials. This system is composed by a flow cell with fluid injection control and pressure feedback. The cell can be used for experiments with pore pressure up to 750 PSI. To increase the autonomy of the injection system, three syringe pumps with a volume of 15 ml are used, and the flow control is done through three independent step motors, and can vary between 30 to 10,000 µl/minute. A web application was developed to allow MOGNO users to easily control the system and read the pressure feedback.

Pressure Feedback Control of Aerodynamic Loads on a Delta Wing in Transverse Gusts

A feedback active flow control (AFC) scheme is studied for control of unsteady aerodynamic loads that act on a generic tailless delta wing during transverse gust encounters. The transverse gust and the roll angle of the wing create an unsteady roll moment. The trailing edge actuators generate unbalanced lift increments on the two sides of the model to control the roll moment. Spatially distributed pressure sensors measure surface pressure on the suction side of the wing, and the real-time aerodynamic loads are estimated through models that are identified by the Sparse Identification of Nonlinear Dynamics algorithm. The aerodynamic load estimation is then used as a surrogate to provide the AFC system with a feedback signal to alleviate the unsteady roll moment due to the gust effect. A physical interpretation of the model identification results is made to locate the source of the lift and roll moment fluctuations in gust encounters. Experimental results show that the AFC effect with a momentum coefficient input of 2% is equivalent to 26° elevon deflection in terms of the roll moment change, and the AFC doubles the control authority relative to elevons. The real-time control results show that the pressure feedback control system reduces the mean roll moment error and suppresses the fluctuations to less than 20% of the uncontrolled fluctuation level at a high angle of attack.

Investigation of pressure feedback technique to control ramp based SWBLI

Shock wave boundary layer interaction (SWBLI) and associated boundary layer separation create undesirable phenomena such as enhanced aero-thermodynamic loads, localized turbulent spots, unsteadiness, drag enhancement, pressure recovery losses in high-speed flow applications. It necessitates an investigation on the control of shock-induced boundary layer separation. Therefore, a pressure feedback technique (PFT) to control the boundary layer separation has been studied numerically on a two-dimensional flat plate and ramp configuration. PFT consists of a channel that drains fluid from the separated region and reintroduces it in the core flow under the influence of pressure difference. The effect of various freestream, wall, and geometric conditions on the separation controllability of the PFT is examined. It has been observed that PFT with injection located near the upstream influence point and suction at the ramp foot reduces the length of the separation bubble by 12.15%. Variation of injection location marginally affects the separation reduction capability of PFT, while the performance of PFT is greatly dependent on suction location. The parametric study noted that the optimum suction location, for which the separation size is minimum, shifts downstream with increasing freestream Mach number, wall temperature, and ramp angle. Again the optimum suction location shifts upstream as freestream stagnation temperature to wall temperature ratio increases. Reynolds number is seen to have no impact on the optimum suction location. Moreover, freestream stagnation temperature to wall temperature ratio, which is a governing parameter in SWBLI studies, is also a relevant factor in the mechanism of PFT. Finally, the present limited investigation revealed that the suction end of the PFT positioned between Xsu/L = 1.12 to 1.194 provides a minimum size of shock-induced separation for varying freestream and wall conditions.

Dynamics of homogeneous cavitation with pressure feedback

Theoretical studies of homogeneous cavitation have largely been based on the classical nucleation theory. However, existing cavitation models cannot adequately describe its dynamics at nanosecond timescale, which has been called for in other fields. We develop a model coupling nucleation kinetics with cavity growth and pressure feedback as saturation mechanisms. Our numerical studies reveal the exponential dependence of cavitation characteristics such as saturation cavity density and most probable cavity radius on model parameters: Tolman length and initial pressure. This work also sheds light on the possibility of accurately determining Tolman length, whose value has a large spread in the literature.

Review on the Geophysical and UAV-Based Methods Applied to Landslides

Landslides (LS) represent geomorphological processes that can induce changes over time in the physical, hydrogeological, and mechanical properties of the involved materials. For geohazard assessment, the variations of these properties might be detected by a wide range of non-intrusive techniques, which can sometimes be confusing due to their significant variation in accuracy, suitability, coverage area, logistics, timescale, cost, and integration potential; this paper reviews common geophysical methods (GM) categorized as Emitted Seismic and Ambient Noise based and proposes an integrated approach between them for improving landslide studies; this level of integration (among themselves) is an important step ahead of integrating geophysical data with remote sensing data. The aforementioned GMs help to construct a framework based on physical properties that may be linked with site characterization (e.g., a landslide and its subsurface channel geometry, recharge pathways, rock fragments, mass flow rate, etc.) and dynamics (e.g., quantification of the rheology, saturation, fracture process, toe erosion, mass flow rate, deformation marks and spatiotemporally dependent geogenic pore-water pressure feedback through a joint analysis of geophysical time series, displacement and hydrometeorological measurements from the ground, air and space). A review of the use of unmanned aerial vehicles (UAV) based photogrammetry for the investigation of landslides was also conducted to highlight the latest advancement and discuss the synergy between UAV and geophysical in four possible broader areas: (i) survey planning, (ii) LS investigation, (iii) LS dynamics and (iv) presentation of results in GIS environment. Additionally, endogenous source mechanisms lead to the appearance of deformation marks on the surface and provide ground for the integrated use of UAV and geophysical monitoring for landslide early warning systems. Further development in this area requires UAVs to adopt more multispectral and other advanced sensors where their data are integrated with the geophysical one as well as the climatic data to enable Artificial Intelligent based prediction of LS.

Thrust Control of Lab-Scale Hybrid Rocket Motor with Wax-Aluminum Fuel and Air as Oxidizer

This article explores the throttling aspect of the hybrid rocket motor through experiments using a lab-scale motor. The lab-scale motor utilizes a wax-Al based fuel and compressed air as the oxidizer. The oxidizer flow rate was modulated using a PID controller to study the closed-loop thrust control performance of the motor. Numerical simulations and cold flow tests were carried out to identify the suitable gains for the PID control algorithm. Pressure feedback was used in the control algorithm to obtain the closed-loop thrust control. The resultant closed-loop system followed the reference pressure accurately during the step input response test of the system. The maximum error in the observed chamber pressure was 1.86% for a reference pressure of 4.69 bar, which corresponds to a reference thrust of 117.6 N. The response of the system for a ramp input, with linear thrust variation from 78.4 N to 127.4 N, showed that the measured thrust followed the desired ramp profile with a root-mean-square error of 1.99 N. A ramp-down test with the same thrust range produced a root-mean-square error of 6.2 N.

Suppression of pressure feedback of the rotating detonation combustor by a Tesla inlet configuration

With the increase in the inlet throat area, the rotating detonation combustor (RDC) can obtain higher pressure gain. However, the pressure feedback caused by the rotating detonation wave (RDW) can affect the upstream components of combustion chamber and interfere with the stable operation of RDC. Therefore, to obtain outstanding performance, it is imperative to investigate the suppression of pressure feedback. In this study, kerosene and 28.5% oxygen-enriched air (at room temperature) were taken as the propellant, and the tesla valve inlet configuration was applied to RDC, and the effect was compared with that of the traditional inlet configuration to suppress pressure feedback. A series of experiments were conducted to examine the operation characteristics of Tesla RDC and the effect and mechanism of suppressing pressure feedback. Under similar conditions, Tesla RDC can effectively transform the longitudinal pulsed detonation (LPD) mode into the rotating detonation (RD) mode, thus expanding the operating range of RDC. RDC under the exit nozzle with a small area ratio (0.25) was successfully realized. The operating range of Tesla RDC can be expanded by 300% and 94.7% at an exit area ratio of 0.5 and 0.65, respectively. The bypass channel in Tesla valve inlet configuration is the key to expanding the operating range. Directing pressure feedback to the bypass channel can effectively weaken the influence on the main inlet channel and shorten the inlet recovery time. Two quantitative evaluation indexes of pressure feedback were established; one is the percentage of the pressure fluctuating amplitude in the air plenum to the pressure amplitude of the detonation wave (PFdw), and the other is the static pressure of the air plenum, PFap. By analyzing the dynamic pressure signal upstream of the combustor, it was found that pressure disturbance is in the form of a pressure wave during the upstream return of the combustor, and the return speed is close to the local sound speed. Pressure feedback is mainly suppressed at the inlet throat, and PFdw is reduced by approximately 14% due to drainage of the bypass channel. Tesla RDC exhibits a good suppression effect on LPD mode, PFdw is significantly lower in the large exit nozzle area ratio, and the minimum value is 23%. PFap has an approximately linear relationship with the equivalence ratio, and the minimum value is 7.7%. Overall, this study demonstrates that Tesla RDC has excellent potential in widening the operation range and suppressing the pressure feedback, providing an innovative method for improving the performance of RDC.

Effects of a Real-time Plantar Pressure Feedback during Gait Training on the Weight Distribution of the Paralyzed Side and Gait Function in Stroke Patients

Effects of a Real-time Plantar Pressure Feedback during Gait Training on the Weight Distribution of the Paralyzed Side and Gait Function in Stroke Patients

An attempt to implement partially premixed combustion strategy in a multi-cylinder CRDI engine: A detailed experimental and wavelet transform analysis

The main objective of this research was to effectively employ the n-butanol fuel in advanced combustion strategy ‘partially premixed combustion (PPC)’ and provide the maximum possible replacement of diesel fuel. An experimental study was conducted on a multi-cylinder turbocharged intercooler CRDI engine to optimize the injection timings and diesel/n-butanol blended fuels based on performance, emissions, and combustion characteristics, including cyclic variability, in order to achieve the PPC strategy without compromising thermal efficiency significantly. The combustion characteristics analysis indicate that adding n-butanol fuel into diesel fuel combined with advanced injection (16° CA BTDC) timing leads to a drastic decrease in smoke emission as well as increases in NOX emission than diesel fuel. However, DB20 fuel at 8° CA BTDC injection timing achieved low-temperature PPC mode and reduced NOX (8.08%↓) and smoke (48%↓) emissions simultaneously compared to diesel fuel at 2 bar BMEP engine load. In addition, wavelet power spectrum (WPS) and global wavelet spectrum (GWS) analysis were utilized to investigate the temporal and spectral fluctuations in the partially premixed combustion parameter (indicated mean effective pressure) at optimum injection timing (8° CA BTDC). Results reveal that DB20 possesses lesser cyclic variations with higher frequency (at period 2–6 cycles) intermittent fluctuation in partially premixed combustion at 2 bar BMEP engine load than other tested fuels. A statistical analysis of IMEP variations was also performed to validate the temporal variation in the IMEP time-series signals of the WPS results. The results of WPS could be used to establish an efficient engine control method based on in-cylinder pressure feedback.

Resilience of visually guided weight shifting to a proprioceptive perturbation depends on the complexity of the guidance stimulus

BackgroundWhole-body tracking of visual motion cues is used in balance training to improve weight shifting ability in old age and sports. Research questionHow tracking of a complex (pink noise) and a periodic visual target motion during anteroposterior weight shifting affects postural and muscle responses to unilateral hip vibration. MethodsTwenty-six participants performed 160 anteroposterior weight shifting cycles while tracking the vertical motion of a visual target, concurrently receiving Center of Pressure (CoP) feedback. They were randomly divided to groups; (a) the Constant group tracked a visual target motion constructed by 3 sinusoids of different amplitude, and (b) the Pink group tracked a complex visual target motion constructed by a pink noise generation process. Between the 60th and the 120th cycle, vibration was applied to the right gluteus medius, introducing a sideways CoP deviation. CoP displacement and electromyographic (EMG) responses of soleus, tibialis anterior and peroneus longus were recorded and summarized in blocks of 3 cycles. ResultsSideways CoP deviation induced at the onset/offset of unilateral hip vibration was smaller for the Pink than the Constant group. The Pink group demonstrated greater tibialis anterior and peroneus longus EMG activity around the most anterior sway peak while soleus EMG was similar for the two groups. Both groups successfully coupled weight shifting amplitude to the target motion, but the Pink group tracked the target motion with a greater delay compared to the Constant group. SignificanceWhole body tracking of complex visual motions evokes perception-based action and increases ankle muscle co-activation making sway more resilient to a proprioceptive perturbation induced by unilateral hip vibration. Complex visual guidance motions should be considered when designing balance rehabilitation regimes, aiming at improving weight shifting ability and dynamic balance control.

A Platform for Stop-Flow Gradient Generation to Investigate Chemotaxis.

The ability of artificial microswimmers to respond to external stimuli and the mechanistical details of their origins belong to the most disputed challenges in interdisciplinary science. Therein, the creation of chemical gradients is technically challenging, because they quickly level out due to diffusion. Inspired by pivotal stopped flow experiments in chemical kinetics, we show that microfluidics gradient generation combined with a pressure feedback loop for precisely controlling the stop of the flows, can enable us to study mechanistical details of chemotaxis of artificial Janus micromotors, based on a catalytic reaction. We find that these copper Janus particles display a chemotactic motion along the concentration gradient in both, positive and negative direction and we demonstrate the mechanical reaction of the particles to unbalanced drag forces, explaining this behaviour.

Online Deflection Compensation of a Flexible Hydraulic Loader Crane Using Neural Networks and Pressure Feedback

The deflection compensation of a hydraulically actuated loader crane is presented. Measurement data from the laboratory are used to design a neural network deflection estimator. Kinematic expressions are derived and used with the deflection estimator in a feedforward topology to compensate for the static deflection. A dynamic deflection compensator is implemented, using pressure feedback and an adaptive bandpass filter. Simulations are conducted to verify the performance of the control system. Experimental results showcase the effectiveness of both the static and dynamic deflection compensator while running closed-loop motion control, with a 90% decrease in static deflection.

Modal Space Controller for Hydraulically Driven Six Degree of Freedom Parallel Manipulator

This paper presents the Modal space decoupled control for a hydraulically driven parallel mechanism has been presented. The approach is based on singular values decomposition to the properties of joint-space inverse mass matrix, and mapping of the control and feedback variables from the joint space to the decoupling modal space. The method transformed highly coupled six-input six-output dynamics into six independent single-input single-output (SISO) 1 DOF hydraulically driven mechanical systems. The novelty in this method is that the signals including control errors, control outputs and pressure feedbacks are transformed into decoupled modal space and also the proportional gains and dynamic pressure feedback are tuned in modal space. The results indicate that the conventional controller can only attenuate the resonance peaks of the lower eigenfrequencies of six rigid modes properly, and the peaking points of other relative higher eigenfrequencies are over damped, The further results show that it is very effective to design and tune the system in modal space and that the bandwidth increased substantially except surge (x) and sway (y) motions, each degree of freedom can be almost tuned independently and their bandwidths can be increased near to the undamped eigenfrequencies.

Design and rationale for the supermarket and web-based intervention targeting nutrition (SuperWIN) for cardiovascular risk reduction trial

The prevalence of chronic diseases is increasing largely due to suboptimal dietary habits. It is not known whether individualized, supermarket-based, nutrition education delivered by registered dietitians, utilizing the advantages of the in-store and online environments, and electronically collected purchasing data, can increase dietary quality. The supermarket and web-based intervention targeting nutrition (SuperWIN) for cardiovascular risk reduction trial is a randomized, controlled dietary intervention study. Adults identified from a primary care network with 1 or more risk factors were randomized at their preferred store to: (1) standard of care plus individualized, point- of-purchase nutrition education; (2) standard of care plus individualized, point- of-purchase nutrition education enhanced with online shopping technologies and training; or (3) standard of care alone. Educational sessions within each store's clinic and aisles, emphasized the dietary approaches to stop hypertension (DASH) diet. The primary assessment was an intention-to-treat comparison on the effects of the dietary interventions on mean change in DASH score (90-point range) from baseline to 3 months (post-intervention). Additional outcomes included blood pressure, lipids, weight, purchasing behavior, food literacy, and intervention feedback. Between April 2019 to February 2021, 267 participants were randomized (20 excluded due to coronavirus disease pandemic). Median age was 58 years, 69% were female, 64% had a college degree, 53% worked full-time, 64% were obese, 73% were treated with blood pressure and 42% with cholesterol medications, and most had low-to-moderate diet quality. The SuperWIN trial was designed to provide a rigorous evaluation of the efficacy of 2 novel, comprehensive, supermarket-based dietary intervention programs.