Dynamic Pressure Sensors Research Articles

Robust Tactile Descriptors for Discriminating Objects From Textural Properties via Artificial Robotic Skin

In this paper, we propose a set of novel tactile descriptors to enable robotic systems to extract robust tactile information during tactile object explorations, regardless of the number of the tactile sensors, sensing technologies, type of exploratory movements, and duration of the objects’ surface exploration. The performance and robustness of the tactile descriptors are verified by testing on four different sensing technologies (dynamic pressure sensors, accelerometers, capacitive sensors, and impedance electrode arrays) with two robotic platforms (one anthropomorphic hand and one humanoid), and with a large set of objects and materials. Using our proposed tactile descriptors, the Shadow Hand, which has multimodal robotic skin on its fingertips, successfully classified 120 materials (100% accuracy) and 30 in-hand objects (98% accuracy) with regular and irregular textural structure by executing human-like active exploratory movements on their surface. The robustness of the proposed descriptors was assessed further during the large object discrimination with a humanoid. With a large sensing area on its upper body, the humanoid classified 120 large objects with multiple weights and various textures while the objects slid between its sensitive hands, arms, and chest. The achieved 90% recognition rate shows that the proposed tactile descriptors provided robust tactile information from the large number of tactile signals for identifying large objects via their surface texture regardless of their weight.

Development of measurement and calibration techniques for dynamic pressures and temperatures (DynPT): background and objectives of the 17IND07 DynPT project in the European Metrology Programme for Innovation and Research (EMPIR)

This project has five specific objectives: To provide traceability for dynamic pressure and temperature through development of measurement standards and validated calibration procedures; To quantify the effects of influencing quantities on the response of dynamic pressure and temperature sensors, in order to determine the appropriate calibration procedures and measurement uncertainties for industrial measurements; To develop new measurement methods and sensors for measuring dynamic pressure and temperature in demanding industrial applications, and to demonstrate the improved accuracy and reliability obtained with those; To validate all of the methods and sensors developed in this project through demonstrations in selected industrial applications; and To ensure by close engagement with industry, that the developed calibration and measurement techniques and technology are adopted by them. The challenge is that in many industrial applications pressure and temperature measurements are performed under dynamically changing conditions. The aim of this project is to improve the accuracy and reliability of pressure and temperature measurements in these challenging conditions. A European joint research project named Development of measurement and calibration techniques for dynamic pressures and temperatures (shortname DynPT) started in the summer 2018.

Experimental Assessment of a Methodology for the Indirect in-Cylinder Pressure Evaluation in Four-Stroke Internal Combustion Engines

Recent innovations in engine control and diagnostics are providing room for development of innovative combustion approaches (e.g., low-temperature combustion) able to minimize the creation of pollutants. To ensure the constant fulfillment of the prescribed thermodynamic conditions, however, a fast real-time monitoring of the in-cylinder pressure is needed. To this end, dynamic pressure sensors, flush-mounted on the cylinder head, are commonly used. With this approach, the measurement accuracy is high, but the durability is limited by the harsh working conditions. The installation on the cylinder head is also complex. The development of robust and effective indirect measurement systems could then represent the enabler of a further development of this technology. In the present study, an innovative methodology to measure the in-cylinder pressure has been conceived and extensively tested on a four-stroke single-cylinder engine. The proposed approach is based on the analysis of the mechanical stress on the engine studs by means of a piezoelectric strain washer. This solution allows the user for a rapid and cost-effective sensor installation, described in the paper along with the signal post-processing techniques. Results showed good accuracy and robustness of the methodology, making the results of practical use for engine control.

Flow visualization study of flow-induced acoustic resonance in closed side branches

The phenomenon of flow-induced acoustic resonance is encountered when an acoustic mode of a side branch is coupled with the flow instability oscillations, which may generate undesirable vibrations of components in pipe systems. In particular, flow-induced acoustic resonance has caused some problems in nuclear power plants. In this study, the characteristics of the flow-induced acoustic resonance in square closed side branches are investigated experimentally. Three different aspect ratios of L/b = 5, 6 and 7, where L is the branch height and b is the branch width, are investigated with Mach number up to 0.22. The flow structures in different acoustic and hydrodynamic modes are visualized using a high speed camera, and the frequencies counted by visual measurement agree well with the frequencies measured by dynamic pressure sensors. The effects of side branch height on the amplitude and frequency characteristics of the acoustic resonance are demonstrated. The results indicate that the maximum normalized pulsation amplitudes in different resonance modes decreases in branch height, acoustic mode and hydrodynamic mode. The branch height has little influence on the Strouhal number at onset of resonance, which is about 0.55 for the first hydrodynamic mode and 0.95 for the second hydrodynamic mode in this work. The maximum normalized fluctuating pressure at the first acoustic mode occurs at a Strouhal number close to 0.43. The hysteresis phenomenon in the evolution of the fluctuating pressure as a function of the velocity is analyzed.

A non-premixed rotating detonation engine using ethylene and air

Only a few studies on ethylene-air rotating detonation engines were conducted due to the great difficulty of quick ethylene-air mixing. Hydrogen or oxygen was added into ethylene-air mixtures, or premixed ethylene-air mixtures were used in some previous studies, to obtain rotating detonation waves. Non-premixed rotating detonation waves of high speeds for ethylene and air sources at room temperatures were obtained in the present study, proving ethylene is feasible for air-breathing rotating detonation engines. The hollow combustor channel here had an outer diameter of 100 mm. Fuel and air were injected into the combustor from 150 cylindrical orifices of a diameter 0.8 mm and a circular gap with a throat width of 1 mm, respectively. The detonation speeds were 1256–1653 m/s for the air flow rates 465–689 g/s and equivalence ratios 0.47–1.06. Most of the speeds were above 80% of Chapman-Jouguet values. Both high-speed images and dynamic pressure sensors showed there was one rotating detonation wave in all the operating conditions.

The effect of turbulent jet induced by pre-chamber sparkplug on combustion characteristics of hydrogen-air pre-mixture

Effect of turbulent jet ignition induced by pre-chamber sparkplug (PCSP), a simper version of turbulent jet ignition pre-chamber system without fuel injection, on the air-hydrogen combustion characteristics was conducted based on an optical constant volume chamber under varied equivalence ratio conditions. The dynamic pressure sensor and schlieren system were used to evaluate the heat release and flame propagation characteristics. The results confirm the feasibility of PCSP type turbulent jet. The jet increase the flame propagation speed significantly compared to standard ignition, which shorten ignition delay and combustion duration, advance T50 largely, and increase the maximum combustion pressure slightly. As a result, the combustion intensity is increased largely, especially under lean regime, the combustion intensity index can be as high as 1.7 at certain equivalence ratio. In addition, the PCSP turbulent jet reduces the sensitivity of heat release to variation of equivalence ratio, which is helpful to simplify the combustion controlling strategy. Furthermore, with the enhancement of the flame propagation, the tendency of knocking combustion can be suppressed potentially.

Unsteady pressure fluctuations measured on a hammerhead space vehicle and comparison with Coe and Nute's 1962 data

A detailed survey of pressure fluctuations was conducted on a replica of the generic, “hammerhead” shaped space vehicle tested more than half century ago by Coe and Nute (1962). A large number of current and past space vehicles follow this general hammerhead configuration. The present test was conducted in the 11-by-11 ft Transonic Wind Tunnel of NASA Ames Research Center over the critical transonic Mach number range of 0.6 ≤ M ≤ 1.2 where typical vehicles encounter very high levels of surface pressure fluctuations during ascent through the atmosphere. Out of the many different types of instrumentations used for this test, data from the dynamic pressure sensors are presented in this paper. In addition, shadowgraph flow visualizations, and a qualitative measure of turbulent fluctuations, estimated from high-speed photography, are also presented. The data set provided a clear insight into the local high level of fluctuations from the formation of the transonic shocks on the payload fairing and also from the impingement of the separated shear layer on the second stage. Space–time correlation showed interesting physics of upstream propagation of pressure fluctuations on the payload fairing when local shock waves were present. A comparison of the magnitude of pressure fluctuations between the present test and that done earlier by Coe and Nute showed good agreement when the limited frequency bandwidth of equipment used in the latter was accounted for. Similarly, when accounting for the differences in the free-stream dynamic pressure, the spectra of surface pressure fluctuations were in reasonable agreement between the present and Coe–Nute tests. The present test provides a far more complete picture of pressure fluctuations due to the usage of a large number of pressure transducers (216 versus 30), wider frequency bandwidth (50 kHz versus 1 kHz), and unsteady pressure-sensitive paint.

Laser ignition of a multi-injector LOX/methane combustor

This paper reports the results of a test campaign of a laser-ignited combustion chamber with 15 shear coaxial injectors for the propellant combination LOX/methane. 259 ignition tests were performed for sea-level conditions. The igniter based on a monolithic ceramic laser system was directly attached to the combustion chamber and delivered 20 pulses with individual pulse energies of $${33.2 \pm 0.8 \,\text{ mJ }}$$ at 1064 nm wavelength and 2.3 ns FWHM pulse length. The applicability, reliability, and reusability of this ignition technology are demonstrated and the associated challenges during the start-up process induced by the oxygen two-phase flow are formulated. The ignition quality and pressure dynamics are evaluated using 14 dynamic pressure sensors distributed both azimuthally and axially along the combustion chamber wall. The influence of test sequencing on the ignition process is briefly discussed and the relevance of the injection timing of the propellants for the ignition process is described. The flame anchoring and stabilization process, as monitored using an optical probe system close to the injector faceplate connected to photomultiplier elements, is presented. For some of the ignition tests, non-uniform anchoring was detected with no influence onto the anchoring at steady-state conditions. The non-uniform anchoring can be explained by the inhomogeneous, transient injection of the two-phase flow of oxygen across the faceplate. This characteristic is verified by liquid nitrogen cold flow tests that were recorded by high-speed imaging. We conclude that by adapting the ignition sequence, laser ignition by optical breakdown of the propellants within the shear layer of a coaxial shear injector is a reliable ignition technology for LOX/methane combustors without significant over-pressure levels.

A Passive Wireless Microelectromechanical Pressure Sensor for Harsh Environments

A microelectromechanical systems (MEMS) capacitive-type passive wireless pressure sensor designed to operate in harsh environments at temperatures up to 1000 °C is presented. The pressure sensor has a sapphire-based diaphragm and structural body, and a platinum-based capacitive element. The capacitive element is configured as a part of a slot patch antenna that is designed to operate in a far-field sensing mechanism with a Ku-band electrical resonant frequency of 15 GHz. The electrical ground plane resides on the backside of the diaphragm, which deflects in response to an applied pressure. The electrical resonant frequency of the pressure sensor changes as a function of the applied pressure to the diaphragm. An increase in the applied pressure, for example, results in a decrease in the electrical resonant frequency. The sensitivity of the pressure sensor is related to the change in applied pressure to the change in the electrical resonant frequency. Three proof-of-concept dynamic pressure sensors are reported using silicon-based diaphragms with antenna diameters of 5.6, 5.7, and 5.8 mm, and measured sensitivities of 2.2, 2.2, and 5.1 kHz/Pa, respectively, up to 900 Pa. In addition, three proof-of-concept static pressure sensors are reported with corresponding measured sensitivities of 3.4, 3.1, and 2.5 kHz/Pa up to 900 Pa. A high-temperature dynamic pressure sensor designed for harsh environments is also reported using a sapphire-based diaphragm with an antenna diameter of 3.8 mm and measured sensitivity of 21.7 kHz/Pa up to 800 Pa. [2017-0210]

Large dynamic range pressure sensor based on two semicircle-holes microstructured fiber

This paper presents a sensitive and large dynamic range pressure sensor based on a novel birefringence microstructured optical fiber (MOF) deployed in a Sagnac interferometer configuration. The MOF has two large semicircle holes in the cladding and a rectangular strut with germanium-doped core in the center. The fiber structure permits surrounding pressure to induce large effective index difference between the two polarized modes. The calculated and measured group birefringence of the fiber are 1.49 × 10−4, 1.23 × 10−4, respectively, at the wavelength of 1550 nm. Experimental results shown that the pressure sensitivity of the sensor varied from 45,000 pm/MPa to 50,000 pm/MPa, and minimum detectable pressure of 80 Pa and dynamic range of better than 116 dB could be achieved with the novel fiber sensor. The proposed sensor could be used in harsh environment and is an ideal candidate for downhole applications where high pressure measurement at elevated temperature up to 250 °C is needed.

A novel polarization demodulation method using polarization beam splitter (PBS) for dynamic pressure sensor

Abstract In this paper we propose a new design to demodulate polarization properties induced by pressure using a PBS (polarization beam splitter), which is different with traditional polarimeter based on the 4-detector polarization measurement approach. The theoretical model is established by Muller matrix method. Experimental results confirm the validity of our analysis. Proportional relationships and linear fit are found between output signal and applied pressure. A maximum sensitivity of 0.092182 mv/mv is experimentally achieved and the frequency response exhibits a

Design and fabrication of distributed Bragg reflector multilayers for dynamic pressure sensing.

A novel 2D-surface shock pressure sensor is designed and tested based on 1D-Photonic Crystal, i.e., Distributed Bragg Reflector Multilayer (DBR/ML) structures. The fast opto-mechanical response of these structures to changes in layer thicknesses and refractive indices are ideally suited for dynamic pressure sensing. They offer the potential to minimize acoustic impedance mismatch between the material layers, and most importantly, the potential to monitor both temporal and spatial (lateral) variations during shock compression. In this feasibility study, different materials and device designs are investigated to identify material/device design combinations with optimum response to dynamic loading. Structural and material effects are studied in terms of spectral and mechanical properties, structure stability, and the ease of fabrication process. Structures comprising of different numbers of SiO1.5/SiO1.7 bilayer stacks are modeled, and fabricated. A 10-bilayer structure placed under a dynamic compressive load of ~7.2 GPa, exhibits a blueshift of 29 nm with a response time of ~5 ns which is well within the shock pressure rise time measured with PDV velocimetry. This promising result successfully demonstrates the feasibility of the specifically designed DBR/ML structure as a dynamic pressure sensor.

Two-dimensional approach for the numerical simulation of large bore reciprocating compressors thermodynamic cycle

The performance of large reciprocating compressors is strongly dependent on the geometry of gas chambers and valve pockets, both directly influencing the pressure losses along the flow path. Reliable and accurate numerical models are necessary for a proper prediction of the thermodynamic cycle of the compressor, hence of both the efficiency and the absorbed power. In order to account for the effect of the geometrical features, the detail level of the modeling technique needs to be suitable for capturing the most significant phenomena related to the physics involved. To this end, CFD simulations can represent a viable tool for the analysis of the working cycle. Due to the complexity of the geometry and the large extent of the fluid domain, unsteady three-dimensional CFD simulations are very demanding in terms of computational resources, resulting in unreasonably lengthy simulations and specialized hardware requirements.The present paper describes a two-dimensional CFD modelling strategy aimed at reducing the computational effort by ensuring a compromise between the accuracy of the results and the simulation costs. A simplified geometry is used to allow the reduction of the three-dimensional fluid domain to an equivalent two-dimensional representation. The suitability of using two-dimensional models for the numerical simulation of the thermodynamic cycle of large reciprocating compressors is analyzed and discussed. In the paper, the simulation results of a double-acting large bore cast iron cylinder are compared to experimental measurements. A satisfactory agreement was obtained when comparing the numerical data to the measurements of dynamic pressure sensors placed in the cylinder head, clearance volume adjustment plugs and suction and discharge nozzles. A comparison with the simulation results of low-order numerical models is also shown to highlight the enhancement in the performance predictability.The matching between experimental and simulated results, together with the short calculation time, confirms the high potential of the proposed solution in predicting the expected performance of the machine, in terms of indicated power and specific work. Moreover, additional benefits are related to the possibility of investigating the pressure oscillations and distributions in the cylinder chambers, and the mass flow rates for the analysis of the suction and discharge pipelines.

Experimental research and numerical simulation of the punch forming of aluminum foil based on a laser-induced cavitation bubble

This study introduces a novel punch forming method based on a laser-induced cavitation bubble. The laser-induced cavitation bubble serves as a stamping force source and applies the shock wave and microjet generated by the bubble to facilitate the punch forming of aluminum foil. A numerical simulation method is implemented to simulate the growth and collapse processes of the laser-induced cavitation bubble. In addition, the explicit dynamics analysis system of ANSYS Workbench is used to simulate the punch forming of aluminum foil. A high-speed camera and a silicon piezoresistive high-frequency dynamic pressure sensor are utilized to compare and verify the simulation results. Finally, the conclusion is presented, which indicates that the shock wave, but not the microjet, plays an important role during aluminum foil punch forming.

Ultrafast Dynamic Pressure Sensors Based on Graphene Hybrid Structure.

Mechanical flexible electronic skin has been focused on sensing various physical parameters, such as pressure and temperature. The studies of material design and array-accessible devices are the building blocks of strain sensors for subtle pressure sensing. Here, we report a new and facile preparation of a graphene hybrid structure with an ultrafast dynamic pressure response. Graphene oxide nanosheets are used as a surfactant to prevent graphene restacking in aqueous solution. This graphene hybrid structure exhibits a frequency-independent pressure resistive sensing property. Exceeding natural skin, such pressure sensors, can provide transient responses from static up to 10 000 Hz dynamic frequencies. Integrated by the controlling system, the array-accessible sensors can manipulate a robot arm and self-rectify the temperature of a heating blanket. This may pave a path toward the future application of graphene-based wearable electronics.

Material removal prediction for contact wheels based on a dynamic pressure sensor

This paper investigates material removal prediction for contact wheels which are widely used in robotic surface finishing process. In particular, a novel methodology is proposed by using a dynamic pressure sensor as the feedback during the polishing process. Based on the pressure sensor’s feedback, a special form of material removal model is developed taking into account of discretized nature of the dynamic pressure sensor. The curve fitting is subsequently derived to map the discretized material removal prediction into continuous ones. The experimental results are reported to verify the proposed methodology, which has the ability to predict material removal in a precise manner with respect to various polishing forces, workpiece geometries, and contact wheel types.

Study on hydraulic characteristics of sabo dam with a flap structure for debris flow

The front part of the flow is very important and complex in the case of debris flow where there is an accumulation of large boulders. It is important to control or dampen the energy of the frontal part of a debris flow for the safety of the downstream area because the impact pressure of debris flow is much greater than that of clear fluid. The main objective of this study is to analyze the hydraulic characteristics of the proposed dam (i.e. closed-type dam with flap). The vertical pressure distribution of this type is compared with conventional dam types. In the experiments, the total pressure associated with major debris flows was recorded in real time by a system consisting of four dynamic pressure sensors installed on different types of dam. The results from experimental data clearly show that the dam with the flap has advantages of capturing the debris flow with large boulders and controls the total pressure by flow circulation due to presence of the flap structure compared to a closed-type dam without flap. Furthermore, the empirical coefficients of hydrodynamic and solid collision models were proposed and compared with available coefficients.

MEMS-Based acoustic sensors for fluid mechanics and aeroacoustics

This talk presents the development of several microelectromechanical systems (MEMS)-based acoustic transducer technologies for fluid mechanics and aeroacoustics applications. Specifically, this presentation will focus on several aluminum nitride piezoelectric MEMS dynamic pressure sensors and microphones. These devices offer the promise of reducing cost, improving performance, and increasing mounting flexibility over existing conventional microphone technologies. Specifically, a transducer with no external power requirement has a key advantage for a large-channel count, widespread deployment. The modeling and design aspects of these devices are reviewed. First, the electroacoustic transduction is predicted via piezoelectric composite plate theory. Lumped element models are then synthesized to describe the dynamic characteristics of the transducer diaphragm and the cavity/vent structure. Constrained nonlinear design optimization using a sequential quadratic programming scheme is then performed to determine the design parameters. Representative results for several applications will then be presented. Finally, unresolved technical issues are summarized for future sensor development.

Experimental Verification of Buffet Calculation Procedure Using Unsteady Pressure-Sensitive Paint

Typically, a limited number of dynamic pressure sensors is employed to determine the unsteady aerodynamic forces on large, slender aerospace structures. This paper describes a robust calculation procedure based on frequency-specific correlation lengths and validation from an experiment conducted on a flat panel coated with fast-response pressure-sensitive paint. The first part of the paper describes the procedure used to analyze the pressure-sensitive paint images and a calibration method using dynamic pressure transducers. Excellent comparison in spectra, coherence, and phase, measured via pressure-sensitive paint and dynamic pressure sensors, validates the pressure-sensitive paint data. The second part of the paper describes the buffet validation process, the first step of which was to use pressure histories from all pixels to determine the true force fluctuations. In the next step, only a selected number of pixels was chosen as virtual sensors, and a correlation-length-based buffet calculation procedure was applied to determine modeled force fluctuations. By progressively decreasing the number of virtual sensors, it was observed that the present calculation procedure was able to make a close estimate of the true unsteady forces only from eight sensors. It is believed that the present work provides the first validation of a buffet calculation procedure.

Compression and shear mode ionic polymer-metal composite (IPMC) pressure sensors

In this work, two types of dynamic pressure sensors based on ionic polymer-metal composites (IPMCs) in compression and shear deformation modes are designed, prototyped, and tested in a shock pressure tube. Although IPMCs offer appropriate properties such as flexibility, light weight, easy processing, resilience and high sensitivity to be used as sensors, there are only limited studies on applicable IPMC sensors and almost all of these devices were developed based on bending deformation. For a better understanding of the electromechanical sensing performance of the IPMCs, the charge current generation mechanisms due to external pressure in both compression and shear modes are developed based on the streaming potential hypothesis. The direct assembly process (DAP) is applied to fabricate some pressure sensor samples of each type for experimental evaluation. An equivalent circuit with parallel resistance and capacitance of the IMPCs samples, estimated by an impedance analyzer, is used to design an appropriate signal conditioner. A shock pressure tube setup is then utilized for performance evaluation of the fabricated devices. The results demonstrate that IPMCs as dynamic pressure sensors represent an appropriate linearity, sensitivity and consistency in both compression and shear modes. It is found that IPMC sensors in shear mode have a higher sensitivity compared with its compression mode counterpart.