Mass Flow Sensor Research Articles

EFFECTS OF TIME-VARYING INFLOW RATES ON COMBINE YIELD MONITOR ACCURACY

The Yield Monitor Test Facility (YMTF) was used to evaluate the GreenStar®. mass flow sensor in a 9600 clean grain elevator under dynamically varying inflow rates. It was found that the GreenStar®. yield sensor predicted accumulated mass with less than 4% error (under dynamically varying step and ramp flow rates) within normal operating conditions of 4.2 to 16.9 kg/s (10 to 40 bu/min) and predicts flow at upper limits of 20 kg/s with a 7.3% error. The yield sensor followed ASAE Draft Standard X578 variable step flow rates, while operating under 20 kg/s, but exhibited significant errors for flows above 20 kg/s. The maximum error in accumulated mass for the variable step profile was less than 2%, while the approximate average instantaneous flow error at steady state was approximately 4.4% with a 3.4% standard deviation. It was found that transient flow had maximum accumulated flow errors of approximately 5%, while oscillating flow had errors around 2.5%. These errors were attributed to the fact that the transient flow maintains flow at the extremity of the GreenStar®. operation range (based on 12.7 kg/s calibration) for longer periods. Additionally, 2-s time averaging of flow readings smoothed noise in the original signal with minimal loss of signal definition.

The Time Responses of Spirometric Values in Response to Single Doses of Inhaled Salbutamol

Background : An assessment of the presence and the degree of reversibility of airflow obstruction is clinically important in patients with asthma or chronic obstructive pulmonary disease. However, the time responses of spirometric parameters in response to bronchodilator have not been well investigated. Methods: We studied 15 patients with asthma. Spirometric and mini-Wright peak expiratory flow measurements were performed at 15, 30, 45, and 60 minutes after using single dose() of inhaled bronchodilator, salbutamol. Results : The mean values of forced expiratory volume in one second() and forced vital capicaty(FVC) were significantly increased at 60 minutes after using bronchodilator in comparison to 15 minutes. And peak expiratory flow rate measured by either mass flow sensor or mini-Wright peak flow meter were significantly increased at 45 minutes after using bronchodilator in comparison to 15 minutes. Conclusions : To appropriate evaluation of the bronchodilator response in patients with reversible airflow limitation, it would be useful measuring either or PEF at the later time point 60 or 45 minutes in comparison to 15 minutes after using bronchodilator.

Lifetime prediction for mechanically stressed low temperature co-fired ceramics

Multilayer ceramics based on LTCC (low temperature co-fired ceramics) are gaining increasing interest in the manufacturing of high-integrated devices for microelectronic applications. In many applications the parts are exposed to mechanical stresses, which is an important issue regarding the reliability of the device. To predict the life time of LTCC multilayer devices, and to extend the application range of LTCC, basic mechanical data of this material are needed. In this paper sintered LTCC laminates are investigated concerning their flexural strength, crack growth rate, and life time prediction. The flexural inert strength of the investigated LTCC material is about 450 MPa. In applications with a stress level of 100 MPa, like mass flow sensors for the measurement of injected fuel quantities, acceptable lifetimes are achieved. This means that LTCC is an interesting material to fabricate devices, in which LTCC fulfils the requirements of a functional and structural material.

Model based diagnosis of the air path of an automotive diesel engine

A model based diagnosis system for the air-path of a turbo-charged diesel engine with EGR is constructed. The faults considered are air mass-flow sensor fault, intake-manifold pressure sensor fault, air-leakage, and the EGR-valve stuck in closed position. A non-linear engine model, with four states, is constructed. The diagnosis system is then constructed in the framework of structured hypothesis tests and by using observers estimating unknown fault-parameters. To handle modeling errors a new method for adaptive thresholds is proposed. The diagnosis system is successfully evaluated in a real car driving on the road.

Development of a Flow Model for the Design of a Momentum Type Beet Mass Flow Sensor

A lot of research is done to monitor yield during harvesting. Combined with a positioning system, this information can be used to produce yield maps. Based on the yields of successive years, site-specific field management can be done, aiming for higher local economic and ecological yield efficiencies. In this research, a curved plate mass flow sensor for sugar beet is designed with the aid of a mathematical model. The principle is based on measuring the impulse flow colliding with the plate. For granular materials, an accuracy of 2% is achieved. The mass flow sensor for sugar beet is integrated as a curved side rack in the cleaning channel of the harvester. The side rack is mechanically isolated from the frame. A theoretical model of the beet flow over the turbines of the cleaning unit is calculated and incorporates all physical parameters that influence the mass flow measurement by the momentum sensor. The flow density and friction coefficients with the rack and the turbine characterise the mass flow. From the model, the influence of the different parameters (slope, beet velocity, friction, length of the plate) on the momentum is investigated. The force exerted on the rack of the cleaning unit is measured, from which the momentum can be indirectly calculated. A measurement device is constructed, minimising the influence of the harvesting conditions and the material properties. After calibration, measurements are carried out on the cleaning unit of a Dewulf R6000T (two-phase system) and an Agrifac ZA 215 EH (one-phase system). Research is done to construct the sensor independent on friction properties between beets and the rack. Major influence comes from the velocity of the transported material. Variations in beet speed have to be registered continuously with a Doppler radar meter. Influences of a varying slope can also be corrected regarding the instantaneous beet velocities. More accurate measurements are done when the sensor is installed on bigger spinning wheels because of higher momentum due to a higher centrifugal force and hence a higher signal to noise ratio. To evaluate the model, only average mass flows and flow speeds could be used to predict the executed moments. When comparing the integrated measured momentum and the scale weight of the harvester bin, the error never exceeds 3% when using the derived equation.

Reliability aspects of microsensors and micromechatronic actuators for automotive applications

In modern cars microsensors and micromechatronic actuators play an essential and still increasingly important role as the interface between the vehicle with its complex functions of motor management, chassis systems, safety as well as comfort and convenience on the one hand and the respective electronic control units on the other hand. They have to fulfill their task in a harsh environment over the entire lifetime of an automobile. Therefore reliability aspects have moved more and more into the focus of engineering and research activities in microsystem technology. A methodical procedure is described that allows reliability issues to be approached efficiently. The implementation of the methodology is illustrated with real-life examples of reliability aspects of hot film mass air flow sensors, inertial sensors as well as piezoelectric actuators.

Fundamental Mass Flow Measurement of Solid Particles

A generic mass flow measurement device was developed as a variation on the theme of counting. In a hypothetical infinitely sparse mass flow, the number of passing particles could be counted in a time frame and multiplied by the mean mass per particle to obtain a mass flow per time unit. In a mass flow of realistic density, however, particles travel in cluster formation and direct counting of individual particles is impossible. If a method could be available that reconstructs the original number of particles in a cluster, the mass flow can be computed for realistic clustered mass flows. This reconstruction algorithm was developed in this research; it uses the measured cluster lengths to reconstruct the total number of particles in each passing cluster. The lengths of the clusters were measured with an optoelectronic device. The reconstruction algorithm was developed using simulation, augmented by clustering theory. For identical diameter particle flow, simulation results showed that the number of particles in a cluster could be reconstructed using a very simple reconstruction formula. This formula uses only the total number of clusters per time frame and the total number of individual particles measured in the same time frame. However, identical diameter flow is not realistic, since even identical particles are measured with a certain error. Reconstruction of the realistic distributed diameter particle flow was approximated using the identical particle method. The optical mass flow sensor has major advantages over traditional methods. It is virtually insensitive to vibrations, contamination, temperature drift, and misalignment and the underlying measurement concept is well understood. But most importantly, the sensor does not require calibration. The mass flow of identical particles (4.5 mm air gun pellets) was measured with an error smaller than 3% even for high density flow rates.

Design of a Friction Independent Mass Flow Sensor by Force Measurement on a Circular Chute

A mass flow sensor for bulk flow measurements is designed. The sensor consists of a curved chute and the force executed by the flow on the chute is a measure for the force. By properly selecting the projection angle of the force, i.e. the direction in which the force is measured, the sensor can be made almost independent of the friction coefficient of the bulk. The selection of the projection angle involves an optimisation problem. To carry out the optimisation, a physical model of the differential force is derived. The differential force is the force executed on the chute by an infinitesimal mass. Based on the model of the differential force, a starting value for the optimisation process is computed. After the optimisation the influence of friction on the measurement is less than 0·5% per 0·1 change of the friction coefficient. For some installation conditions, the effect of friction on the force measurement can be completely eliminated.

NON-LINEAR SYSTEMS REPRESENTATION USING ARMAX MODELS WITH TIME-DEPENDENT COEFFICIENTS

An approach that models a non-linear process operating over a large dynamic range is developed and validated. This approach is based on stochastic Time-varying AutoRegressive Moving Average with eXogeneous inputs (TARMAX) models. The TARMAX model coefficients are explicit functions of time and vary in a deterministically organised fashion. A novel model parameter estimation method fully based on linear operations is presented. The estimation approach is characterised by a low computational complexity and requires no initial guess of the parameter values. The ability of the approach to model non-linear processes is validated by addressing problems dealing with improving the estimation of mass air flow going into an automobile engine. First, a TARMAX model is used to capture the dynamics of the engine process relating air flow provided by a laboratory grade sensor and three input signals available in the engine electronic controller. The TARMAX model is used to simulate the complex relationship between the output and the three input signals. Second, TARMAX models are used to anticipate the future response of a hot-wire-based mass air flow sensor (MAF) in order to obtain an accurate estimate of the cylinders air charge. The estimated TARMAX models prove to have good simulation and prediction capabilities. All models are estimated using actual production vehicle data.

An Introduction to Microelectromechanical Systems Engineering

If you've not been involved in MEMS (MicroElectroMechanical Systems) technology or had the cause to use MEMS devices, then you may wonder what all the fuss is about. What are MEMS anyway? What's the difference between MEMS and MST (MicroSystems Technology)? What are the advantages over existing technologies? If you have ever found yourself pondering over such questions, then this book may be for you. As the title suggests, the main aim is to provide an introduction to MEMS by describing the processes and materials available and by using examples of commercially available devices. The intended readership are those technical managers, engineers, scientists and graduate students who are keen to learn about MEMS but have little or no experience of the technology. I was particularly pleased to note that Maluf has dedicated a whole chapter to the important (and often difficult) area of packaging. The first three chapters provide a general overview of the technology. Within the first three pages we are introduced to the MEMS versus MST question, only to discover that the difference depends on where you live! The United States prefer MEMS, while the Europeans use the handle MST. (Note to self: tell colleagues in MEMS group at Southampton). A good account is given of the basic materials used in the technology, including silicon, silicon oxide/nitride/carbide, metals, polymers, quartz and gallium arsenide. The various processes involved in the creation of MEMS devices are also described. A good treatment is given to etching and bonding in addition to the various deposition techniques. It was interesting to note that the author doesn't make a big issue of the differences between bulk and surface micromachined devices; the approach seems to be `here's your toolbag - get on with it'. One of the great strengths of this book is the coverage of commercial MEMS structures. Arising as they have, from essentially a planar technology, MEMS devices are often elaborate three-dimensional creations, and 2D drawings don't do them much justice. I have to say that I was extremely impressed with the many aesthetic isometric views of some of these wonderful structures. Pressure sensors, inkjet print nozzles, mass flow sensors, accelerometers, valves and micromirrors are all given sufficient treatment to describe the fundamental behaviour and design philosophy, but without the mathematical rigour expected for a traditional journal paper. Chapter 5 addresses the promise of the technology as a means of enabling a new range of applications. The concept of using MEMS devices as key elements within complex systems (or even microsystems!) is explored. The so-called `lab-on-a-chip' approach is described, whereby complex analytical systems are integrated onto a single chip together with the associated micropumps and microvalves. The design and fabrication of MEMS devices are important issues by themselves. A key area, often overlooked, is that of packaging. Painstaking modelling and intricate fabrication methodologies can produce resonator structures oscillating at precisely, say, 125 kHz. The device is then mounted in a dual-in-line carrier and the frequency shifts by 10 kHz because of the additional internal stresses produced. Packaging issues can't be decoupled from those of the micromachined components. Many of these issues, such as protective coatings, thermal management, calibration etc, are covered briefly in the final chapter. Overall, I found this book informative and interesting. It has a broad appeal and gives a good insight into this fascinating and exciting subject area. Neil White

A robust flow sensor for high pressure automotive applications

Abstract In this paper, a micromachined mass flow sensor mounted on a high pressure stable substrate is presented to measure on board the different injection quantities needed in modern direct injection (DI) systems for optimum performance of the engine. To detect the injection end/begin as well as the injection rate as precisely and fast as possible, the sensor is completely integrated into the nozzle body close to the injection holes for the first time. The thermal measurement principle is chosen, as gasoline and diesel fuel quantities can be detected and therefore, the use of this present flow sensor is not restricted to one of these different types of combustion engines. The fabrication process of the molybdenum (Mo) thin film sensors on an LTC (low temperature co-fired) ceramic chip is described. Additionally, FEM simulations concerning the velocity profile in the injection nozzle are performed and the electrical heating power of the hot film anemometer at different overheat ratios is analytically calculated. Finally, the injection rate measurements up to 60 MPa (600 bar) with the nozzle-integrated thin film sensor are presented and their additional information compared to signals gained from an injection amount indicator (EMI), which is part of the high-pressure hydraulic test bench, are discussed.

Selection of Actuators and Sensors for Surge Control

For surge control in compression systems, a suitable combination of actuators and sensors must be selected. The goal is to identify the combinations for which there exists a controller that locally stabilizes the linearized compression system model and meet additional control objectives. The latter are quantified in terms of a bound on an H-infinity norm. With this we aim to stay close to the nominal operating point in the face of disturbances, noise, and actuator limitations. The considered selection method is more rigorous than previously found in literature, in the sense that multivariable, dynamic output feedback is the focus and that different performance specifications are handled simultaneously. Though the method was originally developed fot linear systems, it can be used for the nonlinear compression system model by linearizing the model on a grid of nominal operating points. Among the proposed actuators and sensors, the close-coupled valve and mass flow sensor are identified as the most promising. The results are sustained by the physics of the problem.

TEST OF TEMPERATURE AND STRAY–LIGHT EFFECTS ON MASS–FLOW SENSOR FOR COTTON YIELD MONITOR

The performance of detectors and light sources used in optical massflow sensors for cotton yield monitors areaffected by internal temperature changes of the sensor. Straylight variation in the duct of cotton pickers can affect theaccuracy of the cotton yield monitor. Specific measures to reduce the temperature and straylight effects were used in thedesign of a cotton flow sensor at Mississippi State University. The performance of the cotton flow sensor was tested withvarying operating temperatures and stray light around the sensor. With an operating temperature variation of 18
C (32
F),sensor output changed 0.76%. The effect of stray light on the sensor was tested both indoors and outdoors. As the solar lightintensity around the sensor increased by a factor of 15, the sensor output changed 1%. For an indoor test, two 500W halogenlights were employed to create stray light for the test. Sensor outputs obtained with and without the stray light were verystrongly correlated with cotton weight that passed by the sensor (R 2 = 0.98). Test results indicated that, at operatingtemperatures between 4 and 31
C (40 and 88
F) and with large straylight variations, the performance of the cotton flowsensor was not significantly affected.

Fueling Control of Spark Ignition Engines

Presented in this paper is an adaptive, model based, fueling control system for spark ignition-internal combustion engines. Since the fueling control system is model based, the engine maps currently used in engine fueling control are eliminated. This proposed fueling control system is modular and can therefore accommodate changes in the engine sensor set such as replacing the mass-air flow sensor with a manifold air pressure sensor. The fueling algorithm can operate with either a switching type O 2 sensor or a linear O 2 sensor. The fueling control system is also parceled into steady state fueling compensation and transient fueling compensation. This feature provides the distinction between fueling control adaptation for transient fueling and steady state fueling. The steady state fueling compensation utilizes a feedforward controller which determines the necessary fuel pulsewidth after a throttle transient to achieve stoichiometry. This feedforward controller is comprised of two nonlinear models capturing the steady state characteristics of the fueling process. These models are identified from an input-output testing procedure where the inputs are fuel pulsewidth and mass-air flow signal and the output is a lambda signal. These models are adapted via a recursive least squares method to accommodate product variability, engine aging, and changes in the operating environment. The transient fueling compensation also utilizes a feedforward controller that captures the essential dynamic characteristics of the transient fueling operation. This controller is measured using a frequency domain system identification approach. This proposed fueling control system is demonstrated on a Ford 4.6L V-8 fuel injected engine.

Model Based Diagnosis of the Air Path of an Automotive Diesel Engine

A model based diagnosis system for the air-path of a turbo-charged diesel engine with EGR is constructed. The faults considered were air-mass flow sensor fault, intak~manifold pressure sensor fault, air-leakage, and the EGR-valve stuck in closed position. A non-linear engine model, with four states, is constructed. The diagnosis system is then constructed in the framework of structured hypothesis tests, and by using adaptive observers. The diagnosis system issuccessfully evaluated in a real car driving on the road.

A moment-of-momentum flux mass air flow measurement device

A unique air flow rate measurement device has been developed and tested foruse in the Axial Fan Research and Development facility at Michigan StateUniversity. The subject mass air flow meter is located downstream of a widevariety of test fan and component geometries. These can significantly changethe velocity profile entering the metering nozzles. For this reason a pointmeasurement of a characteristic velocity in the nozzle outlet would notprovide a viable experimental technique for the flow rate evaluation. Thisalso negates the option of using a simple nozzle discharge coefficient.An integral measurement technique was therefore implemented. A 90° turningpassage supported on a knife edge pivot was used to create a measurable netmoment-of-momentum flux. The resistive moment provided by a strain gauge forcetransducer was used to infer this net flux. The acceleration of the flow frominlet to outlet of the 90° turn and the larger contribution of theoutlet moment-of-momentum flux provide the desired insensitivity to thenon-uniform inlet flow conditions. A calibrated nozzle was used to determinethe `force-mass flow rate' transfer function.

Microsensors for Automotive Applications – Metrology and Test

AbstractAccording to market surveys automotive microsensors will evolve into a multi-billion dollar business by 2005. Key roles are attributed to inertial sensors for passenger safety systems, and mass flow and pressure sensors for engine management systems. Thin film techniques together with silicon bulk or surface micromachining have been established as preferential processes to achieve reduction of sensor size, weight and cost along with improvements of sensor functionality and reliability. Enhanced sensor performance often pushes the limits of process technology and therefore the need arises very early in the MEMS design process to identify materials and geometry related parameters which are critical with respect to their tolerance band specifications. In order to control these critical parameters, automated wafer level test procedures need to be developed (based preferentially on electrical quantities) and additionally considered for in the sensor design phase (design for test). In analogy to microelectronics 2D wafer maps of critical parameters may give hints on how to improve process stability and how to adapt the sensor design in order to optimize yield. Examples of critical model parameter variations include thermal conductivity, thickness, and shear modulus of thin films.

Overview of automotive sensors

An up-to-date review paper on automotive sensors is presented. Attention is focused on sensors used in production automotive systems. The primary sensor technologies in use today are reviewed and are classified according to their three major areas of automotive systems application-powertrain, chassis, and body. This subject is extensive. As described in this paper, for use in automotive systems, there are six types of rotational motion sensors, four types of pressure sensors, five types of position sensors, and three types of temperature sensors. Additionally, two types of mass air flow sensors, five types of exhaust gas oxygen sensors, one type of engine knock sensor, four types of linear acceleration sensors, four types of angular-rate sensors, four types of occupant comfort/convenience sensors, two types of near-distance obstacle detection sensors, four types of far-distance obstacle detection sensors, and and ten types of emerging, state-of the-art, sensor technologies are identified.

Materials in Aerial Application --- Part 2: Experimental Model Validation

A system was developed to measure the mass flow of granular fertilizer material in aerial spreader ducts. The flow process was regarded as the sequential passage of clusters containing multiple particles with varying diameters. An optical sensor was used to measure the cluster lengths on the fly. In a low-density flow regime, the diameter of each particle could be measured individually (this is called the "single-particle approach"). After conversion to a volume of a sphere and multiplication by the true material density, the mass flow could be computed. In a high-density mass flow regime (called the "mass flow approach"), particles form clusters, and cluster lengths would be measured instead of particle diameters. The first step in performing mass flow measurement was to develop a reconstruction algorithm that estimates the number of particles in a cluster from the measured cluster length. This algorithm, called the Exponential Estimator, was developed using simulation and is reported in Part 1. This article, Part 2, describes the use of the mass flow sensor as well as the reconstruction algorithm to assess the accuracy of the complete system. Tests were carried out under laboratory conditions, using mass flows of spherical particles as well as urea fertilizer under varying flow velocities and densities. The mass flow of identical spherical particles of 4.45 mm diameter was measured with an accuracy of 3%, even under high-density flow conditions. For granular fertilizer, the flow was measured with an accuracy of 2% for high-density flows and 4% for low-density flows.

Characteristics of Piezoresistive Mass Flow Sensors Fabricated by Porous Silicon Micromachining

Piezoresistive flow sensors with four different types of micro-cantilever structures were fabricated by using (100), n/n+/n three-layer silicon wafer and their characteristics were investigated. Piezoresistors were formed through boron diffusion and its value was about 1 kΩ. Three dimensional micro-cantilevers were fabricated by porous silicon micromachining technique and the cantilevers were curled by annealing at 450°C. Wheatstone bridge was formed with two piezoresistors and two fixed resistors in order to measure the output response of the fabricated sensor. The output voltage was increased with increasing cantilever length while the detectable measurement range was extended with decreasing length of micro-cantilever. The output voltage of the fabricated sensors was increased with the quotient of 3.2 of the flow rate.