RU117188U1 - AUTOMATED COMPLEX OF ENSURING HYDROMETEOROLOGICAL MEASUREMENTS IN STORM CONDITIONS WITH MOVING OBJECTS - Google Patents

Abstract

1. An automated complex for ensuring hydrometeorological measurements in stormy conditions from moving objects, characterized by the fact that it includes an accelerometer and an inclinometer installed in a special box at a certain distance from the measuring system and connected by a cable with an analog-to-digital converter connected by control signals and measurement signals through the interface line with the control computer. ! 2. The automated complex according to claim 1, characterized in that the entire range of possible measurements is used to compensate for the pitching - the coordinates of the vessel, the speed of movement and the course of the vessel, acceleration and tilt angles along three axes. ! 3. The automated complex according to claim 1, characterized in that the used ADC of the NI USB-6008/6009 Data Acquisition Device (DAC) allows conversion and synchronization of the incoming data.

Description

The field of technology. The utility model relates to the field of meteorological measurements and oceanology, specifically to automated complexes for compensating for ship pitching during micrometeorological measurements in marine conditions from moving bases (ships, sea buoys) in the presence of surface waves in the interests of micrometeorological and meteorological measurements to calculate the true wind speed and characteristics of atmospheric turbulence when measured from ships and other mobile platforms.

The level of technology.

Measurements of turbulent pulsations from the side of the vessel are significantly complicated by low levels of turbulence, a more aggressive environment, and distortion of signals by the movements of the device itself due to sea waves (ship roll). The hull of the vessel and its superstructures resist air flow and distort it; therefore, the installation of devices is of great importance. In addition, the ship moves not only relative to the ground, but also relative to the water, therefore, to calculate the true wind, you need to know the location of the ship, its course and the direction of the longitudinal axis of the ship relative to the ground, as well as the speed of movement and direction relative to the water. When measuring from the side of the vessel, errors also arise due to the movement of the sensors in the vertical direction as a result of the pitching of the vessel, the oscillations of the sensor as a result of the pitching of the vessel and the yaw of the vessel at the heading [Kretschmer et al. 1972]. Spectra of vertical wind speed are especially distorted.

Wind wave is the process of formation, development and propagation of waves caused by wind on the sea surface. This is one of the main hydrometeorological factors that determine the safety and economic efficiency of navigation. The pitching creates dangerous rolls, makes it difficult to determine the position of the vessel, in addition to speed loss, the excitement causes yaw and avoidance of the vessel from a given course. Wind waves have two main features. The first feature is irregularity: disordered sizes and waveforms. The crests of the waves move not only in the direction of the wind, but also in other directions. Such a complex structure of the perturbed sea surface is explained by the vortex, turbulent nature of the wind forming the waves. The second feature of excitement is the rapid variability of its elements in time and space and is also associated with the wind. However, the size of the waves depends not only on the wind speed, the duration of its action, the area and the configuration of the water surface are essential. Therefore, accounting for the motion of the vessel due to sea waves during meteorological measurements is extremely difficult, especially in stormy conditions.

There are three sources of distortion in the calculation of the flows caused by the movement of the vessel [Hare ,. 1992]:

1) the simultaneous inclination of the anemometer due to pitching, rolling, and yaw of the bow at the heading;

2) the angular velocity of the anemometer, caused by the rotation of the vessel relative to the moving coordinate system (sea);

3) the translational speed of the vessel relative to the absolute coordinate system.

Based on the method proposed for aircraft measurements [Axford, 1968] in [Fujitani, 1985], a technique was developed for correcting the influence of vessel motion on the measured wind speed, which resulted in wind relative to a fixed surface [Repina, Smirnov 2008]. Variants of this technique were used to correct measurements from sea buoys and ships in [Anctil et al., 1994; Edson et al., 1998]. The coordinate system in this study is right-handed with the axis OX along the vessel’s tank, OY — perpendicular to the side, and OZ — vertically upward. (Fig 1)

The angular velocity ϕ is positive when the side is lowered, the angular speed θ is positive when the side is lowered and the angular speed ψ is positive counterclockwise when viewed from above. Following the work [Anctil et al. 1994], the real wind vector can be obtained from the equation:

U _true = T (U _obs + Щ _obs × R) + V _mot

Where Ω _obs is the measured angular velocity vector, T is the transition matrix from the coordinate system associated with the vessel to the true coordinate system, V _mot is the vessel velocity vector relative to the water, R is the distance between the anemometer and the compensation system.

Using the hypothesis of small angles, three separate rotations in the matrix T can be performed in any order. In this work, we use the matrix T proposed in [Goldstein, 1950] and finalized in [Anctil et al. 1994].

The angular velocity vector Ω _obs is defined in our right-handed coordinate system as follows:

where the point means the time derivative of the Euler angles. R depends on the specific vessel and the location of the sensors.

The vessel velocity vector relative to the water is calculated by integrating the acceleration a, which exists in the ship's reference frame. It is necessary to take into account the average speed of the vessel relative to the water.

Those. we can write:

And finally

That is, to achieve the result, it is necessary to change the angles of inclination of the vessel and acceleration in three directions, which is provided by an automated system for compensating the pitching of the vessel during micrometeorological measurements in sea conditions from moving bases (ships, sea buoys). The vessel velocity vector is taken from the data of the ship's navigation system.

Formulation of the problem. The objective of the utility model is to correct pitching during micrometeorological measurements from moving objects in the presence of moderate and strong sea waves. The technical result is an increase in the accuracy of measuring wind speed and atmospheric turbulence characteristics from moving objects.

The solution of the problem. The achievement of the claimed technical result and, as a result, the solution of the problem is ensured by the fact that the Automated complex for providing hydrometeorological measurements in stormy conditions from moving objects according to the utility model includes an accelerometer and an inclinometer installed in a special box at some distance from the measuring system and connected by cable to analog-to-digital Converter, connected by control signals and measurement signals through the interface line ide with the control computer. The ADC provides signal conversion and data synchronization. The interface communication line is made cable with the RS232 interface. Registration is done using National Instruments software, the VI Data Logger software component. The speed and movement of the vessel are recorded through the GPS system directly connected to the computer.

Achievement of the task and technical result. The automated complex for providing hydrometeorological measurements in stormy conditions from moving objects is made in the form of an accelerometer (1) and an inclinometer (2) installed in a special box at a certain distance from the measuring system and connected by a cable to an analog-to-digital converter (4) connected by a control signals and measurement signals through the interface line of communication with the control computer (6). The ADC provides signal conversion and data synchronization. Registration is done using National Instruments software, the VI Data Logger software component. The speed and movement of the vessel are recorded through the GPS system (3), directly connected to the computer (6).

In general, the system provides reliable registration of the three components of the vessel’s acceleration, the vessel’s tilt angles in three directions, the vessel’s speed and course, data synchronization and data pairing with the data of an automated complex for recording and processing micrometeorological measurements in the surface atmospheric layer

The indicated advantages of the complex provide a reduction in the errors of micrometeorological measurements in the drive layer of the atmosphere from moving objects.

Link to the drawings. Figure 1 presents the coordinate system for the correction of pitching, figure 2. - a functional diagram of an automated complex for providing hydrometeorological measurements in stormy weather conditions from moving objects, Fig. 3 - spectra of horizontal and vertical wind speeds and their cospectra under different stratification conditions before (left panel) and after pitching correction, Fig. 4 - spectra of vertical wind speed with and without pitching correction.

Description in statics. The automated complex for providing hydrometeorological measurements in stormy conditions from moving objects contains measuring elements (Figure 2): accelerometer (1) standard ADXL330, inclinometer (2) standard STS 360 and GPS (3) standard Garmin 17N. The signals are fed to the inputs of the analog-to-digital converter NI USB 6008 (4). The 3-axis ADXL330 accelerometer measures three acceleration components. The sensor is located on a board with three operational amplifiers. Power supply - +5 volts. The characteristics of the sensor are presented in table 1. The ADC is connected to the power supply (5). Signals from the ADC and GPS are sent to the computer (6).

Table 1 Parameter Value Note Range of measured accelerations ± 4g From full scale Transformation nonlinearity ± 0.3% On any of two axes Axis direction orthogonality error ± 0.1% On any of two axes Channel interference ± 1% On any of two axes Sensitivity 330 mV / g Maximum on any axis Output Offset at Zero Acceleration 1.5 v On any axis, typical value Working strip X and Y axes 1600 Hz Without external filter capacitor Z 550 Hz Without external filter capacitor

The inclinometer (2) STS-360 allows you to measure tilt angles in three projections. Range of measurements - 360 °. The device is characterized by high accuracy and reliability. The signal is transmitted via RS232. Product specifications are presented in Table 2.

table 2 Type of STS-360-RS232 Rev. Range 360 ° Accuracy ± 0.1 ° Resolution ± 0.1 ° Temperature stability Digital compensation Working temperature -10 ° + 70 ° Exit RS232 (9600 Baud) Time constant <0.3 s Food 8-15 VDS

Three acceleration components and three tilt angles are supplied to the inputs of the NI USB 6008 analog-to-digital converter (4). Registration is performed using National Instruments software, the VI Data Logger software component. The NI USB-6008 DRC is connected to the computer via a full-speed USB interface and contains eight channels for inputting analog signals (AI), two channels for generating analog signals (AO), 12 channels for digital input / output (DIO) and a 32-bit counter. The characteristics of the DRC are presented in table 3.

Table 3 Characteristic USB-6008 Resolution with analog input 12 bit (differential connection) 11 bit (connection with common drive) Maximum sampling rate (single channel) 10 Hz Maximum sample rate (multiple channels) 10 Hz Digital Output Configuration Open collector

Description in dynamics.

Figure 3 shows the spectra of vertical and horizontal wind speeds and the cospectra between them under different stratification conditions before and after pitching correction using an Automated complex to compensate for pitching of a ship during micrometeorological measurements in marine conditions from moving bases using the method proposed above. The shaded area shows the standard error of the mean. U is the average wind speed, f is the frequency in Hz, z is the height of the anemometer, and ∗ is the dynamic speed, σ _w is the standard deviation of the vertical wind speed. L is the scale of Monin-Obukhov. 285 spectra were used, 30 of them for stable stratification, 194 for unstable and 61 for neutral.

Figure 4 shows a separate spectrum of the vertical wind speed, according to the data obtained on the ship when working on the Black Sea, using the pitching correction system and without it. It can be seen that the pitching introduces disturbance into the spectral region in the region of 0.1 Hz, which corresponds to a wave period of 8 sec.

Information sources:

1. Kretschmer S.I., Panin G.N., Ipatov V.V. Measurement of pulsations of humidity over the sea // Izv. USSR Academy of Sciences, Atmospheric and Ocean Physics, 1972, v. 8, No. 7

2. Anctil, F., M. A. Donelan, W. M. Drennan, and H. C. Graber, Eddy-correlation measurements of air-sea fluxes from a discus buoy, J. Atmos. & Oceanic Tech., Vol. 11, pp. 1144-1150.

3. Axford, D.N., On the accuracy of wind measurements using an inertial platform in an aircraft and an example of a measurement of the vertical mesostructure of the atmosphere, J.Appl. Meteorol., 7, 645-666, 1968.

4. Edson J. B., Hinton A. A., Prada K. E., Hare J. E. Fairall C.W. Direct Covariance Flux Estimates from Mobile Platforms at sea // J. Atmos. Oceanic Technol. 1998. V.15, P.547-562.

5. Fujitani, T., Method of turbulent flux measurement on a ship using a stable platform system, Pap. Meteorol. Geophys., 36, 157-170, 1985.

6. Goldstein, H., Classical Mechanics, 399 pp., Addison-Wesley-Longman, Reading, Mass., 1950.

7. Hare, J. E, 1992: Shipboard eddy-covariance measurements of the turbulent fluxes of heat, moisture, and momentum. MS Thesis, Penn State University, 207 pp.

Claims (3)

1. An automated complex for providing hydrometeorological measurements in stormy conditions from moving objects, characterized in that it includes an accelerometer and an inclinometer installed in a special box at a certain distance from the measuring system and connected by a cable to an analog-to-digital converter connected by control and measurement signals through an interface line of communication with the control computer. 2. The automated complex according to claim 1, characterized in that the whole complex of possible measurements is used to compensate for pitching - the coordinates of the vessel, the speed and course of the vessel, accelerations and tilt angles along three axes. 3. The automated complex according to claim 1, characterized in that the NI USB-6008/6009 ADC used by the data acquisition device (DRC) allows the conversion and synchronization of incoming data.