NON-INVASIVE METHOD AND DEVICE TO MEASURE THE FLOW RATE OF A RIVER, OPEN CHANNEL OR FLUID FLOWING IN AN UNDERGROUND PIPE OR CHANNEL

Abstract

A non-invasive microwave measuring device (01) is for calculating the flow rate of a fluid. The device (01) includes a non-invasive microwave fluid velocity measuring device (03) having a patch antenna or horn antenna to generate a microwave signal (14) that is transmitted at a specific elevation angle α towards the fluid surface (16) and to receive the reflected microwave signal (15) from the fluid surface (16) with a doppler shift frequency. The measuring device (03) is suspended from a drone (02) by a suspension system (04). The suspension system (04) eliminates vibration noise generated by the drone (02). At least one vibration sensor eliminates false velocity readings. At least one angle sensor compensates for Pitch, Roll and Yaw from the drone (02) that influence the fluid surface velocity measurement.

Claims

1. A non-invasive microwave measuring device for calculating the flow rate of a fluid, the device comprising: a non-invasive microwave fluid velocity measuring device comprising a patch antenna or horn antenna to generate a microwave signal that is transmitted at a specific elevation angle towards a fluid surface and to receive the microwave signal reflected from the fluid surface with a doppler shift frequency; a drone to which is suspended the measuring device via a suspension system, said suspension system eliminating vibration noise generated by the drone; one or more vibration sensors to identify and eliminate false velocity readings induced by the drone; one or more angle sensors to compensate for Pitch, Roll and Yaw from the drone that influence fluid surface velocity measurement and determine a final angle from the measuring device towards the fluid surface.

2. The device according to claim 1, wherein the non-invasive microwave fluid velocity measuring device comprises a 3D control system with three motors able adapted to automatically reposition the non-invasive microwave measuring device to compensate for the Pitch, Roll and Yaw of the drone.

3. The device according to claim 1, wherein the non-invasive microwave fluid velocity measuring device is associated to a measuring device comprising GPS and altimeter sensors.

4. The device according to claim 3, wherein the non-invasive microwave fluid velocity measuring device is associated to an interface to capture GPS and altimeter data from the drone.

5. The device according to claim 1, comprising a camera and light to facilitate pilotage in underground pipes and channels (22).

6. The device according to claim 4, wherein the non-invasive microwave fluid velocity measuring device comprises a recording device to record pictures or videos, together with fluid velocity measurements and/or GPS and altimeter data.

7. The device according to claim 1, wherein the non-invasive microwave fluid velocity measuring device comprises one or more of: a level or distance measuring device, or a wind speed and direction measurement device.

8. The device according to claim 1, wherein the suspension system comprises three or more tubes connected to each other by ropes, the tubes connecting the velocity measuring device to the drone, the velocity measuring device being attached to a first end of the tubes and the drone being attached to a second end of the tubes.

9. The device according to claim 8, wherein the three or more tubes have different lengths to give an angle for the measuring device compared to the water fluid surface and horizontal plane of the drone, angle that is measured by the one or more angle sensors.

10. The device according to claim 8, wherein elastic ropes are provided in the tubes and used to suspend the measuring device, an upper end of the elastic ropes being connected to the suspension system which is attached to the drone and a lower end of the elastic ropes being attached to the measuring device, the lower end of the elastic ropes being free from the tubes and longer than the tubes.

11. The device according to claim 10, wherein elasticity of the elastic ropes is chosen to absorb undesired vibrations, with vertical movements of the measuring device remaining insignificant.

12. The device according to claim 1, wherein the suspension device comprises a rigid upper plate connected to the drone and a rigid lower plate connected to the non-invasive measuring device, both plates and are connected with silent block dampers.

13. A non-invasive method for measuring velocity measurement and distribution of a fluid flowing through a pipe or channel or in a river or open channel, the method using a non-invasive microwave fluid velocity measuring device suspended from a drone and comprising one or more vibration sensors, said method comprising the steps of: a. generating microwave signals by using a patch antenna or horn antenna; b. receiving microwave signals from a flowing fluid surface (16); c. generating a plurality of discrete data expressed in amplitude as a function of time from the generated microwave signals and the reflected microwave signals with Doppler frequency shifts; d. transforming a spectrum of data expressed in the temporal domain into a frequency domain via a Fourier transform to fit a first Gaussian curve; e. determining global measured velocity and global velocity distribution via the first Gaussian curve; f. measuring mechanical vibrations of the drone during the steps (a) and (b) of generating and receiving signals, to determine a sequence of vibration data being measured by the vibration sensor; g. generating, from the vibration data, a plurality of discrete data expressed in amplitude as a function of time; h. transforming a spectrum of vibration data expressed in the temporal domain into a frequency domain via a Fourier transform to fit a second Gaussian curve; i. determining measured vibration induced velocity and vibration induced velocity distribution via the second Gaussian curve. j. applying a correction to the global measured velocity and the global velocity distribution obtained in step (e) by subtracting the measured vibration induced velocity and vibration induced velocity distribution obtained in step (j) to eliminate the vibrations of the drone in calculation of real velocity measurement and real velocity distribution of the fluid.

14. The method according to claim 13, wherein the fluid surface velocity is determined from the generated microwave signals and the microwave signals with Doppler frequency shifts and is compensated for Pitch, Roll and Yaw from the drone by taking into account data measured by one or more angle sensors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 01 describes the complete system (01) including the drone (02), suspension system (04), non-invasive velocity measuring device (03) and optional accessories (05), (06) and (07).

[0044] FIG. 02 describes how the non-invasive velocity measuring device (03) is attached to the drone (02) using the suspension system (04).

[0045] FIG. 03A describes in detail the suspension system (04) attaching the non-invasive velocity measuring device (03) to the drone (02).

[0046] FIG. 03 B describes an alternate suspension (04) attaching the non-invasive velocity measuring device (03) to the drone (02).

[0047] FIG. 04 describes the transmitted (14) and returned (15) microwave signal from the non-invasive measuring device (03) attached to the drone (02).

[0048] FIG. 05 describes the vibration signal (17) induced by the drone (02) and the measuring signal (18) from the reflected microwave signal.

[0049] FIG. 06 describes the Pitch, Roll and Yaw of the drone.

[0050] FIG. 07 describes the effect of the Pitch on the measured signal.

[0051] FIG. 08 describes the effect of the Yaw on the measured signal.

[0052] FIG. 09 describes a method for measuring a river or open channel surface velocity.

[0053] FIG. 10 describes the Roll effect by constant wind speed and direction on where the velocity measurement is taken.

[0054] FIG. 11 describes the Roll effect by changing wind speed and direction on where the velocity measurement is taken.

[0055] FIG. 12 describes a second method for measuring a river or open channel surface velocity.

[0056] FIG. 13 describes a measurement taken by the device (01) in an underground pipe or channel (22).

[0057] FIG. 14 describes two methods of taking the surface velocity in an underground pipe or channel (22).

[0058] FIG. 15 describes an alternate method which consists in continuously adjusting 3D moving to the non-invasive measuring device (03), using Pitch (19), Roll (20) and Yaw (21) motors.

DESCRIPTION OF THE INVENTION

[0059] The invention relates to a non-invasive method and device for profiling the surface velocity of a river, open channel or underground conduit that is difficult, dangerous or impossible to access by an operator. The equipment (01) comprises a drone (02) carrying a non-invasive velocity measuring device, preferably a microwave Radar device (03). This device is suspended to the drone with a suspension system (4) that drastically reduces any vibrations generated by the drone (02). The drone is piloted by an operator from the riverbank or side of an open channel or from a bridge or from distance over Internet or Satellite control or in autopilot mode. The drone can be flown far enough from piers that can induce flow disturbances. To measure the flow rate of underground conduits (22), the drone can be piloted through an inspection manhole or other access to be flown over the fluid surface to be measured.

[0060] The drone is preferably flown at a specific constant distance over the fluid surface, so that it won't be hit by floating debris carried by the fluid. The distance can be anything from close to 0.5 m to several meters depending on the application and the floating debris.

[0061] An additional distance measuring device (05) could be carried by the drone as well, but usually the accuracy of the GPS and altimeter from the drone is good enough to position the drone exactly over the fluid surface. The GPS coordinates and altitude could be gathered from the drone (02) by the measuring device (07) associated to the non-invasive velocity measuring device (03) over an appropriate communication link or could be generated by an optional GPS receiver and altimeter included in the measuring device (07) associated to the non-invasive velocity measuring device (03). Modern drones usually can fly accurately at predefined positions which can be repeated over time, avoiding handling the GPS and altimeter data. Over the appropriate communication link or over any suitable command, the device (07) can indicate to the drone (02) that the measurement of a defined spot of the fluid surface is terminated and that the drone (02) can fly to the next defined measuring spot.

[0062] Optionally a wind speed and direction device (06) can be used to validate the velocity data or correct them if necessary. Wind velocity information is usually interesting only when the water surface velocity is slow.

[0063] FIG. 02 shows the drone (02) with the velocity measuring device (03) with is attached to the drone using a special suspension device (04). The length of the suspension legs (08) can be of equal length as shown in FIG. 02 or can have different length as shown in FIG. 03A where the front legs are shorter than the back legs in order to automatically give an angle for the measuring device compared to the water surface and horizontal plane of the drone.

[0064] FIG. 03A shows a detailed view of the suspension system which is made out of lightweight rigid and robust tubed and rods. Usually carbon fibre tubes and rods are preferred. Three or more tubes (08) can be used. They are firmly attached using a mechanical structure made out of roads (09). Within the tubes (08) elastic ropes (10) are used in order to suspend the measuring device (03). The elastic ropes are fixed at the upper end to the suspension system which is attached to the drone (02). At the lower end the ropes (10) are free from the tubes (08) and slightly longer than the tubes. The measuring device will be attached to the elastic ropes. The elasticity of the ropes will be chosen so that the undesired vibrations are absorbed and that the vertical movements remain insignificant.

[0065] FIG. 03 B shows a detailed view of an alternate suspension system using a lightweight rigid upper plate (11) which is attached to the drone and a lower lightweight rigid plate (12) which is attached to the non-invasive measuring device (03), both plates (11) and (12) are connected with silent block types dampers (13) having the requested elasticity and suspension characteristics for the application.

[0066] It is important that the measuring device used to be carried by drones has specific additional features allowing precise measurements. Among those features angle sensors and vibration sensors are required.

[0067] Despite the elastic suspension system, mechanical vibrations can be induced by the propellers of the drone (02). Those vibrations are usually at stable frequency which can be interpreted by the measuring system as a Doppler shift frequency representing a velocity measurement that should be discarded, as explained in more details below. The water velocity spectrum is based on the microwave signal returned by the flowing water with a Doppler frequency shift proportional to the water velocity. The microwave radar system can use a horn antenna or patch or patch array antenna.

[0068] FIG. 04 shows the microwave measuring device (03) suspended to the drone (02) sending a microwave signal (14) out to the water surface (16), said water surface reflecting a return signal (15).

[0069] Preferred steps for converting a velocity spectrum into a fluid surface velocity are described in the document EP 3 011 278. They are the following. Each reflected pulse generates a measurement data. The number of reflected pulses in a sequence of measurements will generate a number of discrete data expressed in amplitude as a function of time. The spectrum of data expressed in the temporal domain is transformed into a frequency domain via a discrete Fourier transform (DFT), and preferably, a fast Fourier transform (FFT). Then a Gaussian curve is fitted on the spectrum of discrete data expressed in the frequency domain and the parameters of the Gaussian curve, namely the mean p and the standard deviation 6 respectively represent the measured velocity and the velocity distribution.

[0070] In FIG. 05, the velocity spectrum with its fitted Gaussian curve (18) is illustrated, but the signal resulting from the vibration induced by the propellers (17) is also represented. The Doppler frequency analysis cannot differentiate the signal generated by the vibration and the signal generated by the flowing fluid, both are received as velocity signals and the microprocessor cannot decide which signal to take and will jump between both signals. If the measuring device is equipped with one or more vibration sensor(s) as in the present invention, a correction can be applied to the result. Indeed, vibration sensor is able to identify and eliminate falls velocity readings induced by the drone (02) (linked to the vibration induced by the propellers). Such mechanical vibrations can be interpreted as velocity reading(s) (17) being more energetic than the real velocity measurement (18) as shown in FIG. 05. This/those sensor(s) will only detect the mechanical vibrations and only the doted Gaussian curve will appear on the analyses from the vibration sensor(s). The same signal analysis approach is taken. Each sample generates a measurement data. The number of samples in a sequence of measurements will generate a number of discrete data expressed in amplitude as a function of time. The spectrum of data expressed in the temporal domain is transformed into a frequency domain via a discrete Fourier transform (DFT), and preferably, a fast Fourier transform (FFT). Then a Gaussian curve is fitted on the spectrum of discrete data expressed in the frequency domain and the parameters of the Gaussian curve, namely the mean p and the standard deviation 6 represent the measured vibration induced velocity and the vibration induced velocity distribution. Having the sole p and 6 from the vibration signal, it can easily mathematically be removed from the combined signal (named also “global signal” in the present invention), leaving the sole fluid velocity information (18).

[0071] The drone is an unmanned aerial vehicle that will have its Pitch, Roll and Yaw when moving or staying over the fluid surface as shown in FIG. 06.

[0072] As shown in FIG. 07, the Pitch will modify the elevation angle α from the microwave measuring device suspended, and this angle α has a direct influence on the resulting calculation of the horizontal fluid velocity as the measured velocity needs to be divided by the cosine of that angle α. It is very important that a microwave measuring device carried by a drone is equipped with an adequate measuring device for the Pitch angle as it changes with wind speed and direction. The Roll and Yaw are less important as the Roll doesn't directly influence the measuring result of the fluid velocity, but only slightly shifts the position of the illuminated section of the fluid surface. The Yaw influences directly the measured fluid velocity but the Yaw angle remains usually small and the correction remains small.

[0073] FIG. 08 shows the influence of the Yaw. When the microwave beam is not parallel with the Fluid Flow Direction FFD arrow but has an angle B, the measured velocity needs to be divided by the cosine of the Yaw angle B.

[0074] FIG. 09 shows an example of a river section that needs to be measured. The shape of the riverbed (17) has been measured and is stored in the measuring device. The water level combined to the riverbed shape allows to calculate the total width of the surface from the wetted section W, traverse distance from one riverbank to the other. This total width W is divided in a number n of sections having the same width wa, wb, . . . wn. Each area is calculated for each section A, B, C . . . N. In the example shown in FIG. 09, section A will be considered as a triangle, section B, C, E, & F will be considered as a trapeze, section D as a sum of two trapezes and section G as the sum of a trapeze and a triangle.

[0075] The device (01) (drone (02) and non-invasive microwave measuring device (03)) is piloted in the way that the microwave beam illuminates the centre part of each section A, B, C N, driving the device at distance da, db, dc . . . dn from one riverbank.

[0076] An alternate method would be to determine sections A, B, C N having the same area instead of the same width, and pilot the device (01) in the position to illuminate the centre part of each section of equal area with the microwave beam.

[0077] FIG. 10 shows the influence that a constant Roll angle would have on the device (01) position, (distance da, db, dc, . . . dn) to illuminate the centre part of each section with the microwave beam (constant Roll angle due to a constant wind speed and direction).

[0078] FIG. 11 shows the influence that a changing Roll angle would have on the device (01) position, (distance da, db, dc, . . . dn) to illuminate the centre part of each section with the microwave beam (changing Roll angle due to a changing wind speed and direction).

[0079] The flowrate for each section N can be calculated following the continuity equation Q.sub.N=Vavg.sub.N*A.sub.N; were Q.sub.N is the flowrate from section N, Vavg.sub.N is the average velocity in the section N and A.sub.N is the area from section N. The average velocity of section N, Vavg.sub.N can be calculated from the measured surface velocity in the section N, Vmeas.sub.N multiplied by the correction factor of section N, K.sub.N.

[0080] The correction factor K.sub.N from section N, is determined using the width wn of the section N, the average fluid depth in section N and a mathematical model computing those data to calculate the correction factor K.sub.N.

[0081] To total river flowrate is the sum of all individual flowrates in each section: Q.sub.TOT=Q.sub.A+Q.sub.B+Q.sub.C+ . . . Q.sub.N.

[0082] An alternate method is described in FIG. 12 and consists in moving the device (01) (drone (02) with non-invasive microwave measuring system (03)) at constant speed over the hole width W of the river from one riverbank to the other. The speed of the device (01) in meter per second divided by the time taken for a full measurement sequence gives the distance d in meter. The area under this distance d (A, B, C, . . . N) can be calculated knowing the shape of the riverbed and the water level.

[0083] The flowrate for each section N can be calculated following the continuity equation Q.sub.N=Vavg.sub.N*A.sub.N were Q.sub.N is the flowrate from section N, Vavg.sub.N is the average velocity in the section N and A.sub.N is the area from section N.

[0084] The average velocity of section N, Vavg.sub.N can be calculated from the measured surface velocity in the section N, Vmeas..sub.N multiplied by the correction factor of section N, K.sub.N.

[0085] The correction factor K.sub.N from section N, is determined using the width d of the section N, the average fluid depth in section N and a mathematical model computing those data to calculate the correction factor K.sub.N.

[0086] The total river flowrate is the sum of all individual flowrates in each section: Q.sub.TOT=Q.sub.A+Q.sub.B+Q.sub.C+ . . . Q.sub.N.

[0087] FIGS. 13 & 14 are showing the application when the device (01) (drone (02) & non-invasive microwave measuring device (03)) is used in underground channels or pipes (22). Depending on the hydraulic conditions and especially the water level, the device can be piloted to make several individual measurements in individual sections (A, B, C, N) of equal width d or take one measurement in the centre of the conduit over a width D.

[0088] If the measurement is taken over individual sections, the flowrate for each section N can be calculated following the continuity equation Q.sub.N=Vavg.sub.N*A.sub.N; were Q.sub.N is the flowrate from section N, Vavg.sub.N is the average velocity in the section N and A.sub.N is the area from section N.

[0089] The average velocity of section N, Vavg.sub.N can be calculated from the measured surface velocity in the section N, Vmeas..sub.N multiplied by the correction factor of section N, K.sub.N.

[0090] The correction factor K.sub.N from section N, is determined using the width d of the section N, the average fluid depth in section N and a mathematical model computing those data to calculate the correction factor K.sub.N.

[0091] To total flowrate in the channel is the sum of all individual flowrates in each section: Q.sub.TOT=Q.sub.A+Q.sub.B+Q.sub.C+ . . . Q.sub.N.

[0092] If only one measurement is taken in the centre of the channel, the Vmeas over the distance D is taken and multiplied by a correction factor K to determine Vavg.

[0093] The correction factor K is determined using the shape and dimension of the channel, the water depth and the velocity distribution represented by σ. A mathematical model computes those data and calculates the correction factor K. Q=Vavg.*A, where Q is the flowrate, Vavg. is the average velocity in the wetted area and A is the surface from the wetted area.

[0094] In underground channels the drone (02) will be equipped with camera and light to facilitate the pilotage.

[0095] FIG. 15 describes an alternate method avoiding many corrections made on the raw measured surface velocity, which consists in continuously adjusting the 3D moves of the non-invasive measuring device (03), using 3 individual motors, the Pitch motor (19), the Roll motor (20)(20) and the Yaw motor (21), to counteract the effects of Pitch, Roll and Yaw of the drone.