Device for measuring speed using a keel probe

Description

Technical field

[0001] The invention relates to a device for speed detection with a keel probe, which has a flow velocity probe which is enclosed by a casing body forming a Venturi nozzle. State of the art

[0002] Such a device is known, for example, from WO 87 / 06710 A1, namely a device for measuring the flow velocity of a free flow in space, which, starting from a known Venturi tube, can be used to measure the flow velocity in a pipe over a large angular range with respect to the flow direction or the blowing direction. The static pressures are measured at two longitudinally different points on a flow body of varying thickness, and their difference is calculated. In addition, the flow velocity probe can be enclosed by a casing body forming a Venturi nozzle. US5365795 discloses a keel probe having a flow velocity probe enclosed by a casing body forming a Venturi nozzle. GB2558709 A discloses a similar device, but this does not have a Venturi nozzle and static pressure probes.The use of dynamic pressure sensors to determine directional information is shown in US2019301969 A1.

[0003] DE 19735724 A1 discloses a sensor for attachment to a support frame in a gas turbine engine. The sensor comprises a casing tube having a front opening for the intake of flow air and several openings in the tube casing. Within the casing tube, a pressure sensor and a temperature sensor are arranged next to one another in such a way that both the pressure sensor and the temperature sensor are exposed to air flow in a defined manner. For this purpose, at least six vent openings are provided in the tube.

[0004] A keel probe is a further development of a pitot tube and is used to measure the total pressure in moving flows. The keel probe has the advantage over a pitot tube of being less sensitive to the angle of attack. The keel probe essentially consists of a venturi nozzle with a pitot probe inside. The venturi nozzle deflects the flow in an axial direction, thus ensuring a more constant flow towards the pitot probe. In addition to the geometry of the venturi nozzle, the position of the pitot probe in the axial direction within the venturi nozzle also plays a key role in the sensitivity to the angle of attack. A disadvantage is the difficulty of determining the exact wind direction in space for different sensor orientations. Using the keel probe principle, wind speed can be reliably measured, but not wind direction over large angular ranges.Problems can arise at angles of attack greater than +-60°.

[0005] Venturi nozzles consist of a piece of pipe with a narrowing of the inlet and a widening of the outlet cross-section, for example by two cones directed towards each other, which are possibly united by a cylindrical tube at the point of their smallest diameter.

[0006] The flow direction can be determined using a multi-hole probe. In practice, two- or four-hole probes, four-hole probes, wedge probes, or cylindrical probes are used for this purpose. The risk of determining the flow direction using the pressure method is the reliability of the calibration. The problem with calibration is that the flow around the probe head is highly unsteady when the direction changes. In addition, the flow around it depends heavily on the turbulent flow. Local separation effects in oblique flow can occur at different locations depending on the flow, which means that calibration must be performed for all conditions.

[0007] Currently available measuring devices for determining wind speed are usually very large and, especially when combined with the necessary evaluation unit, not always easy to install. Wind measurements on moving objects are now predominantly performed using pitot, dynamic pressure, and multi-hole probes. Therefore, when measuring on moving objects, not only time but also the measurement location and wind direction constantly change. Depending on the dynamics of the moving object, this can result in interference with the actual wind measurement.

[0008] Inertial navigation systems are 3D measurement systems with an inertial measurement unit as the central sensor unit with multiple acceleration and angular rate sensors. By integrating the measured accelerations and angular rates, the spatial movement of vehicles or aircraft, for example, is continuously determined. However, an absolute position like with GPS cannot be determined. The main advantage of inertial navigation systems is that they can be operated without a reference, i.e., independently of any positioning signals. However, sensor drift is unavoidable.

[0009] WO 2017 197 524 A1 discloses a method and device for monitoring the fluid dynamic resistance of an object such as a bicycle, a ground vehicle, a watercraft, an aircraft, or part of a wind turbine. For this purpose, an array of sensors is provided that detects the power consumption for driving the object, the air speed and direction relative to the movement of the object, and the traveling speed of the object. The following sensor values ​​can also be recorded: temperature, altitude, and humidity for measuring air density. Sensor values ​​can also indicate inclination angle and forward acceleration.

[0010] A fluid sensing device known from US 2018 321272 A1 comprises an outer body having a front side, a rear side and an interior space, wherein the outer body includes a fluid inlet arranged at the front side, one or more vent openings arranged behind the fluid inlet to allow the passage of fluid through the fluid sensing device and at least one load sensor coupled to the inner body to measure a fluid resistance force on the inner body. Description of the invention

[0011] The invention is therefore based on the object of creating a device for speed detection of the type described above, which enables proper measurement of wind speed and wind direction with compact dimensions.

[0012] The invention achieves this object in that the casing body is designed as a multi-hole pitot tube with holes distributed around the casing circumference. The holes in the casing body, distributed around the casing circumference, are preferably evenly distributed in a plane perpendicular to the longitudinal axis of the flow velocity tube, and the holes associated with a common plane are connected to the pitot tube sensors via pitot channels of equal length. These measures enable proper measurement of wind speed and wind direction.

[0013] The keel probe provides the flow velocity S u US , the x-component of the incoming flow velocity in the sensor-fixed coordinate system, i.e., in the direction of the flow velocity probe's longitudinal axis. The flow velocity in the keel probe can be measured using a Pitot tube, ultrasound, or a hot-wire measurement. The flow rectification by the keel probe arrangement is crucial for determining the incoming flow-independent main wind velocity. S u US . Preferably, the flow velocity can be measured via a pitot tube within the keel probe and a static pressure sensor to determine a differential pressure on the inner casing, which provides information regarding the relative wind speed. Problems can arise at angles of attack greater than +-60°. For these angle ranges, a query must be stored in the evaluation software that recognizes these ranges and informs the user. The user can then position the sensor in a more optimal position for the angle of attack.

[0014] The sheath probe, i.e. the sheath body designed as a multi-hole pitot tube with holes distributed over the sheath circumference, enables the measurement of an angle transformation matrix A SW with the two flow angles, the vertical angle of attack α, and the side angle of attack β , relative to the sensor-fixed coordinate system. The angle transformation matrix is ​​measured via the holes in the shroud body distributed around the shroud circumference, i.e., via the pressure measurement points on the shroud surface. The individual measurement points for determining the angle of attack can be located at the front inside, front outside, rear outside, rear inside, and centrally outside the shroud body.

[0015] Another problem with today's common anemometers on moving objects is the calibration of the individual wind components. In classic multi-hole probes, all three wind components are recorded via the same pressure measuring points on the probe head. This makes calibration difficult because calculating the absolute velocity from the individual pressure signals is very sensitive to angular changes. This also significantly influences the measurement accuracy of the approach flow directions. The inventive device for velocity detection solves this problem by measuring the flow velocity in the sensor's longitudinal direction and the approach flow direction separately. The flow velocity in the sensor direction is measured by a keel probe that is insensitive to the approach flow angle, while the approach flow direction itself is measured by a multi-hole pitot tube with holes in the casing body distributed around the circumference.All three flow components can then be calculated from both sensors.

[0016] For the best possible measurement results, we recommend connecting dynamic pressure sensors to the holes, preferably via dynamic pressure channels. Each dynamic pressure channel leads to a separate dynamic pressure sensor to prevent any mutual interference between the measurements at the individual measuring points.

[0017] The holes in the casing body, distributed around the casing circumference, are evenly distributed around the longitudinal axis of the flow velocity probe in a plane perpendicular to the longitudinal axis of the flow velocity probe, so that the flow angle can be accurately calculated from any differential pressures present at the measuring points in a plane. For this purpose, the holes assigned to a common plane are connected to the dynamic pressure sensors via dynamic pressure channels of equal length, ensuring consistent measurement conditions, particularly response times, for all measuring points assigned to a common plane.

[0018] To improve the resolution of the flow angle to be determined, it may be advantageous if at least two spaced planes with holes distributed over the casing circumference are provided in the direction of the longitudinal axis of the flow velocity probe.

[0019] By providing an inertial navigation system, preferably embedded in the casing body, and / or a global positioning system, preferably embedded in the casing body, i.e., by at least one additional position and attitude sensor in the multisensor, the dynamic disturbances of the object movement itself can be measured and corrected accordingly. For this purpose, the position and velocity of the device in space can be determined. Using the additional information of the three-dimensional device velocity S v S in space, the absolute wind velocity S v W can be calculated from the incident flow velocity S v US . v W <none / > <mprescripts / > S <none / > = v US <none / > <mprescripts / > S <none / > − v S <none / > <mprescripts / > S <none / >

[0020] To improve the measurement accuracy, a temperature (°C) and / or humidity (RH) sensor can be embedded in the jacket body.

[0021] Additionally, it is possible to connect additional sensors via technical interfaces, i.e., in particular, to integrate them into the speed detection sensor according to the invention, and thus to collect additional environmental data (e.g., climate data such as temperature and humidity or road surface data, etc.) in a data logger and include it in immediate or later evaluation. The invention is recommended for use in the development of new aerodynamic vehicles or parts thereof, in particular to validate CFD simulations with real data.

[0022] With the device according to the invention, real, local flow conditions on moving objects can be recorded.

[0023] Another application is the expansion of the capabilities of automated and autonomous driving systems to include the recording of local flow conditions and flow ratios.

[0024] When calculating the various spatial speeds from the sensor data recorded by the inertial navigation system, a drift occurs due to an integration error inherent in the system, which accumulates over the measurement period. This integration error can be compensated for using the wind data, which precisely determines and stores the wind speed and direction at any time. The individual sensor signals can be fused using various filters, such as complementary filters, Kalman filters, or similar. This allows integration errors to be compensated for by using the quasi-stationary states of the individual sensors for comparison. If, for example, the sensor does not detect any oblique flow, ie the main flow velocity is the correct speed and the angular rates are also constant, it is possible to compare the integrated traveling speed with the measured wind speed.

[0025] The device according to the invention has a compact housing in which all calculations are carried out internally, for which purpose a computer unit with an autonomous power supply is provided. Brief description of the invention

[0026] The drawing shows an example of the subject matter of the invention. Fig. 1 shows a device for speed detection in a view obliquely from the front, Fig. 2 shows the device in a view obliquely from the rear, Fig. 3a) to d) shows the device in a simplified section in different movement and flow states and Fig. 4 shows a circuit diagram of a device according to the invention. Ways to implement the invention

[0027] The device 1 for speed detection comprises a keel probe 2, which has a flow velocity probe which is enclosed by a casing body 3 forming a Venturi nozzle, wherein the casing body 3 is designed as a multi-hole dynamic pressure probe with holes 4 in the casing body 3 distributed over the casing circumference.

[0028] The holes 4 in the casing body 3, which are distributed over the casing circumference, are preferably arranged uniformly distributed around the longitudinal axis of the flow velocity probe in a plane perpendicular to a longitudinal axis of the flow velocity probe.

[0029] At least two spaced planes with holes distributed around the circumference of the casing are provided in the direction of the flow velocity probe's longitudinal axis. However, a single plane can also be sufficient.

[0030] An inertial navigation system (INS), a global positioning system (GPS), and an evaluation and communication unit are preferably arranged in the shell body. Temperature (°C) and / or humidity (RH) sensors are also preferably provided in the shell body.

[0031] In Fig. 3 a) bis d ) are exemplary movement and flow conditions which can lead to incorrect measurement results with individual sensors according to the state of the art.

[0032] Case a) The sensor velocity S v S and the wind vector S v US point in opposite directions. The results are acceptable, but aligning the device in the wind according to case c) would be better and more accurate.

[0033] In cases b) and d), the same global wind S v W prevails. In case b), the inflow direction of the wind vector S v US is in the direction of the sensor axis. Using the direction known, for example, from the INS and / or GPS data and the magnitude of the sensor velocity S v S, the global wind S v W can be calculated.

[0034] In case d), the sensor velocity S v S is directed along the sensor axis. The oblique flow recorded by the multi-hole pitot tube allows the angle of incidence to be calculated and indicates the presence of global wind S v W . Both cases b) and d) yield the same result.

[0035] The device according to the invention comprises a wind sensor with a keel probe and multi-hole pitot tube, means for speed and position detection, and additional sensors for measuring air temperature, humidity, and ambient pressure. All calculations are performed by a microcontroller integrated into the device. The sensor output variables are subsequently transmitted to a terminal device via a wired or wireless interface, such as Wi-Fi, Bluetooth, ANT+, or the like. The sensor has its own power supply. This comes either from a built-in battery with a charging circuit or includes components with particularly low energy consumption that obtain the required energy by generating energy from the environment, for example, the wind.

Claims

1. An apparatus (1) for velocity detection comprising a Kiel probe (2) having a flow velocity probe which is encompassed by a shell element (3) forming a Venturi nozzle, characterized in that the shell element (3) is designed as a multi-hole dynamic pressure probe having holes (4) in the shell element (3), arranged distributed across the circumference of the shell, in that the holes (4) in the shell element (3) arranged distributed across the circumference of the shell are preferably arranged uniformly distributed about a longitudinal axis of the flow velocity probe in a plane which is perpendicular to the longitudinal axis of the flow velocity probe and in that the holes (4) allocated to a common plane are connectable to the dynamic pressure sensors via dynamic pressure channels of identical length.

2. An apparatus according to claim 1, characterized in that dynamic pressure sensors are connected to the holes (4), wherein the holes (4) preferably connect to the dynamic pressure sensors via dynamic pressure channels.

3. An apparatus according to claim 1, characterized in that, in the direction of the longitudinal axis of the flow velocity probe, at least two planes spaced apart from each other are provided with holes (4) arranged distributed across the circumference of the shell.

4. An apparatus according to one of claims 1 to 3, characterized by an inertial navigation system (INS), which is preferably embedded in the shell element (3).

5. An apparatus according to one of claims 1 to 4, characterized by a global positioning system (GPS), which is preferably embedded in the shell element (3).

6. An apparatus according to one of claims 1 to 5, characterized by a temperature (°C) and / or relative humidity sensor (rF), which is preferably embedded in the shell element (3)