Wind tunnel balance

Abstract

The invention relates to a wind tunnel balance for a vehicle test stand, comprising: at least one fastening device (21) which is designed to hold a vehicle (1) placed on the wind tunnel balance in a predetermined position; at least one measuring means (7) for recording measurement values, in particular the forces between the fastening device (21) and a support; wherein at least one acceleration sensor (11) coupled to the fastening device (21) is provided for correcting dynamic effects of the wind tunnel balance on the at least one measurement value from the measuring means (7).

Description

[0001] AIP GmbH & Co. KG November 2025

[0002] 220750PC

[0003] Wind tunnel scale

[0004] The present invention relates to a wind tunnel balance that enables highly accurate measurements; in particular, dynamic forces can be taken into account using the wind tunnel balance according to the invention.

[0005] Various designs of wind tunnel balances are known in the prior art, which serve to measure the aerodynamic forces and moments that a vehicle experiences during a wind tunnel test.

[0006] To closely approximate the real-world conditions of the airflow around a vehicle during road travel, this situation is simulated, for example, in specially designed wind tunnels with one or more integrated treadmills (“rolling road”). The treadmills move beneath the vehicle at a speed roughly equivalent to the airflow speed towards the vehicle.

[0007] Single-belt, three-belt, or five-belt systems are commonly used to measure the forces acting on a two-axle vehicle during aerodynamic tests in a wind tunnel. Single-belt systems feature a belt unit with a wide, continuous track that rotates on two rollers or drums. For aerodynamic tests, the vehicle is positioned with all wheels on this single track and fixed relative to it. In three-belt systems, the vehicle rests with the wheels of different axles arranged one behind the other on separate belts, while another belt runs between them as a center belt unit. In a five-belt test rig configuration, a center belt unit and, to the side, a belt unit are positioned under each of the vehicle's four wheels.

[0008] The belts are supported by so-called weighing pads at the points where the vehicle's wheels rest on them. In some state-of-the-art designs, the belts are held in place by a weighing frame. AIP GmbH & Co. KG November 2025

[0009] 220750PC

[0010] During the measurement, the car is held in position and prevented from rolling away by fastening devices, such as so-called sill supports.

[0011] Forces are measured, for example, by introducing the forces at the weighing pads and the sill supports into a movable weighing frame, where they are recorded by suitable sensors and then evaluated by a computer.

[0012] The sill supports and wheel supports are connected to the weighing frame, while the central track and other covers are not connected to the scale. The moving central track allows for the adjustment of equal airflow on and under the vehicle. This arrangement enables the measurement of all forces acting on the vehicle in the X, Y, and Z directions. The corresponding torques Mx, My, and Mz on the vehicle can also be calculated.

[0013] EP 1 656 541 Bl shows a wind tunnel scale with a single-band load cell. The vehicle is positively connected to a weighing frame by means of sill supports.

[0014] In DE 11 2009 000 488 B4, the vehicle is held in position by struts. The forces are measured using load cells.

[0015] In state-of-the-art measuring devices, forces can be recorded statically over a long averaging period. The weighing frame, such as the one described in DE 10 2011 085 640 Al, and other parts of such a measuring setup have considerable mass. As a result, due to the inertia and elasticity of force-transmitting components of the wind tunnel balance, oscillations can occur during dynamic measurements. The oscillation systems can then reach their resonant frequency. AIP GmbH & Co. KG November 2025

[0016] The 220750PC has a resonant frequency in the desired measurement range, thus at least distorting the dynamic measurement. Single-mass oscillators exhibit one resonance point, while multi-mass oscillators exhibit several. This behavior limits the measuring devices to quasi-static measurements. At the very least, their usable frequency range is severely restricted.

[0017] The resonant frequency is determined by dividing the square root of the spring rates by the masses. The resonance amplification depends on the damping of the system. In largely undamped systems, it is not uncommon for the measured values ​​to increase by a factor of 10 at resonance. Damping these oscillating systems is difficult in practice because, firstly, the measuring ranges are very small, and secondly, friction should be avoided, as it can negatively affect the accuracy of the measurement.

[0018] It is therefore an object of the invention to provide a wind tunnel scale and a method for determining the vehicle masses involved in a vehicle with a wind tunnel scale, which provide improved measurement accuracy and in particular can better take dynamic forces into account during measurement.

[0019] This problem is solved by a wind tunnel scale and a method for determining the vehicle masses involved in a vehicle using a wind tunnel scale, according to the independent claims. Preferred embodiments of the invention are specified in the dependent claims.

[0020] According to one aspect of the present invention, a wind tunnel scale according to the invention for a vehicle test rig can have the following: at least one fastening device configured to hold a vehicle placed on the wind tunnel scale in a predetermined position; at least one measuring means for recording measured values, in particular the forces between the fastening device and a support; wherein, for correcting dynamic effects of the wind tunnel scale on the AIP GmbH & Co. KG November 2025

[0021] 220750PC provides at least one measurement value of the measuring instrument, at least one acceleration sensor coupled to the mounting device.

[0022] The support is, for example, part of a frame of the wind tunnel balance or is formed on the floor of a test hall or test stand in which the wind tunnel balance is located.

[0023] When a wind force, generated for example by a wind tunnel used as a vehicle test rig, acts on the vehicle, it is prevented from rolling away in the X-direction. The corresponding force component is introduced into the mounting device and measured by the measuring instruments. The mounting device is attached, for example, to a frame of the wind tunnel scale, and the measuring instruments can be arranged between the frame and the mounting device to transmit the force and thus detect a force between the mounting device and the frame. The detected force is related to a wind force exerted on the vehicle by the wind in the wind tunnel.

[0024] The measuring instruments and the acceleration sensor are, for example, connected to a control system for the wind tunnel scale or a control system for a vehicle test bench that includes the wind tunnel scale, in particular a wind tunnel.

[0025] Recording acceleration values ​​using the accelerometer makes it possible to account for dynamic inertial forces when measuring wind power. Such inertial forces can otherwise significantly distort the measurement result. Vibrations of the entire system, consisting of the wind tunnel scale and the vehicle, also play a role here.

[0026] According to a further aspect of the present invention, a wind tunnel scale according to the invention for a vehicle test rig can comprise the following: a weighing frame which is supported by one or more measuring means in the Y-direction and / or in the X-direction and / or Z-direction; at least AIP GmbH & Co. KG November 2025

[0027] 220750PC a sill support configured to hold a vehicle placed on the wind tunnel scale in a predetermined position, in particular relative to the weighing frame; wherein the measuring means are configured to record measured values, in particular the forces between the weighing frame and supports of the weighing frame; and wherein, to correct dynamic effects of the wind tunnel scale on the at least one measured value of the measuring means, at least one acceleration sensor coupled to the sill support is provided.

[0028] In this patent application, directional terms are used; the X-direction corresponds to the direction of travel of the vehicle and is assumed to be horizontal; the Z-direction runs orthogonally upwards to the X-direction and is therefore assumed to be vertical; the Y-direction points orthogonally away from the plane formed by the X-direction and the Y-direction, i.e., perpendicular to the direction of travel.

[0029] Sill supports are, for example, solid rods or tubes that are attached to the vehicle's frame to support the vehicle. They are typically mounted on the underside of the vehicle, engaging with it. The vehicle essentially rests on these sill supports, which extend vertically. The vehicle can be attached to one or more of the sill supports using bolted connections. Sill supports preferably have a small cross-section, for example, between 30 and 40 mm in diameter, to minimize their aerodynamic impact while still providing maximum vehicle rigidity. Sill supports can have a round cross-section or, for aerodynamic advantages, an oval or teardrop-shaped cross-section.

[0030] When a wind force generated by the wind tunnel acts on the vehicle, it is prevented from rolling away in the X-direction, with the corresponding force component being introduced into the weighing frame. The weighing frame is, for example, attached to a frame of the wind tunnel scale, and measuring devices are arranged between the frame and the weighing frame, which, for example, measure a force. AIP GmbH & Co. KG November 2025

[0031] The 220750PC measures the force between the weighing frame and the frame. The measured force is related to a wind force exerted on the vehicle by the wind in the wind tunnel.

[0032] For example, the acceleration sensor is fixed directly to the sill support or mounting bracket and is specifically designed to detect at least the accelerations of the vehicle's mass. This allows the dynamic displacements of the vehicle occurring during wind tunnel measurements to be recorded very directly and accurately. The faster the changes in the airflow within the wind tunnel occur, the more important it is to consider the inertial aspects of the vehicle and / or wind tunnel scale in order to obtain reliable measurement results.

[0033] For example, at least one additional acceleration sensor can be provided on the weighing frame to detect the accelerations of the frame's mass. The weighing frame represents a significant mass within the wind tunnel scale system. Due to the coupling of the vehicle and the weighing frame, the latter moves along with the vehicle during measurements. The additional acceleration sensor also allows for the inclusion of elasticities in the transmission path from the vehicle to the weighing frame.

[0034] The accelerometer can be configured to detect accelerations in one or more of the directions X, Y, and Z. Likewise, to detect accelerations in multiple directions from X, Y, and Z, one accelerometer can be provided for each direction. One or more of the accelerometers can also be configured as rotational accelerometers to detect rotational accelerations. The advantage here is that acceleration forces can be considered separately for each direction, enabling a more accurate determination of the static wind force acting on the vehicle in the wind tunnel. This allows acceleration and vibration components from the power plants to be factored out. AIP GmbH & Co. KG November 2025

[0035] 220750PC will be used, thus enabling the determination of a corrected, more accurate measurement result.

[0036] For example, the measuring means comprise at least one measuring device, in particular a force sensor, for acquiring measured values ​​in the X-direction and / or at least one, preferably two, measuring devices, in particular force sensors, for acquiring measured values ​​in the Z-direction. This allows forces and displacements resulting from wind forces on the vehicle to be detected. Furthermore, measuring devices for acquiring measured values ​​in the Y-direction can be provided, for example, to determine lateral forces on the vehicle.

[0037] The wind tunnel balance can comprise at least one belt unit, which has at least one belt unit frame on which at least one conveyor belt is provided for positioning the vehicle, which is wrapped around at least two rollers. The belt unit enables particularly realistic wind tunnel tests on vehicles, as it allows the wheels to rotate according to a desired driving speed and the corresponding movement of the ground beneath the vehicle. This allows the effects of the wheels and the vehicle-ground system to be realistically simulated and taken into account during the measurements.

[0038] For example, at least one measuring device, in particular a force measuring device, coupled to the belt unit, especially a bearing point of the treadmill, is provided for recording measured values ​​in the Z-direction. The measuring device on the belt unit, especially at the bearing point of the treadmill, offers the possibility of recording interactions in the form of forces between the wheel and the belt unit. Additionally, an acceleration sensor can also be provided at at least one bearing point for recording accelerations in the Z-direction. This allows dynamic forces from imbalances in the wheel or during acceleration processes to be recorded and taken into account by the control system of the wind tunnel balance. AIP GmbH & Co. KG November 2025

[0039] 220750PC

[0040] For example, the weighing frame is mounted so that it can move relatively freely, and at least one sill support is coupled to the weighing frame, in particular attached to it; the measuring means are designed such that measured values, in particular forces, between the support and the weighing frame can be recorded. The support is, for example, part of a frame of the wind tunnel scale, with which it is attached, for example, to the floor of a test hall. Measuring the forces allows the determination of the forces on the vehicle resulting from an airflow over the vehicle. For example, the weighing frame is suspended and is displaced relative to the support along with the vehicle attached to it. Forces between the support and the weighing frame can be determined, for example, by means of strain gauge load cells arranged between the support and the weighing frame.

[0041] At least two of the measuring devices can be coupled to the weighing frame at different points along the X-direction and configured to record measurements in the Z-direction, and / or at least two of the measuring devices can be coupled to the weighing frame at different points along the Z-direction and configured to record measurements in the X-direction. This allows the measuring devices to easily determine tilting moments of the vehicle or the weighing frame about the transverse axis, i.e., torques about the Y-axis.

[0042] At least two of the acceleration sensors can be coupled to the weighing frame at different points with respect to the X-direction and configured to detect acceleration values ​​of the weighing frame in the Z-direction and / or at least two of the acceleration sensors can be coupled to the weighing frame at different points with respect to the Z-direction and configured to detect acceleration values ​​of the weighing frame in the X-direction and / or wherein at least two of the acceleration sensors can be coupled to the weighing frame at different points with respect to the Y- AIP GmbH & Co. KG November 2025

[0043] 220750PC

[0044] The direction must be coupled to the weighing frame and set up to capture acceleration values ​​of the weighing frame in the X direction.

[0045] For example, one or more of the measuring devices are designed as strain gauges, in particular strain gauge load cells, or piezoelectric force transducers; and / or the weighing frame is supported in the X and / or Y directions essentially solely by the measuring devices. Strain gauges, for example, designed as strain gauge load cells, can be attached with particular flexibility and allow the determination of forces without significant relative deformations or displacements. Piezoelectric force transducers offer the advantage that dynamic fluctuations in forces can be resolved well. The weighing frame can, for example, be floatingly mounted or suspended, so that it is held in position essentially solely by the measuring devices in the X and Y directions. This allows for low-friction mounting, accurate measurements, and a simple design.

[0046] At least one of the measuring devices can be bypassed by means of a switchable force transducer, particularly a piezoelectric one, connected in parallel. This allows a measuring device, such as a strain gauge load cell, to be bypassed. As a result, its elasticity within the system is eliminated, and its influence on the measurement results is reduced.

[0047] For example, the wind tunnel balance is designed to correct at least one value recorded by the measuring instrument with at least one acceleration value measured by the accelerometer and the accelerated mass. This allows for a more accurate determination of the actual static forces acting on the vehicle due to wind pressure in the wind tunnel. Disturbing forces caused by dynamic vibrations of the vehicle-wind tunnel balance system can be factored out by the control system. Overall, this reduces the susceptibility to errors and enables more accurate measurement results with the wind tunnel balance. AIP GmbH & Co. KG November 2025

[0048] 220750PC

[0049] The wind tunnel balance can be configured to correct the measured value of the measuring instrument by adding the inverse transfer function, which results from the mass of the weighing frame and the spring stiffness of its bearings. By integrating the known inverse transfer function of the system, the control system can deliver more accurate measurement results by reducing dynamic influences on the measurements.

[0050] For example, the wind tunnel balance includes a high-pass filter used to correct the output value of the accelerometer for offset values ​​and an integrator for integrating the acceleration, in particular the corrected output value, to determine a velocity.

[0051] An inventive method for determining the dynamic behavior of a system consisting of a vehicle and a wind tunnel scale comprises at least the following step: Exciting a vehicle arranged on the wind tunnel scale with a oscillator, in particular an electromechanical oscillator, at various frequencies and determining the excitation frequency-dependent motion values ​​of the vehicle and preferably also of a weighing frame of the wind tunnel scale in one or more of the directions X, Y, and Z using accelerometers. For example, a specific frequency spectrum is traversed using the oscillator, and vibrations of the vehicle or the weighing frame are detected. Specific acceleration amplitudes can be assigned to specific frequencies. The result is curves that represent accelerations versus frequency. Particularly high accelerations indicate, for example, natural frequencies of the system consisting of the wind tunnel scale and the vehicle.The measurement results can be used to improve the accuracy of the wind tunnel measurements by incorporating them into the control system. This means that the wind tunnel measurements are corrected using acceleration values ​​assigned to specific frequencies at particular points on the wind tunnel balance or the vehicle. AIP GmbH & Co. KG November 2025.

[0052] 220750PC

[0053] The dynamic transfer behavior of the system between the vehicle and the wind tunnel scale can be modeled using the measured motion results.

[0054] Capturing the movement of vehicle components or the wind tunnel scale across different excitation frequencies allows for the modeling of the dynamic transfer behavior of the vehicle-wind tunnel scale system. Computer-aided modeling tools are used for this purpose.

[0055] Another method according to the invention for weighing a vehicle with a wind tunnel scale comprises at least the following steps: arranging the vehicle on the wind tunnel scale; supporting the vehicle by means of a fastening device on a mounting bearing of the wind tunnel scale; recording measured values, in particular forces, between the fastening device and the mounting bearing in at least one direction and simultaneously recording at least one acceleration value by means of at least one acceleration sensor coupled to the vehicle and / or the fastening device; correcting at least one of the measured values ​​of the measuring means by means of at least one of the acceleration values.

[0056] The mounting bearing is, for example, attached to the floor of a test hall or wind tunnel, or as part of a support frame for the wind tunnel balance, to which the other components of the wind tunnel balance, such as the belt unit frame, are mounted. The mounting bearing is, for example, firmly connected to the hall floor, and the two can be connected to each other by means of a bolted connection between the mounting bearing and the fastening device.

[0057] Another method according to the invention for determining the vehicle masses involved in a vehicle using a wind tunnel scale comprises the following steps: arranging the vehicle on the wind tunnel scale; supporting the vehicle by means of at least one sill support on a weighing frame. AIP GmbH & Co. KG November 2025

[0058] 220750PC of the wind tunnel scale; recording of measured values, in particular forces, by means of measuring instruments between the weighing frame and at least one support bearing in at least one direction and simultaneously recording at least one acceleration value by means of at least one acceleration sensor coupled to the vehicle and / or the sill support; correction of at least one of the measured values ​​of the measuring instruments by means of at least one of the acceleration values.

[0059] The wind tunnel balance according to the embodiments described above can advantageously be integrated into a wind tunnel as a test rig, according to the invention. In the wind tunnel, air is accelerated to a desired speed, for example by means of a blower, and directed towards a test object, in particular a motor vehicle. The air impacting the vehicle generates forces that act upon the vehicle.

[0060] The wind tunnel scale's measuring instruments can detect these forces and their changes. For example, a force acting on the vehicle from the oncoming airflow pushes it downwards, thus acting in the Z-direction. Therefore, the vehicle's weight measured by the wind tunnel scale will be greater than it would be without the oncoming airflow. Similarly, the wind tunnel scale can detect wind forces on the vehicle in the direction of travel, i.e., the X-direction. It can also detect lateral forces on the vehicle resulting from the oncoming airflow, i.e., forces perpendicular to the direction of travel, i.e., in the Y-direction, which is useful, for example, in modeling crosswind scenarios.

[0061] The acceleration sensors enable the measurement of both vibrations at the wind tunnel scale and the vehicle when air flows towards the vehicle at a constant speed, as well as dynamic effects when the speed of the air flowing towards the vehicle changes. AIP GmbH & Co. KG November 2025

[0062] 220750PC

[0063] When simulating higher speeds, for example 140 km / h, vibrations commonly occur in the vehicle and the wind tunnel balance. In current technology, these vibrations often lead to inaccurate measurement results. The vibrations are caused by instabilities in the airflow over the vehicle or the wind tunnel balance, particularly in the mounting structure. Turbulent boundary layer shedding can occur as the airflow passes the vehicle and the wind tunnel balance. In some cases, parts of the vehicle or the wind tunnel balance act similarly to a Helmholtz resonator being blown by the oncoming airflow. By taking these phenomena into account when recording the vibration-induced movements of the vehicle or the wind tunnel balance using accelerometers, the measurement results can be significantly improved.

[0064] The speed of the oncoming air changes, for example, when simulating different driving speeds or weather-related wind conditions, such as gusts. The faster the speed of the air flowing towards the vehicle changes, the greater the dynamic effects become, caused, for example, by the inertia of the masses involved in the vehicle and the wind tunnel scale. These dynamic effects are particularly relevant when simulating wind forces on sports and racing cars, as the airflow speed can change very rapidly. Recording the vibrations using acceleration sensors can also be advantageous for this problem, in order to obtain more meaningful measurement results.

[0065] It is in line with the invention that the aforementioned process features of the invention can be combined with the described device features of the invention. It is further in line with the invention that the aforementioned device features of the different embodiments can be combined with one another. AIP GmbH & Co. KG November 2025

[0066] 220750PC

[0067] The invention is described below by way of example with reference to the accompanying schematic drawings. These show:

[0068] Fig. 1 shows a wind tunnel scale with a vehicle arranged on it according to a first embodiment in a schematic side view in the image above, and in a top view in the image below;

[0069] Fig. 2 shows a wind tunnel scale with a vehicle arranged on it according to a second embodiment, shown in a schematic side view in the image above and in a top view in the image below.

[0070] Fig. 3 shows a simplified model of a wind tunnel balance in which the forces are introduced directly from a fastening device into measuring instruments in a simplified schematic view;

[0071] Fig. 4 shows a simplified model of a wind tunnel scale in which the forces from sill supports are introduced into a weighing frame in a schematic view;

[0072] Figs. 5a and 5b show the force behavior above over time and below over frequency of the wind tunnel balances according to the first embodiment in a schematic view;

[0073] Figs. 6a and 6b show the force behavior above over time and below over frequency of the wind tunnel balances according to the second embodiment in a schematic view;

[0074] Fig. 7 shows the acceleration over time of the wind tunnel balance according to Figs. 2 and 4 in a schematic view;

[0075] Fig. 8 shows the force behavior over time in a wind tunnel balance where the movement of the sprung masses is detected and compensated by means of acceleration sensors, without considering the parasitic effects. AIP GmbH & Co. KG November 2025

[0076] 220750PC

[0077] Damping;

[0078] Fig. 9 shows the force behavior over time in a wind tunnel balance where the movement of the sprung masses is detected and compensated for by means of acceleration sensors, taking accelerations and damping into account; and

[0079] Fig. 10 shows a compensation arrangement for determining the forces over the frequency in the range from 0 to e.g. 20 Hz.

[0080] The following section describes various examples in detail with reference to the figures. Identical or similar elements in the figures are designated with the same reference symbols. However, this is not intended to limit the description to the examples provided; rather, the subject matter described can also include modifications of features from the described examples and combinations of features from different examples.

[0081] Fig. 1 shows a wind tunnel scale with a vehicle 1 arranged on it according to a first embodiment in a schematic side view in the image above, and in a top view in the image below.

[0082] The top view is shown without vehicle 1. The wind tunnel scale is intended for a vehicle test rig.

[0083] In this embodiment, the wind tunnel balance comprises a belt unit 17, which has a belt unit frame 15 on which a treadmill 13 is arranged, the treadmill being wound around two rollers 19. A motor vehicle 1 is positioned on the treadmill 13, on which wind resistance measurements can be carried out in the wind tunnel. In this embodiment, the treadmill 13 is supported from below at the points where the tires of the vehicle 1 are located on the treadmill 13 by bearings 3 against the AIP GmbH & Co. KG November 2025

[0084] 220750PC

[0085] The belt unit frame 15 is supported. Likewise, the treadmill 13 can be supported against a frame of the wind tunnel scale or the floor of a test hall or test rig.

[0086] A fastening device 21, for example a sill support or rocker panel, is provided which is designed to hold the vehicle 1 in a predetermined position on the conveyor belt 13.

[0087] The wind tunnel balance further comprises measuring means 7 with which measured values, in particular forces acting on the vehicle, can be recorded in at least one force direction, but preferably in the X and Y directions. In this embodiment, the measuring means 7 are provided between the rod-shaped fastening element 21 and a base assembly of the wind tunnel balance or a support of the test rig. In this embodiment, the measuring means 7 are based on strain gauge-based load cells. The forces in the Z direction are measured by the conveyor belt 13 and the aerodynamic support bearing 3 with the sensors 10.

[0088] In this embodiment, an acceleration sensor 11 is provided on the mounting device 21 to detect accelerations of the vehicle mass. In this embodiment, the acceleration sensor 11 is positioned near the point where the mounting device 21 makes contact with the vehicle 1 to ensure the best possible transmission of the accelerations or vibrations present on the vehicle 1.

[0089] When measuring force in the Z direction, an accelerometer is not required because the mass of the bearing 3 is small.

[0090] In this embodiment, vehicle 1 is equipped with an acceleration sensor 11 that can detect its acceleration in the X and Y directions. AIP GmbH & Co. KG November 2025

[0091] 220750PC

[0092] In this embodiment, all the sensors and measuring instruments 7, 10, and 11 mentioned are connected to a control unit for the wind tunnel balance for evaluating the measured values, which is not shown here. The control unit for the wind tunnel balance can also be designed as part of the control system for a test rig, in particular a wind tunnel, into which the wind tunnel balance is integrated.

[0093] Fig. 2 shows a wind tunnel scale with a vehicle 1 arranged on it according to a second embodiment in a schematic side view in the image above, and in a top view in the image below.

[0094] The second embodiment differs from the first embodiment in that it provides a five-belt test rig arrangement, comprising a central treadmill 13 and, arranged laterally in the Y-direction, a lateral treadmill 14 under each of the four wheels of the vehicle 1. In contrast to the first embodiment, in the second embodiment the vehicle 1 does not rest on the central treadmill 13, but rather on the adjacent lateral treadmills 14.

[0095] In this embodiment, the lateral conveyor belts 14 are, like the conveyor belt 13 of the first embodiment, each formed as part of a belt unit with a belt unit frame and rollers for deflecting and tensioning the respective conveyor belt 14. In this embodiment, two sill supports 5 on the left side of the vehicle (in the direction of travel) and two sill supports 5 on the right side of the vehicle (in the direction of travel) hold the vehicle in position relative to a weighing frame 6. The other components largely correspond to those of the first embodiment, to which reference is made earlier in this description.

[0096] The vehicle wheels of vehicle 1 are supported on the laterally mounted running belts 14. Further forces acting on the vehicle are represented by the AIP GmbH & Co. KG November 2025

[0097] 220750PC

[0098] The rocker panel supports 5 are transferred to the weighing frame 6. The conveyor belts 14 are supported on the weighing frame 6 by means of their belt unit frames; for example, the belt unit frames are firmly connected to the weighing frame 6 by a bolted connection.

[0099] The weighing frame 6 is supported by measuring elements 10 in the Z-direction, by measuring elements 9 in the Y-direction, and by measuring elements 7 in the X-direction. In this embodiment, the measuring elements 7, 9, and 10 have a measuring function and also support the weighing frame 6. The support of the weighing frame 6 in the X-direction is clearly visible in the image, at least partially by the measuring element 7 arranged between the weighing frame 6 and a bearing 3. The wind tunnel scale is mounted, for example, on the floor of a test hall or wind tunnel by means of the bearing 3. The measuring elements 10 are also visible in the image; in this embodiment, they support the weighing frame 6 on the floor in the Z-direction and also enable measurements in the Z-direction. For example, the measuring elements 7, 9, and 10 are designed as load cells based on strain gauges.

[0100] Since the weighing frame 6 with the measuring instruments 7, 9, 10 forms a "spring-mass oscillator", an acceleration sensor 11a is advantageous for detecting the movement; in this embodiment, the acceleration sensor 11a is attached to the weighing frame 6. The acceleration sensor 11a can detect accelerations in one direction, but preferably accelerations in all three directions, X, Y, Z.

[0101] Fig. 3 shows a simplified model of a wind tunnel balance in which the forces are introduced directly from a fastening device 21 into measuring instrument 7 in a simplified schematic view.

[0102] A rectangle on the left of the image symbolizes vehicle 1 with its mass. The force measuring device 7, together with the small mass, forms the first "spring-mass oscillator." Due to the small mass, the resonant frequency is above the desired maximum frequency. The vehicle mass 1, together with AIP GmbH & Co. KG, November 2025

[0103] 220750PC

[0104] Spring rate of the fastening device 21, the second “spring mass oscillator”. Although no damping elements are integrated, parasitic damping 21a is always present.

[0105] Fig. 4 shows a simplified model of a wind tunnel scale in which the forces from sill supports 5 are introduced into a weighing frame 6 in a schematic view.

[0106] Rectangle 1 represents the vehicle mass. Spring 5 is the sum of the spring rates of four sill supports 5. The mass 1 of the vehicle forms a "spring-mass oscillator" with spring 5. The mass of the weighing frame 6 forms a second "spring-mass oscillator" with measuring instrument 7. The movements of masses 1 and 6 are detected by acceleration sensors. These sensors can detect movements in all three directions. Damper symbols 21b and 21c represent the parasitic damping.

[0107] Fig. 5a shows the force behavior of the wind tunnel balance according to Fig. 1 or 3 over time and Fig. 5b shows the forces over frequency.

[0108] It is clearly visible that the measured values ​​are significantly elevated at or near the resonance point. Figures 6a and 6b show the force curves of the balance according to Figures 2 and 4, respectively. The two masses involved also reveal two resonance points.

[0109] In Figures 5 and 6, the system is excited with 1000 N. In the case of resonance, the measurement result is inaccurate, i.e., 15 times higher than the excitation value. This demonstrates the importance of compensating for the dynamic effects of the wind tunnel balance using control technology.

[0110] The masses involved are, for example: weighing frame 5000 kg, vehicle 3000 kg. The spring stiffnesses are: measuring instrument (items 7, 9, 10) 21 x 10⁷ N / m, fastening device (item 21) 1.33 x 10⁷ N / m. The weighing frame (item 6) was manufactured by AIP GmbH & Co. KG in November 2025.

[0111] The 220750PC has a damping constant of 4000 Ns / m. The damping of the vehicle (Exhibit 1) varies from vehicle to vehicle. At higher damping rates, the resonance peak becomes lower, but wider.

[0112] Fig. 5a shows a schematic view of the force behavior over time in a wind tunnel balance where the force measuring device (Bz. 7, 9, 10) is bridged by a second force measuring device (Bz. 7, 9). Fig. 5b shows a schematic view of the force behavior over frequency in a wind tunnel balance where the force measuring device (Bz. 7, 9) is bridged by a second force measuring device (Bz. 7, 9).

[0113] Figs. 6a and 6b show the force behavior above over time and below over frequency of the wind tunnel balances according to the first and second embodiments in a schematic view.

[0114] Fig. 7 shows the acceleration over time of the wind tunnel balance according to Figs. 2 and 4 in a schematic view.

[0115] The measured accelerations at the motor vehicle 1 connected to the rocker panel support 5 are shown as a solid line and at the weighing frame 6 (scale) as a dashed line.

[0116] Fig. 8 shows the force behavior over time in a wind tunnel balance where the movement of the sprung masses is detected and compensated by means of acceleration sensors without taking parasitic damping into account.

[0117] The measured forces were corrected using the measured accelerations, taking into account the masses involved. This takes into account the physical law "force = mass times acceleration". AIP GmbH & Co. KG November 2025

[0118] 220750PC

[0119] Fig. 9 shows the force behavior over time in a wind tunnel balance where the movement of the sprung masses is detected and compensated by means of acceleration sensors, taking accelerations and damping into account.

[0120] This takes into account the physical law "force = damping times velocity" (F = k x v). The damping force is compensated using the oscillation velocity integrated from the acceleration and the damping constant; both are added together. If all parameters are set correctly, an error-free force display is achieved up to, for example, 20 Hz, which is represented in the image as a horizontal line at 1000 Newtons.

[0121] Fig. 10 shows a compensation arrangement for determining the forces over the frequency in the range from 0 to e.g. 20 Hz.

[0122] For static precision measurements, the acceleration is switched off, and the output filter (low-pass) 56 is set to a low frequency, e.g., 0.2 Hz. If higher frequencies are to be measured, the force measured by the precision sensor 50 is added to the measured values ​​of the correction branch. For this purpose, the signal from the accelerometer 11 is filtered by a high-pass filter 51 to remove offset values. The correction signal 54 is calculated by multiplying this signal by the mass involved. The acceleration signal is then integrated 52, which determines the vibration velocity v. The vibration velocity v is also converted into a correction force using the damping constant 53. The adder 55 calculates a total force from the three forces. The output filter 56 is set to either 0.2 Hz (precision) or 20 Hz (fast), depending on the desired result. Accordingly, the switch 57 is only closed for fast measurements.

[0123] The compensation arrangement is shown here for a single-mass oscillator, but according to the invention it can also be designed for a two-mass or three-mass oscillator. The case of a three-mass oscillator AIP GmbH & Co. KG November 2025

[0124] 220750PC can be given, for example, in the case of a split weighing frame 6, consisting of two mass-bearing components that can be moved relative to each other.

[0125] The invention has been described in detail with reference to exemplary figures. The described features can be combined in whole or in part, and the present invention is not limited to the described embodiments.

[0126] AIP GmbH & Co. KG November 2025

[0127] 220750PC

[0128] Reference symbol list

[0129] 1 vehicle

[0130] 3 Uprising Camps

[0131] 5 Sill support

[0132] 6 weighing frames

[0133] 7, 9, 10 measuring instruments

[0134] 11, 11a Accelerometer

[0135] 13 Treadmill

[0136] 14 Treadmill

[0137] 15 band unit frames

[0138] 17 tape units

[0139] 19 roll

[0140] 21 Fastening device

[0141] 21a, 21b, 21c Parasitic suppression

[0142] 50 precision sensors

[0143] 51 High-pass filters

[0144] 52 Integrator

[0145] 53 Damping constant

[0146] 54 Correction signal

[0147] 55 Adders

[0148] 56 output filters

[0149] 57 switches

Claims

AIP GmbH & Co. KG November 2025 220750PC Patent claims 1. Wind tunnel balance for a vehicle test rig with at least one fastening device (21) designed to hold a vehicle (1) placed on the wind tunnel balance in a predetermined position; at least one measuring device (7) for recording measured values, in particular the forces between the fastening device (21) and a support; wherein at least one acceleration sensor (11) coupled to the fastening device (21) is provided to correct dynamic effects of the wind tunnel balance on the at least one measured value of the measuring device (7).

2. Wind tunnel scale for a vehicle test rig with a weighing frame (6) supported by one or more measuring means (7; 9; 10) in the Y-direction and / or in the X-direction and / or Z-direction; at least one sill support (5) configured to hold a vehicle (1) placed on the wind tunnel scale in a predetermined position, in particular relative to the weighing frame (6); wherein the measuring means (7; 9; 10) are configured to detect measured values, in particular the forces between the weighing frame (6) and supports of the weighing frame (6); and wherein, to correct dynamic effects of the wind tunnel scale on the at least one measured value of the measuring means (7; 9; 10), at least one acceleration sensor (11) coupled to the sill support (5) is provided.

3. Wind tunnel balance for a vehicle test stand according to claim 1 or 2, wherein the acceleration sensor (11) is fixed directly to the sill support (5) or fastening device (21) and wherein the acceleration sensor (11) is in particular configured to detect at least accelerations of the mass of the vehicle (1). AIP GmbH & Co. KG November 2025 220750PC 4. Wind tunnel scale for a vehicle test stand according to claim 2 or 3, wherein at least one additional acceleration sensor (11a) is provided on the weighing frame (6) for detecting the accelerations of the mass of the weighing frame (6).

5. Wind tunnel scale for a vehicle test rig according to claim 1 or 2, wherein the acceleration sensor (11) is configured to detect accelerations in one or more of the directions X, Y and Z and / or one of the acceleration sensors (11) is provided for each direction to detect accelerations in several directions from X, Y and Z.

6. Wind tunnel scale for a vehicle test stand according to claim 1, wherein the measuring means (7) comprise at least one measuring means, in particular a force sensor, for measurement in the X direction and / or at least one, preferably four, measuring means (10), in particular force sensors, for measurement in the Z direction.

7. Wind tunnel scale for a vehicle test stand according to at least one of the preceding claims, further comprising: at least one belt unit (17) having at least one belt unit frame (15) on which at least one treadmill (13) is provided for arranging the vehicle (1) on it, which is wrapped around at least two rollers (19).

8. Wind tunnel scale for a vehicle test stand according to claim 7, wherein at least one measuring device coupled to the belt unit (17), in particular a force measuring device, is provided for recording measured values ​​in the Z direction.

9. Wind tunnel scale for a vehicle test rig according to one of the preceding claims, wherein the weighing frame (6) is mounted to be relatively movable, and wherein the at least one sill support (5) is coupled to the weighing frame (6), in particular attached to it, and AIP GmbH & Co. KG November 2025 220750PC wherein the measuring means (7; 9; 10) are provided in such a way that measured values, in particular forces, between the support and the weighing frame (6) can be recorded with them.

10. Wind tunnel scale according to at least one of the preceding claims, wherein at least two of the measuring means (7; 9; 10) are coupled to the weighing frame (6) at different locations with respect to the X-direction and are configured to acquire measured values ​​in the Y-direction and / or Z-direction and / or wherein at least two of the measuring means (7; 9; 10) are coupled to the weighing frame (6) at different locations with respect to the Z-direction and are configured to acquire measured values ​​in the X-direction and / or Y-direction.

11. Wind tunnel scale according to at least one of the preceding claims, wherein at least two of the acceleration sensors (11) are coupled to the weighing frame (6) at different locations with respect to the X-direction and are configured to detect acceleration values ​​of the weighing frame (6) in the Z-direction and / or wherein at least two of the acceleration sensors (11) are coupled to the weighing frame (6) at different locations with respect to the Z-direction and are configured to detect acceleration values ​​of the weighing frame (6) in the X-direction and / or wherein at least two of the acceleration sensors (11) are coupled to the weighing frame (6) at different locations with respect to the Y-direction and are configured to detect acceleration values ​​of the weighing frame (6) in the X-direction.

12. Wind tunnel balance according to at least one of the preceding claims, wherein one or more of the measuring means (7; 9; 10) are formed as strain gauges, in particular strain gauge force transducers, or piezoelectric force transducers; and / or the weighing frame (6) is supported in the X-direction and / or Y-direction substantially solely by the measuring means (7; 9; 10). AIP GmbH & Co. KG November 2025 220750PC 13. Wind tunnel balance according to at least one of the preceding claims, wherein at least one of the measuring means (7; 9; 10) can be bridged by means of a switchable, in particular piezoelectric, force transducer arranged in parallel thereto.

14. Wind tunnel balance according to at least one of the preceding claims, wherein the wind tunnel balance is configured to correct at least one value detected by means of the measuring means (7; 9; 10) with at least one acceleration value measured by the accelerometer (11; 11a) and the accelerated mass.

15. Wind tunnel balance according to at least one of the preceding claims, wherein the wind tunnel balance is configured to add the inverse transfer behavior resulting from the mass of the weighing frame (6) and the spring stiffness of its bearing in order to correct the measured value of the measuring means (7; 9; 10).

16. Wind tunnel balance according to at least one of the preceding claims, wherein a high-pass filter (51) is provided for correcting the output value of the acceleration sensor (11; 11a) of offset values ​​and wherein an integrator (52) is provided for integrating the acceleration, in particular the corrected output value, for determining a velocity.

17. Method for determining the dynamic behavior of a system consisting of a vehicle (1) and a wind tunnel scale, comprising at least the following method step: Excitation of a vehicle (1) arranged on the wind tunnel scale by means of an oscillator, in particular an electromechanical oscillator, with different frequencies and determination of excitation frequency-dependent motion values ​​of the vehicle (1) and of a weighing frame (6) of the wind tunnel scale in one or more of the directions X, Y and Z by means of acceleration sensors (11). AIP GmbH & Co. KG November 2025 220750PC 18. Method according to claim 17, wherein the dynamic transfer behavior of the system vehicle (1) wind tunnel scale is modeled using the determined measurement results of the movement over the frequency.

19. Method for determining the vehicle masses involved in a vehicle using a wind tunnel scale, comprising the following steps: (a) Positioning the vehicle on the wind tunnel scale; (b) Supporting the vehicle by means of a fastening device (21) on a support bearing (3) of the wind tunnel scale; (c) Recording of measured values, in particular forces, between the vehicle (1) and the mounting bearing (3) by means of measuring means (10) and simultaneously recording at least one acceleration value by means of at least one acceleration sensor (11, 11a) coupled to the vehicle (1) and / or the fastening device (21); (d) Correction of at least one of the measured values ​​of the measuring instrument (7) using at least one of the acceleration values.

20. Method for determining the vehicle masses involved in a vehicle using a wind tunnel scale, comprising the following steps: (a) Positioning the vehicle on the wind tunnel scale; (b) Supporting the vehicle by means of at least one sill support (5) against a weighing frame (6) of the wind tunnel scale; (c) Recording measured values, in particular forces, by means of measuring means (10), between the weighing frame (6) and at least one support bearing (3) in at least one direction and simultaneously recording at least one acceleration value by means of at least one acceleration sensor coupled to the vehicle and / or the sill support (5); (d) Correction of at least one of the measured values ​​of the measuring instrument (10) using at least one of the acceleration values. AIP GmbH & Co. KG November 2025 220750PC 21. Implementation of a method according to one of claims 17 to 20 on a wind tunnel balance according to one of claims 1 to 16.

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