METHOD FOR IDENTIFYING SLOW TRANSIENT VARIATIONS AND/OR LOCAL SPATIAL VARIATIONS OF A PHYSICAL PROPERTY IN A SET OF DATA POINTS

Abstract

Method for identifying slow transient variations and/or local spatial variations in vehicle related fluid dynamic conditions of a physical property in a set of data points. The method includes obtaining a first set of data points, calculating a temporal filtered value of the representation of the physical property for at least a portion of the first set of data points distributed over the total time period, combining at least a portion of the calculated temporal filtered values to obtain a second set of data points, and analysing in time sequence the second set of data points over at least a portion of the total time period.

Claims

1. A method for identifying slow transient variations and/or local spatial variations in vehicle related fluid dynamic conditions of a physical property in a set of data points, the method comprises the steps of: A) obtaining a first set of data points related to a vehicle body surface, wherein the first set of data points is based on measured values or simulated data, wherein each of said data points is associated with at least i) a point of time, ii) a position in at least two dimensions of the vehicle body surface, and iii) a value representing a measured or simulated fluid dynamic physical property, wherein the physical property is pressure of a fluid, pressure of a mixture of fluids, friction between a surface and a flowing fluid or mixture of fluids, or temperature, wherein the data points in each position are separated in time by a sampling time step, and wherein the first set of data points represents a total time period; B) calculating a temporal filtered value of the representation of the physical property for at least a portion of the first set of data points distributed over the total time period, wherein the temporal filtered value is based on a plurality of values of the representation of the physical property in the same position obtained over an effective filtering time period covering a plurality of data points, wherein the effective filtering time period has a time relation to the data point for which the calculation is carried out and wherein the effective filtering time period is longer than an average sampling time step and shorter than the total time period: C) combining at least a portion of the calculated temporal filtered values of the representation of the physical property with the point of time and position of the corresponding data point in the first set of data points so as to obtain a second set of data points where each value representing the physical property is the temporal filtered value; and D) analysing in time sequence the second set of data points over at least a portion of the total time period.

2. The method according to claim 1, wherein the sampling time step is in the range 0.05-100 milliseconds, preferably in the range 0.1-3 milliseconds.

3. The method according to claim 1, wherein the effective filtering time period is at least 10 times longer, preferably at least 50 times longer, than the sampling time step.

4. The method according to claim 1, wherein the effective filtering time period is in the range 0.01-1 second.

5. The method according to claim 1, wherein the total time period is at least 10 times longer than the effective filtering time period.

6. The method according to claim 1, wherein the total time period is at least 1 second.

7. The method according to claim 1, wherein the temporal filtered value is calculated so as to form a value that lies between a maximum and a minimum of the plurality of values of the representation of the physical property in the same position obtained over the effective filtering time period.

8. The method according to claim 1, wherein the step of calculating the temporal filtered value comprises providing each of the plurality of values of the representation of the physical property with a weight factor.

9. The method according to claim 1, wherein the temporal filtered value is calculated as an arithmetic average of the plurality of values of the representation of the physical property in the same position obtained over the effective filtering time period.

10. The method according to claim 1, wherein the plurality of values of the representation of the physical property in the same position obtained over the effective filtering time period amounts to at least 10 values, preferably at least 50 values.

11. The method according to claim 1, wherein the effective filtering time period has a fixed time relation to the data point for which the calculation is carried out.

12. The method according to claim 1, wherein the effective filtering time period includes the data point for which the calculation is carried out.

13. The method according to claim 1, wherein the effective filtering time period is symmetrically distributed in time in relation to the data point for which the calculation is carried out.

14. The method according to claim 1, wherein each data point is associated with a position in three dimensions.

15. The method according to claim 1, the method further comprising the steps of: applying one or more pressure sensors, friction sensors or temperature sensors in one or more positions of the vehicle body surface; measuring the pressure, 20 friction, or temperature value in each position of the vehicle body surface with the pressure sensor, friction sensor or temperature sensor; obtaining the value representing the physical property from the measured pressure, friction, or temperature value in each position of the vehicle body surface associated with the first set of data points.

16. A non-transitory computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method of claim 1.

17. A cloud computing system configured to carry out the method of claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0044] In the description of the invention given below reference is made to the following figure, in which:

[0045] FIG. 1 shows, in a schematic view, an example of a first set of data points separated by a sampling time step and grouped into an effective filtering time period;

[0046] FIG. 2 shows, in a schematic view, an example of a first set of data points set distributed over a total time period with an example of an effective filtering time period; and

[0047] FIG. 3 shows, in a schematic view, an example of method steps.

DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0048] Those skilled in the art will appreciate that the steps, services and functions explained herein may be implemented using individual hardware circuitry, using software functioning in conjunction with a programmed microprocessor or general purpose computer, using one or more Application Specific Integrated Circuits (ASICs) and/or using one or more Digital Signal Processors (DSPs). It will also be appreciated that when the present disclosure is described in terms of a method, it may also be embodied in one or more processors and one or more memories coupled to the one or more processors, wherein the one or more memories store one or more programs that perform the steps, services and functions disclosed herein when executed by the one or more processors.

[0049] FIG. 1 shows, in a schematic view, an example of a first set of data points t.sub.s separated by a sampling time step t.sub.s and grouped into an effective filtering time period t.sub.f(n). Only a small fraction of the data points t.sub.s contained in the entire first set of data points is shown in FIG. 1. The sampling time step t.sub.s is in this case constant (i.e. the sampling frequency is constant) and in FIG. 1 exemplified to be the time between adjacent n:th and (n+1):th data points t.sub.s(n) and t.sub.s(n+1).

[0050] Each data point t.sub.s contains in this example information on i) a point of time, ii) a position in three dimensions (a position on a bent/curved vehicle body surface) and iii) a value representing an air pressure (at that point of time and at that position).

[0051] The pressure value is not the actual pressure but a value originating from, in this case, a simulated actual pressure.

[0052] Depending on the simulation, the vehicle body may be a simulated vehicle construction or a real vehicle construction. As an alternative, the pressure value may instead be measured by sensors positioned on a real vehicle body surface. Further, the friction or temperature may be simulated or measured instead of the pressure if suitable for a specific evaluation.

[0053] A number of consecutive data points, including the data points t.sub.s(n) and t.sub.s(n+1), are grouped together so as to visualize a first effective filtering time period t.sub.f(n). The length of the first effective filtering time period t.sub.f(n) equals the sum of all sampling time steps within that period. FIG. 1 also shows a second effective filtering time period t.sub.f(n+1), which also includes the data points t.sub.s(n) and t.sub.s(n+1) but which is positioned one sampling step later in time (i.e. one step to the right in FIG. 1). As will be described in more detail below the first effective filtering time period t.sub.f(n) is related to the n:th data point t.sub.s(n) and the second effective filtering time period t.sub.f(n+1) is related to the (n+1):th data point t.sub.s(n+1). Each data point t.sub.s is in a similar way related to a corresponding effective filtering time period t.sub.f (not shown in the figures).

[0054] FIG. 2 shows, in a schematic view, an example of a first set of data points set distributed over a total time period t.sub.tot with an example of an effective filtering time period t.sub.f(n). FIG. 2 may be seen as a scaling of FIG. 1 so that the effective filtering time period t.sub.f(n) is the same in FIGS. 1 and 2. A cut B is placed in the row of data points of FIG. 2 so as to indicate that the total time period t.sub.tot covers much more data points than shown in FIG. 2, which in turn means that the effective filtering time period t.sub.f(n) is much shorter in relation to the total time period t.sub.tot than what might be the impression from a quick look at FIG. 2.

[0055] FIG. 3 shows, in a schematic view, an example of method steps for identifying slow transient variations and/or local spatial variations of a fluid dynamic physical property in a set of data points.

[0056] Step 10 includes obtaining a first set of data points t.sub.s, i.e. all data points indicated in FIG. 2 that represent the total time period t.sub.tot. As mentioned above, each of these data points is associated with i) a point of time, ii) a three-dimensional position on a bent/curved vehicle body surface and iii) a value representing the air pressure (at that point of time and at that position). Further, the data points are separated in time by the sampling time step t.sub.s.

[0057] Step 20 includes calculating a temporal filtered value of the representation of the air pressure for, in this example, all points of the first set of data points distributed over the total time period t.sub.tot. The temporal filtered value is based on the plurality of values of the representation of the air pressure in the same position obtained over the corresponding effective filtering time period t.sub.f, i.e. for the n:th data point t.sub.s(n) the temporal filtered value is in this case based on all air pressure values obtained during the first effective filtering time period t.sub.f(n), for the (n+1):th data point t.sub.s(n+1) the temporal filtered value is based on all air pressure values obtained during the second effective filtering time period t.sub.f(n+1), etc. The temporal filtered value is in this example the arithmetic average of all the air pressure values obtained in the same position within the corresponding effective filtering period. This may be referred to as a moving average.

[0058] The effective filtering time period t.sub.f has a certain time relation to the data point for which the calculation is carried out, and in this example the data point is positioned in the middle of the corresponding filtering time period. As can be seen in FIG. 1 the effective filtering time period t.sub.f is considerably longer, preferably at least around 50-100 times longer, than the sampling time step t.sub.s. As can be seen in FIG. 2 the effective filtering time period t.sub.f is at the same time considerably shorter, preferably at least 10 times shorter, than the total time period t.sub.tot.

[0059] Step 30 includes combining the calculated temporal filtered values of the representation of the air pressure with the point of time and position of the corresponding data point t.sub.s in the first set of data points so as to obtain a second set of data points where each value representing the air pressure is the temporal filtered value. Since the temporal filtered values represents an average value of the air pressure over a longer time (i.e. over the filtering time period), the values are damped in time but not in position. This allows for identification of slow transient variations and local spatial variations of the air pressure in the first set of data points.

[0060] Step 40 includes analysing in time sequence the second set of data points over the total time period t.sub.tot. This is preferably carried out by preparing and sequencing a video (including setting colours to different air pressure ranges so as to indicate variations) to allow for a visual analysis.

[0061] As described above, the first set of data points t.sub.s obtained is related to a vehicle body surface. The first set of data points t.sub.s is based on measured values or simulated data. The simulated data may for example be established from computer simulations of a car body model in different transient wind conditions. Measured values may for example be collected with suitable sensors arranged on a real car body, where one or more pressure sensors, friction sensors or temperature sensors are applied in one or more positions of the vehicle body surface. The car may be placed in a wind tunnel or alternatively the car may be driven in different transient wind conditions. The sensors are measuring the pressure, friction, or temperature value in each position of the vehicle body surface with the pressure sensor, friction sensor or temperature sensor. The value representing the fluid dynamic physical property from the measured pressure, friction, or temperature value in each position of the vehicle body surface associated with the first set of data points is in this way obtained through the sensor measurements.

[0062] The present disclosure has been presented above with reference to specific embodiments. However, other embodiments than the above described are possible and within the scope of the disclosure. Different method steps than those described above, performing the method by hardware or software, may be provided within the scope of the disclosure. Thus, according to an exemplary embodiment, there is provided a non-transitory computer-readable storage medium storing one or more programs configured to be executed by one or more processors of a system for simulation, the one or more programs comprising instructions for performing the method according to any one of the above-discussed embodiments. Alternatively, according to another exemplary embodiment a cloud computing system can be configured to perform any of the method aspects presented herein. The cloud computing system may comprise distributed cloud computing resources that jointly perform the method aspects presented herein under control of one or more computer program products. Moreover, the processor may be connected to one or more communication interfaces and/or sensor interfaces for receiving and/transmitting data with external entities such as e.g. sensors arranged on the vehicle surface, an off-site server, or a cloud-based server.

[0063] The processor(s) (associated with the simulation system) may be or include any number of hardware components for conducting data or signal processing or for executing computer code stored in memory. The system may have an associated memory, and the memory may be one or more devices for storing data and/or computer code for completing or facilitating the various methods described in the present description. The memory may include volatile memory or non-volatile memory. The memory may include database components, object code components, script components, or any other type of information structure for supporting the various activities of the present description. According to an exemplary embodiment, any distributed or local memory device may be utilized with the systems and methods of this description. According to an exemplary embodiment the memory is communicably connected to the processor (e.g., via a circuit or any other wired, wireless, or network connection) and includes computer code for executing one or more processes described herein.

[0064] The invention is not limited by the embodiments described above but can be modified in various ways within the scope of the claims.