Method and device for generating measuring points for a test bench for measuring a physical system

Abstract

Method for providing measurement points (u) for measuring a physical system (2), comprising the following steps: - Providing (S1) several initial measurement points (ustart), each determined by an input value of an input quantity (E) or input values ​​of several input quantities (E) and each exhibiting a gradient with respect to one or more input quantities (E), wherein the measurement points are applied cyclically with a cycle time Δt, such that gradients of one or more input quantities result from the sequence of input values ​​of the input quantities at the successively applied measurement points, wherein differences between the input values ​​of an input quantity from one measurement point to the next determine the gradient of the input quantity E in question; - Successively selecting (S2) one of the initial measurement points (ustart) from a subset or all of the initial measurement points (ustart);- Generating (S3) a set of measurement points (u) depending on the selected initial measurement point (ustart), wherein the generated measurement points (u) are generated with increasing dynamic component, the dynamic component of the measurement point being determined by its gradient(t) = u(t) − u(t − 1) − t; - Applying the generated measurement points (u) to the physical system (2) and acquiring (S4) a resulting output quantity (y), wherein the generation and application of the measurement points (u) based on a selected initial measurement point (ustart) is carried out until the resulting output quantity (y) violates a predefined limit condition.

Description

Technical field The invention relates to methods for creating a set of measuring points to be applied to a physical system to be measured as input variables in order to obtain output values ​​of an output variable. State of the art From DE 10 159 605 A1 a method and apparatus for examining an internal combustion engine is known. From CN 1 02 798 857 A a method for measuring relative speed, radar sensor and automobile is known. When measuring a physical system with measurement points, it is necessary to position the measurement points in such a way that as many combinations as possible of input values ​​and gradients are measured, thus obtaining a space- and dynamically-filling input data space. However, the dynamic limits of the physical system are not known in advance, and specifying limit values ​​for the input values ​​of the measurement points does not guarantee that the measurement points will not exceed a dynamic limit in the physical system that could lead to damage or destruction of the physical system. It is therefore necessary to select the measurement points for performing a measurement of the physical system in such a way that the dynamic limits of the output quantity are not exceeded. Methods for providing input quantities in a static input quantity space are known, and a difficulty lies in dynamically varying the input quantities so that the input quantity space can be measured uniformly within the limits permissible for the physical system, with respect to both the input quantities and their gradients. Disclosure of the invention According to the invention, a method for providing measuring points for measuring a physical system according to claim 1 and a corresponding device according to the dependent claim are provided. Further details are specified in the dependent claims. According to a first aspect, a method for providing measurement points for measuring a physical system is provided, comprising the following steps: - Providing several initial measurement points, each determined by an input value of one or more input quantities and each exhibiting a gradient with respect to one or more input quantities; - Successively selecting one of the initial measurement points from a subset or all of the initial measurement points; - Generating a set of measurement points depending on the selected initial measurement point, wherein the generated measurement points are generated with an increasing dynamic component;- Applying the generated measurement points to the physical system and recording a resulting output quantity, whereby the generation and application of the measurement points based on a selected initial measurement point is carried out until the resulting output quantity violates a predefined limit condition. One objective of the above procedure is to provide measurement points for measuring a physical system, whereby the measurement points provide a distribution of the input values ​​and the distribution of their gradients within an input space that is as uniform as possible, so that the entire permissible static and dynamic input space is covered. At the same time, it should be ensured that the dynamics of the output do not exceed a dynamic limit determined by the physical system, which is specified by the limiting condition. This is achieved by generating measurement points for the physical system as local measurement points around one of the initial measurement points during the measurement process, and by capturing and monitoring the system response in the form of the output variable. If it is determined that the value of the output variable and / or its gradient exceeds predefined limits, the generation of the next measurement points, starting from a new initial measurement point, begins again with static measurement points, and their dynamic component is continuously or stepwise increased until the output variable, with its static or dynamic value, again reaches or exceeds the limit. In this way, it is possible to measure the input variable space with respect to static and dynamic input data points, thus achieving improved coverage of the input variable space using measurement points.In particular, by filling the input space with measurement points, it is ensured that the limit condition is not exceeded by the output. Furthermore, the limit condition can be specified in such a way that, if it is complied with, damage or destruction of the physical system is excluded. It may be provided that one or more input variables from the multiple initial measurement points are supplied in a space- and dynamic-filling manner, in particular as Sobol ramp profiles and / or shifted chirp signal profiles or chirp signal profiles. According to one embodiment, the initial measurement points can be selected in an arbitrary sequence or in a sequence determined by the respective dynamic component of the initial measurement point, in particular in a sequence of increasing dynamic component. It may be provided that the generation of measurement points based on a selected initial measurement point continues until a maximum dynamic component of one of the generated measurement points reaches or exceeds the dynamic component of the initial measurement point. Furthermore, the set of measurement points can be generated using a sinusoidal excitation function based on the initial measurement point. In particular, the sinusoidal excitation function can be provided with a stepwise or continuously increasing frequency for the successively generated measurement points. It may be provided that, when generating the measurement points, the frequency of the sinusoidal excitation function is increased stepwise or continuously up to a predetermined maximum value. According to a further aspect, a device for providing measurement points for measuring a physical system is provided, wherein the device is configured to: - provide several initial measurement points, each determined by an input value of an input quantity or input values ​​of several input quantities and each having a gradient with respect to the one or the several input quantities; - successively select one of the initial measurement points from a subset or all of the initial measurement points; - generate a set of measurement points depending on the selected initial measurement point, wherein the generated measurement points are generated with an increasing dynamic component;- to apply the generated measurement points to the physical system and to record a resulting output quantity, whereby the generation and application of the measurement points based on a selected initial measurement point is carried out until the resulting output quantity violates a predetermined limit condition.; Brief description of the drawings Embodiments are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a test rig for measuring a physical system; Fig. 2 a flowchart illustrating a method for measuring the physical system of Fig. 1; Fig. 3 a schematic representation of a variation of an input variable and a resulting output variable; and Fig. 4 a representation of the generation of local measurement points around a selected initial measurement point. Description of embodiments Fig. 1 shows a test bench 1 for measuring a physical system 2, such as an internal combustion engine. The test bench 1 includes a test device 3 that selects measuring points u for testing or measuring the physical system 2 and applies these points accordingly to the physical system 2. The measuring points u comprise a combination of one or more input values ​​from one or more input variables E with a corresponding gradient s of the one or more input variables. The measuring points are applied cyclically, i.e., in measurement cycles with a cycle time Δt, so that the sequence of input values ​​at successively applied measuring points results in gradients of the one or more input variables. In other words, the differences between the input values ​​of an input variable from one measuring point to the next determine the time gradient of the respective input variable E.The dynamic component of the measurement point is determined by its (temporal) gradient. For each measurement point, an output value of an output quantity y is recorded, and in test setup 3, the measurement points u, i.e., the input values ​​of the input quantities and their gradient values, are stored together with the corresponding output value of the output quantity as measurement data points. These can then serve as the basis for creating a physical mathematical model. The measurement points u are provided according to an input space that specifies a uniform distribution with respect to static and dynamic input values. The creation of measurement points u that cover the input space as uniformly as possible with respect to both their static and dynamic input values ​​is known from the prior art. For example, measurement points u can be generated using a so-called chirp method, a scaled chirp method, a Sobol method, and the like. These methods are suitable for defining the input values ​​of the input variables such that they are uniformly filled with a constant point density with respect to the input space, which is determined by the static input values ​​or the gradient values ​​of the input variables. However, it is not known whether the measurement points u in the input data space lead to impermissible operating points with respect to an intermediate quantity or the output quantity y, with respect to which the physical system 2 is to be measured. Impermissible operating points are operating points that should be avoided to prevent damage or destruction of the physical system 2. Therefore, one or more limit conditions are defined for the output quantity y to be measured, both for its static and dynamic values, with respect to which the output values ​​of the output quantity are to be monitored. The output values ​​y(t) are analyzed and checked with respect to the specified limit conditions. The provision of the measurement points u and their application to the physical system 2 is interrupted if at least one of the one or more limit conditions is met. The test setup 3 thus performs the generation or...The provision of a measurement point u(t+1) to the physical system 2 depends on the corresponding output value y(t) of the output quantity when the previous measurement point u(t) was applied. Fig. 2 shows a flowchart to illustrate a method for the adapted provision of measuring points for measuring a physical system 2. In step S1, initial measurement points are first generated from the input variables that lie within the input variable space. These initial measurement points can be generated, for example, using the methods mentioned above for an input variable space. For a one-dimensional input space, this is illustrated, for example, in Fig. 3. There, the input space for initial measurement points ustart with an input quantity E is shown. The measurement points u are plotted as ustart(t) over ustart(t-1), such that the diagonal D shown corresponds to those input values ​​where two consecutive input values ​​have the same or nearly the same value. Thus, the initial measurement points ustart lying on the diagonal D are static. Initial measurement points ustart deviating from the diagonal D exhibit a dynamic component, which is determined by the sequence of two consecutive initial measurement points ustart(t), ustart(t-1), where successive measurement points change. The magnitude of the change corresponds to the degree of dynamics, i.e.,The greater the change between two successive input values ​​(distance from the diagonal D) of the input quantity, the greater the gradient of the initial measurement point. In step S2, a first or next initial measurement point ustart is selected from the initial measurement points ustart. Since the initial measurement point ustart is considered independently of any preceding or subsequent initial measurement point ustart, it has no dynamic component. This static initial measurement point ustart is applied to the physical system 2. The dynamic component of the respective initial measurement point ustart is disregarded. The selection of the initial measurement points ustart should be uniformly distributed across the input space. Since the initial measurement points ustart are uniformly distributed in the static and dynamic input spaces, the purely static components of the initial measurement points ustart are also uniformly distributed (i.e., a uniform distribution along the diagonal shown in Fig. 3). In step S3, the input value(s) of the selected initial measurement point ustart are varied such that each execution of step S3 yields a local measurement point ulo-kal located within the input space around the selected initial measurement point ustart. Successively generated local measurement points ulokal around a specific initial measurement point ustart are created with increasing dynamic components. This increase can, for example, reach the dynamic component of the selected initial measurement point ustart. That is, the gradient of the local measurement points ulokal generated from the initial measurement point ustart rises to a maximum gradient determined by the dynamic component of the selected initial measurement point ustart. After each local measurement point is created ulocally in the physical system, the associated output quantity y is recorded in step S4 and stored ulocally as a test data point together with the input values ​​of the input quantity of the local measurement point. In step S5, the output value of the output variable y and its gradient are checked against at least one limit condition. The limit condition can, for example, include specifying a maximum and / or minimum value for the output value of the output variable y and / or its gradient. If, in step S5, it is determined that the predefined limit condition is violated by the output value of the output variable (alternative: Yes), the generation of local measurement points is aborted ulocally and the process returns to step S2, where a next initial measurement point ustart is selected. Otherwise (alternative: No), the procedure continues with step S3, generating the next local measurement point ulocally based on the selected initial measurement point ustart. Figure 4 illustrates, for example, how local measurement points ulocally are generated around a selected initial measurement point ustart, exhibiting increasing dynamics. It can be seen that an ellipse K is formed around the static input value of an input variable of the selected initial measurement point ustart. This ellipse covers a range of the static input values ​​(along the diagonal) and also adds dynamic input values, characterized by the points on the ellipse that deviate from the diagonal D shown. In particular, the local measurement points ulocally can be generated using a sinusoidal excitation signal. The frequency of the sinusoidal excitation signal can be f = s / 2π and its amplitude 1. This sinusoidal excitation function ensures that the required gradient (or magnitude of the gradient) s of the initial measurement point ustart is reached at 0, π, 2π, etc.When generating the local measurement points ulokal, the gradient s can be successively, e.g. stepwise, increased until the limit condition for the output quantity y is violated. In this way, the excitation corresponds, for example, to f = i*smax / 2π with i=0, 0.05, 0.1, 0.15...1 with an increasing excitation frequency, where smax corresponds to the slope or gradient of the selected initial measurement point ustart. The gradient is increased stepwise to provide the sinusoidal excitation function, for example, in 5% steps as shown above. In this way, a sequence of local measurement points ulocal is determined around the static selected initial measurement point ustart, which exhibit a stepwise increased dynamic range and measure the area of ​​the input quantity space around the static component of the selected initial measurement point ustart. The selection of the given initial measurement points ustart can be arbitrary or according to a selection scheme. One possible selection scheme involves choosing the initial measurement points ustart from the given set of initial measurement points ustart according to the dynamic component determined by their sequence. For example, the selection can begin with the initial measurement point ustart that exhibits the lowest dynamic component, i.e., the gradient of that initial measurement point ustart determined by the previous initial measurement point ustart. The selection of initial measurement points ustart can then proceed according to increasing dynamic components. Alternatively, the selection can also be made according to decreasing dynamic components of the initial measurement points ustart. If the limit condition is reached by the output quantity before the excitation function with the maximum gradient smax is generated, the application of the excitation function to the selected initial measurement point ustart is terminated and the procedure is determined with the next selected initial measurement point ustart as the basis for creating the local measurement points ulokal. This procedure is performed for some or all of the predefined selected initial measurement points ustart, specifically sequentially with an increasing dynamic component, i.e., an increasing gradient, either until the limit condition for the output quantity is violated or until the maximum gradient smax specified by the initial measurement point ustart is reached. In this way, it is possible to generate measurement points as the local measurement points and apply them to the physical system, ensuring that no critical values ​​are reached by the output quantity y that could damage or destroy the physical system 2 during measurement. At the same time, it is ensured that the best possible uniform coverage of the static and dynamic input quantity space is achieved with the local measurement points ulokal.

Claims

Method for providing measurement points (u) for measuring a physical system (2), comprising the following steps: - Providing (S1) several initial measurement points (ustart), each determined by an input value of an input quantity (E) or input values ​​of several input quantities (E) and each exhibiting a gradient with respect to one or more input quantities (E), wherein the measurement points are applied cyclically with a cycle time Δt, such that gradients of one or more input quantities result from the sequence of input values ​​of the input quantities at the successively applied measurement points, wherein differences between the input values ​​of an input quantity from one measurement point to the next determine the gradient of the input quantity E in question; - Successively selecting (S2) one of the initial measurement points (ustart) from a subset or all of the initial measurement points (ustart);- Generating (S3) a set of measurement points (u) depending on the selected initial measurement point (ustart), wherein the generated measurement points (u) are generated with increasing dynamic component, where the dynamic component of the measurement point is determined by its gradient s ( t ) = u ( t ) − u ( t − 1 ) Δ t; is determined; - Applying the generated measurement points (u) to the physical system (2) and acquiring (S4) a resulting output quantity (y), wherein the generation and application of the measurement points (u) is based on a selected initial measurement point (u start ) is performed in each case until the resulting output variable (y) violates a predetermined limit condition. Method according to claim 1, wherein the limit condition is specified in such a way that, if the limit condition is met, damage or destruction of the physical system (2) is excluded. Method according to one of claims 1 to 2, wherein the one or more input variables (E) of the multiple initial measurement points (ustart) are provided in a space- and dynamically-filling manner, in particular as Sobol ramp profiles and / or shifted chirp signal profiles or chirp signal profiles. Method according to one of claims 1 to 3, wherein the initial measurement points (ustart) are selected in an arbitrary sequence or in a sequence determined by the respective dynamic component of the initial measurement point (ustart), in particular in a sequence of increasing dynamic component. Method according to one of claims 1 to 4, wherein the generation and creation of the measurement points (u) based on a selected initial measurement point (ustart) is carried out until a maximum dynamic component of one of the generated measurement points (u) reaches or exceeds the dynamic component of the initial measurement point (u). Method according to any one of claims 1 to 5, wherein the set of measurement points (u) is generated using a sinusoidal excitation function based on the initial measurement point (ustart). Method according to claim 6, wherein the sinusoidal excitation function is provided with a stepwise or continuously increasing frequency for the successively generated measurement points (u). Method according to claim 6 or 7, wherein when generating the measurement points (u) the frequency of the sinusoidal excitation function is increased stepwise or continuously up to a predetermined maximum value. Device for providing measurement points (u) for measuring a physical system (2), wherein the device is configured to: - provide several initial measurement points (ustart), each determined by an input value of an input quantity (E) or input values ​​of several input quantities (E) and each having a gradient with respect to one or more input quantities (E), wherein the measurement points are applied cyclically with a cycle time Δt, such that gradients of one or more input quantities result from the sequence of input values ​​of the input quantities at the successively applied measurement points, wherein differences between the input values ​​of an input quantity from one measurement point to the next determine the gradient of the input quantity E in question; - successively select one of the initial measurement points (ustart) from a subset or all of the initial measurement points (ustart);- to generate a set of measurement points (u) depending on the selected initial measurement point (ustart), wherein the generated measurement points (u) are generated with increasing dynamic component, where the dynamic component of the measurement point is determined by its gradient s(t) = s ( t ) = u ( t ) − u ( t − 1 ) Δ t; is determined; - to apply the generated measurement points (u) to the physical system (2) and to record a resulting output quantity (y), wherein the generation and application of the measurement points (u) is based on a selected initial measurement point (u start ) is performed in each case until the resulting output variable (y) violates a predetermined limit condition. Computer program which, when executed in a data processing device, is configured to perform all steps of a method according to any one of claims 1 to 8. Machine-readable storage medium on which a computer program according to claim 10 is stored.

Images