Method of determining an output rotational speed of a shaft of a machine

Abstract

A method for determining the output rotational speed (nA1, nA2) of the shaft (26) of a machine (27), particularly an internal combustion engine, using a filter, wherein the characteristics of the filter are determined based on the operating characteristics of the machine (27), wherein the characteristics of the filter are the filter length.

Description

Technical Field

[0001] This invention relates to a method for determining the output rotational speed of a machine shaft. Background Technology

[0002] To operate an internal combustion engine, the engine controller typically calculates various rotational speeds of shafts such as the crankshaft or camshaft. These speeds can be calculated in different ways. The main distinguishing feature of these speeds is the fixed, defined filter length (the crankshaft's rotation angle), along which the speed is calculated by averaging, and this filter length is immutable.

[0003] For example, for internal combustion engines, the so-called stage speed or the so-called single-tooth speed is calculated.

[0004] Currently, only the following application is known where the stage filter length is used to filter engine speed. The stage filter length is defined as the distance between two adjacent top dead centers (top dead centers) of a cylinder and is calculated by dividing the crankshaft angle per working cycle by the number of cylinders in the internal combustion engine. For a four-stroke engine with four cylinders, this means dividing 720°KW (crankshaft angle) by the number of cylinders 4. Therefore, the crankshaft angle per working cycle is 180°KW. For the corresponding four-stroke engine with six cylinders, the crankshaft angle per working cycle is 120°KW. The resulting engine speed is called the stage speed.

[0005] The drawback of phased speeds is that for highly dynamic operating points, the signal is not calculated quickly enough, thus lagging behind the actual engine speed. Therefore, simple phased speeds alone cannot accurately represent these operating points.

[0006] Other applications use the rotational speed derived from the length of a single-tooth filter. The length of a single-tooth filter is the distance between two crankshaft teeth on the crankshaft sensor wheel. For a 60-tooth sensor wheel, the distance between the two crankshaft teeth is 6°KW. The resulting rotational speed is called the single-tooth rotational speed.

[0007] The drawback of single-tooth speed measurement is that it reflects almost all variations in the real speed signal (such as engine compression) and interference on the speed signal with almost no filtering. For this reason, single-tooth speed measurement is unsuitable for most regulation algorithms in engine controllers and is therefore rarely used.

[0008] If other characteristics of the rotational speed are required, they are typically achieved through subsequent calculations (e.g., using a low-pass filter). These calculations can have negative effects, such as causing a time delay in the rotational speed signal when using a filter. Summary of the Invention

[0009] According to a first aspect of the invention, a method is proposed for determining the output speed of a machine shaft, particularly an internal combustion engine shaft, using a filter. The characteristics of the filter are determined based on the machine's operating characteristics, where the filter's characteristics are its length. This means allocating a filter length to the machine's operating characteristics. The determined speed, more precisely the output speed, is then provided for other purposes. Therefore, unlike prior art, there are no switching jumps in the shaft's output speed. That is, as the machine's speed increases uniformly, the determined machine output speed increases similarly or approximately the same or uniformly. Furthermore, it better represents engine dynamics while sufficiently filtering out interference and signal fluctuations.

[0010] According to another perspective of the invention, operating characteristics refer to the operating point and / or dynamics (operating dynamics) of the machine, more precisely, the internal combustion engine. The dynamics can be determined from the operating point, particularly by the operating speed and the associated load. In the starting condition, the load is, for example, very low and the dynamics are high because the shaft speed changes rapidly. In this case, it is advantageous to use a short filter length. This allows for a fast response, i.e., rapid determination of the output speed. This corresponds to a trade-off between a fast response (i.e., rapid determination of the output speed) and good result quality (few disturbances).

[0011] In urban traffic, the engine speed is likely to be only moderately low under moderate load conditions. At this point, dynamics are very low when driving in high gear in economy mode. In such cases, using, for example, a medium or large filter length is advantageous.

[0012] According to another aspect of the invention, the filter length is determined based on characteristic data, particularly characteristic curves, which are related to the rotational speed of the machine's shaft. This achieves a simple method and allows for rapid selection of the filter length.

[0013] According to another aspect of the invention, a rotational speed threshold is provided, and the filter length is changed when the rotational speed threshold is reached. In this way, the filter length can be easily changed as needed.

[0014] According to another aspect of the invention, a large filter length is used when the shaft has a high rotational speed. This achieves maximum suppression of interference, and therefore the best possible quality of the result. Since a short, fast response time is not required in the higher rotational speed range, rapid determination of the output rotational speed is not required. Attached Figure Description

[0015] The accompanying diagram mentioned below illustrates:

[0016] Figure 1 A graphical comparison between the unfiltered rotational speed, the rotational speed averaged over half a stage, and the rotational speed averaged over the entire stage and not zero.

[0017] Figure 2 A graphical comparison of the rotational speeds filtered using a small filter length versus those filtered using a large filter length.

[0018] Figure 3 The first algorithm is used to determine the filter length and output speed by, for example, characteristic curves designed as a family of characteristic curves.

[0019] Figure 4 Another algorithm is used to determine the filter length and output rotational speed.

[0020] Figure 5 Another algorithm,

[0021] Figure 6 It shows that according to Figure 5 The relationship in the embodiments,

[0022] Figure 7 It shows that according to Figure 5 The relationships in the embodiments. Detailed Implementation

[0023] Figure 1 A graphical comparison of three different provided speeds is shown: the unfiltered speed n0 and two different output speeds nA1 and nA2, where the unfiltered speed is here referred to as the single-tooth speed. The output speeds nA1 and nA2 are speeds determined based on the provided speed, such as speed n0, and using correspondingly different filters F1 and F2. Output speed nA1 is determined by filtering over half a stage (filter F1), and output speed nA2 is determined by filtering over the entire stage (filter F2). In this case, the latter is always larger. The depicted cylinder stage S corresponds in angular length to the distance between two adjacent top dead centers.

[0024] Figure 2 The diagram shows the changes in two different output speeds, nA1 and nA2, over time during the startup process. For most of the shown speed range, the determined output speed nA2 deviates relatively significantly from the output speed nA1.

[0025] Figure 3A first algorithm is shown for determining the filter length LF and the output speed nA using characteristic curve 20, for example, designed as a family of characteristic curves. In one step, a signal is detected from the rotation of the shaft 26 of a machine 27, for example, designed as an internal combustion engine, using a sensing device (signal detection step S29), and a variable representing the speed or actual speed n0 is determined, or the actual speed n0 is determined. The so-called duration of the segment between signal detection and speed calculation corresponds here to the required filter length LF. From the determined variable, the filter length LF is determined in step S30 using characteristic curve 20, where the variable represents the speed of the shaft 26 of the machine 10 (e.g., an internal combustion engine), more precisely, the actual speed n0, or is itself the actual speed n0. Each variable corresponding to the speed can be assigned a filter length LF using characteristic curve 20. From this variable and the filter length LF, the output speed is determined in step S32, where the variable represents the speed n0 or the actual speed n0 of the shaft 26. This output speed nA is then used, or can be used, for functions used in controller 35.

[0026] Figure 4 Another algorithm is illustrated in another embodiment for determining the filter length LF and the output rotational speed nA. In one step, a signal is detected from the rotation of the shaft 26 of a machine 27, for example designed as an internal combustion engine, using a sensing device (signal detection step S29), and a variable representing the rotational speed, more precisely the actual rotational speed n0, is determined, or the actual rotational speed n0 is determined. Using this variable, in step 34 it is determined whether the variable is below a lower threshold SGu, above an upper threshold SGo, or between the lower threshold SGu and the upper threshold SGo. Accordingly, three cases can be distinguished:

[0027] In the first case: if the variable representing the rotational speed, more precisely the actual rotational speed n0, or the variable determining the actual rotational speed n0, lies between the lower threshold SGu and the upper threshold SGo, then a filter length LF is assigned to that variable. From this variable and the filter length LF, the output rotational speed nA is determined in step S32, where the variable represents the rotational speed n0 or the actual rotational speed n0 of shaft 26. This output rotational speed nA is then used, or can be used, for functions in controller 640. Controller 640 has a machine-readable storage medium 620 on which a computer program 600 is stored.

[0028] The second scenario: If the variable representing the rotational speed, more precisely the actual rotational speed n0, or the variable determining the actual rotational speed n0, is less than the lower threshold SGu, then the filter length LF is changed or adjusted via a ramp function as long as the variable representing the rotational speed, more precisely the actual rotational speed n0, or the variable determining the actual rotational speed n0, is less than the lower threshold SGu. Therefore, in the first time period dT1u after determining that it is below the lower threshold, the output rotational speed nA is determined in step S32 by the filter shortening amount dLF1u and the thus reduced filter length LF. As long as this variable is less than the lower threshold SGu, the filter length LF is reduced (sloped down) via a ramp function. In the second time period dT2u, the filter length LF is adjusted, and in step S32, the output rotational speed nA is determined by further reducing the filter length LF by the filter shortening amount dLF2u. As long as the variable is less than SGu and has not yet reached the minimum or shortest filter length LFmin, the filter length LF is further changed. Here, these time periods can be of equal length, and the filter shortening amounts can also be equal.

[0029] The third scenario: If the variable representing the rotational speed, more precisely the actual rotational speed n0, or the variable determining the actual rotational speed n0, is greater than the upper limit threshold SGo, then the filter length LF is adjusted via a ramp function as long as the variable representing the rotational speed, more precisely the actual rotational speed n0, or the variable determining the actual rotational speed n0, is greater than the upper limit threshold SGo. Therefore, in the first time period dT1o after determining that the upper limit threshold has been exceeded, the output rotational speed nA is determined in step S32 by the filter extension dLF1o and the thus increased filter length LF. As long as the variable is greater than the upper limit threshold SGo, the filter length LF is increased (upward ramp) via a ramp function. In the second time period dT2o, the filter length LF is adjusted, and in step S32, the output rotational speed nA is determined by further increasing the filter length LF by the filter extension dLF2o. As long as the variable is greater than SGo and has not yet reached the maximum or longest filter length LFmax, the filter length LF is further changed. Here, these time periods can be of equal length, and the filter shortening amount can also be equal.

[0030] Based on the determined variables, in step S30, the filter length LF is determined, for example, increased or decreased, using threshold values ​​(upper threshold, lower threshold). These variables represent the rotational speed of the shaft 26 of the machine 10 (e.g., an internal combustion engine), more precisely, the actual rotational speed n0, or are themselves the actual rotational speed n0. The variable corresponding to each rotational speed can be assigned the filter length LF using characteristic curve 20. Based on this variable and the filter length LF, the output rotational speed nA is determined in step S32, where the variable represents the rotational speed n0 or the actual rotational speed n0 of the shaft 26. This output rotational speed nA is then used, or can be used, for functions in the controller 35.

[0031] Figure 5 Another algorithm is illustrated in another embodiment for determining the filter length LF and the output rotational speed nA. Here, a rotational speed-related factor f is continuously determined (step S40), and using this factor, a weighted average LFwa is formed between the rotational speed nLFmin using a small filter length LFmin and the rotational speed nLFmax using a large filter length LFmax. This method effectively yields a method for determining a variable filter length LF, which depends not only on the rotational speed n0 but also on a very finely graded filter length LF. Furthermore, the weighting allows for consideration of the effects at rotational speeds where the influence of the filter length LF is small and at rotational speeds where the influence of the filter length LF is large. Figure 5 An exemplary feasible scheme for determining the output rotational speed nA is shown in the figure.

[0032] The factor f is multiplied by the single-tooth speed n1Z (step S41) and provided to the addition section for addition in step S44. The factor f is also subtracted by 1 at the subtraction section (step S42). The resulting stage speed nSeg is multiplied by the result obtained in step S42 in step S43. This result is then added to the result obtained in step S41 in step S44 to obtain the output speed nA. This output speed nA is then provided to the controller 640 for further operation.

[0033] Figure 6 and Figure 7 It shows that according to Figure 5 The relationships in the embodiments. Figure 6 The evolution of the filter length LF with rotational speed n0 from the initial length / minimum length LFmin, and its linear evolution to the maximum length LFmax, which no longer changes from a specific rotational speed nALFmax. Figure 7 The figure shows the change of rotational speed nALFmin over time corresponding to the rotational speed n0, determined using only the minimum length LFmin; the change of rotational speed nALFmax determined using the target filter length / maximum length LFmax, depending on the change of n0 over time; and the change of rotational speed nALFmin determined using only the minimum length LFmin, depending on the change of n0 over time.

Claims

1. A method for determining the output rotational speeds (nA1, nA2) of the shaft (26) of a machine (27), particularly an internal combustion engine, by means of a filter, wherein, The characteristics of the filter are determined based on the operating characteristics of the machine (27), wherein the characteristic of the filter is the length of the filter.

2. The method according to claim 1, characterized in that, The operating characteristics are the operating point and / or dynamics of the machine (27).

3. The method according to any one of the preceding claims, characterized in that, The length of the filter is determined based on characteristic data, particularly characteristic curves, which are related to the rotational speed (n0) of the shaft (26) of the machine (27).

4. The method according to any one of the preceding claims, characterized in that, A rotational speed threshold is set, and the length of the filter is changed when the rotational speed threshold is reached.

5. The method according to claim 4, characterized in that, The length of the filter is gradually changed.

6. The method according to any one of claims 1, 2, or 3, characterized in that, A factor (f) related to the rotational speed (n0) of the shaft (26) of the machine (27) is continuously determined, wherein the weighted average of the filter lengths (FLwa) is determined by a filter having a first length and a filter having a second length.

7. The method according to any one of the preceding claims, characterized in that, The rotational speed of the crankshaft or camshaft of a machine (27) designed as an internal combustion engine is used as the rotational speed (n0) of the shaft (26).

8. A computer program (600) configured or set to perform all or each step of the method according to any one of claims 1 to 5, or the computer program is programmed such that when executed on a computer, the computer program performs the method according to any one of claims 1 to 5.

9. A machine-readable storage medium (620) having a computer program (600) according to claim 8 stored thereon, or having a computer program (600) according to claim 8 stored thereon for use in the method according to any one of claims 1 to 7.

10. A controller (640) configured to perform all steps of the method according to any one of claims 1 to 7, or the controller is programmed to be used in the method according to any one of claims 1 to 7.

Images