Generation of Measurement Strategy for Measuring a Measurement Object

Abstract

A method for determining an altered measurement strategy for measurement of a measurement object using a coordinate measuring machine includes measuring the measurement object according to an initial measurement strategy. The method includes determining a measurement quality of the measurement. The method includes, in response to the measurement quality being greater than a predetermined target minimum measurement quality, altering the initial measurement strategy to produce the altered measurement strategy. The altering is performed such that at least one of time required to measure the measurement object in accordance with the altered measurement strategy is reduced, computational outlay required to measure the measurement object in accordance with the altered measurement strategy is reduced, and data storage capacity required to measure the measurement object in accordance with the altered measurement strategy is reduced.

Claims

1. A method for determining an altered measurement strategy for measurement of a measurement object using a coordinate measuring machine, comprising: measuring the measurement object according to an initial measurement strategy; determining a measurement quality of the measurement; and in response to the measurement quality being greater than a predetermined target minimum measurement quality, altering the initial measurement strategy to produce the altered measurement strategy, wherein the altering is performed such that at least one of: time required to measure the measurement object in accordance with the altered measurement strategy is reduced, computational outlay required to measure the measurement object in accordance with the altered measurement strategy is reduced, and data storage capacity required to measure the measurement object in accordance with the altered measurement strategy is reduced.

2. The method of claim 1 further comprising, using the altered measurement strategy, measuring at least one of the measurement object and a second measurement object.

3. The method of claim 1 wherein the measurement strategy is altered in such a way that the measurement quality is reduced.

4. The method of claim 1 wherein the measurement quality is determined by virtue of determining at least one measurement quality parameter that represents the measurement quality.

5. The method of claim 4 wherein the measurement quality parameter is a relationship between measurement uncertainty and a manufacturing tolerance known in advance.

6. The method of claim 5 wherein the measurement strategy is altered in such a way that the measurement quality is reduced.

7. The method of claim 5 wherein a variable that represents accuracy, repeatability, reproducibility, linearity, and/or stability of the measurement in accordance with the measurement strategy is determined as measurement quality.

8. The method of claim 1 wherein a variable that represents the accuracy, repeatability, reproducibility, linearity, and/or stability of the measurement in accordance with the measurement strategy is determined as measurement quality.

9. The method of claim 1 wherein a GR&R test or a test pursuant to VDA Volume 5 is carried out to determine a variable representing the measurement quality.

10. The method of claim 1 further comprising, in response to the measurement quality being greater than a target minimum measurement quality known in advance, altering at least one measurement quality-relevant parameter of the measurement strategy.

11. The method of claim 10 wherein the at least one measurement quality-relevant parameter is or represents at least one of: a sensor parameter of a sensor of the coordinate measuring machine, a number of measurement points to be captured by the sensor during a predetermined time interval, a parameter of the spatial distribution of the measurement points to be captured, a speed of a relative movement between measurement object and sensor, a number of measurement trajectories, a length of a measurement trajectory, a filter parameter for filtering the measurement values, an evaluation parameter for evaluating the measurement values, and a parameter for temperature compensation.

12. The method of claim 11 further comprising, in response to the measurement quality being greater than the target minimum measurement quality known in advance, at least one of: reducing the number of measurement points to be captured by the sensor within a predetermined time interval; increasing the movement speed of a relative movement between measurement object and sensor; and reducing the spatial distribution of the measurement points to be captured.

13. The method of claim 1 wherein altering the measurement strategy includes altering at least one of: a filter method for filtering the measurement values, an evaluation method for evaluating the measurement values, a temperature compensation method for temperature compensation, a test plan, a sensor type, a measuring device type, a measurement object clamping concept, an illumination concept, and a type of relative movement between the measurement object and sensor of the coordinate measuring machine.

14. The method of claim 1 further comprising: determining a sensor quality during the measurement; and altering at least one sensor parameter of a sensor of the coordinate measuring machine in response to the sensor quality being greater than a target minimum sensor quality known in advance, wherein the sensor parameter is altered so as to reduce at least one of: the time required to measure the measurement object in accordance with the altered measurement strategy, the computational outlay required to measure the measurement object in accordance with the altered measurement strategy, and the data storage capacity required to measure the measurement object in accordance with the altered measurement strategy is reduced.

15. An apparatus for determining an altered measurement strategy for measurement of a measurement object, the apparatus comprising: a coordinate measuring machine configured to measure the measurement object in accordance with an initial measurement strategy; and an evaluation device configured to determine at least one measurement quality, wherein, in response to the measurement quality being greater than a predetermined target minimum measurement quality, the initial measurement strategy is altered so as to reduce at least one of: time required to measure the measurement object in accordance with the altered measurement strategy; computational outlay required to measure the measurement object in accordance with the altered measurement strategy; and data storage capacity required to measure the measurement object in accordance with the altered measurement strategy.

16. The apparatus of claim 15 wherein the coordinate measuring machine is configured to measure, using the altered measurement strategy, at least one of the measurement object and a second measurement object.

17. A non-transitory computer-readable medium storing instructions including: using a coordinate measuring machine, measuring a measurement object according to an initial measurement strategy; determining a measurement quality of the measurement; and altering the initial measurement strategy in response to the measurement quality being greater than a predetermined target minimum measurement quality, wherein the altering is performed such that at least one of: time required to measure the measurement object in accordance with the altered measurement strategy is reduced, computational outlay required to measure the measurement object in accordance with the altered measurement strategy is reduced, and data storage capacity required to measure the measurement object in accordance with the altered measurement strategy is reduced.

18. The computer-readable medium of claim 17 wherein the instructions further include measuring, using the altered measurement strategy, at least one of the measurement object and a second measurement object.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0087] The present disclosure will become more fully understood from the detailed description and the accompanying drawings.

[0088] FIG. 1 is a schematic flowchart of a method according to the invention.

[0089] FIG. 2 is a schematic flowchart of a method according to the invention in a further embodiment.

[0090] FIG. 3 is a schematic flowchart of a method according to the invention in a further embodiment.

[0091] FIG. 4 is a schematic block diagram of an apparatus according to the invention.

[0092] In the drawings, reference numbers may be reused to identify similar and/or identical elements.

DETAILED DESCRIPTION

[0093] FIG. 1 shows a schematic flowchart of a method according to the invention for determining a measurement strategy for measuring a measurement object 2 using a coordinate measuring machine 1 (see FIG. 4). A measurement strategy is defined, for example by a user or in (partly) automated fashion, in a first step S1. This measurement strategy can also be referred to as initial measurement strategy. Alternatively, an altered measurement strategy can also be used if the method has been carried out previously.

[0094] In a second step S2, the measurement object 2 is measured in accordance with the initial measurement strategy, for example by the coordinate measuring machine 1 illustrated in FIG. 4.

[0095] The measurement quality of the measurement carried out in the second step S2 is determined in a third step S3. This measurement quality depends on the measurement quality-relevant parameters of the measurement strategy, which were already explained above. However, the measurement strategy additionally also depends on ambient conditions, such as, e.g., the temperature, an incidence of light, a degree of dirtying. Further, the measurement quality depends on the quality of the shape of the workpiece. The latter can change dynamically, e.g., reduce, if the manufacturing of the workpiece becomes less accurate, for example on account of wear of tools for production.

[0096] A check is carried out in a fourth step S4 as to whether the measurement quality determined in the third step S3 is greater than a predetermined target minimum measurement quality, in particular greater by more than a predetermined amount, e.g., by more than 5%. If the measurement quality is less than the target minimum measurement quality, measures for improving the measurement quality, which are not described in any more detail in this disclosure, are carried out. If the measurement quality is equal to or greater than the target minimum measurement quality, but not greater by more than a predetermined amount, the method can be terminated without altering the current measurement strategy.

[0097] If the measurement quality is greater than the predetermined target minimum measurement quality, in particular by more than the predetermined amount, the measurement strategy is altered in a fifth step S5 and determined as new measurement strategy, i.e., as measurement strategy to be applied in future. In this case, the change in the fifth step S5 is implemented in such a way that the time required to measure the measurement object 2 in accordance with the altered measurement strategy and/or the computational outlay required to measure the measurement object 2 and/or the data storage capacity required to measure the measurement object 2 are/is reduced. Hereinafter, in an illustrated sixth step, the measurement object 2 can be measured in accordance with the altered measurement strategy, for example by the coordinate measuring machine 1 illustrated in FIG. 4.

[0098] It is possible for the method to be carried out repeatedly, in particular until the measurement quality determined in the fourth step S4 equals or is greater than the target minimum measurement quality, but not greater by more than a predetermined amount.

[0099] To this end, the measurement strategy altered in the fifth step S5 can be used in the second step S2 for the measurement when the method is carried out again, in order to determine the measurement quality of the measurement again and, where necessary, to determine a further altered measurement strategy. Consequently, the method can return to the second step S2 after the fifth step S5, in particular if the measurement quality continues to be greater than the predetermined target minimum measurement quality or greater than the predetermined target minimum measurement quality by more than a predetermined amount.

[0100] FIG. 2 shows a schematic flowchart of a method according to the invention in a further embodiment. This embodiment is substantially the same as the embodiment of the method illustrated in FIG. 1.

[0101] However, a manufacturing tolerance of the measurement object, for example a tolerance of at least one test feature, is additionally determined in the first step S1. The latter can be determined in model-based fashion, for example on the basis of a CAD model. Then, in accordance with the embodiment illustrated in FIG. 1, a measurement object 2 (see FIG. 4) is measured on the basis of the measurement strategy in a second step S2 and the measurement uncertainty is determined in a third step S3, with the measurement quality then being determined as a relationship between this measurement uncertainty and the manufacturing tolerance known in advance.

[0102] According to this, the fourth step S4 is carried out in accordance with the embodiment illustrated in FIG. 1, wherein the target minimum measurement quality is, e.g., 1/10 and the fifth step S5 is carried out if the relationship ascertained in the third step S3 is more than 5% less than 1/10.

[0103] Then, the number of measurement points to be captured by the sensor of the coordinate measuring machine 1 (see FIG. 4) in a predetermined time interval is reduced in the fifth step S5. Alternatively or cumulatively, the movement speed, in particular a maximum speed or an average speed, of the relative movement between measurement object 2 and sensor 3 is increased.

[0104] FIG. 3 shows a schematic flowchart of a method according to the invention in a further embodiment. In contrast to the embodiment illustrated in FIG. 1, the measurement quality is determined in a first partial step S3a of the third step S3, with a sensor quality being determined in a second partial step S3b. In a first partial step S4a of the fourth step S4, the measurement quality ascertained in the first partial step S3a of the third step S3 is then evaluated, in accordance with the fourth step S4 in the exemplary embodiment illustrated in FIG. 1.

[0105] However, if the measurement quality is greater than the target minimum measurement quality known in advance, there is in a second partial step S4b of the fourth step S4 a comparison of the sensor quality ascertained in the second partial step S3b of the third step S3 with the target minimum sensor quality known in advance.

[0106] If the ascertained sensor quality is not greater than the corresponding target value, it is possible to carry out measures, not described in detail, for improving the measurement quality and/or the sensor quality.

[0107] However, if said quality equals the target minimum sensor quality known in advance or if it is located in an admissible range, the measurement strategy is altered in a first alternative step S5_1 and the altered measurement strategy is determined as new measurement strategy, with, however, no sensor parameter of the sensor, i.e., no sensor quality-relevant parameter, being altered by the change.

[0108] If the sensor quality is greater than the target minimum sensor quality known in advance, the measurement strategy is altered in a second alternative step S5_2 by altering a sensor parameter in such a way that the time and/or the computational outlay and/or the data storage capacity required to measure the measurement object in accordance with the measurement strategy are/is reduced.

[0109] Here, the alternative steps S5_1, S5_2 denote steps that are carried out as alternatives to one another when the fifth step S5 is carried out.

[0110] If the measurement quality determined in the first partial step S4a of the fourth step S4 equals the target minimum measurement quality or if it is located in a predetermined admissible range (and consequently there is no change in the measurement strategy), there naturally can also be a check as to whether the sensor quality equals the target minimum sensor quality or is located in a predetermined admissible range. If this is not the case, measures for improving the sensor quality, which are not explained in more detail, can be carried out.

[0111] FIG. 4 shows a schematic block diagram of an apparatus 3 according to the invention for determining a measurement strategy for measuring a measurement object 2 using a coordinate measuring machine 1. It comprises an evaluation device 4 embodied as a computing device, which, for example, can comprise a microcontroller or an integrated circuit or be embodied as such. Further, the apparatus 3 comprises the coordinate measuring machine 1. Then, the measurement object 2 is able to be measured by means of the coordinate measuring machine 1, which is represented in this example as a tactile coordinate measuring machine 1 with a stylus 5 and a probe ball 6, in accordance with an initial measurement strategy, which may have been specified, for example, by a user by means of an appropriate input device 7. Here, the coordinate measuring machine 1 produces measurement values during the measurement of the measurement object 2 in accordance with the initial measurement strategy, which measurement values can then be evaluated by the evaluation device 4. In this case, the evaluation device 4 can apply an appropriate evaluation method. The evaluation device 4 can also apply an appropriate filter method for filtering the measurement values.

[0112] Further, the measurement quality of the utilized measurement strategy can be determined by the evaluation device 4. Further, the evaluation device 4 can alter the measurement strategy if the measurement quality is greater than a predetermined target minimum measurement quality, wherein the change is implemented in such a way that the time and/or computational outlay and/or data storage capacity required to measure the measurement object 2 are/is reduced, with the altered measurement strategy then being determined as new measurement strategy for measuring the measurement object 2 and further measurement objects, in particular the same or similar measurement objects. This measurement strategy can then be stored, for example in a storage device 8 of the evaluation device 4 or an external storage device (not illustrated) data-connected to the evaluation device 4.

[0113] In this case, the evaluation device 4 can also serve as a control device for controlling the coordinate measuring machine 1 for the purposes of measuring the measurement object 2.

[0114] The term non-transitory computer-readable medium does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave). Non-limiting examples of a non-transitory computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc). The phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

LIST OF REFERENCE SIGNS

[0115] 1 Coordinate measuring machine [0116] 2 Measurement object [0117] 3 Apparatus [0118] 4 Evaluation device [0119] 5 Stylus [0120] 6 Probe ball [0121] 7 Input device [0122] 8 Storage device [0123] S1 First step [0124] S2 Second step [0125] S3 Third step [0126] S3a, S3b Partial steps of the third step [0127] S4 Fourth step [0128] S4a, S4b Partial steps of the fourth step [0129] S5 Fifth step [0130] S5_1 First alternative step [0131] S5_2 Second alternative step