Position-Measuring Device and Method for Operating the Position-Measuring Device

• US 20130301059A1
• Filed: 05/08/2013
• Published: 11/14/2013
• Est. Priority Date: 05/08/2012
• Status: Active Grant

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Mayer, Elmar, Frese, Daniel
• Granted Patent: US 10,197,388 B2
• Time in Patent Office: Days
• US Class Current: 356/614
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01D 3/08 with provision for safeguarding the apparatus, e.g. against abnormal operation, against breakdown
• CPC Class Codes: G01D 5/24457 Failure detection
• CPC Class Codes: G01D 5/3473 Circular or rotary encoders

Abstract

A position-measuring device includes a measuring standard, a scanning unit, and a rotary bearing by which the measuring standard or the scanning unit is rotationally mounted. The measuring standard and the scanning unit are rotatable in relation to each other. The scanning unit generates output signals, on the basis of which a rotary angle associated with the relative motion of the measuring standard and the scanning unit is able to be determined. A monitoring device monitors the rotary bearing for the occurrence of bearing faults and is adapted to detect and analyze at least one measured variable for a plurality of different relative positions of the measuring standard in relation to the scanning unit, in order to determine deviations from a setpoint behavior of the measured variables on the basis of the measured variable detected for a plurality of relative positions.

Claims

1. A position-measuring device, comprising:

a measuring standard;

a scanning unit adapted to scan the measuring standard for position-determination;

a rotary bearing by which the measuring standard or the scanning unit is rotationally mounted, so that the measuring standard and the scanning unit are rotatable in relation to each other when the position-measuring device is in operation, the scanning unit adapted to generate output signals, on which an angle or rotation associated with the relative movement of the measuring standard and the scanning unit is determinable; and

a monitoring device adapted to monitor the rotary bearing for occurrence of bearing faults;

wherein the monitoring device is adapted to detect and analyze at least one measured variable for a plurality of different relative positions of the measuring standard in relation to a detector device of the scanning unit, in order to determine deviations from a setpoint behavior of the measured variables on the basis of the measured variable detected for a plurality of relative positions.

2. The position-measuring device according to claim 1, wherein the monitoring device is adapted to detect and analyze a measured variable that is characteristic for the output signals of the scanning unit.

3. The position-measuring device according to claim 1, wherein the monitoring device is adapted to detect a measured variable generated from the output signals of the scanning unit.

4. The position-measuring device according to claim 1, wherein the monitoring device is adapted to detect and analyze an amplitude of the output signals of the scanning unit.

5. The position-measuring device according to claim 1, wherein the monitoring device is adapted to detect and analyze a phase of the output signals of the scanning unit.

6. The position-measuring device according to claim 1, further comprising a memory assigned to the monitoring device and adapted to store the measured variable detected for different relative positions of the measuring standard in relation to the scanning unit.

7. The position-measuring device according to claim 1, wherein the measured variable is detected at a plurality of locations of the measuring standard.

8. The position-measuring device according to claim 7, wherein the locations of the measuring standard at which the measured variable is detected in each case are formed by segments of the measuring standard.

9. The position-measuring device according to claim 7, wherein the locations of the measuring standard at which the measured variable is detected in each case are distributed on the measuring standard in axially symmetric manner.

10. The position-measuring device according to claim 7, wherein for each location of the measuring standard at which the examined measured variable is detected, a diametrically opposed location of the measuring standard is provided, at which the examined measured variable is detected as well, diametrically opposed locations of the measuring standard being able to be transferred into each other by a 180°

rotation.

11. The position-measuring device according to claim 8, wherein a value of the measured variable averaged across the particular segment is utilized as representative of the examined measured variable for a particular segment of the measuring standard.

12. The position-measuring device according to claim 1, wherein the monitoring device is adapted to analyze variations of the examined measured variable as a function of the relative position of the measuring standard in relation to the scanning unit.

13. The position-measuring device according to claim 12, wherein for the analysis, the examined measured variable is checked for periodicity.

14. The position-measuring device according to claim 12, wherein for the analysis, the examined measured variable is monitored for deviations from an average value that results when averaging the examined measured variable across a maximally possible relative movement of the measuring standard and the scanning unit of up to 360°

.

15. A method for operating a position-measuring device, comprising:

scanning a measuring standard by a scanning unit for a position measurement while the measuring standard and the scanning unit are rotated with respect to each other by a rotary bearing;

checking the rotary bearing for bearing faults by a monitoring device while the position-measuring device is in operation;

detecting and analyzing, by the monitoring device, at least one measured variable for a plurality of different relative positions of the measuring standard in relation to detection means of the scanning unit, in order to determine deviations from a setpoint behavior of the measured variables on the basis of the measured variable detected for a plurality of relative positions.

16. The method according to claim 15, wherein the at least one measured variable is detected for a plurality of different relative positions of the measuring standard in relation to a detection device of the scanning unit, a rotary motion of the measuring standard in relation to the scanning unit taking place.

17. The method according to claim 15, further comprising recording the at least one measured variable for a plurality of different relative positions of the measuring standard in relation to a detection device of the scanning unit, the detection device including a plurality of detector elements which are set apart from each other along the measuring standard, to thereby determine the measured variable at different locations of the measuring standard.