Position measuring device

• US 5,687,103 A
• Filed: 05/12/1995
• Issued: 11/11/1997
• Est. Priority Date: 10/13/1994
• Status: Expired due to Term

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr Johannes Heidenhain GmbH
• Inventors: Hofbauer, Hermann, Strasser, Erich, Hagl, Rainer, Bielski, Steffen, Wastlhuber, Robert
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): MILLER, CRAIG S
• Application Number:
  US08/440,446
• Time in Patent Office: 914 Days
• Field of Search: 364/474.28, 364/474.31, 364/514 R, 364/556, 364/560, 364/577, 364/737, 364/741, 371/2.1, 371/48, 371/67.1, 371/68.1, 371/68.2, 371/68.3
• US Class Current: 702/150
• CPC Class Codes: G01D 3/08 with provision for safeguarding the apparatus, e.g. against abnormal operation, against breakdown
• CPC Class Codes: G01D 5/2497 Absolute encoders G01D5/2454 takes precedence
• CPC Class Codes: H03M 1/161 in pattern-reading type converters, e.g. with gearings
• CPC Class Codes: H03M 1/285 of the unit Hamming distance type, e.g. Gray code

Abstract

The invention concerns a device and a method for serial data transmission. In the position measuring device there is provided a memory, in which specific parameters of the position measuring device are kept. These parameters can be sent on the data line to a processing unit, by which the measurement values are transmitted during the position measurement. By receiving the parameters, the processing unit is adjusted to the connected position measuring device.

Claims

1. Position measuring device with a device for serial data transmission between the position measuring device and a processing unit, the position measuring device comprising a component with a connection logic, in which a code word defining the absolute position is formed from the sampling signals of at least one sampling device, which can be taken to an output component, which causes a bit-serial transmission of the code word across a data line coupling the position measuring device and processing unit in response to a first command (status) sent by the processing unit, the position measuring device also having several memory regions with specific parameters of the position measuring device saved in one of the several memory regions, which can also be transmitted serially to the processing unit across said data line in response to a second command (status) sent by the processing unit, which allows the processing unit to be adapted to these parameters, and another one of the several memory regions is used for decoding commands sent by the processing unit to the position measuring device on said dataline as serial binary data words.

2. Position measuring device according to claim 1 further comprising a clock in the processing unit transmitting clock pulse sequences to a clock input of the output component, wherein the data line is connected to an output of the output component, wherein position measuring values and the parameters can be transmitted, synchronized with the clock pulse sequence, in bit-serial fashion to the processing unit over the data line.

3. Position measuring device according to claim 2 wherein the clock is provided in the processing unit and the clock pulse sequences can be sent to the clock input of the output component across a timing line.

4. Position measuring device according to claim 2 wherein the information as to the number of cycles required for transmission of the position measurement value is saved as specific parameters in one of the several memory regions.

5. Position measuring device according to claim 1 wherein at least one of the several memory regions contains user-specific parameters to which the parameters can be sent from the processing unit to the position measuring device across the data line.

6. Position measuring device according to claim 1 wherein error monitoring is integrated in the position measuring device and at least one of the several memory regions is used to store alarm or error messages which can be read by the processing unit over the data line.

7. Position measuring device according to claim 6, wherein an error message as reason for an alarm can be read out from the memory by a command (status) of the processing unit, and this command (status) can also be taken as binary data word serially to the position measuring device on said data line.

8. Position measuring device according to claim 1 wherein a signal having a LOW level is on the data line when the position measuring device is in a resting state.

9. Method for serial data transmission between a position measuring device and a processing unit, the method comprising the steps of:

transmitting commands (status) bit-serially as data words from the processing unit to the position measuring device;

instructing the position measuring device to either execute a command (status), and to send a position measurement value as a binary data word or a parameter saved in the position measuring device as a binary data word to the processing unit in dependence on the command (status), or receive parameters from the processing unit and store them in a memory region, wherein the commands (status), the parameters, and the position measurement values are transmitted on a common data line.

10. Method according to claim 9 wherein the commands (status) parameters, and position measurement values are transmitted in synchronized time by a clock pulse sequence.

11. Method according to claim 10 wherein the clock pulse sequence is transmitted from the processing unit across a timing line to the position measuring device.

12. Method according to claim 11 wherein the information as to the number of cycles required for transmission of a position measurement value is saved in the position measuring device, this information is read by the processing unit, and the required number of cycles for the transmission of the measurement value is provided to the position measuring device by the processing unit.

13. Method according to claim 10, 11, or 12 wherein at one edge of the clock pulse sequence the formation and storage of the particular absolute position measurement value in the position measuring device is brought about and after a predetermined calculation time (t_c), a start message is transmitted from the position measuring device to the processing unit, after the start message, an alarm message and/or an error message is transmitted to the processing unit, and subsequently the data word of the position measurement value is transmitted to the processing unit.

14. Method according to claim 9 wherein a memory region is provided in the position measuring device, in which error information is saved in event of error or exceeding of set tolerances, which is read out on request of the processing unit.

15. Position measuring device with a device for serial data transmission between the position measuring device and a processing unit, the position measuring device comprising:

a component with a first connection logic in which a code word defining the absolute position is formed from the sampling signals of at least one lower-resolution code track with at least one higher-resolution code track, which can be sent to an output component, which brings about a bit-serial transmission of the code word across a data line coupling the position measuring device and processing unit in response to a command (status) sent by the processing unit, there being a second connection logic provided in the processing unit with the same function as the first connection logic, and sampling signals can also be sent directly to the processing unit by bypassing the connection logic wherein the sampling signals are converted to a data word by the second connection logic, so that the code word is compared to the data word formed in the processing unit, and an error signal is output if the code word and data word do not agree.

16. Position measuring device according to claim 15 wherein the sampling signals are saved in the position measuring system and, after a request signal of the processing unit, the saved sampling signals and the code word are transmitted serially one after the other on the data line to the processing unit.

17. Position measuring device according to claim 16 wherein the position measuring device is an angle measuring device with several code disks, connected together via reducing gear, and sampling signals of lower-resolution code tracks are combined with at least one sampling signal of a higher-resolution code track in the connection logic.

18. Position measuring device with a device for serial data transmission between the position measuring device and a processing unit, the position measuring device comprising a component with a connection logic, in which a code word defining the absolute position is formed from the sampling signals of at least one sampling device, which can be sent to an output component, which brings about a bit-serial transmission of the code word across a data line coupling the position measuring device and processing unit in response to a command (status) sent by the processing unit, the sampling signals forming two code groups with one higher and one lower-resolution code group, and a shift between at least one sampling signal of the higher-resolution code group and a sampling signal of the lower-resolution code group with respect to a nominal position is monitored and when a predetermined tolerance region is exceeded, a warning signal is output.

19. Position measuring device according to claim 18 wherein the shifting of one edge of one of the sampling signals of the lower-resolution code group is monitored, checking to see whether the edge lies within a tolerance region determined by at least one of the sampling signals of the higher-resolution code group.

20. Position measuring device according to claim 19 wherein the tolerance region is half the period of the sampling signal, which has twice the frequency of the sampling signal with lowest resolution of the higher-resolution code group.

21. Position measuring device according to claim 19 wherein the tolerance region is determined by logical combination of several sampling signals of the higher-resolution code group.

22. Position measuring device according to claim 21 wherein the tolerance region is determined by a logical OR operation between the two next higher-resolution sampling signals relative to the sampling signal with lowest resolution of the higher-resolution code group.