Method and system for transmitting data among various memory units of position measuring devices

The present invention relates to a method, as well as to a system for transmitting data among various memory units of position measuring devices.

A memory unit is typically found inside the scanning unit of linear position measuring devices that are based on an optical scanning principle. Generally the memory unit is in the form of an EEPROM. It is customary for data specific to the particular position measuring device to be stored in the memory unit. These data are written into the memory unit either by the current user or by the manufacturer of the position measuring device. The data includes, for instance, data on the zero adjustment, clock pulse number, scale section, and other parameters. When a scanning unit of this kind breaks down, it is necessary to rewrite the specific data required for operation into the memory unit of the replacement scanning unit. This entails a large effort, particularly when working with a large quantity of stored data or measuring system-specific information. Moreover, difficulties can arise when reconstructing the original data.

Similar problems arise when the memory units in question are not disposed in the scanning unit, but elsewhere in the particular position measuring device. This is the case, for example, in rotary position measuring devices.

The present invention is a simplified and reliable method and system which permits the data in a memory unit being replaced to be passed on to a new memory unit, when replacement of a memory unit of the position measuring device is needed. The present invention provides for an automatic transfer, such as an automatic copying of the data from the first memory unit to be replaced, into the new, second memory unit. This can be more easily done when memory unit replacement is not necessitated by defects in the first memory unit. For example, a replacement can be necessary due to other problems with the scanning unit, when the memory unit is disposed in the scanning unit.

The user-specific data from the first memory unit to be replaced can be accepted rather simply into the new, second memory unit. Generally, such user-specific data cannot be reconstructed by the measuring system manufacturer as easily as the data that had been written into the memory unit by the measuring system manufacturer. It is important then that the replacement can be performed by the user rather than only by the manufacturer.

In addition, the method according to the present invention, permits the user to recognize whether the data transfer has been carried out correctly, or, in some instances, if transfer problems have occurred. It is even possible in one especially advantageous specific embodiment to identify the cause of the errors in the case of an incorrect data transfer. There are several ways in which errors can be recognized or faults can be identified. According to the invention, even in the case of a possibly defective signal processing unit or processor, the data from a scanning unit to be replaced can be automatically transferred into the new memory unit.

Moreover, the embodiments in accordance with the present invention ensure that the electrical consumption of the position measuring device does not rise significantly. This quality is important since, as a rule, the evaluation unit downstream from the position measuring device in question is only designed for supplying power to one single scanning unit.

In one aspect, the invention is a method for transmitting data among memory units of at least one position measuring device, said data being stored in a first one of the memory units, comprising connecting the memory units with a data transmission line, transmitting the data from the first memory unit into a second memory unit, such that after the data are transmitted, the data of the first memory unit are at least partially contained in the second memory unit.

In another aspect, the invention is a system for transmitting data among memory units of at least one position measuring devices, the data being stored in the memory units. The system comprises a data transmission line adapted to connect the memory units to transmit data from a first memory unit into a second memory unit, and means for controlling transmission of the data such that once the data are transmitted, the data of the first memory unit are at least partially stored in the second memory unit.

The present invention is not limited to devices operating on one specific scanning principle for producing positionally dependent signals in the particular position measuring device. Rather, it can be used in optical, magnetic, capacitive, as well as in inductive position measuring devices. In addition, the present invention can also be used in conjunction with position measuring devices where the memory units are disposed in the scanning unit.

Further advantages as well as details pertaining to the present invention are derived from the following description of an exemplary embodiment, with reference to the enclosed drawings.

In the Drawings:

FIG. 1 is a schematic block diagram of a position measuring device;

FIG. 2 is a schematic representation of a first and second scanning unit, one unit being used to replace the other;

FIG. 3 is a detailed circuit diagram showing arrangements of two scanning units during the data transmission; and

FIG. 4 is a flow chart showing an exemplary embodiment of the method according to the present invention.

A schematic block diagram of a position measuring device is shown in FIG. 1 . The position measuring device includes a scale M, a scanning unit AE being movably arranged in measuring direction x in relation thereto. By scanning a graduation marking arranged on scale M, position-dependent scanning signals are produced in scanning unit AE and are transmitted via a line L to a downstream evaluation unit AWE for further processing. Further details pertaining to the particular scanning operation are omitted here, since they are not essential to the invention.

The present invention is not dependent upon the type of positionally dependent scanning signals produced. Provision can be made, for example, with the aid of the position measuring device, to produce incremental positional signals, absolute positional signals, combinations thereof, and other types of signals. In the same way, the present invention is not limited to applications in linear measuring arrangements, i.e. it is also possible to use it in rotary measuring arrangements.

The described position measuring device can be preferably used in conjunction with a numerically controlled machine tool, in order, for example, to determine the relative position of the tool and of the workpiece.

The present invention is described on the basis of an exemplary embodiment, which is depicted in FIGS. 2-4. In particular, an explanation follows of the procedure required when it becomes necessary to exchange the scanning unit of a position measuring device. The memory units having the specific data of the position measuring devices are disposed, in this exemplary embodiment, in the scanning units. However, the arrangement of the memory unit in the scanning unit is not essential to the present invention since the memory unit can be, for example, in a different location on the rotary position measuring device, or even on a circuit board.

FIG. 2 schematically depicts the two scanning units AE 1 and AE 2 of a position measuring device, when it is necessary to replace first scanning unit AE 1 with second scanning unit AE 2 , due to a defect. During the replacement, new scanning unit AE 2 is linked via line L with the downstream evaluation unit (not shown in FIG. 2) and is also supplied via line L with current. Scanning unit AE 1 to be exchanged is already no longer connected on the output side with the evaluation unit. The two scanning units AE 1 and AE 2 are interconnected via a schematically indicated data transmission line DL. For this purpose, suitable detachable electrical connections are provided on the two scanning units AE 1 , AE 2 . These can be, for example, suitable plug-in connections or the like.

In this exemplary embodiment, data transmission line DL includes altogether four line components TL 1 -TL 4 , which are used to transmit information, or to partially supply current to scanning unit AE 1 to be replaced. During the process, in one embodiment of the invention, line component TL 3 is used to transmit data, and a clock signal for synchronizing the data transmission is transmitted via line component TL 2 . Line component TL 4 interconnects the two ground connections of scanning units AE 1 , AE 2 , while the two connection terminals of scanning units AE 1 , AE 2 , which are connected to +5V, are interconnected via line component TL 1 . In the depicted exemplary embodiment, visual display means AM 1 , AM 2 in the form of two LEDs, are integrated in line component TL 1 .

In the following description, further details will be discussed with regard to the functioning of display means AM 1 , AM 2 , in conjunction with the detailed description of the method according to the present invention.

In the place of data transmission line DL that is formed by a plurality of line components TL 1 -TL 4 , and within the scope of the present invention, alternative data transmission formats can also be used between the two scanning units AE 1 , AE 2 , and the memory units, respectively. For example, a suitable wireless data transmission system can also be used.

The two scanning units AE 1 can be identical in design. The most important components of these two subassemblies are briefly explained in the following. In FIGS. 2 and 3, for the sake of clarity, those elements of scanning units AE 1 , AE 2 , used for producing the positionally dependent scanning signals are omitted. In the case of optical or photoelectric position measuring devices, the omitted elements can be, for example, a light source, one or a plurality of scanning graduations such as scanning scale graduation markings, as well as of one or a plurality of optoelectronic detector elements.

In the illustrated exemplary embodiment, each of the two scanning units AE 1 , AE 2 can include a processor unit CPU 1 , CPU 2 , a signal processing unit SVE 1 , SVE 2 , a memory unit MEM 1 , MEM 2 , as well as a plurality of switching elements SE 1 1 , SE 1 2 , SE 1 3 , SE 1 4 SE 2 1 , SE 2 2 , SE 2 3 , SE 2 4 . For clarity, not all of the switching elements of the scanning units are shown in FIG. 2 .

The processor units CPU 1 , CPU 2 are each used, inter alia, for synchronizing or controlling the signal processing sequences in the two scanning units AE 1 , AE 2 . The scanning signals detected in each case in signal processing units SVE 1 , SVE 2 are processed and suitably conditioned for signal transmission to the evaluation unit. Writeable and readable memory units MEM 1 , MEM 2 , in turn, contain specific data of the position measuring device in question, which are required for operating the position measuring device. Memory units MEM 1 , MEM 2 can be designed, for example, as EEPROMs. The data in question can be, for instance, data pertaining to the scale graduation section of an absolute position measuring device to be scanned by the particular scanning unit AE 1 , AE 2 . In addition, machine-specific data can likewise be stored, such as information pertaining to clock pulse number, zero adjustment, and other parameters.

In conjunction with the design of scanning units and the employed memory units explained in known methods heretofore, reference is additionally made to EP 0 660 209 BI of the Applicant. The functioning and significance of the various switching elements SE 1 1 , SE 1 2 , SE 1 3 , SE 1 4 SE 2 1 , SE 2 2 , SE 2 3 , SE 2 4 are explained in greater detail with reference to FIG. 4 and FIG. 3, in the course of the following description of the method according to the present invention, and of the system according to the present invention.

Instead of completely re-inputting the various data into the new, i.e. second memory unit MEM 2 , which is time-consuming, the present invention provides for transmitting and copying the data stored in the old, i.e. first memory unit MEM 1 , into the second memory unit MEM 2 , via a substantially automated data transmission. This eliminates the need for the more expensive, manual inputting and reconstruction of this data from the first memory unit MEM 1 .

One exemplary embodiment of the method according to the present invention is described with reference to the flow chart in FIG. 4 . In a first method step S 1 , the two scanning units AE 1 and AE 2 are interconnected via a data transmission line DL.

In subsequent step S 2 , the new, i.e. second scanning unit AE 2 is connected via line L to the evaluation unit. It is subsequently checked in step S 3 via processor unit CPU 2 of new scanning unit AE 2 whether it is possible to access memory unit MEM 1 of first scanning unit AE 1 , to determine whether the two scanning units AE 1 and AE 2 are, in fact, properly interconnected. If this is not the case, an initialization program begins in step S 4 a in processor unit CPU 1 , to set the processor unit in a functional operating state.

If, on the other hand, it is possible to access first memory unit MEM 1 , then in accordance with method step S 4 , at least one portion of the data of first memory unit MEM 1 is transferred into second memory unit MEM 2 , so that once the data have been transmitted, the specific data of first memory unit MEM 1 are at least partially contained in second memory unit MEM 2 . When the data transmission and copying procedure is concluded, it is subsequently checked in step S 5 with the aid of second processor unit CPU 2 , whether the data transmission was correctly performed. This can be achieved, for example, by checking specific portions of the transmission protocol. As a function of this check test, a display means AM 1 , AM 2 is then activated in step S 6 to indicate whether the copying procedure was properly carried out. Display means AM 1 , AM 2 can be activated via processor unit CPU 2 , which for this purpose, at least controls switching element SE 2 4 .

In the illustrated exemplary embodiment, visual display means AM 1 , AM 2 , can be LEDs, that when integrated in data transmission line DL, are used as display means AM 1 , AM 2 . For example, constant luminous operation of the LEDs indicates that the data transmission has been properly carried out. On the other hand, a flashing mode of the LEDs indicates that the data transmission was faulty. In this case, it is also possible to indicate or to encode the particular type of error encountered during data transmission through use of different flashing modes. For example, flashing two times followed by a pause can indicate a read error; flashing three times followed by a pause indicates, on the other hand, a write error, etc.

It is also possible in this manner to encode various types of errors and to activate the display means accordingly. The embodiment that uses the LEDs as visual display means AM 1 , AM 2 merely represents one possible specific embodiment of suitable display means. In addition, provision could also be made, for example, for an indication on a suitable display, or for suitable acoustical indicator means.

In connection with display means AM 1 , AM 2 , as a general principle one single visual display means would suffice. However, to ensure when using LEDs that data transmission line DL can be connected independently of direction to the two scanning units AE 1 , AE 2 , two LEDs are provided in this preferred exemplary embodiment as visual display means AE 1 , AE 2 .

If it is ascertained in this manner that the data transmission has been successfully carried out, then the data transmission is ended. If, on the other hand, an error is indicated via display means AM 1 , AM 2 , then the particular user can implement the method according to the present invention once again or, if indicated, several times, until a correct data transmission is achieved. Accordingly, data are transmitted in an operator-friendly manner from first memory unit MEM 1 of scanning unit AE 1 to be replaced, into memory unit MEM 2 of new scanning unit AE 2 .

Further details concerning the circuit engineering of one specific embodiment of the device according to the present invention are described in the following discussion, with reference to FIG. 3 . In FIG. 3, the detailed circuit arrangements of the two scanning units AE 1 and AE 2 are depicted during the course of the data transmission. As explained at the outset, second scanning unit AE 2 is connected to the downstream—not illustrated—evaluation unit. This unit, according to the present invention, merely supplies current to the new, second scanning unit AE 2 via the two lines +5V, GND.

On the part of second scanning unit AE 2 , transistor T 2 is switched into conduction for the data transmission. In this case, the transistor T 2 base is connected via a resistor to +5V, and the emitter to GND. Except for 0.1V, line GND* is identical to GND. Applied to the control input of switching element SE 2 5 , not shown in FIG. 2, there is a logic LOW level, which results in switching element SE 2 5 remaining open. Therefore, the two other switching elements SE 2 2 and SE 2 3 remain closed. Address lines A 0 2 , A 1 2 , TEST 2 , as well as A 2 2 of memory unit MEM 2 are each connected to logic LOW level. Thus, by way of the illustrated circuit elements, a sufficient current supply for memory unit MEM 2 is ensured.

Scanning unit AE 1 is linked to scanning unit AE 2 via line components TL 1 -TL 4 of data transmission line DL. By way of the depicted connection variant, it is ensured that scanning unit AE 1 is not connected to GND, but rather to GND*. Due to the selected component configuration, a resistance of approximately 300 Ω is applied between +5V and GND, so that all GND connections have a potential of nearly +5V. This, in turn, has the effect that switching element SE 1 1 of scanning unit AE 1 , designed as transistor T 1 , is closed. Accordingly, a logic HIGH level is applied to the control input of switching element SE 1 5 , so that switching element SE 1 5 is closed. This, in turn, gives rise to switching elements SE 1 2 and SE 1 3 being opened, so that memory unit MEM 1 of first scanning unit AE 1 is separated from signal processing unit SVE 1 .

Even in the case of a defective signal processing unit SVE 1 , this system ensures that memory unit MEM 1 can be read out. Memory unit MEM 1 , as well as switching elements SE 1 1 -SE 1 5 are supplied during the data transmission on the part of first scanning unit AE 1 via GND* and +5V on line components TL 4 , TL 1 . First memory unit MEM 1 is connected, for purposes of data transmission, to second scanning unit AE 2 , i.e., to second memory unit MEM 2 via line components TL 2 , TL 3 . Address lines AO 1 , Al 1 and TEST, of memory unit MEM 1 are all connected, in turn, to logic LOW level. On the other hand, due to the circuit configuration selected, address line A 2 1 is connected in this state to logic HIGH level. Accordingly, the distinction can be made between the two memory units MEM 1 , MEM 2 in the step described above, on the basis of the differing levels of address lines A 2 1 (LOW) and A 2 2 (HIGH).

The described circuit arrangement also ensures that, during data transmission, the current consumption rises only by the amount of current consumption of one memory unit, as well as by the amount of current consumption of the switching elements. This is important insofar as the downstream evaluation unit that normally provides a current supply to the scanning units, is only designed for supplying one single scanning unit.

The circuit arrangement described above represents only one possible exemplary embodiment of the invention. A number of other advantageous possible implementations exist, which are also within the scope of the invention.