WO2003021839A2 - Transmission of measurement data - Google Patents

Abstract

The invention relates to a method for the contactless transmission of measurement data via at least one transmission channel between a measuring device, which comprises at least one sensor, and an evaluation device, said measuring device being mounted on an object that can be displaced in relation to the evaluation device, in particular on a machine-tool component that rotates during operation. According to said method: energy is transmitted from the evaluation device to the measuring device by means of an inductive coupling between a transmitter of the evaluation device and a receiver of the measuring device; the load in the measuring device is determined by measuring the current in the evaluation device; measurement data determined by the sensor is transmitted to the evaluation device by means of a load modulation in the measuring device; and the transmission channel is calibrated by applying a calibration load to the measuring device. The invention also relates to a device for the contactless transmission of measurement data.

Description

 measuring data

The invention relates to a method and a device for the contactless transmission of measurement data via at least one transmission channel between a measurement device comprising at least one sensor and an evaluation device, the measurement device being attached to an object that is movable relative to the evaluation device.

The contactless transmission of measurement data is generally known. The frequently missing, inadequate or complex consideration of the current conditions in the overall arrangement at the time of the data transmission is problematic. The variables influencing the evaluation of the transmitted data include in particular the varying coupling strength between transmitting and receiving devices used for data transmission, which is essentially determined by the distance between the transmitter and receiver. Difficulties are also often caused by the necessary distinction at the receiving end between the signals corresponding to the measurement data to be transmitted on the one hand and signals not to be used for data evaluation on the other hand, which e.g. result from interference effects or are caused by electrical consumers of the measuring device and which are superimposed on the actual measuring signals.

The object of the invention is to provide a way of ensuring the identification and evaluation of measurement data in a contactless transmission in a simple and reliable manner. This object is achieved on the one hand by the features of the independent method claim and in particular by the fact that inductive coupling between a transmitting device of the evaluating device and a receiving device of the measuring device transmits energy from the evaluating device to the measuring device, and current measurement in the evaluating device the instantaneous load in the Measuring device is determined, measured data determined by load modulation in the measuring device with the sensor are transmitted to the evaluation device, and the transmission channel is calibrated by applying a calibration load to the measuring device.

According to the invention, a current measurement is carried out in the evaluation device. The measured current is a measure of the current load, i.e. for the energy consumption in the electrical circuit of the measuring device, to which energy is transmitted inductively via the receiving device.

Due to the load modulation taking place in accordance with the measurement data to be transmitted, signals corresponding to the measurement data are measured during the current measurement. The current measured in the evaluation device thus contains the information sought, i.e. the measured values determined with the sensor.

The current measured in the evaluation device is dependent in particular on the total load in the relevant circuit of the evaluation device and on the coupling strength determined essentially by the distance between the transmitting device and the receiving device. Both the total load in the measuring device and the distance between the sending device and the receiving device can change during a measurement data acquisition period, for example due to temperature leads to a change in the current measured in the evaluation device even if the measured variable detected by the sensor does not change.

According to the invention, this source of error is eliminated by calibrating the transmission channel by applying a calibration load to the measuring device. With the calibration load, the current conditions of the overall system, in particular the current total load and the current coupling strength, can be taken into account in the evaluation. In the case of current measurement, signals which are generated by the load modulation for the transmission of the sensor measured values can thus be clearly identified and evaluated as such.

According to the invention, the application of the calibration load for the current measurement thus defines a reference level which takes the current conditions into account, with respect to which the current signals corresponding to the measured values and generated by appropriate load modulation are measured.

According to the invention it can be a calibration load of known size, so that the absolute size of the calibration load can be included in the evaluation. Measured values, in particular transmitted analogously, can thereby be transmitted and evaluated particularly reliably and with high accuracy.

The method according to the invention is preferably used in conjunction with processing machines such as, for example, grinding, drilling and milling machines. In this application, the movable object to which the measuring device is attached is a component rotating at comparatively high speeds, such as drive shafts, chucks, tool carriers or tools. On A significant advantage of the measurement data transmission according to the invention is the low design effort. In particular, the number and weight of the components required on the movable object is minimal according to the invention.

In a particularly preferred practical exemplary embodiment of the invention, temperature values are transmitted as measurement data, which are determined on the movable object by means of at least one temperature sensor.

With the invention, temperature measurements can be carried out on moving objects and in particular on components of machine tools rotating at high speeds without contact. Both passive resistive sensors and active temperature sensors with voltage output can be used as temperature sensors. Furthermore, according to the invention, several temperature measurements can be carried out simultaneously at spatially separate locations on the movable object or on the rotating component of a processing machine, since the invention enables multichannel transmission of measurement data without problems, in which e.g. a transmission channel is assigned to each temperature sensor. A multi-channel transmission of measurement data is discussed in more detail elsewhere.

In principle, however, the type of sensor used is arbitrary in the invention. Thus, according to the invention, the measured values of, for example, strain gauges, pizeo elements or position sensors, with which neutral positions of actuators used for balancing are detected, can be transmitted without contact. In the transmission method according to the invention, it is also preferably provided that a threshold value is determined from the comparison of current measurements without and with calibration load and a distinction is made in the evaluation device between signals above and below the threshold value. The determination of the threshold value creates a criterion with which a distinction can be made between a "1" state and a "0" state, particularly with regard to digital measurement data transmission. The calibration load also creates a reference level for analog data transmission, which enables a reliable and precise evaluation of the measured values determined with the sensor.

The measurement data transmission can, in particular, take place in various ways according to the invention, depending in particular on whether one or more sensors are used and whether one or more transmission channels are provided.

The measurement data can thus be transmitted without being requested and in particular at predetermined time intervals. This implements automatic data transmission, for example at regular time intervals.

Alternatively, it is also possible according to the invention that the measurement data are transmitted to a request signal transmitted from the transmitter to the measuring device. A single transmission channel is consequently used here both for energy transmission and for bidirectional data transmission.

Furthermore, measurement data of several sensors can be transmitted in succession according to the invention. In this case, preference is given to carry a synchronization signal, whereby the measurement data can be clearly identified.

For example, Measurement data from several sensors can be transmitted via a single channel. Alternatively, several transmission channels can be provided, via which the measurement data of several sensors are transmitted. The transmission channels can differ from one another with regard to the transmission frequency, a transmission channel preferably being assigned to each sensor.

Depending on the power bandwidth of the transmission system and the selectivity of the receiving device, this results in a certain number of available transmission channels.

Another exemplary embodiment of the invention proposes to initiate measurement data transmission by changing the transmission frequency. A specific transmission frequency can be provided, via which no data transmission takes place and which is also referred to as the idle frequency. By temporarily changing to the idle frequency, a renewed one-time measurement data transmission in the relevant channel can be initiated upon return to a sensor frequency provided for data transmission.

Furthermore, it can be provided according to the invention that control signals are transmitted from the transmitting device to the receiving device with which at least one device provided on the movable object is controlled and / or with which the measurement data is requested to be transmitted. The controllable devices can be, for example, actuators which are provided in the object in the form of electric motors for adjusting balancing weights or in the form of piezo elements for applying bending moments which serve for balancing.

The object on which the invention is based is also achieved by the features of the independent device claim and in particular by the fact that the device has an evaluation-side current measuring device and an evaluation-side transmission device and a measuring-side receiving device, between which energy can be transmitted by inductive coupling from the evaluation device to the measuring device which can determine the instantaneous load in the measuring device, comprises means for modulating the load in the measuring device and means for applying a calibration load to the measuring device.

In a practical embodiment of the transmission device it is provided that the measuring device comprises a control unit which is designed to read out the sensor and to convert read-out measured values into measured data to be transmitted. The control unit preferably comprises a microcontroller.

The control unit can be provided in the form of a single electronic component or chip, with which all the necessary processes, such as, for example, the voltage supply to the measuring device, the communication with the sensor and possibly with other devices provided on the movable object, the load modulation in accordance with those determined with the sensor Measured values and the application of the calibration load can be controlled. A matching circuit connected between the control unit and the sensor can be provided to adapt the sensor to the control unit.

Further embodiments of both the transmission method according to the invention and the transmission device according to the invention are also specified in the subclaims, the description and the drawing.

The invention is described below by way of example with reference to the drawing. Show it:

1 shows a schematic overview of a device for contactless data transmission according to an embodiment of the invention,

2 is a block diagram of a transmission device of the transmission device of FIG. 1,

Fig. 3 is a block diagram of a receiving device of the

1, and

Fig. 4 is a diagram for explaining a possibility for a calibration and data transmission according to the invention.

According to FIG. 1, the transmission device according to the invention comprises an evaluation device 19 which is arranged on a fixed object 22 and has a transmission device 23 which comprises a transmission coil 24. At a distance D from the transmitting coil 24 there is a receiving coil 26 of a receiving device 25 which is arranged on an object 21 which can be rotated relative to the fixed object 22 and is part of a measuring device 17. The movable object 21 is, for example, a rotating shaft of a processing machine.

The measuring device 17 further comprises a sensor 15 which transmits measurement data M to the receiving device 25 or which is read out by the receiving device 25. An actuator 37 is also attached to the rotating shaft 21, e.g. is used to balance the shaft 21 and to which control signals S can be transmitted by the receiving device 25.

A plurality of sensors 15 and a plurality of actuators or other devices 37 to be controlled can also be arranged on the shaft 21.

A plurality of transmission channels 13, in the example shown five channels, are available between the transmission coil 24 and the reception coil 26. In principle, any number of transmission channels 13 can be used, although it is also possible to provide only a single transmission channel.

Energy can be transmitted inductively from the transmitting device 23 to the receiving device 25 via each transmission channel 13, data can also be transmitted to the receiving device 25 by frequency modulation, and measurement data, which are determined by means of the sensor 15, are retransmitted to the evaluation device 19 also via the respective transmission channel 13. Everyone Transmission channel 13 thus enables both energy transmission and bidirectional data transmission.

The e.g. Signals S to be transmitted to the actuators 37 of the shaft 21 are input on the fixed object 22 into the transmission device 23, which also provides the measurement data M determined on the shaft 21 by means of the sensor 15 for further evaluation.

2, the transmission device 23 comprises a module 41 for frequency modulation. The respective transmission frequency is modulated with data S to be output. A digital data transmission can take place, in which a data word to be transmitted is binary coded. Depending on the length of the respective data words, these can be transmitted statically by assigning exactly one frequency to each state, while in particular with longer data words the individual bits are transmitted one after the other. Furthermore, direct transmission of analog data is also possible through analog frequency modulation of the transmission frequency.

With the signal generated in the modulation module 41, which typically has a frequency of e.g. has about 100 kHz, a transmission output stage 42 is driven. The power amplifier 42 can be deactivated if no data is to be transmitted. In this case, in order to ensure the energy supply of the measuring device 17 on the shaft 21 and possibly other electrical devices on the shaft 21, a power bridge can be provided with which the transmitter coil 24 is controlled directly.

Furthermore, a voltage supply for the transmission output stage 42 is provided, which comprises a current measuring device 35. The one Direction 35 measured analog current signal representing a measure of the receiver load on the shaft 21 is filtered and fed in analog form to further evaluation in order to determine the measurement data M.

The receiving device shown in FIG. 3 comprises a module 43 for voltage supply connected to the receiving coil 26, in which the induced alternating voltages are rectified and smoothed. The remaining electrical devices on the shaft 21 are supplied with the raw voltage obtained in this way.

Furthermore, a module 44 for frequency demodulation is provided, with which the signals received by the receiving coil 26 are demodulated and the signals S obtained in this way are transmitted to the relevant devices in accordance with their determination, e.g. to control actuators 37.

The sensor 15 is connected to a control unit 29 with which the load modulation is carried out. All of the functions required for this can be integrated in a module which is supplied with voltage via module 43. The entire receiving device 25 can be formed by a single chip, in which, in addition to the load modulation, the voltage supply 43 as well as the frequency demodulation 44 and possibly other processes can be carried out and which is directly connected to the receiving coil 26.

According to the invention, the control unit 29 can selectively apply a predetermined calibration load to the relevant electrical circuit on the shaft, which is supplied with voltage via the receiving coil 26. For this purpose, the control unit 29 comprises a microcontroller which controls all functions and automatically carries out the calibration and data transmission in accordance with a program stored in a memory as soon as energy is available after switching on the transmitting device 22 arranged on the stationary object 22. As an alternative or in addition, the control unit 29 can have its own energy supply, for example in the form of a battery unit. In order to save weight and space on the shaft 21, an external energy supply of all electrical devices on the shaft 21 via the transmitting device 23 on the fixed object 22 is preferred.

The sensor 15 can be a passive sensor or an active sensor. In the case of a passive sensor or an active sensor with an output voltage unsuitable for the respective control unit 29, an adaptation circuit, not shown in FIG. 3, is provided.

If, for example, a passive resistive sensor 15 is used, which e.g. is designed as a temperature sensor or strain gauge, it can be adapted to the control unit 29 by means of a bridge circuit. In the case of a passive, e.g. The adapter circuit can serve as an acceleration sensor for charge amplification. Furthermore, the matching circuit can perform a voltage boosting function, e.g. to adapt an unreinforced passive sensor or an active sensor with an unsuitable output voltage to the respective control unit 29.

The diagram of FIG. 4 shows, by way of example, the calibration of a transmission channel and the data transmission of an 8-bit data word. The upper curve in FIG. 4 shows the transmitted energy or power P, which is activated by activating and deactivating the transmitting device 23 at a time t0 and switched off at a later time t1.

The lower curve in Fig. 4 shows the power consumption, i.e. the current measured with the current measuring device 35 of the transmitting device 23 on the stationary object 22, which represents a measure of the instantaneous total load L in the circuit on the shaft 21 containing the receiving coil 26.

When the transmitting device 23 is switched on, a first calibration phase i begins without a calibration load, in which only an existing base load 31 is measured. A calibration load 33 is then automatically switched on in accordance with a program stored in the control unit 29 or when requested by a corresponding command signal which is transmitted from the transmitting device 23 to the measuring device 17, as a result of which a second calibration phase ii is initiated. The total load measured with the current measuring device 35 is thus composed of the base load 31 and the calibration load 33. From the load or current values which are determined during the calibration phase i without calibration load 33 and the calibration phase ii with calibration load 33, a threshold value 27 or cutting level is calculated in the evaluation device 29, which is used for the evaluation of the calibration phases i, ii measurement data 11 to be transmitted is used.

4, following the second calibration phase ii, the transmission of a bit sequence is shown which consists of a start bit, an 8-word data word and a stop bit. The respective bit states de "1" or "0" are generated by switching on or off a given load, ie an electrical load, by means of the control unit 29 in accordance with the measured value to be transmitted by the sensor 15 read out by the control unit 29. The load used for the load modulation can in principle be any electrical consumer, for example integrated in the control unit 29 or the microcontroller, in the circuit containing the receiving coil 26. In principle, the calibration load 33 itself can also serve as a modulation load.

The measured values of the sensor 15 are consequently coded on the shaft 21 by the control unit 29 by a load modulation and, as a result, are thus mapped onto the temporal course of the electrical current measured on the fixed object 22, as a result of which the measured values are available on the fixed object 22 and by evaluating the measured current can be read.

The calibration according to the invention by applying the calibration load 33 makes the measurement data transmission independent of the coupling strength between the transmitter coil 24 and the receiver coil 26, which varies with the distance D between the two coils 24, 26. Such changes in distance, which make data evaluation on the fixed object 22 difficult or impossible without calibration according to the invention, are caused in operation of processing machines, for example, by temperature-related changes in length that cannot be predicted and a change in the width of the air gap, which is typically 0.5 to 1 mm lead between the transmitting coil 24 and the receiving coil 26. The invention ensures that in a digital measurement data transmission generated by switching on the respective load, "1" states are recognized as such in the current measurement and are distinguished from "0" states, and for an analog measurement data transmission the application of the invention also means that Calibration load 33 created a reference value, which ensures a meaningful evaluation of the transmitted measurement data during the current measurement.

The calibration according to the invention can be carried out once before or at the start of a data transmission phase. It is also possible to carry out a calibration process before each individual data transmission. Both slow and fast changes in the coupling strength or the distance D between the transmitter coil 24 and the receiver coil 26 as well as other factors influencing the current measurement can be taken into account in this way when evaluating the measured current.

In particularly preferred applications of the invention, the energy transfer from the evaluation device 19 to the measuring device 17 takes place with a comparatively low power of, for example, 100 mW. Depending on whether slowly or rapidly changing measured variables are to be examined, the respective transmission frequency is, for example, about 100 kHz for slow processes and e.g. about 27 MHz for fast processes.

In the case of slowly changing measured variables, such as, in particular, the temperature at one or more measuring points on the shaft 21, it is provided in an application scenario, for example, that no data is sent to the measuring device 17 or to the temperature sensor 15 and the temperature values measured by the sensor 15 in the form of serial ones Transfer measurement data conditions, for example 10 temperature measurements are carried out per second.

In another application scenario in which fast processes are to be examined, e.g. the measured values of a piezo sensor serving as an acceleration sensor are transmitted in analog form to the evaluation device 19, a bandwidth of 0 to 100 kHz being provided.

While in the example of the slow temperature measurements and fast acceleration measurements mentioned above, the power transmitted to the shaft 21 is approximately in the range of the order of magnitude of 100 mW, other applications are also possible in which much larger powers of, for example, 10 W are transmitted.

For example, in an application in which the processing machine comprises a balancing head with balancing weights that can be adjusted for balancing by means of electric motors, e.g. In five transmission channels with transmission frequencies of around 90, 95, 100, 106 and 113 kHz, five static operating states for the motor control and a neutral position control are transmitted to the balancing head. The retransmission of measured values from the balancing head to the evaluation device 19 on the stationary object 22 serves, for example, to transmit the "neutral position reached" state or to transmit information about the total motor current consumption.

According to a further application, which is characterized by a particular flexibility, certain measuring sensors or also actuators on the shaft 21 can be specifically selected in order to selectively either read out measured values or actuators such as electric motors or piezoelectric motors. to control zoactuators. Here, two different frequencies of, for example, about 95 and 100 kHz are used, both the data transmission to the sensor or to the actuator and the return transmission of measurement data determined with the sensor or sensors to the evaluation device 19 is carried out serially. A serial data word modulated on the two different frequencies is transmitted with the transmitting device 23. Depending on the information content of this data word serving as a command, following its receipt on the shaft 21, either measurement data are transmitted or actuators are activated.

LIST OF REFERENCE NUMBERS

1 1 measurement data

13 transmission channel

15 sensor

17 measuring device

19 evaluation device

21 movable object

22 fixed object

23 transmitter

24 transmitter coil

25 receiving device

26 receiving coil

27 threshold

29 control unit

31 basic load

33 calibration load

35 current measuring device

37 Device, actuator

41 Frequency modulation

42 transmitting power stage

43 Power supply

44 Frequency demodulation

D coupling distance

L load

P power

Claims

 Expectations Method for the contactless transmission of measurement data (11) via at least one transmission channel (13) between a measuring device (17) comprising at least one sensor (15) and an evaluation device (19), the measuring device (17) being connected to a device relative to the evaluation device (19 ) movable object (21) is attached, in particular to a component of a processing machine rotating during operation, in which, by inductive coupling between a transmitting device (23) of the evaluation device (19) and a receiving device (25) of the measuring device (17) from the evaluation device ( 19) energy is transmitted to the measuring device (17), the instantaneous load in the measuring device (17) is determined by current measurement in the evaluation device (19), measurement data (11) determined by load modulation in the measuring device (17) with the sensor (15) ) are transmitted to the evaluation device (19), and by applying a calibration load (33) to the measuring device seal (17) the transmission channel (13) is calibrated. Method according to Claim 1, characterized in that temperature values are transmitted as measurement data (1 1) which are determined on the movable object (21) by means of at least one temperature sensor (15). 3. The method according to claim 1 or 2, characterized in that a calibration load (33) of known size is switched on. 4. The method according to any one of the preceding claims, characterized in that a threshold value (27) is determined from the comparison of current measurements without and with calibration load (33) and in the evaluation device (19) between signals above and below the threshold value (27) is distinguished. 5. The method according to any one of the preceding claims, characterized in that the measurement data (11) are transmitted digitally. 6. The method according to any one of claims 1 to 4, characterized in that the measurement data (1 1) are transmitted analogously. 7. The method according to any one of the preceding claims, characterized in that the calibration load (31) is applied when switching on the transmitter (23) or after switching on before a first data transmission. 8. The method according to any one of the preceding claims, characterized in that a new calibration is carried out at predetermined time intervals. 9. The method according to any one of the preceding claims, characterized in that the transmission of the measurement data (1 1) takes place with an applied calibration load (33). 10. The method according to any one of the preceding claims, characterized in that the measurement data (1 1) are transmitted without being requested and in particular at predetermined time intervals. 1 1. The method according to any one of claims 1 to 9, characterized in that the measurement data (11) are transmitted to a request signal transmitted by the transmitter (23) to the measuring device (17). 12. The method according to any one of the preceding claims, characterized in that measurement data (11) of a plurality of sensors (15) are transmitted in succession, a synchronization signal preferably being transmitted before a measurement data transmission. 13. The method according to any one of the preceding claims, characterized in that measurement data (11) of a plurality of sensors (15) are transmitted via the same transmission channel (13). 14. The method according to any one of claims 1 to 12, characterized in that measurement data (1 1) of a plurality of sensors (15) are transmitted via a plurality of transmission channels (13), which preferably differ from one another in terms of the transmission frequency, preferably each sensor (15) a transmission channel (13) is assigned. 15. The method according to claim 14, characterized in that a measurement data transmission is initiated by a change in the transmission frequency, in particular by a temporary change to a transmission frequency via which no data transmission takes place. 16. The method according to any one of the preceding claims, characterized in that at least the load modulation is carried out by a control unit (29) comprising in particular a microcontroller, by means of which the measurement values obtained by reading out the sensor (15) are converted into measurement data (1 1) to be transmitted. 17. The method according to any one of the preceding claims, characterized in that control signals are transmitted from the transmitting device (23) to the receiving device (25) with which at least one on the movable object (21) provided means (37), in particular an actuator, controlled and / or with which the measurement data (1 1) are requested to be transmitted. 18. Device for the contactless transmission of measurement data (1 1) via at least one transmission channel (13) between a measuring device (17) and an evaluation device (19), in particular for carrying out the method according to one of the preceding claims, wherein the measuring device (17) at least comprises a sensor (15) and is attached to an object (21) movable relative to the evaluation device (19), in particular to a component of a processing machine rotating during operation, with an evaluation-side transmitter device (23) and a measurement-side receiver device (25), between which energy can be transmitted by inductive coupling from the evaluation device (19) to the measuring device (17), an evaluation-side current measuring device (35) with which the instantaneous load in the measuring device (17) can be determined, means (29) for modulating the load in the measuring device (17), and Means (29) for applying a calibration load (33) to the measuring device (17). 19. The apparatus according to claim 18, characterized in that the sensor (15) is designed as a temperature sensor. 20. The apparatus according to claim 18 or 19, characterized in that the sensor (15) is a passive sensor. 21. The apparatus according to claim 18 or 19, characterized in that the sensor (15) is an active sensor. 22. Device according to one of claims 18 to 21, characterized in that the measuring device (17) comprises a control unit (29), in particular comprising a microcontroller, which is used for reading out the sensor (15) and for converting read-out measured values into transmitting measurement data (11) is formed. 23. Device according to one of claims 18 to 22, characterized in that a matching circuit is provided between the control unit (29) and the sensor (15).