# Patent

## Title
Sensor device for a fluid power apparatus

## Abstract

A sensor device for a fluid power apparatus and in particular a pneumatic cylinder comprises at least one sensor for producing at least one sensor value on the basis of a property or a condition of the fluid power apparatus, and a sensor communication means for the transmission of the at least one sensor value. As regards the sensor device there is a provision such that it includes a reading means for reading apparatus identification data characterizing the fluid power apparatus and the sensor device is adapted for the transmission of the apparatus identification data by way of the sensor communication means.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority based on German Application No. 10 2007 015 111.1 filed on Mar. 29, 2007, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a sensor device for a fluid power apparatus and in particular a pneumatic cylinder with at least one sensor for producing at least one sensor value on the basis of a property or a condition of the fluid power apparatus, and a sensor communication means for the transmission of the at least one sensor value and to a fluid power apparatus fitted with such a sensor device.
2. Description of the Related Art
The fluid power apparatus can for example be a pneumatic cylinder, an electropneumatic hybrid drive or the like. The sensor is responsive to properties or operational states of the apparatus, as for example a position of the piston, pressures in chambers of the cylinder or the like. By way of the sensor communication means, as for instance a digital output interface, the sensor device transmits sensor values, as for example pressure values, position values or the like, of the fluid power apparatus, for example to a controller or regulator for the apparatus. The controller or regulator controls or regulates the apparatus on the basis of the sensor values. A position regulation means finds, on the basis of the sensor values, which constitute actual values, e. g. the desired target position of the piston.
In order to perform such regulation tasks the regulation means must be parameterized in an elaborate procedure. For this purpose for example sensor data, as for example measurement ranges of the sensor device, must be set in the regulation means by parameters. Furthermore elaborate parameterizing must be performed on the basis of physical properties of the fluid power apparatus to be controlled or regulated, as for example travel displacements, piston diameters or the like.
SUMMARY OF THE INVENTION
One object of the invention is to provide a simplified operational concept for a sensor device.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in the present invention the sensor device includes a reading means for reading apparatus identification data characterizing the fluid power apparatus and the sensor device is adapted for the transmission of the apparatus identification data by way of the sensor communication means. Moreover a fluid power apparatus fitted with such a sensor device is suitable for achieving the object of the invention.
One basic principle of the invention is that the sensor device provides an additional functionality: addition to sensor values it also transmits apparatus identification data of the apparatus, whose operational states, properties or the like are sensed by it. The sensor communication means, which is in any case present, is utilized in addition for such communication tasks. For the communication of apparatus specific identification data no separate interface and no transmission means on the fluid power apparatus is needed. The sensor may for example include a position sensor, a pressure sensor a temperature sensor or a force sensor.
The apparatus identification data may for example comprise the type of the apparatus, a serial number of the apparatus, physical quantities as for example length, effective surface of an actuator member or a piston, pressure values and more particularly maximum pressures, rated operating pressures, force output values force output values as related to the pressures set, a working stroke or the like. Furthermore kinematic data of the fluid power apparatus, f. i. speed values such as a maximum speed or a rated operating speed, a braking distance or the like may represent apparatus identification data.
The apparatus identification data may for example be saved to a sensor memory. For instance the sensor device may have a micro-controller, which comprises a sensor memory. It is furthermore possible to use a sensor memory, such as a flash memory or an E(E)Prom for the storage of the apparatus identification data.
It is an advantage furthermore for sensor identification data, which characterize the sensor device, to be saved in the sensor memory. The sensor device is responsible for the output of such sensor identification data, also via the sensor communication means. The sensor identification data may for example comprise the sensor type, the serial number, measurement ranges of the sensor, resolution, zero point or the like.
The sensor memory is able to be programmed with the respective identification data (sensor identification data) and/or apparatus identification data. For instance it may be a question of the sensor memory'S being a flash memory.
In the system of the invention the apparatus identification data are more or less saved on board the sensor device. On the fluid power apparatus itself no further means are necessary, as for example a storage chip for saving the apparatus identification data. However this possibility does exist.
The reading means of the sensor device for example comprises a receiving means for receiving of apparatus identification data transmitted by the fluid power apparatus. The reading means may be constituted by the receiving means or e comprised in the receiving means. Furthermore the reading means may be a separate means, as for example an optical reader or a wireless receiver connected to the receiving means. The apparatus identification data are stored in accordance with this part of the invention at least partly in a apparatus memory of the fluid power apparatus and are passed on to the sensor device, which communicates the apparatus identification data by way of the sensor interface.
It is admittedly possible for the receiving means to have a wired connection with the apparatus memory of the fluid power apparatus, as for example by way of electrical contacts. However it is advantageous to have a wireless connection, in the case of which the receiving means is joined in a wireless manner with the fluid power apparatus. Wireless for example means transmission by light, radio or the like. A so-called radio frequency identification (RFID) chip may be arranged on the fluid power apparatus.
Furthermore a hybrid design is possible, i. e. a part of the apparatus identification data are saved on board the sensor device in the sensor memory, whereas other data, as for example the type characteristic of the fluid power apparatus are saved in the apparatus memory. The fluid power apparatus then transmits the type characteristics to the sensor device, which then passes on such type characteristics in addition to other apparatus identification data, such as physical properties of the apparatus, by way of the sensor communication means. In this respect it is also possible for the sensor device to retrieve, on the basis of first apparatus identification data communicated by the fluid power apparatus, second apparatus identification data in its sensor memory. Accordingly the fluid power apparatus may communicate, for example, its type characteristic to the sensor device or the sensor device may read such type characteristic from the fluid power apparatus and on the basis of the type characteristic may find further apparatus identification data in the sensor memory, as for example physical properties assigned to the type characteristic, of the fluid power apparatus.
The sensor communication means preferably possesses at least one bus interface, as for example a field bus interface. It is an advantage for there also to be a second bus interface in the sensor device so that the sensor device may be concatenated with further components of the bus. Thus for example further sensor devices can be concatenated, f. i. sensor devices in accordance with the invention for the transmission of apparatus identification data or also prior art sensor devices not suitable for the transmission of apparatus identification data.
It is an advantage for the sensor device to transmit the apparatus identification data automatically, as for example as part a signing in procedure during coupling up with an automated system. The sensor device can however communicate the apparatus identification data as a response to interrogation, for example of a master control or regulation means.
Preferably the sensor memory is a non-volatile memory. Accordingly the apparatus identification data will be kept even upon a failure of the power supply.
It is an advantage however for the sensor device to have an electrical power storage means, and more particularly a long term storage means. Accordingly it is possible for the control means to be operated in a self-sustaining manner independent of an external power supply. The battery, as for example a battery with a long lifetime, is preferably able to be replaced. Owing to having the electrical energy storage means on board the sensor device simple installation is possible. Furthermore it is quite possible for the sensor device to be encapsulated so that it comes within a high electrical safety class and/or has a high degree of electromagnetic compatibility. Operation with the energy storage means is more particularly convenient in the case of a wireless sensor communication means. Accordingly no line connections are necessary in order to couple the sensor device with an automated system, a regulation system or the like. The electrical energy storage means may serve for saving the data held in the sensor memory, inter alia the apparatus identification data. In addition to the electrical energy storage means or as an alternative thereto it is possible to provide a local energy producing unit, as for example solar cells, an electrical generator operated with fluid, or the like, in the sensor device. The local energy producing unit will for example produce electric current, which is stored in a buffer storage means, as for example capacitor, of the sensor device.
For long term operation of the sensor device it is also advantageous for it also to have an energy economizing function. For instance the sensor device may after a predetermined time of inactivity switch over to an energy economy quiescent mode. On receiving an interrogating message, on a change in the condition of the fluid power apparatus to be sensed or the like, the sensor device will be reactivated and will communicate, for example sensor values, apparatus identification data or the like.
The sensor device may be an integral part of the fluid power apparatus, and for example can be integrated in its housing. For instance the sensor device may be mounted in an end plate of a pneumatic cylinder.
However a modular concept is also advantageous, that is to say the sensor device is a sensor module able to be arranged on the fluid power apparatus and more particularly detachably secured to it. The sensor device may for example be secured on an end plate or in a groove in the cylinder housing. Furthermore attachment by screwing, clipping or adhesive bonding is possible. The modular concept does however mean the advantage that the sensor device may be readily detached in the case of a failure or if it is required somewhere else.
The sensor device preferably has electrical contacts, which on arrangement on the fluid power apparatus provide a connection with the memory of the fluid power apparatus. Here, as explained above, the apparatus identification data are stored at least in part. It will be clear that wireless transmission between the apparatus memory and the sensor device arranged on the apparatus is possible.
Furthermore it is possible for the sensor module to be designed as a sort of intermediate module which while being able to be operated detached from the fluid power apparatus, nevertheless is responsive to its conditions and/or properties. More particularly in the case of this concept it is an advantage if the sensor device communicates in a wireless manner with a memory of the fluid power apparatus in order to read out the apparatus identification data from it, if the data are not alternatively held on board the sensor device in its sensor memory. The intermediate module may for example be a position measuring system, which is arranged at a certain distance from the fluid power apparatus. Furthermore it is possible for the intermediate module to be in the form of a pressure sensor which is arranged on a fluid line connected with the fluid power apparatus.
The fluid power apparatus may be designed in a variety of different forms. Thus it can for example be a power cylinder, as for example a piston rod-less power cylinder or one with a piston rod, a pneumatic servicing device, a vacuum means, as for example a suction means, a pneumatic valve or the like. The fluid power apparatus may however also be a so-called hybrid drive, that is to say a drive, which has a fluid power as for example a pneumatic, drive component or a functionally coupled electrical drive component.
In connection with the modular concept, in which the sensor device constitutes a separate unit, it is to be stressed that this configuration is also regarded as an invention in its own right in conjunction with exclusively electrical drives, that is to say as a patentable subcombination. The sensor device transmits apparatus identification data of the electrical drive by way of its sensor communication means.
It is an advantage for the sensor device to possess diagnostic means for diagnostic data concerning the fluid power apparatus, as for example wear data, data as regards the number of duty cycles, as regards pressure fluctuations indicative of an error or the like. The sensor device transmits the diagnostic data preferably by way of its sensor communication means. Furthermore a display provided on the sensor device, such as an LCD display, LED's or the like is an advantage.
Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of embodiments thereof in conjunction with the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 diagrammatically shows an automated system having two valve clusters and one central routing means.
FIG. 2 shows a fluid line with integrated electrical conductors for the connection of an actuator with a valve cluster in accordance with FIG. 1.
FIG. 3 shows a diagrammatic side elevation of a fluid power actuator with a sensor arrangement, which transmits apparatus identification data characterizing the actuator by way of a sensor communication means.
FIG. 4 shows an actuator with a sensor device constituting a separate unit and installed on the actuator, such sensor device also transmitting apparatus identification data of the actuator by way of a sensor interface.
FIG. 5 shows an actuator with a memory, in which apparatus identification data characterizing the actuator are stored, such data being transmitted by a sensor device constituting a separate unit and being installed on the actuator, via a sensor communication interface thereof.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The working embodiments of the invention include partially similar or functionally equivalent components which are not described twice over and are provided with the same reference numerals.
In the case of an automated system 10 valve clusters 11a and 11b are controlled by a central master control means 12, as for example a routing computer 13. The valve clusters 11a and 11b are connected with valve cluster communication means 14a and 14b for external communication on a system bus 15, for example a field bus, by way of external interfaces 96, for example bus interfaces. The control means 12 control the valve clusters 11a and 11b via the system bus 1, which is connected in a wired or a wireless manner.
The valve clusters 11a and 11b comprise valve modules 16, which are placed in a row with the communication means 14a and 14b. The valve modules 16 serve for fluid control of the fluid power apparatus 17, for example pneumatic actuators 18a and 18b. The actuators 18a and 18b are pneumatic drive cylinders 66, which as illustrated may have piston rods although designs without piston rods or with an additional electrical drive part are possible. The regulation modules 25a and 25b are also designed for the regulation of electrical or combined fluid power and electrical drives. Thus for example instead of the pneumatic actuator 18d an electrical drive could be provided.
The valve clusters 11a and 11b are run on compressed air, for example from a compressed air source 19. The compressed air source 19 supplies, for example, servicing apparatus 20, as f. i. filters and oilers, which prepare compressed air for the valve clusters 11a and 11b. The servicing apparatus 20 is in the present case separate from the valve clusters 11a and 11b, although it could for example constitute components of the valve cluster 11b. 
From the central control means 12 the valve modules 16 receive control instructions for the pneumatic control of the actuators 18a and 18b via the system bus 15. The communication means 14a and 14b transmit the control instructions so received by way of internal communication buses 21 to the valve modules 16. The communication buses 21 serve for internal communication of the valve clusters 11a and 11b. 
While the valve cluster 11a is controlled exclusively externally by way of the system bus 15, the valve cluster 11b has a local control competence in the form of control means 22. The control means 22 are designed in the form of control modules, which are placed in circuit between the valve modules 16 and the communication means 14b in the form of a communication module.
Optionally it is possible for the valve cluster 11b to have a local control means 94 for its control, f. i. of the valve modules 16, as for example a separate control module. The communication means 14b as well can be designed in the form of such a local control means 94 for the valve cluster 11b. For this purpose the communication means 14b will then for example have a processor 95, which transmits control instructions by way of communication bus 21, for example to the valve modules 16.
The control means 22 control valve means 23, which for their part control actuators 18c and 18d. The actuators 18c and 18d constitute, for example, servo drives. Admittedly the actuators 18c and 18d could constitute two drives independent of each other. However the actuators 18c and 18d are mechanically coupled with each other. In the drawing this is diagrammatically indicated since the actuator 18d is arranged on a force output means of the actuator 18c for example on its piston rod. A mechanical coupling may however be realized indirectly, for example if the actuators 18c and 18d constitute the drives of a gantry or carriage traveling in the X and the Y directions.
The valve means 23 are valves separate from the valve cluster 11b and connected with a compressed air network 24 supplied by the compressed air source 19 with compressed air. The valve means 23 control the compressed air supply to the actuators 18c and 18d, which are for example pneumatic drive
cylinders. The valve means 23 and the actuators 18c and 18d also consitute fluid power apparatus 17.
The control means 22 regulate the actuators 18c and 18d by control of the valve means 23 for regulation. The control means 22 are for example regulation modules 25a and 25b. The regulation modules 25a and 25b fit in well with the modular concept of the valve cluster 11b. They are able to be placed in line with the valve modules 16 and the communication means 14b. The regulation modules 25a and 25b are coupled at internal bus interfaces 26 with the internal communication bus 11b. The regulation modules 25a and 25b may receive messages by way of the communication bus 21, as for example control instructions from the control means 12 and may transmit messages, as for example indications, which the communication means 14b passes on to the control means.
For their regulation tasks the regulation modules 25a and 25b have separate regulation communication interfaces 27 for the issue of target values 28 and the reception of actual values 29. The communication interfaces 27 are real time interfaces. The communication interfaces 27 comprise digital bus interfaces 27a. The valve means 23 are connected by way of bus lines 30a and 30b with the communication interfaces 27 so that each fluid power unit to be regulated comprising a respective valve means 23 and one of the actuators 18c and 18d has a separate regulator bus line 30a or 30b available for it. Accordingly rapid communication is possible between the units to be regulated and the assigned regulation module 25a and 25b. Between each regulation module 25a and 25b and its arrangement to be regulated 23 and 18c or 23 and 18d there is a separate physical connection. The actual values 29 are then transmitted by these connections.
As an alternative the regulation module 25a could be a regulator for two actuators and regulate both arrangements 23, 18c and 23 and 18d via the bus line 30a and an optional bus line 30c leading to the regulation module 25a in lieu of the bus line 30b. 
The actual values 29 contain pressure sensor values 33 for example, which are generated by pressure sensors 31 of a sensor arrangement 32 of the valve means 23. The pressure sensors 31 are for example arranged on ports of pressure lines, by which the actuators 18c and 18d are joined with the valve means 23. To this extent the valve means 23 constitute sensor means. The valve means 23 transmit the pressure sensor values 33 by means of a bus coupler 34 which to this extent constitutes a sensor communication interface, on the respective bus line 30a or 30b to the regulation module 25a or 25b. 
Sensor means 35c and 35d arranged on the actuators 18c and 18d produce further sensor values as actual values 29, for example pressure values, temperature values and/or position values 36.
The sensor means 35c and 35d are coupled serially with the valve means 23 via bus lines 37a and 37b. For this purpose it is however also possible for the connection contacts for the valve means 23 to have separate bus couplers. It is however possible for the bus lines 37a and 37b at the valve means 23 to be looped through to the corresponding connection contacts of the bus couplers 34. In any case the connection of the sensor devices 35c and 35d and of the valve means 23 is simplified because these means are coupled with each other in series because only one connection line leads to the regulation or communication interfaces 27.
The adjustment of parameters, in particular regulation parameters and/or a selection of the type of regulation (position regulation, pressure regulation, position regulation with slave pressure regulation) and/or a diagnosis of the modules of the valve cluster 11b, f. i. of the regulation modules 25a and 25b, may be undertaken at some central position using a user device 57, as for example a notebook. The user device 57 is able to be connected with a user device interface 58 of the communication means 14b and is thus able to be connected with the internal communication bus 21. Then parameters may be loaded from the user device 57 to the valve cluster 11b, for example the regulation modules 25a and 25b or any other modules. Furthermore a diagnosis is possible using the user device 57. Thus for example the regulation modules 25a and 25b can transmit failure messages, indications as regards a number of duty cycles already performed or other diagnostic data to the user device 57.
It will be clear that wireless operation or diagnosis is also possible, for example using a user device 59, which communicates with the communication means 14b in a wireless fashion.
The putting into operation of the automated system 10 and diagnosis and/or parameterizing of the regulation modules 25a and 25b is simplified by an auto-identification concept. The fluid power apparatus 17 or means assigned to it, as for example sensor means 35a. 35b and 35c assigned to the actuators 18a through 18c, comprise or constitute ident data transmission means 60, which transmit apparatus identification data 61a, 61b, 61c, 61d and 62 to receiving means 63 for the identification data 61a through 61c and 62 of the valve clusters 11a and 11b. The identification data 61a through 61d characterize the pneumatic actuators 18a, 18b, 18c and 18d. The identification data 62 characterize the valve means 23.
The apparatus identification data 62 of the valve means 23 are saved in an optionally present memory 64. In the case of the valve means 23 assigned to the actuator 18d in addition the apparatus identification data 61d can be saved as well, which characterize the actuator 18d. The actuator 18d has f. i. no memory of its own for saving its identification data and furthermore no interface to transmit such data to the valve cluster 11b. 
The valve means 23 responsible for fluid control of the actuator 18c communicates the apparatus identification data 16c thereof, which it receives by way of the line 37b, via the bus line 30b on to the regulation communication interface 27.
The regulator communication interfaces 27 constitute or include receiving means 63 for the apparatus identification data 62 and 61c and also apparatus identification data 61d of the actuator 18d. On the basis of such apparatus identification data, which for example comprise the working strokes of the actuators 18c and 18d, the regulator modules 25a and 25b regulate the actuators 18c and 18d. In this respect it is possible for the regulator modules 25a and 25b to directly evaluate the apparatus identification data 61c, 61d and 62 for the generation of regulation parameters. Accordingly for example maximum pressures may serve for example for the limitation of pressure of the compressed air by pressure regulation. Furthermore it is possible, using the internal communication infrastructure, namely the internal communication bus 21 and the communication 14b means 14b, for the regulation modules 25a and 25b to transmit the respective apparatus identification data 61b, 61d and 62 to the user device 57, which generates the regulation parameters therefrom and transmits same to the regulation modules 25a and 25b using the said communication path.
The sensor means 35a transmits the apparatus identification data 61a in a wireless fashion to a receiving means 63 comprised in the valve cluster communication means 14a. 
The actuator 18b is connected by a conventional pressure line 86 and a fluid connection line 87, which has a fluid duct 88 and data lines 89, with the valve cluster 11b. The data lines 89 are for example arranged in a casing 90 encircling the fluid duct 88. On plugging in the fluid connecting line 87 contacts (not illustrated) of the valve cluster 11b and of the sensor means 35b are connected with the data lines 89 so that simultaneously a fluid connection and a data connection are produced between the valve cluster 11b and the sensor device 35b and also the actuator 18b. 
The sensor device 35b transmits the apparatus identification data 61b in a wired manner, f. i. by way of the data lines 89, to a receiving means 63, which for example is comprised in the valve module 16 driving the actuator 18b. 
For saving and transmitting the apparatus identification data 61a through 61d and 62 different transmission concepts and memory concepts are possible. In the case of the automated system 10 it is preferred for sensor means to transmit the apparatus identification data 61a, 61b, 61c, 61d and 62 to the receiving means 63.
The valve means 23 comprises the pressure sensors 31 and to this extent constitutes a sensor device. Its bus coupler 34 to this extent constitutes a sensor communication means and the memory 64 with the apparatus identification data 62 and/or 61d constitutes a sensor memory.
The apparatus identification data 61c are not transmitted by the actuator 18c itself but by the sensor device 35c assigned to it. The sensor device 35c is arranged on the housing of the actuator 18c, for example in the longitudinal direction on the side and comprises a position sensor 65 which transmits position values 36 of an actuator member 67c of the actuator 18c by way of sensor communication interface 68c. The sensor communication interface 68c comprises a bus interface 81, for example a bus coupler, for a bus connection by way of the valve means 23 to the regulation communication interface 27.
The apparatus identification data 61c, which characterize the actuator 18c and for instance comprise the diameter of the actuator member 67c, the travel displacement of the actuator member 67c in a housing 69c of the actuator 18c or the like, are saved in a sensor memory 70c. The memory 70c is preferably programmable, for example by way of a programming interface 71 able to be connected with the user device 57. The sensor communication means 68c comprises electrical read contact as a reading means 76c for reading the sensor memory 70c. 
The actuator 18c need not have any intelligence of its own for saving the apparatus identification data 61c. 
The sensor means 35c may be supplied with electrical power for example by way of its sensor communication interface 68c, i. e. a bus coupler.
The sensor means 35a on the contrary, which also comprises a position sensor 65, has an electrical long term energy storage means 72, for example a lithium battery, for long term service independent of an external power supply. Furthermore for data transmission, as for example for the transmission of position values produced by a position sensor 65, no line connections are necessary either. The sensor device 35a has a wireless communication means 68a, which for example with the Wireless Fidelity (WiFi) standard.
In a sensor memory 70a of the sensor device 35a sensor identification data 73 are held, as for example the resolution of the position sensor 65, an initial position and an end position of the measurement range of the position sensor 65. Apparatus identification data 61a of the fluid power apparatus 17, as for example the diameter of the actuator member 67a, the maximum force available at a force output of the actuator 67a (f. i. at the piston rod) or the like are saved in an apparatus memory 74 of the fluid power apparatus. The apparatus memory 74 is mounted f. i. in a cover 75a of the housing 69a and includes a rewritable memory, f. i. an EEPROM. The apparatus memory 74 is programmed during manufacture of the fluid power apparatus 17 so that its apparatus identification data 61a are available and for example may be read out by a reading apparatus, as for example the user device 59.
It is an advantage to use a sensor communication interface for the transmission of the apparatus identification data stored in the fluid power apparatus, for example the actuator 18a. A reading means 76a, for example a data interface with electrical contacts of the sensor communication means 68a, reads the apparatus memory 74 via electrical connections 77.
The electrical connections 77 are automatically made during arrangement or assembly of the sensor means 35a designed in the form of a sensor module 78. A housing 79 of the sensor device 35a extends as far as the housing cover 75a so that contacts 80 of the sensor device 35a and of the actuator 18a touch and produce the electrical connections 77.
Alternatively a wireless concept is possible, in which the apparatus identification data 61 are for example saved in an apparatus memory 75′ able to be read in a wireless manner, for example in a radio frequency identification (RFID) module. The reading means 76 is in this case a wireless reading interface, for example an RFID reading device. A transmission means of the apparatus memory 74′ gets the transmission power, necessary for the transmission of the apparatus identification data) 61a, through the sensor device 35a, for example by way of an electrical connection (not illustrated) or as transmission energy transmitted by the transmission of an interrogation message on the part of the reading means 76.
The apparatus identification data 61a read from the apparatus memories 74 or 74′ may also be first apparatus identification data, on the basis of which the sensor device 35a finds second apparatus identification data 61a′ in its sensor memory 60a. The identification data 61a′ are for example data, which complement the identification data 61a. Thus for example the apparatus identification data 61a may include the type characteristic of the actuator 18a, on the basis of which the sensor device 35a finds further characteristics of the actuator 18a, as for example its mechanical properties. Furthermore in the case of every sensor device in accordance with the invention, as for example in the case of the sensor device 35a, it is possible for the sensor device to convert or complement the sensor values on the basis of the apparatus identification data. Thus for example the sensor device 35a may provide the position values 36 with particulars in metric units, when it has found the specific travel displacement of the actuator member 67a on the basis of the apparatus identification data 61a. The sensor device 35b can specifically find a force output of the actuator 82a on the basis of the pressure sensor values 85 and provide an output thereof in f. i. newtons as force values.
While the sensor devices 35a and 35c constitute sensor modules 78 able to be detachably arranged on the actuators 18a and 18c and therefore in case of need may be replaced by other different types of sensor devices preferably in accordance with the invention, which for example comprise pressure sensors or the like, one sensor device 35b is an integral part of the actuator 18b. 
The sensor device 35b has a position sensor 65 and also pressure sensors 84, which for example are arranged at gcompressed air ports 83a and 83b. A sensor communication means 68b transmits position values 36 and pressure sensor values 85 of the pressure sensor 84 in a wired manner. In principle separate data lines could be provided for this. The sensor communication means 68b is however connected with the data lines 89 of the fluid connection line 87.
By way of data lines 89 the sensor device 35b transmits the position sensor values 36 and the pressure sensor values 85 and furthermore, for example on signing up with the valve cluster 11b or on interrogation from the valve cluster 11b, the apparatus identification data 61b characterizing the actuator 18b. The apparatus identification data 61b are saved in a sensor memory 70b of the sensor device 35b. 
The sensor device 35b furthermore has a processor 91, which for example counts the duty cycles of the actuator 18b and/or detects trouble conditions on the basis of the pressure sensor values 84, or the like. The processor constitutes a component of a diagnostic facility 93 and transmits such information as diagnostic data 92 by way of sensor communication means 68b.

## Claims

1. A sensor device for a fluid power apparatus, the sensor device comprising:
a housing separate from the fluid power apparatus;
at least one sensor for producing at least one sensor value on the basis of a property or a condition of the fluid power apparatus, the at least one sensor being disposed in the housing; and
a sensor communication means for the transmission of the at least one sensor value, the sensor communication means being disposed in the housing, wherein the sensor device includes a reading means configured to obtain apparatus identification data representing at least one mechanical property of the fluid power apparatus that is not sensed in the fluid power apparatus by the at least one sensor, the sensor device being adapted for transmission of the apparatus identification data by using the sensor communication means, the sensor device being configured to convert or complement the at least one sensor value based on the apparatus identification data, the reading means being connected with a receiving means for the reception of apparatus identification data transmitted by the fluid power apparatus or reading apparatus identification data from an apparatus memory of the fluid power apparatus, said device being adapted for locating second apparatus identification data in the sensor memory on the basis of first apparatus identification data transmitted by the fluid power apparatus.

2. The sensor device as set forth in claim 1, wherein the apparatus identification data includes at least one physical property of the fluid power apparatus.

3. The sensor device as set forth in claim 1, comprising a sensor memory in which the apparatus identification data are stored.

4. The sensor device as set forth in claim 3, wherein the sensor comprises memory sensor identification data characterizing the sensor device stored therein and the sensor device is responsible for output of the sensor identification data by way of the sensor communication means.

5. The sensor device as set forth in claim 3, wherein the sensor memory is able to be programmed by a user with the apparatus identification data.

6. The sensor device as set forth in claim 3, wherein the sensor memory is a non-volatile memory.

7. The sensor device as set forth in claim 1, wherein the reading means is connected with a receiving means for the reception of apparatus identification data transmitted by the fluid power apparatus or reads apparatus identification data from an apparatus memory of the fluid power apparatus.

8. The sensor device as set forth in claim 7, wherein the receiving means is designed for wireless communication with the fluid power apparatus.

9. The sensor device as set forth in claim 7, wherein said device is adapted for locating second apparatus identification data in the sensor memory on the basis of first apparatus identification data transmitted by the fluid power apparatus.

10. The sensor device as set forth in claim 1, wherein the sensor communication means include at least one bus interface and in particular a field bus interface.

11. The sensor device as set forth in claim 1, wherein the said device is adapted for automatic transmission of apparatus identification data as part of a signing up procedure on coupling with an automated system.

12. The sensor device as set forth in claim 1, wherein the said device includes an electrical energy storage means and in particular a long term storage means.

13. The sensor device as set forth in claim 1, wherein said sensor device exhibits an energy economy function, in which it switches over to an energy saving quiescent mode after a predetermined time.

14. The sensor device as set forth in claim 1, wherein said sensor device constitutes an integral component of the fluid power apparatus.

15. The sensor device as set forth in claim 1, wherein said sensor device is in the form of an intermediate module able to be operated remote from the fluid power apparatus.

16. The sensor device as set forth in claim 1, wherein said sensor device constitutes a sensor module able to be arranged on the fluid power apparatus and detachably secured in place thereon.

17. The sensor device as set forth in claim 16, comprising electrical contacts for providing a connection with a memory of the fluid power apparatus when the sensor device is arranged on the fluid power apparatus.

18. The sensor device as set forth in claim 1, wherein the fluid power apparatus includes a valve or a power cylinder or a servicing device or a vacuum means.

19. The sensor device as set forth in claim 1, comprising diagnostic means for retrieving diagnostic data as regards the fluid power apparatus.

20. The sensor device as set forth in claim 19, wherein said sensor device is adapted for the output of the diagnostic data using a display arranged on the sensor device.