METHOD FOR SECURE MONITORING OF THE FUNCTION OF AN ELECTROMAGNETIC TRANSPORTATION DEVICE

Abstract

In order to implement a secure monitoring function for a long-stator linear motor or planar motor, the invention proposes that at least one first measurement value of a first sensor is compared to a predefined plausibility threshold value, and in the event of said plausibility threshold value being exceeded by the first measurement value, an error is identified and an action is triggered.

Claims

1. A method for securely monitoring the function of an electromagnetic transport device in the form of a long stator linear motor or planar motor, wherein a number of sensors are arranged at the long stator linear motor or planar motor and the number of sensors each acquire a measurement value which is suitable for controlling the long stator linear motor or planar motor, wherein at least one first measurement value of a first sensor is compared with a predefined plausibility threshold value, and wherein, when the plausibility threshold value is crossed by the first measurement value, an error is identified and an action is triggered.

2. The method according to claim 1, wherein a rate of change over time of the first measurement value of the first sensor and/or a rate of change over time of a further measurement value of a further sensor are compared with a predefined maximum rate of change over time, and wherein, if the maximum rate of change over time is exceeded, an error is identified and an action is triggered.

3. The method according to claim 1, wherein the first measurement value of the first sensor and/or a further measurement value of a further sensor is compared with an additional measurement value of an additional sensor and a difference is identified, and wherein, if the identified difference deviates from a predefined difference, preferably from a predefined difference of zero, an error is identified and an action is triggered.

4. The method according to claim 3, wherein the additional sensor is positioned adjacent to the first sensor and/or further sensor.

5. The method according to claim 3, wherein an activity of the first sensor is determined as a first measurement value and/or an activity of a further sensor is determined as a further measurement value and an activity of the additional sensor is determined as an additional measurement value.

6. The method according to claim 1, wherein the action comprises the output of a warning and/or an intervention in the control system.

7. The method according to claim 1, wherein a transport unit is arranged movably in a direction of movement along a transport route wherein a plurality of drive magnets arranged at the transport unit in the direction of movement generate a magnetic field at the transport route, or a transport unit is movably arranged in a transport plane, wherein a plurality of drive magnets arranged at the transport unit generate a magnetic field at the transport plane, and wherein at least one measurement value of at least one sensor is dependent on the position and/or the speed and/or the acceleration of the transport unit at the transport route or at the transport plane.

8. The method according to claim 7, wherein from the at least one measurement value a safe position and/or a safe speed and/or a safe acceleration of the transport unit is/are determined.

9. The method according to claim 8, wherein the safe position and/or the safe speed are identified in at least two redundant calculation paths of an evaluation unit.

10. The method according to claim 9, wherein intermediate results and/or results of the evaluations between the at least two redundant calculation paths are compared.

11. The method according to claim 8, wherein the at least one measurement value is compared with a reference value, preferably a reference curve, in order to identify the safe position and/or the safe speed and/or the safe acceleration.

12. The method according to claim 11, wherein information known in advance, preferably information on the arrangement of the drive magnets and/or on the arrangement of the at least one sensor, is used for calculating the safe position and/or the safe speed and/or the safe acceleration.

13. The method according to claim 8, wherein the safe position and/or the safe speed and/or the safe acceleration of the transport unit is/are compared with a predefined maximum value, and, when exceeded, an action is triggered.

14. The method according to claim 8, wherein the safe position and/or the safe speed and/or the safe acceleration of all transport units of the long stator linear motor or planar motor are determined.

15. The method according to claim 1, wherein a transport unit is arranged movably in a direction of movement along a transport route, wherein a plurality of drive magnets arranged at the transport unit in the direction of movement generate a magnetic field at the transport route, or a transport unit is arranged movably along a transport plane and a plurality of drive magnets arranged at the transport unit generates a magnetic field at the transport plane and wherein a propulsion force acting on the transport unit and/or a safe normal force acting on the transport unit is/are determined from the at least one first measurement value.

16. The method according to claim 1, wherein the function of the long stator linear motor or planar motor is monitored when an object or subject is in a predefined safety region of the long stator linear motor or leaves a predefined working region of the long stator linear motor.

17. An electromagnetic transport device in the form of a long stator linear motor or planar motor, on which a number of sensors are arranged, which are connected to a control unit of the long stator linear motor or planar motor and are designed to acquire a measurement value of the long stator linear motor or planar motor and to transmit it to the control unit, wherein an evaluation unit is provided which is designed to compare a first measurement value of a first sensor with a predefined plausibility threshold value and, when the measurement value is exceeded, to identify an error and trigger an action.

Description

[0065] In the following, the present invention is described in greater detail with reference to FIG. 1a to 6 which, by way of example, show schematic and non-limiting advantageous embodiments of the invention. In the drawings,

[0066] FIG. 1a shows the comparison of a first measurement value with a threshold value on a long stator linear motor,

[0067] FIG. 1b shows the comparison of a first measurement value with a threshold value on a planar motor,

[0068] FIG. 2 shows the comparison of the rate of change of a further measurement value with a maximum rate of change,

[0069] FIG. 3 shows the comparison of a further measurement value with an additional measurement value,

[0070] FIG. 4 shows the determination of a safe position/speed/acceleration,

[0071] FIG. 5 shows a curve of a characteristic magnetic field angle and a characteristic magnetic field magnitude as reference curves,

[0072] FIG. 6 shows an evaluation unit with two redundant calculation paths.

[0073] A long stator linear motor can be provided as electromagnetic transport device. That means that the electromagnetic transport device represents a long stator linear motor. FIG. 1a, 2, 3, 4, 6 each show a long stator linear motor 2 with an evaluation unit 3. The stator of the long stator linear motor 2 is designed here as a closed transport route 20. A plurality of drive coils L are arranged one after the other at the transport route 20 in the direction of movement r of a transport unit 1, each of which coils is energized in normal operation under the control of a control unit 4 at a coil current i.sub.m in order to generate a moving magnetic field. The coil current i.sub.m through the respective drive coils L can be fundamentally different from drive coil L to drive coil L. The control unit 4 can be in the form of suitable hardware and/or in the form of software running on suitable hardware. The drive coils L arranged next to one another in the movement direction r are arranged at the transport route 20 on a stationary support structure (only implied in the drawings). Depending on the application and as needed, the transport route 20 can have any shape, and can comprise closed and/or open route portions. The transport route 20 does not have to lie in one plane, but can also be guided in any way in space. Depending on the structure of the transport route 20, for example: in the case of a vertical transport route 20 or a vertical section of the transport route 20, safety functions can also be excluded. Usually a transport route 20 consists of several route segments put together, each with a number of drive coils L. Likewise, switches are known to guide a transport unit 1 from a first transport route 20 to a second transport route 20.

[0074] A number of sensors S1, S2, S3, S4 are arranged on the long stator linear motor, for example on the stator. A magnetic field sensor, for example, can be provided as the sensor S1, S2, S3, S4. Magnetic field sensors can be viewed as sensors which measure a property of a magnetic field, for example the magnetic field intensity (for example a Hall sensor) or the direction of the magnetic field (for example a magnetoresistive sensor).

[0075] A current sensor which determines the coil current i.sub.m through a drive coil L can also serve as sensor S1, S2, S3, S4. As is known, a normal force and/or propulsion force acting on a transport unit can be determined from the coil current i.sub.m.

[0076] According to the invention, an evaluation unit 3 is provided which compares at least one measurement value m1 of a first sensor S1 (only a first sensor S1 is shown by way of example in FIG. 1) with a predefined threshold value G. Thus, the measurement value m1 of the sensor S1 is checked for plausibility, for example, and a deviation of the measurement value m1 from the target value G is identified and an action A is triggered. As action A, for example, a warning signal can be output and/or the control unit 4 of the long-stator linear motor can be intervened in, as indicated in FIG. 1a, 2, 3, 4, 6.

[0077] A planar motor can be provided as electromagnetic transportation device. This means that the electromagnetic transportation device is a planar motor. Analogous to FIG. 1a, a simple example of a planar motor as an electromagnetic transportation system 2 is shown in FIG. 1b. In contrast to the long stator linear motor, the planar motor 2 has a transport plane 20 instead of a transport route 20. A large number m of drive coils Sm are arranged in the transport plane 20, here located in the yz-plane. The drive coils Sm are arranged here in the x-axis and the y-axis only by way of example and are each energized with a coil current i.sub.m in normal operation under the control of a control unit 4 (only shown for some drive coils Sm) in order to generate a magnetic field moving in the transport plane 20. The drive coils Sm can also be connected to the control unit 4 in a different manner in order to energize the drive coils Sm with the coil current i.sub.m. The control unit 4 can be in the form of suitable hardware and/or in the form of software running on suitable hardware.

[0078] A number of sensors S1, S2, S3, S4 are arranged at the planar motor. A magnetic field sensor, for example, can be provided as the sensor S1, S2, S3, S4. Magnetic field sensors can be viewed as sensors which measure a property of a magnetic field, for example the magnetic field intensity (for example a Hall sensor) or the direction of the magnetic field (for example a magnetoresistive sensor).

[0079] A current sensor which determines the coil current i.sub.m through a drive coil L can also serve as sensor S1, S2, S3, S4. As is known, a normal force and/or propulsion force acting on a transport unit can be determined from the coil current i.sub.m.

[0080] According to the invention, an evaluation unit 3 is provided which compares at least one measurement value m1 of a first sensor S1 (only one first sensor S1 is shown as an example in FIG. 1b) with a predefined threshold value G. Thus, the measurement value m1 of the sensor S1 is checked for plausibility, for example, and a deviation of the measurement value m1 from the target value G is identified and an action A is triggered. As action A, for example, a warning signal can be output and/or the control unit 4 of the long stator linear motor can be intervened in. The sensor S1 or the sensors S1, S2, S3, S4 are connected to the control unit 4 by control connections for the transmission of the measurement values m1, m2, m3, m4, wherein the control connections also are connected to the evaluation unit 3 in the figures. A preferably secure bus can also be provided as control connections. The sensors S1, S2, S3, S4 may preferably be connected to the evaluation unit 3 via their own evaluation connection, which is separate from the control connection. This means that the measurement values m1, m2, m3, m4 can be transmitted separately to the evaluation unit 3 via secure lines, which ensures a higher level of security in the evaluation.

[0081] A magnetic field variable, such as a magnetic field angle α1 and/or a magnetic field magnitude A1, can be recorded as measurement value m1. A temperature, a current, etc. can also be recorded as a measurement value m1. A temperature can be used, for example, to “correct” values of magnetic field variables if these are influenced by the temperature. A sensor S1 can of course also supply several physical variables as measurement values m1, for example a magnetic field variable and a temperature. A variable derived from the directly physically measured variable can of course also be viewed as a measurement value m1.

[0082] A rate of change over time dm1(t) of the first measurement value m1 of the first sensor S1 and/or a rate of change over time dm2(t) of a further measurement value m2 of a further sensor S2 can also be compared with a maximum rate of change d_max(t) over time. If the maximum rate of change over time d_max(t) is exceeded, an error is identified and an action A is triggered. This is shown in FIG. 2 and can be used analogously in a planar motor as the electromagnetic transport system 2.

[0083] A certain continuity can thus be assumed as the measurement value m1 for a magnetic field angle α1, for example. If the at least one sensor S1 represents a magnetic field sensor, for example, an excessively high rate of change over time of a magnetic field angle α1 and/or the magnetic field magnitude A1 can indicate a faulty sensor S1 or an error in the processing between the sensor and the evaluation unit or in the evaluation unit. The (physically) maximum possible rate of change is preferably provided as the maximum rate of change d_max(t). The dynamics, i.e. a rate of change over time dm1(t), dm2(t) of the measurement value m1, m2, can be viewed and compared with a predefined maximum possible dynamics, i.e. the maximum rate of change d_max(t). For example, a maximum possible rate of change can be established for the magnetic field angle α1, for example within a safety period ts. If a rate of change dm1(t), dm2(t) of the measurement value m1, m2 above the maximum possible rate is detected in the evaluation unit 3, an error can be inferred. Likewise, a rate of change over time dm1(t), dm2(t) of the magnetic field magnitude A1 can be checked as a measurement variable m1, m2, compared with the maximum possible rate of change d_max(t) and, if exceeded, an error can be inferred and an action A triggered.

[0084] It can also happen that no major changes in temperature are to be expected. Therefore, a temperature sensor as sensor S1 can also deliver a temperature as measurement value m1, m2 and be compared with the maximum possible rate of change dm1(t), dm2(t) of the temperature. The same is of course also possible with other measurement values m1, m2, such as currents, for example.

[0085] A rate of change over time dm1(t) of a measurement value m2 can also be compared with a maximum rate of change over time d_max(t) without comparing the measurement value m1 with a threshold value G. If the maximum rate of change over time d_max(t) is exceeded, an error is also identified in this case and action A is triggered. In this case, the sensor S1 and the measurement value m1 can thus be taken out in FIG. 2 and a safety function can nevertheless be ensured.

[0086] In addition to comparing the first measurement value m1 of the first sensor S1 with a threshold value G, the first measurement value m1 of the first sensor S1 and/or a further measurement value m3 of a further sensor S3 may be compared with an additional measurement value m4 of an additional sensor S4 and in case of a deviation of the first measurement value m1 and/or the further measurement value m3 from the additional measurement value m4, preferably by a tolerance, an error is identified in the evaluation unit 3 and an action A is triggered. In FIG. 4, the first measurement value m1 of the first sensor S1 is compared with a limit value G and the further measurement value m3 of the further sensor S3 is compared with the additional measurement value m4 of the additional sensor S4 and can be used analogously in a planar motor as the electromagnetic transportation system 2. A comparison of the measurement values m1, m3 with additional measurement values m4 is particularly advantageous if the respective sensors S1, S3 are positioned adjacent to the additional sensor s4, since here similar measurement values m1, m3, m4 are to be expected, e.g. similar temperatures and/or similar magnetic field magnitudes.

[0087] If magnetic field angles are available as measurement values m1, m3, m4 and if the magnetic field angles of neighboring sensors S1, S3 are similar, then the magnetic field angles can be treated in the same way as similar magnetic field magnitudes, temperatures, etc. If the magnetic field angles of neighboring sensors S1, S3 are not similar to one another, the relationship between the magnetic field angles of neighboring sensors S1, S3 can be known, so that, based on a first magnetic field angle as the first measurement value m1 of the first sensor S1, an expected magnetic field angle can be inferred as the expected further measurement value of a neighboring further sensor S3. If the further measurement value m3 does not agree with the expected further measurement value, an error can be inferred and an action can be triggered.

[0088] An expected value of an additional measurement value m4 from an additional sensor S4 can also be calculated on the basis of a measurement value m1, m3 from the first sensor S1 and/or from the further sensor S3.

[0089] A further measurement value m3 from a sensor S3 can also be compared with an additional measurement value m4 from an additional sensor S4 and a difference can be determined without comparing the measurement value m1 with a threshold value G. If the determined difference deviates from a predefined difference, preferably from a predefined difference of zero, an error is likewise identified in this case and an action A is triggered. In this case, the sensor S1 and the measurement value m1 can thus be eliminated in FIG. 3.

[0090] The evaluation unit 3 is advantageously connected to all sensors S1, S2, S3, S4 of the long stator linear motor or planar motor 2 and compares the measurement values m1, m2, m3, m4 with the respective threshold values G and triggers an action A in the event of a deviation. An evaluation unit 3 can also be provided fora specific number of sensors S1, S2, S3, S4, for example the sensors of a route segment of the long stator linear motor or the sensors of a plane segment of the planar motor 2.

[0091] At least one transport unit 1, which can be moved along the transport route 20 in the direction of movement r, is usually arranged on a long stator linear motor 2. For this purpose, the at least one transport unit 1 is guided and held in a suitable manner with guide elements 21, 22 (only indicated schematically in the figures) on the stationary transport route 20 in the direction of movement r. The guide elements 21, 22 can be located on one side of the transport route 20 or on two sides. A transport unit 1 has a number of laterally arranged drive magnets M along the direction of movement r, as shown in FIG. 3. The first number of drive magnets M arranged laterally on the opposite side of the transport unit 1 can also be provided. If the transport unit 1 has drive magnets on two sides, drive coils L can be suitably provided on both sides of the transport route 20 (viewed in the direction of motion r) which interact with the respective magnets M to cause a movement of the transport units 1. For movement, it is preferable to supply only the drive coils L in the region of the drive magnets M with power by the coil controller R, wherein this region can also comprise drive coils L which are located before and/or after the transport unit 1. Of course, more than one transport unit 1 can be moved along the transport route 20, wherein each transport unit 1 can be moved (in direction, position, speed and acceleration) by appropriately energizing the drive coils L near the transport unit 1 independently of the other transport units 1, provided there is sufficient separation between the drive magnets M of the transport units 1.

[0092] In a planar motor, the transport unit 1 has magnets M3, M4, which are preferably arranged parallel to the drive coils Sm. In the embodiment shown in FIG. 1b, the magnets M3 are arranged in the x-axis and the magnets M4 are arranged in the y-axis. For movement of the transport unit 1, preferably only the drive coils Sm in the region of the magnets M3, M4 are supplied with power by the control unit 4, wherein this region can also comprise drive coils Sm which are located before and/or after and/or to the side of the transport unit 1. By suitably actuating the drive coils Sm, the transport unit 1 can also be moved in a direction of movement w that is not parallel to one of the axes of the transport plane, as is also shown in FIG. 1b. Of course, more than one transport unit 1 can also be moved in the transport plane, and each transport unit 1 can be moved independently of the other transport units 1 (in direction, position, speed and acceleration) by appropriately energizing the drive coils Sm in the region of the transport unit 1. Current sensors may be provided to determine the position of the transport unit 1 in the transport plane and thus to determine the coils Sm which are currently to be energized and which are located in the transport area 20 at the transport unit 1, for example. Depending on the application and requirements, the transport plane can have any desired shape, and can also be guided in space as desired. Furthermore, the transport plane often consists of a plurality of plane segments arranged next to one another.

[0093] The propulsion force required to move a transport unit 1 of an electromagnetic transportation system 2 is known to be formed by the propulsive-force-generating current component iq (q-component) of a drive current i.sub.A. The drive current i.sub.A corresponds to the vectorial total current of all coil currents i.sub.m of the drive coils Sm acting on the transport unit 1. The transport unit 1 is located at one position and can move in a direction of movement and/or an acceleration in the transport plane 20. Reference is made to FIGS. 4, 5 and 6 to determine the safe position x/safe speed v/safe acceleration a. The method shown in FIGS. 4, 5 and 6 in relation to a long stator linear motor can be used analogously in a planar motor.

[0094] If a long stator linear motor is provided as the transportation system, the drive current is a current vector with a q- and a d-component (current component that generates normal force). If a planar motor is provided as a transportation system, the drive current is a current vector with two q-components and one d-component (current component that generates normal force).

[0095] Thus, for the normal forward movement of the transport unit 1, the propulsive-force-generating current component(s) iq (q-component(s)) is sufficient. The normal force not serving the forward movement is formed by the normal-force-generating current component id (d-component) of the drive current i.sub.A.

[0096] A number of sensors S1, S2, S3, S4 are arranged at the long stator linear motor 2, preferably on the stator, i.e. at the transport route 20 of the long stator linear motor 2 or at the transport plane 20 of the planar motor 2, as mentioned. Measurement values m1, m2, m3, m4 of the sensors S1, S2, S3, S4 can be independent of the position of the transport unit 1 at the transport route 20 or in the transport plane 20, in particular if the temperature is used as the measurement value m1, m2, m3, m4.

[0097] At least one measurement value m1, m2, m3, m4 of at least one sensor S1, S2, S3, S4 can also be dependent on the position of the transport unit 1. The sensors S1, S2, S3, S4 can be arranged along the transport route 20 or the transport plane 21 for determining the position x and/or the speed v and/or the acceleration a of a transport unit 1. For this purpose, position sensors or speed sensors or acceleration sensors can be provided as sensors S1, S2, S3, S4, which directly transmit the safe position x or safe speed v or safe acceleration a of the transport unit 1 to the evaluation unit 3 as a measurement value m1. For this purpose, the measurement values m1, m2, m3, m4 of the sensors S1, S2, S3, S4 can be compared, for example, with threshold values and/or with further measurement values of further sensors S1, S2, S3, S4 and/or the rate of change over time dm1(t), dm2(t), dm3(t), dm4(t) of measurement values m1, m2, m3, m4 from sensors S1, S2, S3, S4 with specified maximum rates of change d_max(t).

[0098] The safe speed v can also be calculated from the safe position x or the time profile of the safe position x. Likewise, the safe acceleration a can also be determined from the safe speed v or the time profile of the safe speed v.

[0099] However, magnetic field sensors can advantageously also be provided as sensors S1, S2, S3, S4. A magnetic field caused by the transport unit 1 can thus be supplied as a measurement value m1 to the evaluation unit 3, wherein the evaluation unit calculates a position x and/or a speed v and/or an acceleration a of the transport unit 1. In order to be able to dispense with own, additional position magnets to cause the magnetic field at the transport unit 1, in particular the already existing drive magnets M of the transport unit can be used to cause the magnetic field. The magnetic field can thus be used to determine the safe position x and/or the safe speed v, preferably in the evaluation unit 3.

[0100] The at least one measurement value m1, m2, m3, m4 can be compared with a reference value, preferably a reference curve 11, in order to determine the safe position x and/or the safe speed v and/or the safe acceleration a. The known principle of pattern recognition can be used to compare the measurement value m1, m2 with the reference curve 11. FIG. 4 shows a calculation of the safe position x and/or the safe speed v and/or the safe acceleration a on the basis of a measurement value m1 from a sensor S1 and can be used analogously in a planar motor as the electromagnetic transportation system 2.

[0101] A magnetic field sensor can convert a magnetic field into an electrical signal in the form of a sin/cos signal, from which a magnetic field angle α1 can be determined using the atan or atan 2 angle function and a magnetic field magnitude A1 using sqrt(sin.sup.2+cos.sup.2). Characteristic magnetic field angles α1 and magnetic field magnitude A1 of a transport unit can thus be viewed as reference curve 11. The course of the reference curve 11, for example a course of a magnetic field magnitude B and a magnetic field angle α, is also repeated for sensors S1, S2, S3, S4 arranged next to one another when the transport unit is moved along the transport route or along the transport plane 20. Depending on the position, different groups of successive sensors S1, S2 are always influenced.

[0102] The safe position x and/or speed v and/or acceleration a of the transport unit 1 can thus be determined using a measurement value m1 compared with a reference curve 11.

[0103] The reference curve 11 can also be determined in advance from the measurement values m1, m2, m3, m4 of a magnetic field sensor S1, S2, S3, S4 by moving a transport unit 1 along the sensor S1, S2, S3, S4 and recording the measurement value m1, m2, m3, m4.

[0104] FIG. 5 shows a typical magnetic field magnitude A0 and a typical magnetic field angle α over the width b of a transport unit 1 (i.e. in the direction of movement r), wherein the edges of the transport unit 1 are shown with broken lines. When speaking of a width b of a transport unit 1, the width across the drive magnets M of the transport unit 1 is of course always meant, since only the drive magnets M cause the magnetic field and can thus be detected. It can also be seen that a transport unit 1, due to scattering processes, generates a magnetic field which extends over the width b. A transport unit can thus also have an influence on a sensor S1, S2 if it is not located directly above it. The typical magnetic field angle α and the typical magnetic field magnitude A can thus serve as reference curves 11.

[0105] Since several drive magnets M are provided here, the magnetic field angle α describes a saw tooth. Each saw tooth is assigned to a unique position of a drive magnet M relative to the respective sensor S1, S2, S3, S4. It can thus be seen that the saw teeth of a magnetic field angle α are repeated several times for a sensor S1, S2, S3, S4. If a measurement value m1 is now recorded by a sensor S1, the safe position x or speed v or acceleration a of the transport unit 1 can be determined by determining the first measured magnetic field angle α1, if the measurement value m1 allows an unambiguous conclusion. This can be made possible, for example, by considering the profile of the measurement value over time.

[0106] For a measurement value m1 it can happen that no clear conclusion is possible. If the magnetic field angle α1 is used as the measurement value m1, a sensor S1, S2 detects the same magnetic field angle α1, α2 several times for different positions of the transport unit 1, since this is repeated due to the plurality of drive magnets M on a transport unit 1, as shown in FIG. 5. Thus, if necessary, a measurement value m1 cannot be uniquely linked to a safe position x or speed v or acceleration a, in particular if only the current measurement value m1 is considered without the time profile. In addition to the first sensor S1, at least one second sensor S2, preferably all sensors S1, S2, S3, S4 that are assigned to a transport unit at a point in time t, can be used in order to obtain at least one second measurement value m2 in addition to the first measurement value m1. An assignment of sensors S1, S2, S3, S4 to a transport unit 1 can then be established, for example, if the measurement value supplied by the respective sensors varies with the change in the position of the transport unit 1.

[0107] From this, for example, several (e.g. two) magnetic field angles α1, α2, several (e.g. two) sensors S1, S2 are determined and viewed as a whole and compared with the reference curve 11, whereby a safe position x or speed or acceleration a of the transport unit 1 can be determined.

[0108] When using one measurement value m1 from one sensor S1, but also when using a plurality of measurement values m1, m2 from several sensors S1, S2, it may happen that due to the combination of the measurement values m1, m2 no clear determination of the safe position or speed v or acceleration is yet possible—if several positions of the transport unit 1 are possible by looking at the measurement values m1, m2 together. In particular, using two measurement values m1, m2 can often not be sufficient.

[0109] To remedy this problem, information known in advance, preferably information on the arrangement of the drive magnets M and/or on the arrangement of the sensor S1, can also be used to calculate the safe position x and/or the safe speed v and/or the safe acceleration a. Reference is made at this point to AT 519 238 B1, which discloses a method for initial position detection. This document also shows how information known in advance can be used for determining the position. In contrast to AT 519 238 B1, however, the present invention does not determine an initial position of the transport unit 1, but rather a safe position x and/or a safe speed v and/or a safe acceleration a.

[0110] For example, starting with the measurement values m1 of the first sensor S1, considering the reference curve 11 and the distances to an adjacent second sensor S2, it can be checked whether the further measurement value m2 of the second sensor corresponds to the expected value (determined from the reference curve 11). The sensor that can be selected as the first sensor S1 is most likely at the center of the arrangement of the drive magnets M, since the profile of the field lines of the magnetic field of the drive magnets M proceeds more favorably in this region. Starting from the first measurement value m1 of the centrally positioned sensor S1 using the reference curve 11, the second measurement value m2 of the second sensor S2 can be checked in order to determine a safe position x of the transport unit 1, possibly using information known in advance.

[0111] The measurement values m1, m2, m3, m4 of all active sensors S1, S2, S3, S4 can also be used and compared with the reference curve 11. In order to identify the active sensors S1, S2, S3, S4, it is possible to determine which sensors S1, S2, S3, S4 have a sufficiently strong magnetic field.

[0112] The determination of the safe position x and/or the safe speed v and/or the safe acceleration a can take place in the evaluation unit 3 in at least two redundant calculation paths, wherein intermediate results and/or results of the evaluations are able to be compared between the calculation paths. In FIG. 5, the redundant calculation paths are designed as parallel calculation units B1, B2, wherein a comparison of intermediate results and/or results of the evaluations is indicated by a double arrow between the calculation units B1, B2. In the event of deviations, action A can be triggered (indicated by the double arrow), since an error in the evaluation of the measurement value m1 can be inferred.

[0113] The safe position x and/or the safe speed v and/or the safe acceleration a of the transport unit 1 can be compared with a predefined maximum value v_max, and if it is exceeded an action A can be triggered. For example, the safe speed v can be compared with a maximum speed v_max.

[0114] If, for example, the maximum value v_max is exceeded by the safe speed v of the transport unit 1, then an action A may be triggered by the evaluation unit 3, as also shown in FIG. 6.

[0115] The safe position x and/or the safe speed v and/or the safe acceleration a of all transport units 2 of the long stator linear motor or planar motor 2 can be determined. If, for example, the safe speeds v of all transport units 1 located on the long stator linear motor or planar motor 2 are compared with the maximum value v_max, if exceeded a momentum block (STO) can be triggered, which implements a safely limited limit (SLS) for the transport units 1. It is also possible first of all to determine the highest occurring speed of all transport units 1 located on the stator of the long stator linear motor or planar motor 2 and then to compare this value with a predefined threshold value.

[0116] Analogous to the above-described determination and processing of the safe position x, speed v and acceleration a, the safe normal force and/or safe propulsion force of a or all of the transport units 1 located on the long stator linear motor or planar motor 2 can be securely calculated directly from a safe measurement value m1 or from a measurement value m1.

[0117] The measurement value m1 can be processed further as described in order to obtain a safe normal force and/or safe propulsion force.

[0118] For example, two redundant calculation paths B1, B2 for determining the safe normal force and/or safe propulsion force are preferably provided in an evaluation unit 3. As described above, intermediate results and/or results of the evaluations between the at least two redundant calculation paths B1, B2 can be compared. The at least one measurement value m1 can also be compared with a reference value, preferably a reference curve 11, in order to determine the safe normal force and/or safe propulsion force. Furthermore, the safe normal force and/or safe propulsion force can be compared with a predefined maximum value/minimum value, and when it is exceeded/undercut an action A can be triggered.

[0119] With reference to FIGS. 4 and 6, it shall be mentioned that, of course, a safe position x and/or safe speed v and/or safe acceleration a are also calculated without comparing the measurement value m1 of the first sensor S1 with a threshold value G.

[0120] It can also be considered whether sensors S1, S2, S3, S4 arranged next to one another are meaningfully active. A sensor S1, S2, S3, S4 is considered to be active, for example, when the associated measurement value m1, m2, m3, m4 reaches or exceeds a certain measurement value, for example a certain magnetic field magnitude. A sensor S1, S2, S3, S4 usually detects a magnetic field when the drive magnets M of a transport unit 1 are above or in the vicinity of the sensor S1, S2, S3, S4. Basically, however, stray fields of the drive magnets M must be taken into account, which can act in particular on sensors S1, S2, S3, S4 located upstream or downstream of the transport unit 1. This can be taken into account, for example, via a specified tolerance with regard to the deviation of the expected from the measured magnetic field.

[0121] The activity of, in particular adjacent, sensors S1, S2, S3, S4 can thus be compared with predefined patterns in order to carry out a plausibility check. The (non)activity of a first sensor S1 can thus be viewed as a first measurement value m1 and the (non)activity of an additional sensor S4 as an additional measurement value m4 in FIG. 3. On the basis of known expansions of transport units 1 over several sensors S1, S4, it can be assumed that a certain number of sensors S1, S4 must be active in series. If a transport unit 1 covers approximately two sensors S1, S2, then at least two successive sensors S1, S2 must always be active. If only one isolated sensor S1, S2 is active and its two adjacently arranged sensors S1, S2 are not, it can be concluded, for example, that there is a fault in the isolated sensor or in an adjacent sensor S1, S2.

[0122] A change in the status of the activity of sensors S1, S2 can also be checked for plausibility. It can be assumed that sensors S1, S2 are activated in groups along the direction of movement r. This means that a sensor S1, S2 can only become active if an adjacent sensor S1, S2 was previously active.

[0123] With a suitable geometric arrangement of the sensors S1, S2 and drive magnets M, it can be assumed, for example, that a sensor S1, S2 may only be active at a point in time if one of the surrounding sensors S1, S2 was active before this point in time and still is at this point. Conversely, the assumption can be made that a sensor S1, S2 can only become inactive at a point in time if one of the surrounding neighboring sensors was active before this point in time and still is active at this point in time. If this assumption is not met, an error can be inferred.

[0124] It can also be analyzed whether an active sensor S1, S2, S3, S4 actually experiences a magnetic field from a transport unit 1. In this case it can be analyzed which sensors S1, S2, S3, S4 are active, but in whose position no transport unit 1 is located at all. If a sensor S1, S2, S3, S4 measures a magnetic field, although it should not be active at all, it can be assumed that there is an error.

[0125] Of course, depending on the detected error, i.e. exceeding or falling below the threshold value of the first measurement value m1, exceeding the maximum rate of change over time dm1, dm2 of a measurement value m1, m2, deviation of the measurement values m1, m2, m3, m4 of various sensors S1, S2, S3, S4, errors when calculating the safe position x/safe speed v/safe acceleration a, or exceeding a maximum value v_max by the safe position a/safe speed v/safe acceleration a, a different action A can be triggered, even if all actions are designated as A in the figures and access the control unit 4.

[0126] Although a long stator linear motor is shown as an example in FIG. 2, 3, 4, 6 as an electromagnetic transportation device 2, the method thus described for securely monitoring the function of a long stator linear motor can be applied analogously to a planar motor. The described methods for securely monitoring the function of a long-stator linear motor, which are not shown in the figures, can also be used in a similar manner to the secure monitoring of the function of a planar motor.

[0127] Furthermore, the evaluation units described in connection with a long stator linear motor, for example according to FIG. 2, 3, 4, 6, which are designed to compare a first measurement value of a first sensor with a predefined threshold value and to determine an error when the measurement value is exceeded and to trigger an action, can be used in an analogous manner in an electromagnetic transportation device 2 in conjunction with a planar motor.