Linear drive system and method for determining two positions of two measuring elements that are moved along a movement path of a linear drive system

Abstract

Linear drive system with a sensor system for detecting the position of several carriers (4) movable along a path of motion (2) defined by a stator of the linear drive system, each carrier being equipped with a measuring element (3), wherein a first carrier (4) is assigned a first measuring element (3) and wherein a second carrier (4) is assigned a second measuring element (3), wherein the sensor system comprises a sensor arrangement (1) comprising several sensors (5) arranged at least along a partial section (17) of the path of motion (2), each sensor being configured for contactless detection of at least one physical quantity dependent on the position of a measuring element (3) along the path of motion (2) and for providing at least one sensor signal dependent on the at least one determined physical quantity, and wherein the sensor system comprises a processing device (9).which is electrically connected to the sensors (5) and which is configured for processing the sensor signals into a first position signal representing the position of the first measuring element (3) along the path of motion (2) and into a second position signal representing the position of the second measuring element (3) along the path of motion (2), wherein the processing device (9) is configured for synchronous acquisition of sensor signals from the sensors (5), wherein the processing device (9) comprises a clock generator and a plurality of sensor interfaces (10) for parallel coupling with the sensors (5), each of the sensor interfaces (10) being connected to the clock generator, which is configured for providing a readout signal to the sensor interfaces (10).

Description

[0001] The invention relates to a linear drive system with a sensor system for detecting a position of a plurality of carriers, each provided with a measuring element, which are movable along a movement path determined by a stator of the linear drive system, wherein a first measuring element is assigned to a first carrier and a second measuring element is assigned to a second carrier, wherein the sensor system comprises a sensor arrangement comprising a plurality of sensors arranged at least along a partial section of the movement path, each of which is designed for contactless detection of at least one physical variable dependent on a position of a measuring element along the movement path and for providing at least one sensor signal dependent on the at least one determined physical variable, and wherein the sensor system comprises a processing device,which is electrically connected to the sensors and which is designed to process the sensor signals into a first position signal representing the position of the first measuring element along the movement path and a second position signal representing the position of the second measuring element along the movement path. Furthermore, the invention relates to a method for determining two positions of two measuring elements that are moved along a movement path of a linear drive system.

[0002] From EP 2 466 269 B1, a position sensor device with a plurality of sensor units is known, wherein the sensor units each contain at least one detection unit suitable for detecting a nearby movement component and are connected to a communication interface which is designed to output a uniform position signal based on individual measurement signals from the plurality of sensor units, wherein the sensor units are designed as individual sensor modules equipped with electrical interface means, which can be arranged in a variable number in series with mutual electrical interlinking and formation of a module string.

[0003] DE 20 2005 016 333 U1 discloses an inductive sensor unit, for example for detecting the position of a vehicle seat, with a plurality of sensor coils which are applied planarly on a printed circuit board, with a conductive actuating element which is guided at a distance on a track over the sensor coils, and with an electrical evaluation circuit which detects changes in the inductance of the sensor coils according to a track position of the actuating element and converts them into electrical signals - in particular into seat position signals, wherein the actuating element is guided over the sensor coils with conductive base surfaces offset in the direction of the track.

[0004] DE 10 2004 018 630 A1 discloses a device for capacitive position detection of an object, comprising a plurality of capacitive probes which are distributed over an area in which a position of the object is to be detected, wherein the probes are each connected to a voltage source via coupling capacitances and can be supplied with a supply voltage, and wherein an evaluation device connected to the probes is provided, with which the probe signals can be processed to form an output signal which is a measure of the position of the object to be detected.

[0005] From DE 10 2013 009 862 A1, a sensor arrangement for position detection for a magnetic device movable along a movement path is known, which has a plurality of sensor units arranged along the movement path, each of which is designed to scan a movement path section and to provide a sensor signal depending on the position of the magnetic device in the respective movement path section, and which has an evaluation device designed to evaluate the sensor signals of the sensor units and to provide a position signal, wherein the evaluation device and the sensor units are connected to a bus communication line, wherein the sensor units are designed to couple digitized sensor signals to the bus communication line and / or wherein the evaluation device and the sensor units are designed for bidirectional communication via the bus communication line.

[0006] D4 DE 60 2004 005 672 T2 describes an inductive sensor for detecting a parameter such as position. The inductive sensor has a receiving antenna electromagnetically coupled to a magnetic field generator via a resonant circuit. The electromagnetic coupling varies depending on the detected parameter, so that a detection signal induced in the receiving antenna represents the detected parameter. A magnetic field generator generates a magnetic field having a first magnetic field component with a first frequency that serves to induce resonance in the resonant circuit, and a second magnetic field component with a second frequency that does not serve to induce resonance in the resonant circuit.The signal processor processes the detection signal to generate a signal component corresponding to a first component of the detection signal at the first frequency, which is adjusted using a second component of the detection signal at the second frequency so as to reduce a noise component of the first component of the detection signal, and determines a value representative of the detected parameter using the signal component.

[0007] DE 10 2010 055 736 A1 relates to a method for evaluating sensor signals from a sensor arrangement formed from sensors arranged in a row along a movement axis of a measurement object mounted in a linearly movable manner, said sensors being designed to determine at least two field components oriented perpendicular to one another which are provided by field generating means on the measurement object, wherein it is provided that, in order to determine the position of the measurement object, a first signal difference between sensor signals of a first sensor pair and a second signal difference between sensor signals of a second sensor pair are determined, wherein one of the sensors of the first sensor pair is arranged between the sensors of the second sensor pair in order to subsequently obtain the position information by interpolation between the first signal difference and the second signal difference.

[0008] From EP 2 166 313 A1, a magnetic sensor for determining a position of a sensor magnet along a path with a plurality of sensor elements is known, to which control electronics are assigned for receiving a sensor element signal from a specific one of the sensor elements, wherein the sensor elements and the control electronics are combined to form a module and are connected to a signal line for transmitting the sensor element signal to evaluation electronics for evaluating the sensor element signals and for determining the position.In order to provide an improved magnetic sensor and an improved method for determining positions of a sensor magnet, it is proposed that the sensor elements are Hall sensors, that the control electronics are designed, on the one hand, to serially receive the control data for a Hall sensor to be activated and, on the other hand, to directly activate the Hall sensors in parallel and in accordance with the control, and that the Hall sensors are directly connected to the signal line designed as an analog Hall signal bus line.

[0009] DE 101 24 761 A1 discloses a sensor array for contactless linear position measurement, comprising at least two magnetic field sensors that emit signals each having a maximum value, a minimum value, and an intermediate half-level. The magnetic field sensors are spaced such that one magnetic field sensor emits a maximum value when the immediately adjacent one emits a half-level signal. For evaluation, the signals of two immediately adjacent magnetic field sensors are divided, and the arctangent is calculated from the result.

[0010] EP 2 466 269 B1 discloses a position sensor device, particularly suitable for use in conjunction with a linear drive device, which comprises a variable number of sensor modules that can be arranged in series to form a module string. The sequential sensor modules are electrically linked to one another and can each generate an individual measurement signal, based on which a uniform position signal is generated and output at a communication interface.

[0011] DE 10 2012 205 903 A1 describes a displacement sensor for non-contact measurement of the relative position of a magnetic field source generating a magnetic field and a magnetic field sensor with respect to each other, wherein the magnetic field source and the magnetic field sensor are movable relative to each other. A plurality of magnetic field probes generate a plurality of position signals, each magnetic field probe detecting at least two spatial components of a magnetic flux density of the magnetic field.A control and calculation unit calculates an output signal of the displacement sensor based on the plurality of position signals, and a storage unit stores the individual position signals, wherein the control and calculation unit calculates a magnitude of the magnetic flux density and compares it with a predetermined threshold value to output the current calculated position signal for each magnetic field probe if the magnitude of the magnetic flux density is higher than the threshold value, and to output a previous stored position signal if the magnitude of the magnetic flux density is less than or equal to the threshold value.

[0012] From DE 10 2010 028 333 A1, a transport device for conveying a product is known, wherein the transport device comprises a movable conveyor element provided for conveying the product, having a grid that extends over a predetermined grid length in the direction of movement of the conveyor element and has a plurality of path increments; a stationary, circumferentially arranged guide rail defining a travel path for the conveyor element, with a plurality of position sensors on the travel path, the distances between which are smaller than the grid length;and a measuring device designed to determine a current position of the conveyor element on the travel path, wherein the measuring device, when the grid enters and / or exits the measuring range of a position sensor, sets the current position to a reference position of the conveyor element on the travel path derived from the position of the corresponding position sensor, monitors at least one of the position sensors in whose measuring range the conveyor element is located, and increments or decrements the current position when a path increment passes a monitored position sensor.

[0013] The object of the invention is to provide a linear drive system and a method for determining two positions of two measuring elements that are moved along a movement path of a linear drive system with improved accuracy.

[0014] This object is achieved for a sensor system of the type mentioned at the outset with the features of claim 1. It is provided that the processing device is designed for synchronous detection of sensor signals from the sensors, wherein the processing device comprises a clock generator and a plurality of sensor interfaces for parallel coupling to the sensors, wherein each of the sensor interfaces is connected to the clock generator, which is designed to provide a readout signal to the sensor interfaces.

[0015] This enables the creation of a precise position image for the at least two measuring elements, preferably for several, in particular for all measuring elements arranged along the movement path. Due to the synchronous acquisition of the sensor signals, measurement errors can be eliminated that are due to the temporally successive and thus sequential acquisition of sensor signals from the sensor elements, as is provided for in the prior art.Such a precise position image is particularly important when one or more measuring elements are moved at the same or different speeds along the movement path, and either the movements of the measuring element(s) are to be influenced based on the at least one determined position signal, or the machining devices intended for machining the measuring elements or workpieces associated with the measuring elements are to be influenced. For example, it can be provided to influence a movement device used for moving the measuring element(s) based on the at least one determined position signal in order to impose a predeterminable speed profile on the measuring element(s).Additionally or alternatively, it may be provided to control one or more processing devices based on the at least one determined position signal in order to enable customized processing of at least one of the measuring elements or of a workpiece assigned to the respective measuring element. Purely by way of example, to illustrate the possible influences, laser marking of a workpiece assigned to a measuring element and moved past a processing device designed as a laser marking system at a predetermined or variable speed can be mentioned. The marking process is adapted depending on the speed of the workpiece in order to always be able to apply the same marking regardless of the workpiece's speed.Even if only a single measuring element is positioned or moved along the movement path, the processing device according to the invention enables a highly accurate determination of the position and / or the movement speed of the measuring element, since the influences of different signal propagation times, such as occur in a serial readout process for several sensors, can be minimized or completely eliminated by the synchronous detection of the sensor signals of the sensor elements in the processing device.

[0016] Preferably, the processing device according to the invention provides for parallel acquisition of sensor signals, in particular all sensor signals from the sensors arranged along the partial section of the movement path. To ensure synchronization in the acquisition of the sensor signals from the sensors, the processing device can be designed to simultaneously address all sensors to be acquired synchronously and also simultaneously to temporarily store the sensor signals provided by the addressed sensors for further processing. For example, it is provided that all sensors to be acquired are addressed by a single trigger signal, wherein this trigger signal is output from a clock generator to all sensors to be acquired via parallel branched lines.When the trigger signal arrives at the individual sensors, they immediately transmit their sensor signals to the processing device, ensuring synchronization. This is especially true given that delays between the sensor signals arriving at the processing device can only occur due to different electrical cable lengths and / or circuit-related tolerances of the individual sensors. However, these delays are completely negligible given the propagation times for the electrical signals and the speeds to be measured, which, for example, can be assumed to be in the range of a few mm / s to 10 m / s in transport systems.

[0017] In principle, the sensors can be arranged along the entire movement path. For practical reasons, it may be advantageous if the sensors are arranged only along a partial section of the movement path. Suitable measures can be taken to ensure that the detection of measuring elements is also possible within a predefined area outside the partial section of the movement path.

[0018] Advantageous further developments of the invention are the subject of the subclaims.

[0019] It is expedient if the sensors are designed to determine at least one physical quantity from the group: magnetic field strength, magnetic field direction, electromagnetic induction, electric field strength, illuminance, sound intensity, in particular as multi-dimensional Hall sensors. For example, it can be provided that the measuring element is designed as a permanent magnet and provides a magnetic field that can be detected by the respective sensors. The sensors can be designed as Hall sensors, in particular as at least two-dimensional Hall sensors. Alternatively, the sensors can also be designed as coils in which a voltage is induced by a relative movement of the measuring element designed as a permanent magnet, which voltage can also be evaluated as a sensor signal.In an alternative embodiment of the sensors, they are designed as inductive proximity switches, in which the oscillation frequency of a resonant circuit comprising an induction coil is detuned by the presence of a sensing element, for example, a ferritic one. This allows information about the relative position of the sensing element to be obtained from this. Sensors designed as capacitive or optical sensors can also be provided as a supplement or alternative.

[0020] When using Hall sensors, three-dimensional Hall sensors can be provided, in particular, which are designed to determine magnetic field strengths in three mutually perpendicular spatial directions. For pure position detection, preferably, only two signals from the three-dimensional Hall sensor are evaluated, which are generated by two mutually perpendicular field strength components, while a third signal, determined by a third field strength component, is ignored. It is particularly preferred that the two magnetic field strength components used for position detection be determined with the same Hall sensor measuring cell, which is read alternately in mutually perpendicular directions.

[0021] In an advantageous development of the invention, adjacent sensors are arranged along the partial section of the movement path in such a way that, along the partial section of the movement path, detection of the measuring element by at least two sensors, each providing a predeterminable minimum sensor signal level, is always guaranteed. Thus, sensor signals from adjacent sensors can always be compared to obtain a particularly precise position signal. If the sensors are arranged at different, in particular irregular, distances from one another along the partial section of the movement path, error compensation for the sensor signals can be carried out in the processing device in order to eliminate the different distances between the sensors and the resulting deviations in the sensor signals.Such compensation can be achieved, for example, by a prior calibration of the sensor system, in which one or more measuring elements are provided with a high-precision displacement measuring system and sensor signals of the displacement measuring system are compared with the sensor signals of the sensor system and stored, for example, in the form of a calibration curve in the processing device.

[0022] In a further embodiment of the invention, it is provided that at least some of the sensors are arranged uniformly with a first pitch along the partial section of the movement path and / or that at least some of the sensors, in particular all sensors, are arranged on a placement path, in particular a placement line, which runs parallel to the partial section of the movement path.

[0023] The pitch here is considered the distance between adjacent sensor cells, each housed in discretely designed housings, while the distance between adjacent housings is referred to as the housing pitch. The sensor signals from those sensors that are evenly arranged with a first pitch along the movement path can preferably be used without prior calibration of the sensor system, since positional deviations of these sensors depend solely on a component tolerance that arises during assembly of the sensors, for example, on a printed circuit board. Since such positional deviations are usually in the range of a few 1 / 100 of a millimeter, it is possible to compare the sensor signals provided by these sensors purely mathematically.Preferably, the arrangement of sensors with the first pitch results in a housing spacing between discretely configured, individually equipped sensors, which is measured based on the detection ranges of the sensors and a range of influence of the measuring elements, and which, in practical terms, corresponds, for example, to at least 50 percent of the extension of the housings used for the sensors along the movement path. This enables a cost-effective sensor system in which an advantageous compromise can be found between the required overlap of detection ranges of adjacent sensors and the number of sensors used.

[0024] Preferably, the measuring elements are mounted on moving components, such as the rotors of a linear motor system, in such a way that adjacent measuring elements are always spaced apart from one another by at least approximately twice the pitch of the sensors arranged in a regular first pitch. This makes it possible to suppress any undesirable influence of a more distant measuring element on sensor signals from sensors intended to detect a more closely arranged measuring element.

[0025] Since it is preferably provided that at least some of the sensors, in particular all of the sensors, are arranged on a placement path, in particular a straight placement line, which runs parallel to the partial section of the movement path, further tolerance influences on the sensor signals of the sensors can be minimized. In particular, a distance between the respective sensors and the measuring element transverse to the movement path is at least substantially constant and thus has only a minor, preferably negligible, influence on the sensor signals of the sensors. This applies in particular when two mutually perpendicular field components of a magnetic flux provided by the measuring element are determined using a multi-dimensional Hall sensor, wherein a first magnetic field component extends along the movement path and wherein a second field component is oriented transversely to the movement path and transversely to a magnetic polarity of the measuring element.In this case, during a relative movement of the measuring element, curves for the respective field components are established at each of the sensors, which correspond to a sine function and a cosine function and which are converted in the sensor or in the processing device with the aid of an arctangent function into a linearized sensor signal which is independent of a distance between the sensor and the measuring element in a direction transverse to the movement path.

[0026] It is advantageous if, at at least one end region of the partial section of the movement path, two adjacently arranged sensors, in particular a first and a second sensor arranged along the movement path and / or a penultimate and a last sensor arranged along the movement path, are arranged with a second pitch that is selected to be smaller than the first pitch. This measure makes it possible to detect the position of a measuring element with sufficient accuracy even if this measuring element is located within a predeterminable measuring window away from the partial section of the movement path. In the same way as with an arrangement of the measuring element along the partial section of the movement path, the assumption is that at least two sensors each provide a predeterminable minimum level of the sensor signal.Provided the measuring element is located within the predeterminable measuring window, for example, a first and a second sensor arranged along the movement path, or a second-to-last and a last sensor arranged along the movement path, each still deliver sensor signals that meet the requirements for the predeterminable minimum level for the sensor signal and thus also enable a comparison of the two sensor signals, thereby enabling the desired precision in position determination. By way of example, it is provided that the sensor device has exactly two sensors arranged at the second pitch relative to each other at each end region of the partial section of the movement path, while all other sensors are arranged according to the first pitch relative to each other.This results in a first and a second sensor arranged along the movement path having a distance corresponding to the second pitch, while the distance from the second sensor to the third sensor corresponds to the first pitch. Furthermore, the second-to-last and the second-to-last sensor are also arranged at a distance according to the first pitch, while a distance between the second-to-last sensor and the last sensor corresponds to the second pitch. By way of example, it can be provided that a housing distance for sensors arranged according to the first pitch corresponds at least approximately to an extension of the housing along the movement path, while a housing distance of sensors arranged according to the second pitch is designed, for example, as a minimum distance between the adjacent housings of the sensors due to production technology.

[0027] It is preferably provided that each of the sensors is accommodated in a separately formed housing and is arranged on a printed circuit extending along the partial section of the movement path and / or that the processing device has a plurality of sensor interfaces which are designed as serial peripheral interfaces.

[0028] It is advantageous if all sensors are housed in identically designed housings, which are particularly designed as SMD housings for surface soldering. For a stationary arrangement of the sensors along the movement path and an electrical connection of the sensors to the processing device, it is preferably provided that the sensors are arranged on a printed circuit, which can be, for example, a printed circuit board or a flexible conductor foil, and which is fixed in a defined manner to a component that determines the movement path, in particular designed as a stator of a linear motor arrangement.The processing device can, for example, be designed as a programmable gate module (FPGA - Field Programmable Gate Array) and comprises a plurality of sensor interfaces, so that each of the sensors arranged along the partial section of the movement path can communicate with the processing device via its own sensor interface. Furthermore, it is provided that each of the sensor interfaces is connected to a clock generator designed to provide a readout signal to the interfaces. Preferably, the clock generator is designed as an oscillator with a predeterminable or fixed clock frequency, so that trigger signals are regularly provided to the sensor interfaces, which can accordingly read out their assigned sensors at regular intervals and feed the readout sensor signals for further processing.Alternatively, it can also be provided that the clock generator outputs trigger signals at irregular time intervals, for example depending on predeterminable operating states of the sensor system and / or the state of a downstream control device.

[0029] According to the invention, the sensor interfaces are designed as serial peripheral interfaces (SPI - Serial-Peripheral Interface) in order to ensure cost-effective and robust communication between the sensors and the processing device.

[0030] It is expedient if the processing device is electrically connected to an output interface, in particular designed as a synchronous serial interface (SSI) or as a Drive-Cliq bus interface (Drive-Cliq is a registered trademark of Siemens AG), which is configured to provide the at least one position signal to a communication system, preferably designed as a multi-conductor arrangement or as a bus system. The output interface has the task of forwarding the position signals determined in the processing device to a control device, in particular a higher-level control device. This control device can, for example, be provided to influence the measuring elements or components assigned to the measuring elements and / or processing devices provided for processing the measuring elements or components.

[0031] In a further embodiment of the invention, the processing device is electrically connected to a display device comprising display elements arranged along a placement path running parallel to the partial section of the movement path, which display elements are configured to output status signals depending on the determined position signals, and / or the partial section of the movement path is formed by a stator of a linear drive system, wherein the measuring element is assigned to a carrier movable along the stator. For example, the display device can be formed from LEDs arranged in a row, which are controlled by the processing device in such a way that those LEDs that are at a minimum distance from the respective measuring element light up with maximum intensity.This enables a particularly quick visualization of the position of the measuring element along the movement path.

[0032] According to the invention, the sensor system is used to detect supports of a linear drive system, in particular a fluidically or electrically operated one, and is preferably attached to a stator of the linear drive system, which is, for example, a cylinder housing of a hydraulic cylinder or pneumatic cylinder, a housing of a hydraulic or pneumatic rotary actuator, or a coil arrangement of an electrodynamic linear motor. The support can, for example, be a piston of a fluid cylinder movably received in a cylinder housing, or a rotor for an electrodynamic linear motor.

[0033] The object of the invention is achieved by a method for determining two positions of two measuring elements that are moved along a movement path of a linear drive system, wherein the method comprises the following steps: contactless detection of at least one physical quantity that is dependent on the position of the respective measuring element along the movement path, with several sensors arranged along a partial section of the movement path, synchronous detection of sensor signals from the sensors by a processing device that is electrically connected to the sensors, processing of the sensor signals to a position signal that represents the position of the measuring element along the movement path, wherein the sensors are designed to detect magnetic field components of the magnetic fields provided by the two measuring elements,wherein at least two mutually perpendicular magnetic field components are detected by the respective sensor and processed into a sensor signal, and wherein the processing device compares the synchronously detected sensor signals of the sensors with a predeterminable minimum level for the sensor signal and processes those sensor signals of at least pairs of adjacent sensors arranged along the partial section of the movement path into at least one position signal which are above the predeterminable minimum level.

[0034] An advantageous embodiment of the invention is illustrated in the drawing. Fig. 1 is a schematic representation of a sensor system used to detect measuring elements attached to carriages for a linear drive system not shown in detail, and Fig. 2 a highly schematic representation of detection ranges and signal levels of individual sensors of the Fig. 1 shown sensor system, and Fig. 3 is a detail enlargement of an arrangement of several sensors with identical pitch, not belonging to the invention.

[0035] One in the Fig. The sensor system 1 shown in Figure 1 is designed to detect the positions of a plurality of measuring elements 3 movable along a movement path 2. Purely by way of example, the measuring elements 3 are designed as cuboid-shaped permanent magnets with a north-south magnetization oriented transversely to the movement path 2, each symbolized by arrows, and are attached to carriages 4 of a linear motor arrangement (not shown in detail) that are movable linearly along the movement path 2. To detect the position of these carriages 4, the sensor system 1 comprises a plurality of sensors 5, which are accommodated, for example, in rectangular housings 6. The housings 6 are arranged, for example, on a rectangular printed circuit 7 in an electrically conductive manner and mechanically firmly connected to the circuit. Each of the sensors 5 comprises a measuring cell (not shown in detail) that is designed to detect a physical quantity.In the illustrated embodiment, the measuring cells of the sensors 5 are each designed as multi-dimensional Hall sensors, which are arranged, for example, along the movement path 2 and normal to the representation plane of the . Fig. 1 aligned magnetic field components of the magnetic field provided by the measuring element 3. To identify the position of the respective measuring cell within the sensor 5, each of the sensors 5 is provided with a center point.

[0036] The sensors 5 are each electrically connected via sensor lines 8 to a processing device 9, which is designed for synchronously detecting signal levels of the respective sensors 5 and for processing the determined signal levels into at least one position signal. Purely by way of example, the processing device 9 is designed as an FPGA and includes a dedicated sensor interface 10 for each sensor 5. The processing device 9 further includes an output interface 11, which can be designed for communication with a higher-level control device (not shown) or with another sensor system (also not shown).For example, the output interface is designed as a Drive-Cliq bus interface and thus enables bus communication with a higher-level controller (not shown) from the controller manufacturer Siemens, which is designed for coupling sensors using the Drive-Cliq bus protocol.

[0037] The sensors 5 are applied to the printed circuit 7, for example, along a mounting path 12 running parallel to the movement path and, in the illustrated embodiment, linear. For example, the sensors 5 can be designed for surface solder mounting (SMD surface mount device) and, during the manufacture of the sensor system 1, are placed on the printed circuit 7 using a pick-and-place method with the aid of an automatic mounting system (not shown).

[0038] By way of example, it is provided that the sensors 5 are arranged at two different pitches along the movement path 2. When viewing the sensors 5 from left to right, the first sensor 5.1 and the second sensor 5.2 are arranged at a minimum distance 15 from one another, which results from the size of the housing 6. The sensors 5.3, 5.4, 5.5 and 5.6 following the second sensor 5.2, in contrast, are arranged at a larger distance 16. The last two sensors 5.6 and 5.7, in contrast, are again arranged at the minimum distance 15 from one another. The larger distance 16 can also be referred to as the first pitch, while the smaller distance 15 can also be referred to as the second pitch.

[0039] The processing device 9 is configured to process only sensor signals from those sensors 5 whose signal level lies above a predeterminable minimum level. Furthermore, the processing device 9 is configured to provide a position signal for a position of a measuring element to the output interface 11 only if at least two adjacently arranged sensors 5 each provide a sensor signal with a signal level lying above the predeterminable minimum level and if a comparison of the two sensor signals leads to a plausible position signal. Due to these conditions stated above, it follows that the sensor system 1 is not designed to detect the entire movement path 2, but rather to detect a Fig. 1 symbolically marked section 17 of the movement path 2.

[0040] Furthermore, the processing device 9, through its internal architecture, which can be embodied in particular as an FPGA, is configured to synchronously capture the sensor signals of all sensors 5. This avoids errors that could occur, for example, during the detection of moving measuring elements 3 and the sequential detection of sensor signals from sensors. Rather, by synchronously controlling all sensor interfaces 10 with a clock generator (not shown) assigned to the processing device 9, the processing device 9 also performs a synchronous query of all sensors 5.The sensor signals arriving at the sensor interfaces 10 can then be further processed either in parallel or sequentially in the processing device 9 to form one position signal or, if appropriate, several position signals; this depends on whether only one measuring element 3 or several measuring elements 3 are located within the section 17 of the movement path 2 that can be detected by the sensor system 1.

[0041] As can be seen from the presentation of the Fig. 1 and Fig. 2, the section 17 of the movement path 2 extends laterally beyond a length 18, which is determined by the housings 6 of the sensors 5. The boundaries 19, 20 of the section 17 result from an interaction of a highly schematically represented magnetic minimum flux density 21 of the measuring element 3 designed as a permanent magnet with purely exemplary triangularly formed detection areas 22 of the sensors 5. It is assumed, for example, that a sensor 5 can only provide a sensor signal with a signal level above a predeterminable minimum level if there is an overlap of the exemplary trapezoidally limited magnetic minimum flux density 21 with the respective detection area 22 of the sensor 5. The left in the Fig. 2 is arranged such that the minimum flux density 21 covers the detection range 22 of both sensor 5.1 and sensor 5.2. This results in the signal levels shown purely schematically under the respective sensors 5. In the same way, the right boundary 20 results for the partial section 17, without a corresponding measuring element 3 being arranged here. Thus, as soon as a measuring element 3 approaches the sensor system 1, for example, coming from the left along the movement path 2, the sensors 5.1 and 5.2 provide usable sensor signals to the processing device 9 from the point in time at which the measuring element 3 has passed the left boundary 19.From this point on, the sensor system 1 can always process at least two usable sensor signals into one position signal until the measuring element 3 passes the right boundary 20 and thus the condition that the detection areas 22 of at least two sensors 5 are covered by the minimum flux density 21 is no longer met.

[0042] By way of example, the sensor system 1 comprises a display device 30, which is electrically connected to the processing device 9 in a manner not shown in detail. By way of example, the display device 30 is implemented as a series of display elements 31, each arranged at the same pitch and designed in particular as light-emitting diodes. With the display device 30, for example, determined position values ​​for measuring elements 3 can be visualized by lighting up and extinguishing respectively assigned display elements 31, as is shown by way of example in the Fig. 1 is shown.

[0043] The Fig. 3 serves to demonstrate the advantage of arranging the sensors 5 with different pitches 15, 16 along the movement path 2, as is the case with the sensor system according to the Fig. 1 and Fig. 2 is realized. The Fig. 3 only the two left sensors 5.1 and 5.2, as shown in the Fig. 1 and Fig. 2 are known, whereby in the sensor system according to the Fig. 3 all sensors 5 are arranged in the same pitch, so that a distance 25 between the two sensors 5.1 and 5.2 is identical to the distance 23 for the Fig. 1 and Fig. 2 known sensors 5.3 to 5.5. Compared with the Fig. 2 it can be seen that despite the increased distance 16 between the two sensors 5.1 and 5.2 in the embodiment of the Fig. 3 a distance 25 between the left boundary 19 and the second sensor 5.2 is identical to the distance 23 between the left boundary 19 and the second sensor 5.2 according to the Fig. 2. This means that despite an increase in the length of the sensor system according to the Fig. 3 no enlargement of the movement path 2 detectable by the sensors 5 compared to the embodiment according to the Fig. 1 and Fig. 2 occurs. Accordingly, the sensor system according to the embodiment of the Fig. 1 and Fig. 2 a measuring element 3 can be detected within a section 17 of the movement path 2, which is identical to a section not shown in detail for the embodiment of a sensor system according to Fig. 3 is.

Claims

[1] Linear drive system with a sensor system for detecting a position of a plurality of carriers (4) which are movable along a movement path (2) determined by a stator of the linear drive system and each provided with a measuring element (3), wherein a first carrier (4) is assigned a first measuring element (3) and wherein a second carrier (4) is assigned a second measuring element (3), wherein the sensor system comprises a sensor arrangement (1) which comprises a plurality of sensors (5) arranged at least along a partial section (17) of the movement path (2), each of which is designed for contactless detection of at least one physical variable dependent on a position of a measuring element (3) along the movement path (2) and for providing at least one sensor signal dependent on the at least one determined physical variable, and wherein the sensor system comprises a processing device (9),which is electrically connected to the sensors (5) and which is designed to process the sensor signals into a first position signal representing the position of the first measuring element (3) along the movement path (2) and into a second position signal representing the position of the second measuring element (3) along the movement path (2), wherein the processing device (9) is designed for synchronous detection of sensor signals from the sensors (5), wherein the processing device (9) comprises a clock generator and a plurality of sensor interfaces (10) for parallel coupling to the sensors (5), wherein each of the sensor interfaces (10) is connected to the clock generator, which is designed to provide a readout signal to the sensor interfaces (10). [2] Linear drive system according to claim 1, characterized bythat the sensors (5) are designed to determine at least one physical quantity from the group: magnetic field strength, magnetic field direction, electromagnetic induction, electric field strength, illuminance, sound intensity. [3] Linear drive system according to claim 1 or 2, characterized by that adjacently arranged sensors (5) are arranged along the partial section (17) of the movement path (2) in such a way that along the partial section (17) of the movement path (2) detection of the measuring element (3) by at least two sensors (2), each of which provides a predeterminable minimum level of the sensor signal, is always ensured. [4] Linear drive system according to claim 3, characterized bythat at least some of the sensors (5) are arranged uniformly along the partial section (17) of the movement path (2) with a first pitch (16) and / or that at least some of the sensors (5) are arranged on a placement track (12) which runs parallel to the partial section (17) of the movement path (2). [5] Linear drive system according to claim 4, characterized by that at least one end region of the partial section (17) of the movement path (2) two adjacently arranged sensors (5) are arranged with a second pitch (15) which is selected to be smaller than the first pitch (16). [6] Linear drive system according to one of the preceding claims, characterized bythat each of the sensors (5) is accommodated in a separately formed housing (6) and is arranged on a printed circuit (7) extending along the partial section (17) of the movement path (2) and / or that the processing device (9) comprises a plurality of sensor interfaces (10) which are designed as serial peripheral interfaces. [7] Linear drive system according to one of the preceding claims, characterized by that the processing device (9) is electrically connected to an output interface (11) which is configured to provide the at least one position signal to a communication system. [8] Linear drive system according to one of the preceding claims, characterized byin that the processing device (9) is electrically connected to a display device (30) which comprises display elements (31) arranged along a placement path (12) running parallel to the partial section (17) of the movement path (2), which display elements are designed to output status signals as a function of the determined position signals. [9] Method for determining two positions of two measuring elements (3) that are moved along a movement path (2) of a linear drive system, comprising the steps of: contactless detection of at least one physical quantity that is dependent on the position of the respective measuring element (3) along the movement path (2), with a plurality of sensors (5) arranged along a partial section (17) of the movement path (2), synchronous detection of sensor signals from the sensors (5) by a processing device (9) that is electrically connected to the sensors (5), processing of the sensor signals to a position signal that represents the position of one measuring element (3) along the movement path (2), wherein the sensors (5) are designed to detect magnetic field components of the magnetic fields provided by the two measuring elements (3),wherein at least two mutually perpendicular magnetic field components are detected by the respective sensor (5) and processed into a sensor signal, and wherein the processing device (9) compares the synchronously detected sensor signals of the sensors (5) with a predeterminable minimum level for the sensor signal and processes those sensor signals of at least pairs of adjacent sensors (5) arranged along the partial section (17) of the movement path (2) into at least one position signal which are above the predeterminable minimum level.

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