Method and device for detecting at least one reference mark

Abstract

Method for detecting at least one reference mark (57) of a set of increment marks of a sensor wheel (53, 54), wherein the set of increment marks comprises normal increment marks (55) and at least one reference mark (57), wherein a first sensor signal is detected upon a rotational movement of the sensor wheel (53, 54), wherein a normal increment mark (55) and a space (56) following the normal increment mark (55) generate a first increment profile with a first increment period in the first sensor signal, wherein the reference mark (57) and a space (56) following the reference mark (57) generate a second increment profile with a second increment period in the first sensor signal, wherein a second sensor signal is detected at the same time, wherein the second sensor signal is equal to the first sensor signal but phase-shifted by a first phase angle with respect to the first sensor signal,wherein at least one unit (26) for determining a direction of rotation determines a first or second direction of rotation, wherein at least one unit (40) for detecting the reference mark (57) detects the reference mark (57) as a function of the direction of rotation, the first and the second sensor signal, wherein the at least one unit (40) for detecting the reference mark (57) detects the reference mark (57) as a function of a difference signal (17), wherein the difference signal (17) is generated from a difference between the first sensor signal and the second sensor signal, characterized in that the at least one unit (40) for detecting the reference mark (57) additionally detects the reference mark (57) as a function of a summation signal (37), wherein the summation signal (37) is formed from a sum of the first and the second sensor signal.

Description

[0001] The invention relates to a method and a device for detecting at least one reference mark.

[0002] Currently, speed sensors, particularly real-time speed sensors, are used to detect the position, rotational speed, and direction of rotation of a rotating shaft. Specifically, such speed sensors are used to detect the position, rotational speed, and direction of rotation of a crankshaft in a motor vehicle with at least one internal combustion engine. The most precise possible detection of the position, rotational speed, and direction of rotation enables optimal control of the internal combustion engine, for example, to achieve minimal emissions and fuel consumption.

[0003] Essentially, three sensors and operating principles can be distinguished that have become established for use in motor vehicles: 1. Inductive sensors with a magnetically conductive encoder wheel, 2. Hall sensors with a magnetically conductive encoder wheel, 3. Hall sensors with a magnetized encoder wheel.

[0004] In this system, a so-called encoder wheel is rigidly coupled to the crankshaft. The encoder wheel has increment markers, which are typically designed as teeth. When the crankshaft rotates, the encoder wheel turns with it, and the increment markers on the encoder wheel pass the sensor. This rotation of the crankshaft generates a time-varying magnetic field. Depending on this time-varying magnetic field, the sensor generates a time-varying signal. If the increment markers are designed as teeth, for example, each marker generates a rising and then a falling edge as it passes the sensor. A rising edge of the sensor signal occurs when an increment marker enters a measuring range of the sensor. A falling edge of the sensor signal occurs when the increment marker leaves the measuring range of the sensor.The frequency of rising and / or falling edges can be used, for example, to calculate the rotational speed of an internal combustion engine. For this purpose, the increment marks are typically arranged at equal intervals around the circumference of the encoder wheel and are identical in design. So-called gaps are usually arranged between the increment marks. In this case, each increment mark is followed by a gap.

[0005] Other known methods involve a second sensor detecting a second sensor signal, where the second sensor signal is identical to the first sensor signal but phase-shifted relative to it by a first phase angle. By evaluating the sequence of rising and falling edges in the first and second sensor signals, the direction of rotation of the crankshaft can be determined.

[0006] To determine the absolute position or angle of rotation of the crankshaft, it is known to arrange a so-called reference mark on the sensor wheel in addition to the increment marks. A gap also follows the reference mark. The reference mark is designed differently from the increment marks. Due to this different design, the reference mark generates a signal profile when it passes the sensor, which differs from the signal profile of an increment mark. This enables signal-based detection of the reference mark and thus the determination of the absolute position of the crankshaft.

[0007] It is also known from the prior art that a reference mark is formed by at least one missing increment mark. Therefore, such a reference mark can also be called a gap mark. A so-called gap also follows the reference mark. It is also known that a partial circumference of the encoder wheel formed by the reference mark and a gap following the reference mark is longer, e.g., twice as long, than the partial circumference of the encoder wheel formed by an increment mark and a gap following the increment mark. The gap following the reference mark up to the next increment mark can also be configured such that a partial circumference of the encoder wheel formed by this gap is longer, e.g., twice as long, than a partial circumference of the encoder wheel formed by a gap following an increment mark.

[0008] Methods for detecting a reference mark are generally based on the evaluation of time intervals of the edges in the sensor signals.

[0009] DE 10 2005 050 247 A1 discloses a method for detecting at least one reference increment mark from a set of increment marks of an encoder wheel, wherein the set of increment marks comprises normal increment marks and at least one reference increment mark. When the encoder wheel rotates, the set of increment marks, in conjunction with a sensor, generates a first-order edge and a second-order edge in a time-varying signal as they pass over the sensor. The transition time is defined as the time interval between the first-order edge and the preceding second-order edge. The transition time of the first-order edge generated by the at least one reference increment mark differs, during uniform rotation of the encoder wheel, from the transition times of the first-order edges of the normal increment marks.Furthermore, when determining whether the associated first-type flank is generated by the at least one reference increment mark, a rotational speed dynamic that is linked to a temporal change in the rotational speed of the encoder wheel is taken into account.

[0010] DE 197 50 305 A1 discloses a method for evaluating the output signal of a sensor. The sensor scans a rotating element with a number of identical markers and at least one distinguishable marker forming a reference mark. The sensor further provides a speed-dependent pulse sequence with a number of identical pulses and a singular pulse, wherein the time intervals between the pulses are determined in an evaluation unit. Quotients are calculated from these time intervals, which are compared with threshold values ​​to detect the reference mark. A reference mark is marked if the comparison yields a predefined result. A reference mark is ultimately detected only when a second predefined condition is met, whereby the second condition can be determined by counting the pulses of the pulse sequence.

[0011] One disadvantage of the aforementioned methods is that determining position, rotational speed, and direction of rotation by evaluating the time intervals between edges in the sensor signal is prone to errors. For example, the time interval between edges can be influenced by the acceleration or deceleration of the internal combustion engine. This can potentially lead to the erroneous detection of a reference mark that is not actually present. A further disadvantage is that mechanical tolerances and / or electromagnetic interference can affect the quality of the sensor signals and thus reduce the accuracy of the measurement results.

[0012] DE 103 22 689 A1 discloses a crank angle detection device for detecting the crank angle of the crankshaft of an internal combustion engine, and it relates in particular to a crank angle detection device that is capable of identifying the direction of rotation of the crankshaft.

[0013] US Patent 2005 / 0283300 A1 discloses a method and a process for determining the position of an internal combustion engine with a rotating element.

[0014] US Patent 6,573,710 B1 discloses magnetic sensors for determining the speed, direction, rotation and / or position of an element moving relative to the sensor.

[0015] The technical problem is to create an improved method for detecting at least one reference mark, in particular one that is more robust against mechanical tolerances and / or electromagnetic interference and that is independent of rotational speed dynamics.

[0016] The solution to the technical problem arises from the features of independent claims 1 and 7. Further advantageous embodiments of the invention arise from the dependent claims.

[0017] A method is proposed for detecting at least one reference mark from a set of increment marks on a encoder wheel, wherein the set of increment marks comprises normal increment marks and at least one reference mark. The increment marks can be arranged on the circumference of the encoder wheel. Preferably, the increment marks are designed as teeth. Furthermore, the normal increment marks are arranged at equal intervals. So-called gaps are arranged between successive normal increment marks. The length of a normal increment mark refers to the portion of the encoder wheel's circumference formed by that normal increment mark. The length of a gap refers to the portion of the encoder wheel's circumference formed by the gap.The length of the increment mark and the space between it can also be understood as the length of a circular arc with a specific central angle, where the arc is part of a circular cross-section of the encoder wheel. The length of the normal increment marks and the length of the spaces following them can be equal. Furthermore, at least one reference mark is arranged on the circumference of the encoder wheel. A reference mark can, for example, be formed by a missing normal increment mark. It is also conceivable that the length of the reference mark and / or the length of the space following it is longer or shorter than the length of the normal increment marks or the spaces following them.

[0018] During a rotational movement, a first sensor signal is acquired, for example, by means of a first sensor signal acquisition unit. As the encoder wheel rotates, it can, for instance, be moved past the first sensor signal acquisition unit. A standard increment mark and the space following it generate a first increment profile with a first increment period in the initial sensor signal. This first increment profile can, for example, be a rectangular or sinusoidal profile. Here, the first part of the first increment profile is generated by the standard increment mark, and the second part by the space following it.The ratio of the duration of the first part of the first increment profile to the duration of the second part of the first increment profile corresponds to the ratio of the length of the normal increment mark to the length of the interval following the normal increment mark. The first sensor signal is thus a time-varying signal. Similarly, when the encoder wheel rotates, the reference mark in the first sensor signal generates a second increment profile with a second increment period. Several alternatives exist for distinguishing the first and second increment profiles. For example, the second increment period can be shorter, but preferably longer, than the first increment period. Furthermore, the duration of the first part of the first increment profile can be longer, but preferably shorter, than the length of the first part of the second increment profile.The first increment period can also be equal to the second increment period, provided that at least the length of the first part of the first increment profile and the length of the first part of the second increment profile differ. Alternatively, the length of the first part of the first increment profile can be equal to the length of the first part of the second increment profile, or the length of the second part of the first increment profile can be equal to the length of the second part of the second increment profile, provided that the first increment period is not equal to the second increment period. In this case, the increment period is equal to the duration of the first part of the increment profile plus the duration of the second part of the increment profile. The first sensor signal can, for example, have rising and falling edges. A rising edge can, for example,A falling edge of the first sensor signal can be generated by a normal increment mark or a reference mark that is moved into a measuring range of the unit for acquiring a first sensor signal by the rotational movement. A falling edge of the first sensor signal can be generated, for example, if a normal increment mark or the reference mark is moved out of the measuring range of the unit for acquiring a first sensor signal by the rotational movement.

[0019] Simultaneously with the first sensor signal, a second sensor signal is acquired, for example, by a second sensor signal acquisition unit. The second sensor signal is identical to the first sensor signal but phase-shifted relative to it by a first phase angle. For example, the second sensor signal acquisition unit can be spatially offset from the first sensor signal acquisition unit such that a desired first phase angle exists between the first and second sensor signals. Preferably, the first phase angle is 180°. Analogous to the first sensor signal, the second sensor signal also exhibits rising and falling edges, which are generated by the passage of the normal increment markers and the at least one reference marker past the second sensor signal acquisition unit.

[0020] A unit can calculate the rotational speed of the encoder wheel from the first and / or second sensor signal. This calculation utilizes the fact that the first increment period, the duration of the first part of the first increment profile, and the duration of the second part of the first increment profile in the first and second sensor signals depend on the rotational speed of the encoder wheel. For example, a duration can be determined between two consecutive rising or falling edges, and / or between a rising edge and the falling edge following the rising edge. It is also conceivable to perform a frequency analysis of the first and / or second sensor signal and determine a rotational speed based on the frequencies contained within the first and / or second sensor signal.

[0021] At least one unit for determining the direction of rotation defines a first or a second direction of rotation. The first direction of rotation can, for example, be a forward direction and the second direction of rotation a reverse direction. The direction of rotation can be determined, for example, from the first or the second sensor signal. The direction of rotation can be determined from the first sensor signal, for instance, if the rising and falling edges in the first sensor signal have different edge profiles, and the unit for determining the direction of rotation identifies these edge profiles and evaluates them with regard to the direction of rotation.

[0022] Furthermore, at least one unit for detecting a reference mark determines the reference mark depending on the direction of rotation and the first and second sensor signals. This reference mark can be configured in various ways. For example, the length of a standard increment mark can correspond to the length of a circular arc with a first central angle of, say, 3°. Here, the circular arc refers to a circular cross-section of the encoder wheel. Similarly, a space following a standard increment mark can have the length of a circular arc with the first central angle. Alternatively, the length of the reference mark can also correspond to the length of a circular arc with the first central angle, where the length of the space following the reference mark has the length of a circular arc with a second central angle of, say, 15°.If the first central angle is 3° and the second central angle is 15°, the second increment profile generated by the reference mark and the space following the reference mark can also be referred to as an 18° gap. Alternatively, the length of the reference mark can correspond to the length of a circular arc with a central angle of 6°, and the space following the reference mark can also have a length corresponding to the length of a circular arc with a central angle of 6°. This can be referred to as a 12° gap. Of course, other values ​​for the central angles are also conceivable.

[0023] By means of the unit for detecting a reference mark, at least one reference mark on the encoder wheel can be detected, and thus an absolute position or an absolute angle of rotation of the encoder wheel and, for example, a crankshaft rigidly coupled to the encoder wheel can be advantageously determined.

[0024] The proposed method advantageously provides a robust and simple detection of a reference mark within a set of increment marks of an encoder wheel. The proposed method operates independently of measuring the time interval between edges and is therefore advantageously robust against changes in rotational speed dynamics, mechanical tolerances, and electromagnetic interference. Furthermore, by detecting the at least one reference mark, it is advantageously possible to disregard the reference mark when calculating the rotational speed and determining the direction of rotation. This prevents the second increment profile generated by the reference mark and the space following it from distorting the calculation of the rotational speed and / or the determination of the direction of rotation.

[0025] In another embodiment, the unit for determining the direction of rotation determines the first or second direction of rotation from the first and second sensor signals. Here, the unit for determining the direction of rotation can evaluate a sequence of rising and / or falling edges in the first and second sensor signals. Preferably, the unit for determining the direction of rotation can determine the first or second direction of rotation from the first and a third sensor signal, wherein the third sensor signal is, for example, acquired by a unit for acquiring a third sensor signal. The third sensor signal is identical to the first sensor signal but is offset by a second phase angle relative to the first sensor signal. Of course, it is also conceivable that the direction of rotation is determined from the second and third sensor signals.If the direction of rotation is determined from the first and third sensor signals, the second phase angle can be, for example, 90°. If the direction of rotation is determined from the second and third sensor signals, the second phase angle can be selected such that the phase angle between the second and third sensor signals is, for example, 90°. Preferably, the second phase angle is not equal to the first phase angle. It is also conceivable that the first phase angle is twice as large as the second phase angle. By using three units for acquiring sensor signals, a less error-prone calculation of the rotational speed, determination of the direction of rotation, and determination of the absolute position of the encoder wheel can advantageously be carried out.

[0026] Furthermore, the at least one unit for detecting the reference mark detects the reference mark as a function of a differential signal and, according to the invention, as a function of a summation signal. The differential signal is generated from the difference between the first and second sensor signals. The summation signal is generated from the sum of the first and second sensor signals. Of course, it is also conceivable that the differential signal is formed from the first and third sensor signals or from the second and third sensor signals. In this case, however, the summation signal must also be generated from the first and third sensor signals or from the second and third sensor signals. Furthermore, the unit for calculating rotational speed can calculate the rotational speed, for example, from the differential signal.Generating a differential and summed signal advantageously improves robustness against mechanical tolerances during the manufacturing of the encoder wheel and enhances robustness against electromagnetic interference. This leads to increased accuracy in calculating the rotational speed, determining the direction of rotation, and determining the absolute position of the encoder wheel. For example, if the first phase angle is 180°, the differential signal is a mean-value-free signal and exhibits distinct zero crossings on rising and falling edges. These zero crossings can be easily detected, for example, using a comparator. Therefore, when generating a differential signal, it is advantageously unnecessary to adjust the offset of the first and second sensor signals.

[0027] In another embodiment, a zero-crossing detection unit detects at least one zero crossing of the difference signal. A zero crossing is detected when the amplitude of the difference signal undergoes a sign change. A sign change occurs, in particular, on rising edges from a negative to a positive sign and on falling edges from a positive to a negative sign of the amplitude. At the time of a zero crossing, the zero-crossing detection unit generates a trigger signal. The trigger signal allows the time of the zero crossing to be communicated to other units, especially storage units and analog-to-digital conversion units. The zero-crossing detection unit and the other units are connected via a data link, with the trigger signal being transmitted through this connection.The data connection can be implemented, for example, using a bus system, such as a CAN bus.

[0028] A signal edge identification unit identifies a rising or falling edge of the difference signal at the time of the zero crossing. A rising edge of the difference signal can be identified, for example, if the sign of the difference signal's amplitude changes from negative to positive. A falling edge of the difference signal can be identified, for example, if the sign of the difference signal's amplitude changes from positive to negative. Of course, other methods for identifying a rising or falling edge of the difference signal are also conceivable. The time of the zero crossing is transmitted to the signal edge identification unit by the trigger signal from the zero-crossing detection unit.

[0029] Furthermore, a first storage unit or a second storage unit stores the value of the summation signal at the time of the zero crossing. The first storage unit stores the value of the summation signal if the rotation direction determination unit determines the first direction of rotation and the signal edge identification unit identifies a rising edge of the differential signal. Likewise, the first storage unit stores the value of the summation signal if the rotation direction determination unit determines the second direction of rotation and the signal edge identification unit identifies a falling edge of the differential signal. Thus, the first storage unit stores the value of the summation signal when the encoder wheel rotates forward and the differential signal is on a rising edge.When the encoder wheel rotates backward, the edges that are identified as rising edges during forward rotation are identified as falling edges. Accordingly, the first storage unit stores the value of the summation signal during a backward rotation of the encoder wheel if a falling edge is identified.

[0030] The second storage unit stores the value of the summed signal if the rotation direction determination unit determines the first rotation direction and the signal edge identification unit identifies a falling edge of the difference signal. Similarly, the second storage unit stores the value of the summed signal if the rotation direction determination unit determines the second rotation direction and the signal edge identification unit identifies a rising edge of the difference signal.

[0031] Furthermore, the reference mark is detected depending on at least one value stored in the first storage unit and at least one value stored in the second storage unit. It is conceivable that a value stored in the first storage unit is replaced if a new value to be stored in the first storage unit is detected. The same is, of course, possible for a value stored in the second storage unit. It is also conceivable that a predetermined number of values ​​are stored in the first and / or the second storage unit, for example, until a memory overflow occurs. In the event of a memory overflow, the oldest stored value can, for example, be replaced by the newly stored value.This advantageously allows the identification of the at least one reference mark depending on the direction of rotation and whether the signal edges are rising or falling. The direction of rotation, rising edges, and falling edges can be determined in a simple and easily implemented manner. Furthermore, this type of detection of the at least one reference mark allows for the combination of determining the direction of rotation and detecting the reference mark, each based on signal edge identification. This allows, for example, the extension of existing methods for determining the direction of rotation or existing methods for detecting the reference mark. Finally, it also reduces the computational effort required for signal processing to detect the at least one reference mark.

[0032] It is of course conceivable that, instead of the difference signal, the first or second sensor signal could be used to store the value of the summed signal in the first or second unit, depending on a zero crossing of the first or second sensor signal and on a rising or falling edge of the first or second sensor signal. A zero crossing of the first or second sensor signal can be detected, for example, if the offset of the first or second sensor signal is adjusted so that a zero crossing occurs on a rising or falling edge. It is also conceivable that a reference value of the first or second sensor signal is determined, with the reference value lying between a minimum and a maximum amplitude of the first or second sensor signal.For example, the reference value can be the average of the first or second sensor signal. On a rising signal edge, the amplitude of the first or second sensor signal increases from a value smaller than the reference value to a value larger than the reference value. If the amplitude of the first or second sensor signal equals the reference value, a zero crossing can be detected. If the second sensor signal is used to detect a zero crossing and identify a rising or falling edge of the difference signal, the storage of the summed signal value in the first or second unit must be adjusted accordingly, depending on the direction of rotation and whether the edge is rising or falling.

[0033] In a further embodiment, a value of the summing signal is digitized into a digital value of the summing signal at the time of the zero crossing by means of an analog-to-digital conversion unit. Here, the zero-crossing detection unit and the analog-to-digital conversion unit are connected, and the trigger signal can be transmitted from the zero-crossing detection unit to the analog-to-digital conversion unit. The digital value of the summing signal is stored in the first or second unit in the manner described above. Digitization advantageously results in a more noise-independent detection of the at least one reference mark.

[0034] In a further embodiment, a difference is calculated between a value stored in the first storage unit and a value stored in the second storage unit. A comparison unit compares this difference to a predetermined threshold. The at least one reference mark is detected if the difference is smaller than the predetermined value. In particular, the at least one reference mark can be detected if the difference is smaller than the predetermined value and the identification unit identifies a rising edge or a falling edge of the difference signal. In this case, a difference between a value currently stored in the first storage unit and a value currently stored in the second storage unit can be calculated.Calculating a difference represents a particularly simple and advantageous method for detecting at least one reference mark. Naturally, other mathematical and / or logical operations are also possible, depending on the value stored in the first and second storage units. For example, a reference mark can be detected if a value stored in the first unit is less than a predetermined first threshold and a value stored in the second unit is greater than a predetermined second threshold.

[0035] In a further embodiment, an offset and / or a gain of the first sensor signal and / or the second sensor signal and / or the third sensor signal and / or the summation signal and / or the difference signal is adjusted. This advantageously results in simpler signal processing for the detection of the at least one reference mark.

[0036] A device for detecting at least one reference mark among a set of increment marks of an encoder wheel is further proposed. In particular, the device comprises at least one unit for detecting a first sensor signal, wherein a first sensor signal can be detected by means of the unit for detecting a first sensor signal when the encoder wheel rotates. The device further comprises at least one unit for detecting a second sensor signal, at least one unit for determining the direction of rotation, and at least one unit for detecting a reference mark. A second sensor signal can be detected simultaneously with the detection of the first sensor signal by means of the unit for detecting a second sensor signal, wherein the second sensor signal is identical to the first sensor signal but phase-shifted relative to the first sensor signal by a first phase angle.For this purpose, for example, the unit for detecting a second sensor signal can be arranged spatially offset from the unit for detecting a first sensor signal, wherein the spatial offset is chosen such that the first sensor signal is phase-shifted with a desired phase angle relative to the second sensor signal.

[0037] Furthermore, the device can include a unit for calculating rotational speed, wherein a rotational speed can be calculated from the first and / or the second sensor signal using the unit for calculating rotational speed. A first or a second direction of rotation can be determined using the unit for determining the direction of rotation. Using the unit for detecting a reference mark, the at least one reference mark can be detected depending on the direction of rotation and the first and second sensor signals. One of the methods described above can advantageously be carried out using the proposed device.

[0038] In a further embodiment, the device comprises at least one unit for detecting a third sensor signal, wherein a third sensor signal can be detected simultaneously with the first sensor signal by means of the unit for detecting a third sensor signal, the third sensor signal being identical to the first sensor signal but phase-shifted relative to the first sensor signal by a second phase angle. The unit for detecting a third sensor signal can be spatially offset from the unit for detecting a first sensor signal such that the third sensor signal is phase-shifted relative to the first sensor signal by a desired second phase angle.

[0039] In a further embodiment, the device further comprises at least one zero-crossing detection unit, at least one signal edge identification unit, at least one first storage unit, at least one second storage unit, and at least one comparison unit. The zero-crossing detection unit, the signal edge identification unit, the first storage unit, the second storage unit, and the comparison unit can be configured as part of the unit for detecting the at least one reference mark.

[0040] Furthermore, it is conceivable that all the aforementioned units are implemented as individual units or at least partially combined into control units.

[0041] The invention is explained in more detail using an exemplary embodiment. The figures show: Fig. 1 Two exemplary waveforms of a sensor signal (state of the art), Fig. 2 a schematic section of a encoder wheel (state of the art), Fig. 3 a schematic section of another encoder wheel (state of the art), Fig. 4 a schematic representation of sensor signals during a forward rotation and a reverse rotation (state of the art), Fig. 5 a schematic block diagram of a device for detecting at least one reference mark, Fig. 6 exemplary signal waveforms in a gap channel, Fig. 7 more exemplary signal waveforms in a gap channel, Fig. 8 an exemplary progression of values ​​stored in a first storage unit, Fig. 9 an exemplary progression of values ​​stored in a second storage unit, Fig. 10 an exemplary progression of a difference of stored values ​​during a forward rotation and Fig. 11 an exemplary progression of a difference of stored values ​​during a backward rotation.

[0042] In the following, identical reference symbols denote elements with the same or similar technical properties.

[0043] Fig. Figure 1 shows a curve 51 of a sensor signal when the in Fig. 3 shown encoder wheel 54 on e.g. one in Fig. 4 and Fig. The unit 2 shown in section 5 is passed by to capture an initial sensor signal. Further, it shows... Fig. 1 a further course 52 of a first sensor signal, if e.g. the in Fig. 2 shown encoder wheel 53 on, for example, the one in Fig. The unit 2 shown in Figure 4 is passed by the unit 2 for the acquisition of a first sensor signal. The curves 51 and 52 show an output signal of the unit 2 for the acquisition of a first sensor signal as a function of the rotation angle. The curves 51 and 52 each show a rectangular oscillation, which mainly consists of a repeating first increment profile with a first increment period. The curves 51 and 52 also exhibit individual second increment profiles with a second increment period. The first and second increment profiles are generated by passing, for example, the unit 2 by the unit 2 shown in Figure 4. Fig. 2 and Fig. 3 illustrated encoder wheels 53, 54 on e.g. the one in Fig. Unit 2, as shown in section 4, is used to capture a first sensor signal.

[0044] Fig. Figure 2 shows a schematic section of the surface of a encoder wheel 53. For simplified visualization, the surface of the encoder wheel 53 is shown unfolded. The encoder wheel 53 has normal increment marks 55, which are formed as teeth. Furthermore, the encoder wheel 53 has gaps 56 following the normal increment marks 55. The encoder wheel 53 also has a reference mark 57 and a gap 58 following the reference mark 57. It is shown that a normal increment mark 55 has a length equal to the length of a circular arc with a central angle of 3°, where the circular arc refers to a circular cross-section of the encoder wheel 53. The gap 56 following a normal increment mark 55 also has the length of a circular arc with a central angle of 3°.In contrast, the reference mark 57 has a length corresponding to the length of a circular arc with a central angle of 6°. Likewise, the space 58 following the reference mark 57 has a length equal to the length of a circular arc with a central angle of 6°. When the encoder wheel 53 rotates, the encoder wheel 53 is rotated as, for example, in... Fig. Figure 4 shows the path leading past unit 2 to acquire a first sensor signal. A normal increment mark 53 and a gap 56 following a normal increment mark 53 generate a first increment profile with a first increment period. The reference mark 57 and the gap 58 following the reference mark generate a second increment profile with a second increment period. The second increment profile can be described as a 12° gap. The resulting first sensor signal exhibits, for example, the following characteristics: Fig. 1 further course shown 52 on.

[0045] Fig. Figure 3 shows a schematic representation of another encoder wheel 54. Analogous to Fig. 2 The additional encoder wheel 54 has normal increment marks 55 and spaces 56 following the normal increment marks 55. Furthermore, the additional encoder wheel 54 has a reference mark 57 and a space 58 following the reference mark 57. In contrast to Fig. Figure 2 shows that the reference mark 57 has a length corresponding to the length of a circular arc with a central angle of 3°. Furthermore, the gap 58 following the reference mark 57 has a length corresponding to the length of a circular arc with a central angle of 15°. The increment profile generated by the reference mark 57 and the gap 58 following it in the first sensor signal can also be referred to as an 18° gap. The Fig. Figure 1, showing the course of the first sensor signal, illustrates the output signal of, for example, the sensor in the sensor. Fig. Unit 2 shown in section 4 is used to detect a first sensor signal, if that is the case. Fig. 3 further encoder wheel 54 shown, for example, is guided past unit 2 during a rotary movement to detect a first sensor signal.

[0046] Fig. Figure 4 shows exemplary waveforms 60, 62 of a first sensor signal when a further encoder wheel 54 is moved past a unit 2 to detect a first sensor signal, for example by a rotational movement. Here, waveform 61 represents the waveform of an output signal of the unit 2 for detecting a first sensor signal when a forward rotation of the further encoder wheel 54, symbolized by a direction arrow 61, takes place. Another waveform 62 represents the waveform of the output signal of the unit 2 for detecting a first sensor signal when a backward rotation of the further encoder wheel 54, symbolized by a direction arrow 63, takes place.

[0047] Fig. Figure 5 shows a schematic block diagram of a device 1 for detecting at least one reference mark 57, wherein the reference mark is, for example, in Fig. 2 or Fig. Figure 3 shows the device 1. It comprises a unit 2 for detecting a first sensor signal, a unit 3 for detecting a second sensor signal, and a unit 4 for detecting a third sensor signal. The unit 2 for detecting a first sensor signal and the unit 3 for detecting a second sensor signal are spatially offset, as schematically represented by a first distance a. Similarly, the unit 3 for detecting a second sensor signal and the unit 4 for detecting a third sensor signal are spatially offset, as represented by a second distance b. Thus, the unit 2 for detecting a first sensor signal and the unit 4 for detecting a third sensor signal are also spatially offset by a distance a + b.The first distance a generates a first phase angle by which the first sensor signal, detected by unit 2 for the purpose of detecting a first sensor signal, and the second sensor signal, detected by unit 3 for the purpose of detecting a second sensor signal, are phase-shifted. Similarly, the first and second distances a, b generate a second phase shift between the first sensor signal and a third sensor signal detected by unit 4 for the purpose of detecting a third sensor signal. The first, second, and third sensor signals are detected simultaneously when an encoder wheel (not shown) is moved past units 2, 3, 4 for the purpose of detecting sensor signals, for example, by a rotational movement. The device 1 further comprises a so-called velocity channel 10, a direction channel 20, and a gap channel 30.In speed channel 10, the rotational speed n of the encoder wheel is determined, in direction channel 20, the direction of rotation of the encoder wheel is determined, and in gap channel 30, a signal is generated which, in a manner described later, serves to detect the at least one reference mark 57. Speed ​​channel 10 comprises a first addition unit 11, a second addition unit 14, and a multiplication unit 15. Speed ​​channel 10 also includes a unit 12 for adjusting an offset and a unit 13 for adjusting the gain. Furthermore, speed channel 10 includes a unit 16 for calculating a rotational speed n. Here, in . Fig. Figure 5 shows that a differential signal 17 is generated from the first sensor signal and the second sensor signal by means of the first addition unit 11 of the velocity channel 10. The offset and gain of the differential signal 17 are adjusted by means of unit 12 for adjusting an offset and unit 13 for adjusting a gain of the velocity channel 10, and by means of the second addition unit 14 and the multiplication unit 15 of the velocity channel 10. From the adjusted differential signal 17, unit 16 calculates a rotational speed n of the encoder wheel. The direction channel 20 is structured analogously to the velocity channel 10 and comprises a first addition unit 21, a second addition unit 24, a multiplication unit 25, a unit 22 for adjusting an offset, a unit 23 for adjusting a gain, and a unit 26 for determining a direction of rotation of the direction channel 20.In an analogous manner to the speed channel 10, a differential signal 27 is formed from the second and the third sensor signal, a gain and an offset of the differential signal 27 are adjusted, and a forward rotation 61 or a backward rotation 62 is determined by means of the unit 26 to determine a direction of rotation, for example in . Fig. 4 are shown, determined.

[0048] The gap channel 30 comprises a first addition unit 31, a second addition unit 34, a multiplication unit 35, a unit 32 for adjusting an offset, and a unit 33 for adjusting the gain of the gap channel 30. A summation signal 37 is calculated from the first and second sensor signals using the first addition unit 31 of the gap channel 30, and a gain and an offset of the summation signal 37 are adjusted analogously to the velocity channel 10 and the direction channel 20.

[0049] The device 1 for detecting at least one reference mark 57 further comprises a unit 40 for detecting a reference mark 57. The unit 40 for detecting a reference mark 57 includes a logic unit 41, a first storage unit 42, a second storage unit 43, an addition unit 45, a comparison unit 46, a threshold unit 47, and an analog-to-digital conversion unit 48. An output 44 is also shown. The unit 16 for calculating a rotational speed n and the unit 26 for determining a direction of rotation are connected to the logic unit 41 via data transmission. The unit 16 for calculating a rotational speed n transmits the rotational speed n and the differential signal 17 to the logic unit 41. The differential signal 17 is, for example, passed unchanged from the unit 16 for calculating a rotational speed n to the logic unit 41.Unit 26 transmits the direction of rotation of the encoder wheel to logic unit 51 to determine the direction of rotation. Logic unit 41 comprises a unit (not shown) for zero-crossing detection and a unit (also not shown) for identifying signal edges. Zero-crossing detection and edge identification refer to the differential signal 17, which is forwarded from unit 16 to logic unit 41 for calculating the rotational speed n. Logic unit 41 is connected to unit 48 for analog-to-digital conversion, to the first unit 42 for storage, and to the second unit 43 for storage. If the zero-crossing detection unit detects a zero crossing in the differential signal 17, logic unit 41 sends a trigger signal Tr to unit 48 for analog-to-digital conversion.If the analog-to-digital conversion unit 48 receives the trigger signal Tr, it converts an analog value of the summation signal 37 into a digital value 49 of the summation signal 37. If the signal edge identification unit identifies a rising edge in the differential signal 17 and the rotation direction identification unit 26 determines a forward rotation 61 (see . Fig. 4), the logic unit 41 sends a first activation signal A1 to the first storage unit 42, which stores the digital value 49 of the summation signal 37. Similarly, the logic unit 41 sends a second activation signal A2 to the second storage unit 43 when the signal edge identification unit identifies a falling edge of the summation signal 17 and the rotation direction identification unit 26 detects a reverse rotation 63 (see Fig. 4) determined. In this case, the second unit 43 stores the digital value 49 of the summation signal 37. Using the addition unit 45, a difference is calculated between the value currently stored in the first unit 42 and a value currently stored in the second unit 43. This difference is then compared by the comparison unit 46 with a predetermined threshold S, which is stored, for example, in the threshold storage unit 47. If the difference is less than the predetermined threshold S, the comparison unit 46 sends a signal R to the logic unit 46, which in this case detects at least one reference mark 57. Depending on the detection of at least one reference mark 57, a signal of the output 44 can be adjusted.

[0050] Fig. Figure 6 shows exemplary curves 70, 71, 72 of a difference signal 17 and exemplary curves 80, 81, 82 of a summation signal 37. Here, a flux density T in Tesla is shown as a function of a rotation angle of a encoder wheel. A first curve 70 of the differential signal 17 represents a curve of the differential signal 17 for an air gap between a encoder wheel and a unit 2 for detecting a first sensor signal of 0.1 mm. Similarly, a second curve 71 represents a curve of the differential signal 17 for an air gap of 0.8 mm, and a third curve 72 represents a curve of the differential signal 17 for an air gap of 1.5 mm. In a similar manner, a first curve 80 represents the curve of the summation signal 37 for an air gap of 0.1 mm, a second curve 81 represents a curve of the summation signal 37 for an air gap of 0.8 mm, and a third curve 82 represents a curve of the summation signal 37 for an air gap of 1.5 mm.It should be noted that the axis labels on the left are for the difference signals 17 and on the right are for the summation signals 37 (each in Tesla).

[0051] Fig. Figure 7 shows further exemplary curves 83, 84, 85 of a summation signal 37. A fourth curve 83 represents a curve of the summation signal 37 for an air gap of 0.1 mm, a fifth curve 84 represents a curve of the summation signal 37 for an air gap of 0.8 mm and a sixth curve 85 represents a curve of the summation signal 37 for an air gap of 1.5 mm.

[0052] Fig. Figure 8 shows an example of a progression of values ​​of a summation signal 37 stored in a first unit 42 over a number of zero crossings, whereby the values ​​were stored on a rising edge of the difference signal 17 and a forward rotation 61. A circle represents stored values ​​with an air gap of 1.5 mm, a plus sign represents stored values ​​with an air gap of 0.8 mm, and a cross represents stored values ​​with an air gap of 0.1 mm. Here, area 90 shows the values ​​stored in the first unit 42 when, for example, a Fig. 2 Reference mark 57 shown and a space 58 following the reference mark 57 are passed by the units 2, 3, 4 for the purpose of detecting sensor signals.

[0053] Fig. Figure 9 shows an example of the progression of values ​​stored in a second unit (43) over a number of zero crossings. The symbols are analogous to... Fig. 8 selected. A range of 90 displays stored values ​​when the in Fig. The reference mark 57 shown in Figure 2 and the space 58 following the reference mark 57 are passed by units 2, 3, 4 for the purpose of detecting sensor signals. Fig. The values ​​shown here are those that are stored during a forward rotation 61 and a falling edge of the difference signal 17.

[0054] Fig. 10 shows a difference in Fig. 8 values ​​shown, which were stored in a first unit 42 for storage, and the values ​​shown in Fig. The 9 values ​​shown were stored in a second unit 43. The difference is shown over a number of zero crossings. Analogous to Fig. 8 and Fig. The symbols in section 9 denote specific air gap lengths. Fig. Figure 10 shows that in a range 90, the difference between the value stored in the first unit 42 and the value stored in the second unit 43 differs significantly from the other differences. Range 90 corresponds to a section of the difference signal 17 or the summation signal 37, which is generated when the in Fig. 2 The reference mark 57 shown and the space 58 following the reference mark 57 are demonstrated at units 2, 3, 4 for the detection of sensor signals.

[0055] Similarly to Fig. 10 shows Fig. 11 a course of a difference between values ​​stored in a first unit 42 and values ​​stored in a second unit 43 over a number of zero crossings. This involves a reverse rotation 63 (see Fig.4) Here too, the difference in one area 90 differs significantly from the other differences, so that detection of at least one reference mark 57 is possible using a threshold method. Reference symbol list 1 Device for detecting at least one reference mark 2 Unit for capturing a first sensor signal 3 Unit for capturing a second sensor signal 4 Unit for capturing a third sensor signal 10 speed channels 11 first addition unit 12 units for adjusting an offset 13 Unit for adjusting an amplification 14 second addition unit 15 Multiplication unit 16 Unit for determining a rotational speed 17 Differential signal 20 Directional channel 21 first addition unit 22 Unit for adjusting an offset 23 Unit for adjusting an amplification 24 second addition unit 25 Multiplication unit 26 Unit for determining a direction of rotation 27 Differential signal 30 gap channel 31 first addition unit 32 Unit for adjusting an offset 33 Unit for adjusting an amplification 34 second addition unit 35 Multiplication unit 37 Summation signal 40 units for detecting at least one reference mark 41 logic unit 42 first unit for storage 43 second unit for storage 44 Exit 45 Addition unit 46 units for comparison 47 Unit for storing a threshold value 48 units for analog-to-digital conversion 49 digitized value 51 Course of a first sensor signal 52 Further course of a first sensor signal 53 Sensor wheel 54 additional sensor wheel 55 normal increment mark 56 space 57 Reference brand 58 space 60. Course of a first sensor signal during forward rotation 61 Directional arrow for forward rotation 62. Course of a first sensor signal during reverse rotation 63 Directional arrow for reverse turn 70 First course of a difference signal 71 Second course of a difference signal 72 third course of a difference signal 80 first course of a summation signal 81 Second course of a summation signal 82 third course of a summation signal 83 fourth course of a summation signal 84 fifth course of a summation signal 85 sixth course of a summation signal 90 area of ​​a reference brand Trigger signal A1 first activation signal A2 second activation signal S threshold R Signal n rotational speed T flux density

Claims

[1] Method for detecting at least one reference mark (57) of a set of increment marks of an encoder wheel (53, 54), wherein the set of increment marks comprises normal increment marks (55) and at least one reference mark (57), wherein a first sensor signal is detected when the encoder wheel (53, 54) is rotated, wherein a normal increment mark (55) and a space (56) following the normal increment mark (55) in the first sensor signal generate a first increment profile with a first increment period, wherein the reference mark (57) and a space (53) following the reference mark (57) in the first sensor signal generate a second increment profile with a second increment period, wherein a second sensor signal is detected simultaneously, wherein the second sensor signal is equal to the first sensor signal but phase-shifted with a first phase angle relative to the first sensor signal.wherein at least one unit (26) determines a first or second direction of rotation for determining a direction of rotation, wherein at least one unit (40) detects the reference mark (57) depending on the direction of rotation, the first and the second sensor signal, wherein the at least one unit (40) detects the reference mark (57) depending on a differential signal (17), wherein the differential signal (17) is generated from a difference between the first sensor signal and the second sensor signal, . characterized by , that the at least one unit (40) for detecting the reference mark (57) additionally detects the reference mark (57) depending on a summation signal (37), wherein the summation signal (37) is formed from a sum of the first and the second sensor signal. [2] Method according to claim 1, characterized by, that the unit (26) determines the first or second direction of rotation from the first and second sensor signals or from the first and a third sensor signal, wherein the third sensor signal is detected simultaneously with the first sensor signal, wherein the third sensor signal is equal to the first sensor signal but offset by a second phase angle relative to the first sensor signal, wherein the first phase angle is not equal to the second phase angle. [3] Method according to any of the preceding claims, characterized by , that a zero-crossing detection unit detects at least one zero crossing of the difference signal and generates a trigger signal (Tr) at a time of the zero crossing, wherein a unit for identifying signal edges at the time of zero crossing identifies a rising or a falling edge of the difference signal (17), wherein a first unit (42) stores a value of the summation signal (37) if the unit (26) determines the first direction of rotation and the unit for identifying signal edges identifies a rising edge of the difference signal (17), or if the unit (26) determines the second direction of rotation and the unit for identifying signal edges identifies a falling edge of the difference signal (17), wherein a second unit (43) stores a value of the summation signal (37) if the unit (26) determines the first direction of rotation and the unit identifies a falling edge of the difference signal (17) or if the unit (26) determines the second direction of rotation and the unit identifies a rising edge of the difference signal (17), wherein the reference mark (57) is detected depending on at least one value stored in the first unit (42) and at least one value stored in the second unit (43). [4] Method according to claim 3, characterized by , that a value of the summation signal (37) is digitized into a digital value (49) of the summation signal (37) by means of an analog-to-digital conversion unit (48) at the time of the zero crossing, wherein a first unit (42) for storing the digital value (49) of the summing signal (37) stores if the unit (26) determines the first direction of rotation and the unit identifies a rising edge of the differential signal (17) or if the unit (26) determines the second direction of rotation and the unit identifies a falling edge of the differential signal (17), wherein a second unit (43) for storing the digital value (49) of the summing signal (37) stores if the unit (26) determines the first direction of rotation and the unit identifies a falling edge of the differential signal (17) or if the unit (26) determines the second direction of rotation and the unit identifies a rising edge of the differential signal (17), wherein the reference mark (57) is detected depending on at least one value stored in the first unit (42) and at least one value stored in the second unit (43). [5] Method according to claim 3 or 4, characterized by, that a difference is formed between a value stored in the first unit (42) and a value stored in the second unit (43), wherein a unit (46) compares the difference with a predetermined threshold (S), and the reference mark (57) is detected if the difference is less than the predetermined threshold (S). [6] Method according to any of the preceding claims, characterized by , that an offset and / or a gain of the first sensor signal and / or the second sensor signal and / or the third sensor signal and / or the summation signal (37) and / or the difference signal (17) is adjusted. [7] Device (1) for detecting at least one reference mark (57) of a set of increment marks of a encoder wheel (53, 54), wherein the set of increment marks comprises normal increment marks (55) and at least one reference mark (57), wherein the device (1) comprises at least one unit (2) for detecting a first sensor signal, wherein a first sensor signal can be detected by means of the unit (2) for detecting a first sensor signal when the encoder wheel (53, 54) is rotated, wherein a normal increment mark (55) and a space (56) following the normal increment mark in the first sensor signal generate a first increment profile with a first increment period, wherein the reference mark (57) and a space (58) following the reference mark in the first sensor signal generate a second increment profile with a second increment period, wherein the device (1) further comprises at least one unit (3) for detecting a second sensor signal,comprising at least one unit (26) for determining a direction of rotation and at least one unit (40) for detecting the reference mark (57), wherein by means of the unit (3) a second sensor signal can be detected simultaneously with the first sensor signal, wherein the second sensor signal is equal to the first sensor signal, but phase-shifted relative to the first sensor signal by a first phase angle, wherein a first or second direction of rotation can be determined by means of the unit (26) for determining a direction of rotation, wherein the reference mark (57) is detected by means of the unit (40) for detecting the reference mark (57) depending on the direction of rotation, the first and the second sensor signal, wherein the reference mark (57) is detected by means of the unit (40) for detecting the reference mark (57) depending on a difference signal (17), wherein the difference signal (17) is generated from a difference between the first sensor signal and the second sensor signal, characterized by , that by means of the unit (40) for the detection of the reference mark (57) the reference mark (57) is additionally detected depending on a summation signal (37), wherein the summation signal (37) is formed from a sum of the first and the second sensor signal. [8] Device (1) according to claim 7, characterized by , that the first or second direction of rotation can be determined from the first and second sensor signal or from the first and a third sensor signal, wherein the device (1) comprises at least one unit (4) for detecting a third sensor signal, wherein a third sensor signal can be detected simultaneously with the first sensor signal by means of the unit (4) for detecting a third sensor signal, wherein the third sensor signal is equal to the first sensor signal, but phase-shifted with a second phase angle relative to the first sensor signal. [9] Device (1) according to claim 7 or 8, wherein the device further comprises at least one unit for detecting a zero crossing, at least one unit for identifying signal edges, at least one first unit (42) for storage, comprising at least one second unit (43) for storage and at least one unit (46) for comparison, wherein by means of the unit for detecting a zero crossing a zero crossing of a difference signal (17) can be detected and a trigger signal (Tr) can be generated at a time of the zero crossing, wherein the difference signal (17) can be generated from a difference between the first sensor signal and the second sensor signal, wherein, by means of the unit for identifying signal edges, a rising or a falling edge of the difference signal (17) can be identified at the time of the zero crossing, where at the time of the zero crossing, depending on an analog or digitized value (49) of a summation signal (37) can be stored in the first or second storage unit (42, 43) depending on a direction of rotation determined by means of the unit (26) for determining a direction of rotation and depending on an edge of the differential signal (17) identified by means of the unit for identifying signal edges, wherein the summation signal (37) can be generated from an addition of the first sensor signal and the second sensor signal, where, using the unit (46) for comparison, a difference between the value stored in the first unit (42) and in the second unit (43) is comparable to a predetermined threshold (S).

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