Method for processing electrical signal and control device of camshaft adjuster or of internal combustion engine for carrying out method

Abstract

The invention relates to a method for processing an electrical signal (S), which is generated continuously over time and on the basis of measurements from sensors (23, 24, 25) and is transmitted via lines (20, 22) influenced by interference variables, having the following features: establishing a scan rate interval (T); establishing a quantization level (Q1, Q2); distributing the electrical signal to a quantization level (Q1, Q2); determining a number of variations of the quantization level (Q1, Q2) within the scan rate interval (T); all even-numbered variations in the quantization level (Q1, Q2) within the scan rate interval (T) are rejected. The invention also relates to a control device (17, 21) for a camshaft adjuster (7, 8) or for an internal combustion engine (1), which control device carries out a method of this kind.

Description

Technical Field

[0001] The present invention relates to a method for processing electrical signals that vary continuously over time and are generated based on measurements from sensors, and are transmitted via a line affected by interference variables.

[0002] Furthermore, the present invention relates to a control device for an internal combustion engine or a camshaft adjuster. Background Technology

[0003] Various methods of operating the camshaft adjuster are described in DE 102 59 133 A1 and DE 102 42 659 A1. In particular, these publications relate to the interaction between the engine control unit and the camshaft adjuster. A crankshaft drive, functioning as a three-shaft drive, is used as the actuation drive for the camshaft adjuster.

[0004] DE 10 2012 219 297 A1 describes a method for operating a motor vehicle, which includes an engine control unit and additionally a camshaft adjuster control unit. A CAN bus is provided for data transmission. The camshaft adjuster control unit can be activated before the engine control unit has completed its activation.

[0005] WO 2006 / 122 665 A1 describes a topology for generating an actuation signal for an electrically actuated camshaft adjuster. In this document, the control unit is integrated into the adjustment unit. A Hall effect sensor is provided to detect the state of the camshaft adjuster.

[0006] DE 10 2004 041 232 B4 describes a method for operating a camshaft adjuster, which may include an electro-actuated or hydraulically actuated device. In either case, a reference value and / or base value related to the state of the camshaft adjuster is obtained by averaging values ​​from different time points during the operation method.

[0007] In the electric camshaft adjuster, as in the engine control unit, electrical signals from sensors on the trigger wheels of the crankshaft and camshaft are evaluated. Unlike the engine control unit, the wiring between the control unit and the sensors is relatively long. The wiring in the engine compartment is exposed to various interferences.

[0008] Mass shifts caused by high current loads and incident electromagnetic radiation can generate voltage peaks and signal noise in the useful signal. As vehicle electrification increases, the number of interference effects also rises, making reliable signal transmission over long distances impossible to guarantee.

[0009] Therefore, signal evaluation is often difficult and more complex than that in engine control units. Summary of the Invention

[0010] The purpose of this invention is to avoid the disadvantages of the prior art, and in particular to handle electrical signals that have been exposed to electrical interference.

[0011] According to the present invention, this objective is achieved by the method for processing electrical signals according to claim 1. The objective is also achieved by a control device having the features of claim 10. The configuration and advantages of the invention described below in conjunction with the control device also apply similarly to the method, and vice versa.

[0012] The method according to the invention is based on the discovery that voltage peaks and signal noise components radiated into many useful signals have time durations different from their average variations. If the time and / or amplitude variations of the useful signal are approximately known in advance, the proposed method provides a simple way to eliminate the effects of interference without relying on computationally intensive Fourier transform units.

[0013] The method according to the invention is suitable for, for example, signals with continuously varying values. Continuous variation should be understood mathematically as the absence of sudden changes in the signal. For example, this applies to signals whose measurements are continuously varying variables.

[0014] If the timing of the change can be predicted within certain constraints, this method is also well-suited for signals whose values ​​change abruptly, especially when the change occurs periodically.

[0015] It is particularly well-suited for digital or analog signals with distinct edges. For example, a Hall sensor can detect the rotational speed of a shaft using a trigger wheel. The trigger wheel has teeth, which are easily detected by magnetic sensing because edge peaks are generated due to the ratio of the induced voltage to the first derivative of the field change. This does not need to be recorded in its absolute value, but can simply be registered as present / absent, and therefore only needs to be counted.

[0016] A prerequisite for this method is the ability to select an appropriate scan rate interval. This requirement is easily met for many applications because measurements can be based, for example, on previous measurements, and many physical variables do not change abruptly. If no historical measurements are available that can be used meaningfully, the assumptions can be checked for plausibility. For example, for a stationary motor, the speed of its motor shaft can be assumed to be zero.

[0017] The scan rate interval can be set to a fixed value. For this purpose, the scan rate interval can be hardware-coded or established once at the beginning of the method without any subsequent changes. Alternatively, the scan rate interval can be established by open-loop or closed-loop control. Re-establishment can occur after each measurement or can be associated with a predetermined time period, measurement value, and / or external conditions.

[0018] The method also specifies the quantization levels. The number and level of quantization levels depend on the application; for digital signals, two quantization levels are sufficient.

[0019] According to the method of the present invention, the number of changes in the quantization level is determined. A change in the measurement occurs only when a certain threshold is exceeded, allowing the measurement to be assigned to different quantization levels. This reliably eliminates noise and random fluctuations.

[0020] In many applications, interference variables affecting electrical signals are caused by long cables. These interference variables are typically reflected in the signal curve through the first derivative of the interference, which is the cause of voltage peaks. This invention utilizes the fact that these voltage peaks are relatively short in duration and do not cause changes or double variations in the quantization interval. If the scan rate interval is significantly longer than the duration of the average voltage peak caused by interference radiation—for example, by an order of magnitude—the double variations in the quantization level can be safely attributed to the interference. Therefore, the method according to the invention rejects all even-numbered variations in the quantization level within the scan interval.

[0021] In another development, if there are an odd number of changes in the quantization level within the scan rate interval, then all changes in the quantization level within the scan rate interval after the first change are rejected. Therefore, it is only necessary to determine whether there are odd or even numbers of changes in the quantization level within the scan rate interval. Thus, it is not important whether the voltage peak caused by interference radiation appears before or after the changes in the useful signal.

[0022] The proposed method is particularly well-suited for digital signals. However, it is also suitable for analog signals that have been quantized to two or more quantization levels after being transmitted over a line.

[0023] Due to its high robustness, the method according to the invention allows for the use of relatively long wires without additional requirements for shielding. This also opens up the possibility of placing the control device for evaluating the signal at a greater distance, thus allowing for more flexible mounting locations in the internal combustion engine, enabling the control device to be exposed to less heat or better encapsulation.

[0024] Besides voltage peaks caused by EMC radiation, noise also complicates the evaluation of edge peaks. Signal quality can be further improved by pre-filtering the signal. For this purpose, for example, a low-pass filter can be provided. Furthermore, hysteresis can be handled by evaluating logic filters for each edge mode.

[0025] In another development, when two scan rate intervals with an odd number of changes in the quantization level follow each other, the number of changes in the quantization level within the current and previous scan rate intervals is set to zero. This is based on the consideration that the measured value fluctuates around a threshold separating the quantization level, or that the two edges of the interference variable are randomly distributed across two different scan intervals.

[0026] The proposed method is particularly suitable for the control device of an electric or hydraulic camshaft adjuster in an internal combustion engine that performs the method steps. The internal combustion engine is designed as a reciprocating piston engine and includes a crankshaft and at least one camshaft in its basic known structure. An electromechanically adjustable actuation transmission, such as a three-shaft transmission, is provided, particularly a harmonic drive, for adjusting the camshaft. The camshaft adjuster can be operated as follows:

[0027] - Continuously determine the angular position of the crankshaft, wherein the angular change is detected incrementally starting from the reference position of the detection angle;

[0028] - Detect the reference position of the camshaft, especially by means of a trigger disc;

[0029] - Calculate the current angular positions of the camshaft and crankshaft based on the recorded rotor angle changes;

[0030] The difference between the two stated angular positions (i.e., the phase difference between the crankshaft and the camshaft) is calculated and used to control the electric motor that drives the adjustment shaft.

[0031] The reference position of the camshaft is detected, such that the corresponding signal is generally available to the engine control unit of the internal combustion engine under any circumstances. The stated signal contains countable edge peaks.

[0032] The crankshaft angular changes are detected with a resolution finer than that of an electric motor whose rotor is coupled to an adjusting shaft of an actuation drive for joint rotation. Due to the given positive or negative reduction ratio of the actuation drive, very fine resolution of the camshaft angular position is possible.

[0033] In the preferred method, the angular positions of the crankshaft and the electric motor rotor are approximately determined by calculation using a time extrapolation method, and these positions lie between two locations that can be discretely distinguished from each other by means of sensor signals. It is assumed that the shaft in question—i.e., the motor shaft or crankshaft of the electric motor—rotates at a nearly constant speed during the interpolation period.

[0034] An internal combustion engine includes: a crankshaft; at least one camshaft capable of electromechanical adjustment via an actuation transmission (particularly a harmonic drive); an engine control unit; and a camshaft control unit configured to control an actuation motor (i.e., an electric motor) that operates the actuation transmission, wherein the engine control unit is linked to a means for detecting the angular position of the crankshaft, and the camshaft control unit is linked to the engine control unit, and wherein a means for detecting a reference position of the camshaft to be adjusted and a means for detecting the angular position of the shaft of the actuation motor are configured as the sole means for detecting the angular position of the camshaft, and the camshaft control unit is configured to determine the phase angle of the camshaft relative to the crankshaft based on information provided by said means combined with the detected angular position of the crankshaft and the transmission ratio of the actuation transmission.

[0035] The electric actuator of the camshaft adjuster is, for example, a permanent magnet synchronous motor. The electric motor has, for example, four or six pairs of magnetic poles. Changes in the angular position of the electric motor's rotor can be detected, for example, by means of a Hall sensor.

[0036] According to one possible implementation, the engine control unit includes a memory that stores the edges of the crankshaft trigger wheel detected during crankshaft rotation. By detecting both rising and falling edges, not only can higher resolution be achieved compared to detecting only edges of the same type, but a checking mechanism can also be implemented to ensure that the recorded data is not affected by logical inconsistencies. This type of signal processing can also be implemented in a camshaft control unit. Similarly, the camshaft control unit includes a memory.

[0037] Within a scan rate interval, at most one pulse is counted; all other pulses are rejected. The following applies: if an even number of pulses occur (e.g., rise-fall, fall-rise, fall-rise-fall-rise, etc.), then they are considered interference and are completely ignored. If an odd number of pulses occur (e.g., rise, rise-fall-rise, rise-fall-rise-fall-rise, fall-rise-fall-rise-fall, etc.), then only the first edge in the corresponding direction of occurrence is evaluated, and subsequent edges are rejected.

[0038] If the scan rate interval is not chosen to be constant, but rather adjusted to the desired signal sequence, the evaluation of edge patterns from the useful signal and the suppression of edge peaks caused by interference variables work particularly reliably. Therefore, further developments specify that the scan rate interval depends on the velocity of the axis to be measured. The scan rate interval must be chosen such that it is less than the expected minimum duration between two useful pulses and greater than the typical duration of interference.

[0039] Evaluations performed in a control device by counting pulses free up computational power that can be used for other tasks. For example, multi-edge angle calculations for the camshaft and crankshaft can be performed to enable backoff calculations in the event of loss of one of the Hall signals or the crankshaft sensor signal.

[0040] For this purpose, further developments suggest performing calculations for several cam edges (rising and falling) and / or selectively for portions of the signal (e.g., using only every two or three values). For example, this increases the chance of determining reasonable measurements in the event of short bursts of disturbance. Attached Figure Description

[0041] The invention will now be described in more detail with reference to exemplary embodiments. The exemplary embodiments relate to a control device for an electric camshaft adjuster and are schematically illustrated using the accompanying drawings. In the drawings:

[0042] Figure 1 An overview diagram of the components of an internal combustion engine with an electromechanical camshaft adjuster is shown.

[0043] Figure 2 This illustrates the interaction between the engine control unit and the camshaft control unit of an internal combustion engine.

[0044] Figure 3 The relationship between measurements taken on the crankshaft and camshaft of an internal combustion engine is shown.

[0045] Figure 4a The diagram illustrates both the useful signal and the interference signal.

[0046] Figure 4b The diagram illustrates the useful digital signal and the interference signal.

[0047] Figures 5a to 5h The various possible signal patterns that may appear within the scan rate interval are shown. Detailed Implementation

[0048] Constructed as an inline engine and Figure 1 The internal combustion engine, generally identified by reference numeral 1 in the accompanying drawings, includes a crankshaft 2 and two camshafts 3 and 4 (i.e., intake camshaft 3 and exhaust camshaft 4). Unlike the exemplary embodiment shown, the internal combustion engine can also be a reciprocating piston engine with a different design having two intake camshafts and two exhaust camshafts, such as a V-type engine.

[0049] Camshafts 3 and 4 are driven by crankshaft 2 via chain drives 5 and 6. Each camshaft 3 and 4 can be adjusted by means of electromechanical camshaft adjusters 7 and 8. Each camshaft adjuster 7 and 8 has a three-axis drive mechanism configured as a harmonic drive, serving as an actuation drive 9 and 10. The shaft on the input side of the actuation drive 9 and 10 is driven by chain drives 5 and 6. The shaft on the output side of the actuation drive 9 and 10 is connected to the camshafts 3 and 4 to be adjusted for common rotation. The third shaft of each actuation drive 9 and 10 can be driven by an electric motor 11 and 12 associated with the corresponding camshaft adjuster 7 and 8. Here, the motor shaft (denoted as 29) of the electric motor 11 and 12, on which the rotor 28 is mounted, is... Figure 2 Optionally, the actuation drive 9, 10 can be coupled to a third axis via a compensating coupling for common rotation. In an exemplary embodiment, the "third axis" is the inner ring of the wave generator of the actuation drive 9, 10 in the form of a harmonic driver.

[0050] Electric motors 11 and 12 are connected to the camshaft control device 17 via connecting line 13 and signal line 14. The plug and socket connection for connecting line 13 of electric motors 11 and 12 is shown as 15, and the plug and socket connection for signal line 14 is shown as 16. Lines 13 and 14 are connected to plug and socket connection 18 of the camshaft control device 17. Hall signals obtained by means of a Hall sensor (not shown) are transmitted via signal line 14 and provide information about changes in the angular position of rotor 28. The Hall sensor can be classified under a rotor position detection device, generally indicated as 44.

[0051] The camshaft control unit 17 is connected to the engine control unit 21 of the internal combustion engine 1 via a data bus 19 (i.e., CAN bus) and a signal line 20. A crankshaft sensor 23 is connected to the engine control unit 21 via a crankshaft axis 22. The crankshaft sensor 23 scans the crankshaft trigger wheel 27 fixed to the crankshaft 2. Furthermore, sensors 24 and 25 are connected to the engine control unit 21, each of which interacts with a trigger disc 26 connected to the camshafts 3 and 4.

[0052] Figure 2 The diagram illustrates data processing operations in engine control unit 21 (left) and camshaft control unit 17 (right). As can be seen from the diagram, signals generated by trigger disc 26 are processed within engine control unit 21. In an exemplary embodiment, trigger disc 26 schematically has a single raised portion 32. The edge of raised portion 32 is indicated as 33. The edge 33 of trigger disc 26 provides a camshaft trigger in a manner known per se. A logical link is established between the camshaft trigger and the scan of crankshaft trigger wheel 27.

[0053] The crankshaft trigger wheel 27 has teeth 35, which together with the adjacent clearance between two teeth 35 located at an angle each covering 6°. A recess 36 is formed by omitting two teeth, wherein the first tooth 35 adjacent to the recess 36 is reference numeral 34. The signal detected by means of reference numeral 34 is also referred to as the TD signal. A copy of this TD signal, which may be further marked, is transmitted from the engine control unit 21 to the camshaft control unit 17 via signal line 20. Within the camshaft control unit 17, the TD signal indicating the reference angular position of the crankshaft is logically linked to the features of the electric motors 11 and 12.

[0054] Figure 2 The permanent magnet 30 and winding 31 of the electric motors 11 and 12 are shown. Possible outlines of Hall signals HSA, HSB, and HSC, which provide information about changes in the angular position of the rotor 28, are schematically shown. Each combination of Hall signals HSA, HSB, and HSC corresponds to a bit pattern, which in the exemplary embodiment corresponds to bit patterns 010, 011, 001, 101, 100, and 110.

[0055] like Figure 3 As shown, each tooth 35 provides a rising edge Fs and a falling edge Ff. Under good approximation, it can be assumed that the crankshaft speed does not change during a further rotation of one tooth 35. Therefore, the time interval indicating a portion of the time as the crankshaft 2 continues to rotate from one tooth 35 to the next can be used to calculate any angular position of the crankshaft 2 between two teeth 35. In this way, the camshaft reference position (i.e., the angular position of the camshafts 3, 4 where the detected edge 33 is located) can also be assigned to the precise angular position of the crankshaft 2.

[0056] In a comparable manner, the position patterns generated during the operation of electric motors 11 and 12 are used to extrapolate the angular positions of camshafts 3 and 4. The calculation also assumes that motor shaft 29 rotates at an approximately constant angular velocity within the relevant angular range.

[0057] Figure 4a The signal S, received and processed by one of the control devices 17 and 21, is shown. The applied voltage is plotted as it changes over time. The signal S consists of a useful signal 45 and superimposed interference pulses 46a to 46h. Due to the short duration of the interference signal, the interference signal induces a voltage peak due to its short duration.

[0058] The electrical signal S is analog and is converted into a digital signal S' in the first step. Two quantization levels, Q1 and Q2, also represented as low and high, are provided for the digital signal. The following is performed to assign one of the quantization levels:

[0059] If the signal voltage is higher than the upper threshold U2, it is assigned to quantization level Q2 regardless of the actual level. Similarly, if the signal voltage is lower than the lower threshold U1, it is assigned to quantization level Q1. This means that, for example, interference pulses 46b and 46h have no effect on the assignment to quantization level Q1.

[0060] The range between thresholds U1 and U2 defines the transition range. If the voltage changes over time above one of the thresholds or drops below one of the thresholds, and thus reaches the transition range, but does not exceed the other threshold or drops below the other threshold, the quantization levels Q1 and Q2 are not redistributed. Therefore, the interference pulse 46e does not cause redistribution because although the voltage exceeds the lower threshold U1, it then drops below the lower threshold again, whereas it did not previously reach the upper threshold U2.

[0061] All other interference pulses 46a, 46c, 46d, 46f, and 46g are included in the digital signal S'.

[0062] In the next step, the number of changes in quantization levels Q1 and Q2 within the corresponding scan rate interval T is established. All even-numbered changes in quantization levels Q1 and Q2 within the scan rate interval T are rejected, so that only the first change is considered. As described below, this eliminates interference pulses.

[0063] exist Figure 5d The diagram shows, in more detail, the interference pulse 46a that occurs within the first scan rate interval T. The interference pulse 46a forms a double edge and thus creates a double change in quantization levels Q1 and Q2, and is therefore not counted. The same applies to... Figure 5c Interference pulses 46d and 46f are shown in magnified view. Interference pulses 46d and 46f also form double edges and are therefore not counted.

[0064] The interference pulse 46c is located within the range where the useful signal 45 changes from quantization level Q2 to quantization level Q1. Figure 5a The relevant scan rate interval T is shown in the diagram. There are an odd number of edges, therefore the first edge is considered as a change in quantization level from Q2 to Q1. The same applies to the reverse transition. Figure 4a In this process, the reverse transition is provided with a flatter signal rise and two interference pulses 46f and 46g. Figure 5g The corresponding scan rate interval is shown in the figure. The five edges again form an odd number, so that they serve as the change count for quantization levels Q1 and Q2.

[0065] The reduction in the final generation of interference pulses 46a to 46h releases the computing power in control devices 17 and 21 that could be used for other calculations. Figure 3 The trigger disk 26 is shown, which is related to Figure 2The difference with the trigger disk is that calculations are performed on three edges. The phase angle is calculated using the values ​​shown here in the following cases:

[0066] Arrow 1 to 2 × 0° - 0° = 0°

[0067] Arrow 2 points to 2 × 15° - 30° = 0°.

[0068] Arrow 3 to 2 × 90° - 160° = -20°.

[0069] This allows for redundancy and also makes the control loop more stable.

[0070] List of reference numerals

[0071] 1. Internal combustion engine

[0072] 2 Crankshaft

[0073] 3 Camshaft

[0074] 4 Camshaft

[0075] 5. Chain drive device

[0076] 6. Chain drive device

[0077] 7 Camshaft Adjuster

[0078] 8 Camshaft Adjuster

[0079] 9. Actuation and transmission device

[0080] 10 Actuation transmission device

[0081] 11 Electric motor

[0082] 12 Electric motors

[0083] 13 Connecting wires

[0084] 14 signal lines

[0085] 15. Plug and socket connections for connecting cables.

[0086] 16. Plug and socket connections for signal lines.

[0087] 17 Camshaft Control Device

[0088] 18. Plug and socket connection for camshaft control device

[0089] 19 Data Bus

[0090] 20 signal lines

[0091] 21 Engine control unit

[0092] 22 Crankaxis

[0093] 23 Crankshaft Sensor

[0094] 24 sensors

[0095] 25 sensors

[0096] 26 trigger disks

[0097] 27 Crankshaft trigger wheel

[0098] 28 rotors

[0099] 29 Motor Shaft

[0100] 30 permanent magnet

[0101] 31 windings

[0102] 32. Elevation section

[0103] 33 Edge

[0104] 34. Figure Labels

[0105] 35 teeth

[0106] 36 recess

[0107] 37 Evaluation Units

[0108] 38. Annular buffer zone of camshaft control device

[0109] 39 Memory Area

[0110] 40 Memory Area

[0111] 41. Annular buffer zone of engine control unit

[0112] 42 Memory Region

[0113] 43 Memory Area

[0114] 44 Rotor position detection device

[0115] 45 useful signals

[0116] Interference pulses from 46a to 46h

[0117] Ff descent edge

[0118] Fs rising edge

[0119] HSA Hall signal

[0120] HSB Hall signal

[0121] HSC Hall signal

[0122] S signal

[0123] S' digital signal

[0124] T scan rate interval

[0125] TD signal

[0126] P1 Arrow 1

[0127] P2 Arrow 2

[0128] P3 Arrow 3

Claims

1. A method for processing an electrical signal (S), said electrical signal being generated continuously over time and based on measurements from sensors (23, 24, 25), and transmitted via lines (20, 22) affected by disturbance variables, said method having the following characteristics: a) Establish the scan rate interval (T). b) Establish quantitative levels (Q1, Q2). c) Assign the electrical signal to quantization levels (Q1, Q2). d) Determine the number of times the quantization levels (Q1, Q2) change within the scan rate interval (T). e) Reject all even-numbered variations of the quantization level (Q1, Q2) within the scan rate interval (T).

2. The method according to claim 1, characterized in that, In the case of an odd number of changes in the quantization level (Q1, Q2) within the scan rate interval (T), all changes in the quantization level (Q1, Q2) within the scan rate interval (T) after the first change are rejected.

3. The method according to claim 1 or 2, characterized in that, The electrical signal (S) is a digital signal or an analog signal, which is quantized into exactly two quantization levels (Q1, Q2) after being transmitted through the lines (20, 22).

4. The method according to any one of the preceding claims, characterized in that, The electrical signal (S) is filtered.

5. The method according to any one of the preceding claims, characterized in that, In the case where there are an odd number of changes in the quantization level (Q1, Q2) between two consecutive scan rate intervals (T), the number of changes in the quantization level (Q1, Q2) within the current and previous scan rate intervals (T) is set to zero.

6. The method according to any one of the preceding claims, characterized in that, The sensors (23, 24, 25) measure continuously changing variables.

7. The method according to claim 6, characterized in that, The sensors (23, 24, 25) scan the trigger wheel of the camshaft (3, 4) or crankshaft (2).

8. The method according to any one of the preceding claims, characterized in that, The scan rate interval (T) is either controlled in an open loop or controlled in a closed loop by the measured values.

9. The method according to any one of the preceding claims, characterized in that, The scan rate interval (T) is less than 50 μs.

10. A control device (17, 21) for a camshaft adjuster (7, 8) or for an internal combustion engine (1), the control device performing the method according to any one of the preceding claims.

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