阅读说明：本技术 用于验证机电负载的功能性的诊断方法和诊断设备及计算机程序产品和车辆 (Diagnostic method and diagnostic device for verifying the functionality of an electromechanical load, computer program product and vehicle ) 是由 A·瓦肯古特 F·郎格 于 2019-06-25 设计创作，主要内容包括：本发明涉及一种用于以尽可能简单和可靠的方式验证具有灵活或动态电流变化过程的电路中的机电负载的功能性的诊断方法。该诊断方法的一种实施变型在此包括：使用操控信号(2)操控所述机电负载,检测所述操控信号(2)的第一实际值。然后将预给定阈值(4)的数值与第一实际值的数值进行比较,其中只要进行操控,就一直以预给定的时间间隔(△t-1,△t-2)重复所述检测和比较。然后只有在至少两次经历检测和比较时所述第一实际值的数值至少与所述阈值(4)的数值一样大的情况下,才生成确认值,该确认值代表所述机电负载的功能性。(The invention relates to a diagnostic method for verifying the functionality of an electromechanical load in a circuit with a flexible or dynamic current variation process in as simple and reliable a manner as possible. One embodiment variant of the diagnostic method comprises: the electromechanical load is controlled using a control signal (2), a first actual value of the control signal (2) being detected. Then, the value of the predetermined threshold (4) is compared with the first real valueThe values of the values are compared, wherein the control is carried out for a predetermined time interval (Δ t) 1 ，△t 2 ) The detection and comparison are repeated. Then, only if the value of the first actual value is at least as great as the value of the threshold value (4) at the time of at least two detections and comparisons, a confirmation value is generated, which confirmation value represents the functionality of the electromechanical load.)

1. A diagnostic method for verifying the functionality of an electromechanical load in a circuit, the diagnostic method comprising:

a) -steering the electromechanical load using a steering signal (2),

b) detecting a first actual value of the control signal (2), and

c) comparing the value of the predetermined threshold value with the value of the first actual value,

characterized by the following steps

d) As long as the control according to step a) is carried out, a predetermined time interval (Δ t) is always present₁，△t₂) Repeating steps b) and c), and

e) generating a confirmation value only if the value of the first actual value is at least as great as the value of the threshold value (4) at least twice after step c), wherein the confirmation value represents the functionality of the electromechanical load.

2. The diagnostic method according to claim 1, wherein said diagnostic reagent is a reagent,

it is characterized in that

f) Generating a fault value only when the actuation of the electromechanical load according to step a) is ended and only when the first actual value has a value that is at least as great as the value of the threshold value (4) when less than two passes through step c), wherein the fault value represents that the electromechanical load is not functional.

3. Diagnostic method for verifying the functionality of an electromechanical load in an electrical circuit, said diagnostic method comprising

g) Using a steering signal (2) to steer the electromechanical load, an

h) Detecting a first actual value of the steering signal (2),

characterized by the following steps

i) An acknowledgement value is generated only if the value of the first actual value is less than a value of a predefined threshold value (4) at most for as long as a predefined time period (Δ t), wherein the acknowledgement value represents the functionality of the electromechanical load.

4. A diagnostic method for verifying the functionality of an electromechanical load in a circuit, the diagnostic method comprising:

j) -steering the electromechanical load using a steering signal (2),

k) detecting a first actual value of the control signal (2), and

l) setting a second actual value of the control signal (2) that is dependent on the first actual value,

characterized by the following steps

m) onlyTo carry out the control according to step j), a predetermined time interval (Δ t) is always provided₁，△t₂) Repeating steps k) and l), and

n) generating a confirmation value only if the sum of the values of the respective second actual values is at least as great as the value of the predefined threshold value, wherein the confirmation value represents the functionality of the electromechanical load.

5. The diagnostic method according to any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

o) operating the electromechanical load with an electric current.

6. The diagnostic method according to any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

p) the first actual value is the current intensity.

7. The diagnostic method according to any one of claims 4 to 6,

it is characterized in that the preparation method is characterized in that,

q) said second actual value is an electrical work.

8. Computer program product comprising a series of instructions which, when executed by at least one processor, cause a diagnostic device to carry out the method for verifying the functionality of an electromechanical load in an electrical circuit according to any one of the preceding claims.

9. Diagnostic device for verifying the functionality of an electromechanical load in an electrical circuit, having computing means configured to execute a diagnostic method according to any one of the preceding claims 1 to 7.

10. A vehicle having the diagnostic apparatus of claim 9.

Technical Field

The present invention relates to a diagnostic method and a diagnostic device for verifying the functionality of an electromechanical load in an electrical circuit, as well as to a computer program product and a vehicle according to the preambles of the independent patent claims.

Background

In order to ensure the correct functioning of an electromechanical load, also referred to as a load in the following, in an electrical circuit, the electrical properties of the electromechanical load, such as the current intensity and the voltage, are usually monitored during operation.

To this end, a method and a device for monitoring the power of a plurality of consumers from a single source are known from US 6,430,518B 1. To this end, the data detection system detects current and voltage from a common circuit that provides energy to the load branch circuit. These load branch circuits include, for example, consumers whose own load state changes during start-up or shut-down. Transmitters connected to these load branch circuits identify that consumer whose load state has changed. The data processor receives information not only from the sensors but also from the transmitter in order to associate the measured current and voltage information from the common circuit with the respective customer whose own load state changes.

Furthermore, a method for determining a supply voltage of a load and a load are known from US 2016/0313381 a 1. In order to reliably determine the supply voltage of the individual phases of a load in a multi-phase power supply system, in particular a three-phase power supply system, a measuring module is provided, by means of which the supply voltage is determined by means of a matrix operation on the basis of the measured voltages. The matrix operation is used in particular to compensate for potential differences or potential drifts between the measurement system and the supply network without requiring hardware measures such as voltage converters.

Furthermore, a fault prediction system for a distribution system and a monitored load is known from US 9,453,869B 1. To this end, the voltage quality of the electrical system is monitored based on a series of system parameters. The system parameter data is aggregated and analyzed to determine a load factor for the system during the time period, and the derived standard deviation factor is utilized to evaluate the corresponding system. The standard deviation is used to determine an alarm threshold. Continuous monitoring enables the system to notify personnel of a possible failure in one or more system components. In this way, maintenance can be performed before a component fails and the system experiences a fault condition.

A disadvantage of the known prior art is that the characteristics of the consumer, such as the current consumption, must first be analyzed. This means that the electrical properties of the consumer must be preprocessed in order to monitor the power of the consumer in a correct manner or to diagnose a fault correctly. Furthermore, only incorrect handling of the consumer is recorded in the prior art. However, the correct handling of the electromechanical load is not diagnosed.

Disclosure of Invention

The invention is based on the following tasks: the functionality of an electromechanical load with flexible or dynamic current consumption is proven as simple and reliable as possible.

This object is achieved by the subject matter of the independent patent claims. Advantageous embodiments of the invention are disclosed by the dependent patent claims, the following description and the drawings.

The invention is based on the following recognition: in the prior art, in particular in the case of low load currents in electromechanical loads, functional faults are often diagnosed despite the faultless operation of the electromechanical loads. Furthermore, it is not necessary to monitor the current consumption of the electromechanical load during the total operating time of the load. In order to verify the functionality of the electromechanical load, it is sufficient to evaluate the dynamic current variation process in a statistical manner. The invention is based on the following idea: the current consumption of the electromechanical load during its manipulation in samples or within defined time periods is analyzed. The functionality of the electromechanical load can be verified in a simple manner if the current exceeds a threshold value in a sample or within the defined time period.

By the present invention a diagnostic method for verifying the functionality of an electromechanical load in a circuit is provided. In one embodiment, the diagnostic method comprises for this purpose: in step a), the electromechanical load is controlled using a control signal, in step b), an actual value of the control signal is detected, and in step c), a value of a predefined threshold value is compared with a value of a first actual value. Further, the diagnostic method includes: in step d), steps b) and c) are repeated at predetermined time intervals as long as the control according to step a) is carried out. In step e), the diagnostic method further comprises: generating a confirmation value representing the functionality of the electromechanical load only if the value of the first actual value is at least as great as the value of the threshold value at least twice during step c).

In other words, the control signal of the electromechanical load can be sampled at predetermined time intervals until the end of the control. The functionality of the electromechanical load can then only be verified if at least two, preferably three, sampled values, in particular at least two, preferably three, absolute sampled values, are greater than or equal to a defined limit value, in particular a defined absolute limit value.

This yields the following advantages: the diagnostic method can be performed independently of the type of the electromechanical load. This means that it is not necessary to evaluate the electrical characteristics of the electromechanical load in advance, such as the current consumption or the power consumption during switching on or off the electromechanical load. The diagnostic method can thus be used universally and can be implemented in existing circuits in a simple manner. The following advantages are additionally obtained: by waiting for at least two actual values whose own values are greater than or equal to a threshold value, the functionality of the electromechanical load is prevented from being accidentally determined on the basis of a single value, for example due to line disturbances in the circuit. The functionality of the electromechanical load is thus reliably confirmed.

The circuit mentioned here can be designed in particular as an on-board electrical system of a vehicle. It is also contemplated that the electrical circuit may be part of a facility, production facility, or electromechanical facility. The electromechanical load may be realized in particular as a so-called "safety motor", i.e. as a servomotor of a motor vehicle lock. The control signal can preferably be designed as a current signal or as a voltage signal. Correspondingly, the first actual value can be detected as a current intensity or a voltage amplitude, and similarly the threshold value can also be predefined as a current intensity or a voltage amplitude. The predefined time interval may preferably be shorter than the time interval during which the electromechanical load is actuated.

One embodiment of the diagnostic method provides for: generating a fault value in step f) only if the actuation of the electromechanical load according to step a) is ended and only if the value of the first actual value is at least as great as the value of the threshold value when step c) is performed less than twice, wherein the fault value represents that the electromechanical load is not functional.

In other words, a malfunction of the electromechanical load can only be determined without further actuation of the electromechanical load and only if less than two, in particular less than three, of these absolute actual values are greater than or equal to an absolute threshold value.

This yields the following advantages: it may be determined in a traceable manner by the fault value whether the electromechanical load has a functional fault. In addition, accidental fault measurements, for example during switching on or off of the electromechanical load, are therefore also excluded.

The fault value can be present here, for example, as a binary or hexadecimal fault code of one or more bits and can be stored, for example, in a fault memory of the motor vehicle.

The advantages and embodiments of the variants of the embodiment of the diagnostic method also apply at least in part to the other variants of the embodiment of the diagnostic method mentioned below.

In another implementation variation, the diagnostic method includes: in step g) the electromechanical load is manipulated using a manipulation signal, and in step h) a first actual value of the manipulation signal is detected. Furthermore, this embodiment variant comprises generating a confirmation value in step i), which confirmation value represents the functionality of the electromechanical load, wherein the value of the first actual value is at most less than a value of a predefined threshold value for as long as a predefined period of time.

In other words, the manipulation of the electromechanical load can be performed within a manipulation time period using the manipulation signal. In this case, the functionality of the electromechanical load can only be ascertained if the absolute actual value is greater than or equal to an absolute threshold value within a defined time period. Here, the defined time period may preferably be less than or equal to the manipulation time period. The first actual value can be detected in particular as a time profile of the control signal. Therefore, the first actual value may also be referred to as an actual signal. It is particularly preferred that the first actual value is not detected until after a specific transient oscillation time period. The transient oscillation time period may be determined from characteristics of the electromechanical load.

This yields the following advantages: it can be reliably determined whether the electromechanical load is correctly manipulated with the manipulation signal. Another advantage resides in: the described diagnostic method can be implemented in a simple manner in existing circuits. In the case of existing circuits, only the logic is required to be implemented, which confirms the functionality of the electromechanical load in the event of a limit value being exceeded, which is directly linked to a defined time period.

In another implementation variation, the diagnostic method includes: in step j) the electromechanical load is controlled using a control signal, in step k) an actual value of the control signal is detected, and in step l) a second actual value of the control signal is set, which is dependent on the first actual value. The diagnostic method further comprises: in step m), steps k) and l) are repeated at predetermined time intervals as long as the control in step j) is performed, and in step n), a confirmation value is generated which represents the functionality of the electromechanical load if the sum of the values of the respective second actual values is at least as great as the value of the predetermined threshold value.

In other words, the control signal can be sampled at defined time intervals, wherein the resulting sampled values correspond to the respective first actual values. A second actual value can then be formed from the sampled value, i.e. the second actual value is correlated with the first actual value. If the actuation of the electromechanical load is ended, the functionality of the electromechanical load can only be confirmed if the sum of all absolute second actual values is greater than or equal to a predefined absolute reference value.

This yields the following advantages: the corresponding diagnostic method is implemented in a simple manner in existing circuits. Furthermore, it is also possible to prevent the functionality of the electromechanical load from being reliably determined, for example due to a line disturbance trigger in the circuit.

If the first actual value is particularly preferably present as the current intensity, the second actual value can be determined, for example, as the work or power to be performed. This is particularly advantageous in the case of said electromechanical loads, for example driving mechanical components, such as bowden cables.

One embodiment provides that the electromechanical load is controlled by means of an electric current. That is to say, the control signal can be designed as a current. This yields the following advantages: in the case of a known operating voltage of the circuit, the temporal dynamics of the control current can be determined in a simple manner.

Another embodiment provides that the first actual value is the current intensity. In other words, the first actual value may be detected as the current intensity. This yields the advantage that the first actual value can be detected in a simple manner as the amplitude of the temporally changing current profile at a specific point in time or within a specific time period.

Another embodiment provides that the second actual value is an electrical function. In other words, the second actual value can thus be formed as electrical work from the first actual value. This results in the advantage that the mechanical component coupled to the electromechanical load can also be checked indirectly in view of its functionality.

The invention also relates to a computer program product comprising a series of instructions which, when executed by at least one processor, cause a diagnostic device to carry out the method for verifying the functionality of an electromechanical load in an electrical circuit according to any one of the preceding claims.

This means that: the circuit may also have a processor configured to execute a series of instructions. With these instructions, the processor may operate a diagnostic device, which may then perform a diagnostic method for verifying the functionality of the electromechanical load.

The advantage derived therefrom is that a computer program product constructed in this way can be integrated in a simple manner into an existing circuit, whereby the functionality of an electromechanical load in the circuit can be reliably proven.

The invention also relates to a diagnostic device for verifying the functionality of an electromechanical load in an electrical circuit, the diagnostic device being configured to perform a diagnostic method according to any one of claims 1 to 7.

In other words, a diagnostic device may be provided which enables the functionality of the electromechanical load in the circuit to be checked. Here, the diagnostic device may perform at least one of the aforementioned diagnostic methods.

The diagnostic device can be designed, for example, as a microcontroller in the circuit. In particular, the microcontroller can be electrically connected to the electromechanical load and be designed to actuate the electromechanical load or to evaluate an actuation signal of the electromechanical load.

The invention also provides a vehicle having a diagnostic device according to claim 9. The vehicle may be designed in particular as a motor vehicle, passenger vehicle or truck. The vehicle may also be an electric vehicle or a hybrid vehicle, for example.

The invention also comprises a combination of features of the described embodiments. The invention also includes the computer program product according to the invention, the diagnostic device according to the invention and the vehicle according to the invention, which have the features already described in connection with the embodiments of the diagnostic method according to the invention. For this reason, corresponding embodiments of the implementation variants of the diagnostic method are not described here.

Drawings

Embodiments of the present invention are described below. Therefore, the method comprises the following steps:

fig. 1 shows a current profile signal of a servomotor in a motor vehicle over time at constant voltage during unlocking, wherein the functionality of the unlocking motor is determined by sampling the current profile signal;

fig. 2 shows a flow chart of method steps of an embodiment of a diagnostic method for verifying the functionality of an unlocking motor in a motor vehicle;

fig. 3 shows a current profile signal of a servomotor in a motor vehicle over time at constant voltage during unlocking, wherein the functionality of the unlocking motor is determined by checking the time constant of the current profile signal.

The examples set forth below are preferred embodiments of the invention. In the exemplary embodiments, the components of the described embodiments are features of the invention which are to be observed independently of one another, which features also extend the invention independently of one another and are therefore also considered as constituent parts of the invention, individually or in different combinations than those shown. Furthermore, the described embodiments can also be supplemented by other inventive features that have already been described.

In the figures, elements having the same function are provided with the same reference numerals, respectively.

Detailed Description

Fig. 1 shows a diagram 1 of the course of the current over time. In the diagram, the abscissa represents the time t [ ms ] in milliseconds, while the ordinate represents the current I [ a ] in amperes. In particular, fig. 1 shows a control signal 2, i.e. the course of the current of an electromechanical load, here for example a servomotor for a lock in a motor vehicle. In the embodiment shown in FIG. 1, the lock should be unlocked with an unlock command. The unlocking takes place here by actuating the servomotor with a negative current at a constant voltage of 9.5V and a constant temperature of 70 ℃. In these framework conditions, the most critical application for actuating the servomotor is specified, since the current profile in this case is minimal.

In an embodiment which differs from the embodiment shown in fig. 1, the servomotor can be actuated, for example, with a positive current for locking the vehicle. The servomotor for locking or unlocking the lock can be actuated, for example, by a microcontroller, which can be part of the on-board system electronics in the motor vehicle.

As shown in fig. 1, the steering signal may be during a steering time period Δ t_SAnd also transient oscillations in the range of about 0A. For example, if the motor is now controlled by the microcontroller, the current profile can be set for an actuation time interval Δ t, as can be seen in fig. 1_SInternal dynamics. The dynamic change of the control signal 2 can in particular depend on the characteristics of the servomotor. For example, fig. 1 shows that during the actuation period Δ t_SAt the start of the transient oscillation time interval Δ t, e.g. due to switching on the servomotor_EThe transient response of the current can be determined in about 60 ms. Then until a control period Δ t_STo end, the steering signal 2 is transiently oscillated at an approximately constant value of about-0.7A.

To determine the time interval Δ t of the operation_SWhether the electromechanical load, i.e. the servomotor, is correctly operated, the operating signal can be sampled. The samples 3.1, 3.2 can preferably be taken at predetermined time intervals Δ t₁，△t₂The process is carried out. In this case, a predetermined time interval Δ t₁，△t₂Preferably constant. In the figure1 predetermined time interval Δ t₁，△t₂Set to 20 ms. By means of the samples 3.1, 3.2, it is now possible to determine sample values which reproduce the current strength of the control signal 2 at a specific point in time.

These sampled values may then be compared to threshold values, respectively. In the embodiment of FIG. 1, the threshold is set to-150 mA. The threshold value can be predetermined in particular by the sensitivity of the current measuring circuit which detects the current intensity. In this embodiment, therefore, the current measurement circuit is able to detect the current only if the current is outside the limits of +/-150 mA. Within this limit, the current measuring circuit cannot correctly measure the current, that is to say the detected current corresponds to 0A. It is also conceivable to provide a less sensitive current measuring circuit, which can detect the current only if it is outside a limit range of +/-300mA, for example.

In one embodiment of the diagnostic method, it can be provided that at least two sampling values, i.e. for example three sampling values, more precisely the values of the three sampling values, are provided in the control period Δ t_SA value greater than or equal to a predetermined threshold value 4. Only if this condition is met can a confirmation value be generated by the microcontroller, which confirmation value indicates that the servomotor has been correctly actuated. As shown in fig. 1, in this embodiment, during the steering time period Δ t_SThe condition is already met after the fifth sampling 3.1, 3.2.

For example, if this condition is not met in an embodiment different from the embodiment shown in fig. 1, and the absolute sample values are over the control time interval Δ t_SLess than the absolute threshold 4, a fault value may be generated, for example, by the microcontroller, which confirms that: the servo motor is not properly operated.

By checking the functionality of the servomotor in this way, it is possible to prevent the functionality of an electromechanical load being assumed due to an absolute sampling value accidentally exceeding an absolute threshold value. This is the case, for example, in the case of the 20ms samples in fig. 1. At this point in time, the servomotor is still in the on phase, so that the control signal 2 is still oscillating in the transient state. If it is only checked at this point in time whether at least the absolute sampling value is at least equal to the absolute threshold value 4, the functionality of the servomotor is still verified in this case, although the lock of the motor vehicle has not yet been unlocked at this point in time.

In other words, as shown in fig. 1, the diagnostic scheme can be implemented on installed hardware of the onboard power supply system of the motor vehicle, for example in a microcontroller. In this case, for example, the current profile of an electromechanical load, for example a servomotor, can be sampled every 20 ms. Additionally, the sampled values may also be statistically evaluated. For this purpose, fig. 1 shows the current profile of a servomotor, also referred to as a safety motor, of a motor vehicle lock, which is actuated with an unlocking command, at 70 ℃ and 9.5V. In this diagnostic variant, it can be provided that at least two samples, i.e. for example three samples, reach or exceed a threshold value, i.e. a threshold value, of-150 mA, so that a correct actuation of the locking motor takes place. The utilization conditions are as follows: at least two, i.e. for example three, measurements being positive, i.e. the absolute sample value being greater than or equal to the absolute threshold value, should prevent: occasional positive measurements, for example due to disturbances on the line from the microcontroller to the electromechanical load, lead to a false diagnosis.

In another embodiment, as shown in fig. 1, the work done by the servomotor may also be calculated based on the determined sample values. For this purpose, the work can be calculated in addition to the sampled values, i.e. the corresponding current intensities, in the following manner:

wherein U denotes a constant voltage in the vehicle electrical system, e.g. 9.5V,. DELTA.t_XDescribes a predetermined time interval, e.g. Δ t₁And Δ t₂And I denotes the current intensity of the manipulation signal at a specific time point. Thus, if for example regularly at a predetermined time interval Δ t of 20ms₁，△t₂Samples 3.1, 3 were taken.2, the work may be calculated every 20 ms. After the end of the actuation, that is to say during the actuation time interval Δ t_SBesides, it is possible to form the manipulation time period Δ t_SThe sum of all the work in the device and comparing the sum with a set limit value. Thus, according to the embodiment shown in fig. 1, the limit value can be calculated here as:

W_grenz = -150mA 9.5V 20ms = -28.5J。

this means that in this case the correct functionality of the servomotor can only be confirmed if the absolute value of the sum of all the work corresponds to or exceeds the absolute limit value of 28.5J.

In other words, in this further embodiment, the current profile of the servomotor can likewise be sampled, for example once every 20 ms. However, the work performed can then be calculated from these sampled values. For this purpose, each predefined time interval Δ t can be added up₁，△t₂And compared with a reference value, i.e. a limit value. If the sum of the work is lower than said reference value, no correct manipulation of the lock takes place. Thus, the lock is not properly unlocked. If the load current of the electromechanical load, i.e. the control signal 2, is below the threshold value 4, as shown in fig. 1, for example at 40ms, a work of 0J results, since in this case the current is detected as 0A due to the sensitivity of the microcontroller.

Fig. 2 shows a flow chart of method steps of an embodiment of the described diagnostic method. The diagnostic method can be started in a first step 20 if an electromechanical load, for example a servomotor, for unlocking or locking the motor vehicle lock is actuated with an actuation signal. The counter may be zeroed in step 21 after the start and the sampling time may be set to 20ms, for example. Then in step 22, the current value of the electromechanical load's steering signal 2, i.e. for example the current strength, can be detected and compared with a defined threshold value 4. If the current value of the control signal, i.e. the absolute sample value, exceeds an absolute threshold value of 4, which may be set to 150mA, for example, the counter may be incremented in step 22. It may then be checked in step 24 whether the handling of the electromechanical load has ended. If the sample value does not exceed the threshold value in step 22, the counter cannot be incremented and step 24 is directly followed. There are now two possibilities in step 24. If the control has not ended, a new time point for detecting a new sample value can be set in step 25 at the set time interval. Then, at a new sampling point in time, the sampled value can be redetermined and compared to the threshold value 4 in step 22. Thus, steps 22 to 25 can be continued until the end of the control is determined in step 24. If the maneuver is over, the counter reading may be checked in step 26. If in the exemplary embodiment in fig. 2 the counter reading is, for example, greater than or equal to 3, i.e. at least three absolute sample values exceeding the absolute threshold value 4 are detected in step 22, the method can end in step 28. If this condition is not met, a logging can be made in a fault memory in step 27 before the method can be ended in step 28.

Similar to fig. 1, fig. 3 shows a control signal 2 for a servomotor of a motor vehicle lock during unlocking. However, an exemplary embodiment of a further embodiment variant of the diagnostic method is shown here. In this case, the actuation time Δ t can be determined, for example, as a function of the transient response during the switching on of the servomotor_SA predetermined time period Δ t is selected. In particular, the predefined time interval is shorter than the actuation time interval Δ t_S. In the exemplary embodiment in fig. 3, a predefined time interval Δ t of approximately 300ms and a control time interval Δ t of approximately 550ms are shown_S。

In addition to the predefined time interval Δ t, the transient oscillation time interval Δ t can also be set₁Thereby, the start of the diagnostic method can be delayed. In the embodiment shown in figure 3 of the drawings,a transient oscillation time period deltat of about 20ms is obtained₁。

In order to determine whether the servomotor has been correctly actuated according to this embodiment of the embodiment variant of the diagnostic method, the actuation signal 2 can be detected within a predefined time interval Δ t. It can then be determined whether the absolute control signal 2 exceeds the absolute threshold 4 at least once within a predefined time period Δ t. The threshold is set to-150 mA in fig. 3 as in fig. 1.

Fig. 3 shows the control signal 2 during a predefined time interval Δ t during an actual time interval Δ t₃Exceeds a threshold value 4, wherein the actual time interval Δ t₃About 250 ms. Since the servomotor is controlled with a negative current in fig. 3, it is said that the actual time Δ t is approximately 250ms₃The value of the steering signal does not exceed the value of the threshold. Due to the actual time interval Δ t₃Is smaller than a predefined time interval Δ t, and the absolute control signal is present in the predefined time interval Δ t, but in the actual time interval Δ t₃Beyond which an absolute threshold value is exceeded, it can thus be determined that the servomotor is correctly actuated in this case. The microcontroller may then generate a confirmation value representing the correct functionality of the servo motor.

In other words, the diagnostic scheme shown in fig. 3 can also be implemented in installed hardware of the onboard power supply system of the motor vehicle, for example in a microcontroller. For this purpose, logic can be implemented in the microcontroller which only identifies a fault if a defined current threshold, i.e. an absolute threshold value 4, is not reached in direct correlation with a specific time period, i.e. a predefined time period Δ t. For the current threshold, a value of 150mA may be assumed, for example, which is therefore correctly diagnosable in each case. For example, the time period may be set to 300 ms. In this connection, this means in particular: a fault is present only if the current does not exceed the threshold of 150mA for more than 300ms, i.e. the servomotor is not operated correctly.

In general, these examples show how a diagnostic solution for load current can be provided by the present invention.

List of reference numerals

1 current profile over time

2 control signal

3.1 sampling

3.2 sampling

4 threshold value

20 first step

21 second step

22 third step

23 fourth step

24 fifth step

25 sixth step

26 seventh step

27 eighth step

28 ninth step

I current

time t

Δ t predetermined time period

△t₁Predetermined time interval

△t₂Predetermined time interval

△t₃Actual time period

△t_ETransient oscillation time period

△t_SControl time period