CN103745112B - Method for ensuring maximum residue failure rate of signal chain - Google Patents

Abstract

The invention provides a method for ensuring maximum residue failure rate of a signal chain in car safety completeness grade evaluation. The flow path of signals in signal chain evaluation can be used to ensure the maximum residue failure rate according to the following steps: acquiring corresponding PPM values for elements which can not acquire failure modes and corresponding failure rate, wherein the PPM values refer to bad element amount in the designated amount during a designated period; utilizing the acquired PPM values to acquire metering failure rate, acquire the minimum judgment identification rate in all failure modes related to the safety according to the above elements so as to further acquire maximum judgment non-identification rate of the elements; acquiring maximum residue failure rate of the elements related to the safety based on the metering failure rate of the elements and the minimum judgment non-identification rate; acquiring residue failure rate related to the security from the rest elements with failure modes and failure rate; acquiring maximum value of all residue failure rate of the signal chain according to the maximum residue failure rate of the elements.

Description

Method for determining the maximum residual failure rate for a signal chain

technical field

The present invention relates to a method for determining the maximum residual failure rate of a signal chain in automobile safety integrity level assessment, in particular, a method for determining the maximum residual failure rate of a signal chain based on PPM data of components.

Background technique

With the popularity of motor vehicles, the safety of vehicles has become a common concern of technicians and owners of motor vehicles (ie users). In recent years, while continuously improving the quality of various components in the vehicle, there have also been many control mechanisms to improve the overall safety of the vehicle, such as electronic braking systems, such as the Anti-lock Braking System ABS (Anti-lock Braking System) ), electronic stability control ESC (Electronic Stability System) system, etc.

The ABS system can be installed on any car with hydraulic brakes. It uses a rubber airbag in the valve body to give brake fluid pressure to the ABS valve body when the brake is stepped on, and then the airbag uses the air compartment in the middle to return the pressure to avoid the locking point of the wheel. Specifically, the ABS system sends a signal that the wheel will be locked through the sensor installed on the wheel, and the controller instructs the regulator to reduce the oil pressure of the brake cylinder of the wheel, reduce the braking torque, and then recover after a certain period of time. The original oil pressure is continuously cycled in this way (up to 5-10 times per second), so that the wheels are always in a rotating state and have the maximum braking torque.

In contrast to this, if a vehicle without ABS is running, if the brake pedal is pressed hard, the wheel speed will drop rapidly. When the braking force exceeds the friction between the wheel and the ground, the wheel will be locked, and a completely locked wheel will reduce the friction between the tire and the ground. If the front wheels of the vehicle are locked, the driver will not be able to control the driving direction of the vehicle, and if the rear wheels are locked, it is very easy to slip.

It can be seen that the ABS system effectively improves the safety during driving, so the fault detection of the ABS system itself is particularly important. Faults include circuit faults and mechanical faults, such as faults in sensors in the ABS system (including sensor coil resistance, rotor ring gear and sensor output signals, etc.), brake pressure regulators, electronic control units and other components. Therefore, detecting the safety of each component in the ABS system is one of the important factors to ensure driving safety.

In addition to the ABS system, the vehicle contains a variety of large and small components produced by multiple manufacturers. The safe and normal operation of each component obviously plays a vital role in the overall safety of the vehicle. The existing method of evaluating vehicle safety integrity is to learn the quantitative indicators such as the residual failure rate of the signal chain through comprehensive evaluation of the failure mode, failure rate and safety mechanism of each component in a certain signal chain, and to obtain the indicators Comparison with established safety integrity levels (e.g. according to the road vehicle functional safety standard ISO26262) to determine the automotive safety integrity level of the entire signal chain. Such signal chain automotive safety integrity level assessment has become one of the most basic and important tasks in road vehicle functional safety.

Specifically, in the process of evaluating the safety integrity level of such a signal chain vehicle, it is necessary to know the detailed information of the failure modes, failure rates and safety mechanisms of each component on the signal chain. However, in reality these components usually come from different (even foreign) suppliers, and given that some of the information is often kept by the manufacturer as a trade secret because it concerns the core of the product, it leads to a valid assessment of the automotive safety integrity level of the signal chain directly bring obstacles.

In view of the above situation, there is a need for a method that can still evaluate the safety integrity level of the signal chain without knowing the failure mode, failure rate and safety mechanism of some components of the signal chain.

Contents of the invention

In order to solve or at least alleviate the above-mentioned problems in the prior art, the present invention provides a method for determining the maximum residual failure rate of the signal chain by using the PPM data of relevant components in the signal chain, thereby realizing the automotive safety integrity of the signal chain sex ratings.

According to one embodiment of the present invention, there is provided a method for determining the maximum residual failure rate of a signal chain in an automobile safety integrity level assessment, wherein the signal chain refers to a path through which signals flow in the assessment, through the following steps Determine its maximum residual failure rate:

For the component whose failure mode and corresponding failure rate cannot be known, obtain its corresponding PPM value, where the PPM value is the number of bad parts in the specified quantity of the component within the specified period;

Using the obtained PPM value of the component to obtain the count failure rate of the component;

For each of the above components, obtain the minimum diagnostic recognition rate among all safety-related failure modes, and then obtain the maximum diagnostic non-recognition rate of the component;

Obtaining the maximum residual failure rate of the component related to safety based on the counted failure rate of the component and its maximum diagnostic non-recognition rate;

For the remaining components with known failure modes and failure rates, obtain their safety-related residual failure rates;

Combining the maximum residual failure rate of the above components with the residual failure rate of the remaining components, the maximum value of the residual failure rate of the entire signal chain is obtained.

Optionally, the signal chain comprises a sensor and an electronic control unit receiving a signal from the sensor, wherein the failure modes and corresponding failure rates of the sensor are unknown. Wherein, the electronic control unit is an electronic braking system.

Preferably, the sensor is a wheel speed sensor, a steering wheel angle sensor and/or a vacuum sensor, and the electronic braking system is an electronic stability control system.

Preferably, the sensor is a wheel speed sensor, and the electronic braking system is an anti-lock braking system.

Optionally, the product of the counted failure rate and the maximum diagnostic non-identification rate for each failure mode and corresponding failure rate unknown component is taken as the safety-related maximum residual failure rate of the component, and the maximum diagnostic non-identification rate is an integer 1 the difference from the previous minimum diagnostic identification rate obtained in relation to the component.

Optionally, the safety-related residual failure rates of the rest of the components are calculated in the following manner: for each of the remaining components, the failure rate and diagnostic recognition rate in each failure mode are obtained, and the integer 1 and The difference of the recognition rate is taken as the non-diagnosed rate of the component, and the product of the failure rate in each failure mode and the non-diagnosed rate is taken as the residual failure rate of the failure mode; for each component in each failure mode The residual failure rates are summed to obtain the safety-related residual failure rate for the component.

Preferably, the PPM value is the number of defective parts per million pieces per year for the component, and the failure rate per count is $\frac{\mathrm{PPM}}{{10}^6\×365\×\mathrm{twenty\; four}}\×{10}^9.$

It can be seen from the above that by using the PPM value of the component, the present invention can calculate the residual failure rate of the component whose failure mode and corresponding failure rate cannot be known, thereby reducing the difficulty of evaluation and improving the efficiency of signal chain residual failure rate evaluation .

Description of drawings

The above and other advantages of the present invention, and other features and advantages of the disclosed exemplary embodiments will become apparent to those skilled in the art from a further understanding of the present invention from the following detailed description taken in conjunction with the accompanying drawings. However, it should be noted that both the drawings and the specific examples below are only exemplary descriptions made to illustrate the idea of the present invention, and should not be regarded as limiting any aspect of the present invention. The protection scope of the present invention is defined by the contents of the appended claims and their equivalents. In the attached picture,

Figure 1 schematically shows a part of a signal chain in which the solution of the present invention can be implemented;

Fig. 2 schematically illustrates a method according to an exemplary embodiment of the present invention.

Detailed ways

As mentioned above, in the signal chain automotive safety integrity level assessment, the evaluation of the residual failure rate of each component on the signal chain is an important part of the signal chain automotive safety integrity level assessment. Automotive Safety Integrity Level assessment of individual components and the entire signal chain will be discussed below in conjunction with a schematic simplified signal chain shown in Figure 1.

The signal chain shown in Figure 1 includes sensor A, electronic control unit B and signal chain output signal S. Here, the sensor A may be, for example, a wheel speed sensor, a steering wheel angle sensor, a vacuum sensor, etc. or any combination thereof, and the electronic control unit B may be, for example, the above-mentioned ABS system. For the sake of simplicity, FIG. 1 only schematically shows a part of the signal chain in a vehicle. It is obvious that the evaluation method according to the present invention can be applied to any components and related signal chains in the vehicle, and is not limited to the situation shown in FIG. 1 .

In addition, it can be understood that the signal chain mentioned herein refers to the path through which signals flow. Specifically, the path may include any suitable elements, such as sensors, wire harnesses, processors, and the like shown in FIG. 1 . Among them, the signal flowing through the signal chain involves not only the real physical quantity detected by the sensor, but also the information that reflects the size, strength and other indicators of the measured physical quantity output after transmission and processing.

The failure mode of sensor A in Figure 1 is counted as Fi, its corresponding failure rate is Ri, and the corresponding diagnostic recognition rate is Di (where i=1 to n). Among them, Ri refers to the failure probability of sensor A in the corresponding failure mode Fi. Among them, the diagnostic recognition rate Di is the quantified value of the safety mechanism, which is the probability that the sensor A can perform correct diagnostic recognition in a certain working range of the corresponding failure mode Fi. Specifically, for example, if sensor A is a wheel speed sensor, its possible working range is several speed ranges, and if sensor A is a steering wheel handover sensor, its possible working range is some angle ranges, then the corresponding diagnostic recognition rate Di is is the diagnostic recognition rate within a corresponding specific speed range or angle range. Here, those skilled in the art can understand that the diagnostic recognition rate can be obtained by accumulating empirical data or experimental test data during daily use, testing, research, and the like.

Similarly, the failure mode of electronic control unit B in Figure 1 is counted as Fj, its corresponding failure rate is Rj, and the corresponding diagnostic recognition rate is Dj (where j=1 to m).

Assuming that all failure modes of the above components A, B are safety-related, the total residual failure rate RF of the signal chain shown in Figure 1 should be:

$\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; RF</span>}$

Wherein, the difference between the integer 1 and the diagnostic recognition rate D means the probability that the component cannot be diagnosed and recognized, that is, the diagnostic non-recognized rate.

However, it should be noted that the prerequisite for the calculation method of the residual redundancy failure rate of the above signal chain is that the failure mode and failure rate of each component on the signal chain need to be known, because only by knowing these two can the failure rate be obtained. Statistical data of the residual failure rate of components in the mode (otherwise, even if the statistical data of the corresponding diagnostic recognition rate in some specific cases is known, it is impossible to know which failure rate the obtained diagnostic recognition rate statistical data corresponds to, resulting in still being unable to calculate component residual failure rate).

It can be seen that in order to use the above formula to calculate the residual failure rate of the signal chain, the failure mode and failure rate of each component must be known, so as to obtain the corresponding residual failure rate on this basis. However, as mentioned earlier, the failure modes and failure rates of components are often kept as trade secrets by manufacturers, therefore, an alternative way of calculating the residual failure rate of the signal chain needs to be found.

As mentioned above, the present invention calculates the residual failure rate of components whose failure mode and corresponding failure rate cannot be known by using the PPM value, and then calculates the total residual failure rate of the entire signal chain. This is because, among the available information of each component on the signal chain, the PPM (Parts Per Million) value is relatively public product information. Among them, the value of PPM is the amount of bad parts in the specified quantity of components within the specified period. In the following, the number of bad parts per million pieces per year is used as an example of PPM value. Of course, in practice, the selection of the PPM value is not limited to this. For those skilled in the art, the PPM value can also be set to every six months, every three months, every three years, etc. in any suitable period of time, such as every million pieces, every hundred thousand pieces, etc. in any number of components , the number of bad pieces. It can be seen that the specific selection of the PPM value can depend on the specific situation.

The following describes the process of using the PPM value to calculate the residual failure rate of components and even the entire signal chain in conjunction with the signal chain shown in FIG. 1 and the method shown in FIG. 2 . Among them, it is assumed that in the signal chain shown in Figure 1, the failure mode and corresponding failure rate of sensor A are unknown. The failure modes and corresponding failure rates of ECU B are known.

As shown in FIG. 2 , in step 201 , for a sensor A whose failure mode and corresponding failure rate cannot be known, its corresponding PPM value is obtained. Here, as an example, the PPM value is selected as the number of defective parts per million pieces per year for sensor A.

In step 202, the FIT (Failure In Time) value of the element is obtained by using the obtained PPM value of the sensor A. Wherein, FIT represents the failure rate of the sensor A within a certain period of time, for example, within a period of 109 hours. When PPM is the number of bad parts per million pieces of sensor A per year, and the time period is 10 ⁹ hours, the FIT value can be expressed as:

$\frac{\mathrm{<span\; class="notranslate">\; PPM</span>}}{{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 365</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; twenty\; four</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 9</span>}}$

Wherein, the quotient of PPM and (10 ⁶ ×365×24) represents the failure probability of each sensor A per hour, that is, the failure rate of the sensor A.

In step 203, for each such component, such as sensor A, the minimum value of the statistical data of diagnostic recognition rates in all working ranges in all safety-related failure modes is extracted as the minimum diagnostic recognition rate of sensor A. According to the minimum diagnostic recognition rate, its maximum diagnostic non-recognition rate (for example, the difference between 100% and the minimum diagnostic recognition rate) is obtained.

In step 204, based on the failure count FIT value of the component and the maximum diagnosis unrecognized rate,

Obtain the maximum safety-related residual failure rate for this component (sensor A). For example, multiply the FIT value by the maximum diagnostic non-recognition rate to obtain the maximum value of the residual failure rate of sensor A.

In step 205 , for the remaining components (such as the electronic control unit B in FIG. 1 ) whose failure modes and failure rates are known, obtain their safety-related residual failure rates.

In step 206, combined with the maximum residual failure rate of the above-mentioned component (sensor A) and the residual failure rate of other components (electronic control unit B), the two part failure rates are summed to obtain the maximum residual failure rate of the entire signal chain value. The maximum value of the total residual failure rate of the signal chain (RFworstcase) is specifically shown in the following formula:

$\frac{\mathrm{<span\; class="notranslate">\; PPM</span>}}{{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 365</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; twenty\; four</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; MIN</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; RF</span>}}_{\mathrm{<span\; class="notranslate">\; worst\; case</span>}}$

For example, in a specific application, the vehicle manufacturer can estimate the maximum residual failure rate of the wheel speed sensor according to the above method, and the ABS supplier provides the residual failure rate related to its product, then the sum of the two parts can be obtained The maximum residual failure rate. Similarly, ESC suppliers can also provide the residual failure rate related to their products. For other types of sensors, such as wheel speed sensors, steering wheel angle sensors, vacuum sensors, etc., the maximum residual failure rate can be obtained according to the above method, and then These two parts are summed to obtain the maximum value of the corresponding total residual failure rate of the signal chain.

As mentioned above, once the maximum value of the total residual failure rate of the signal chain is obtained, it can be compared with a predetermined safety integrity level (eg according to the road vehicle functional safety standard ISO26262) to evaluate the The safety integrity level of the signal chain. For example, in the example shown above, if the residual failure rate is within 100FIT, then this indicator can meet the requirements of safety integrity level B.

It should be noted that the value of the PPM and the time period of the FIT value mentioned above can be set according to specific needs, application environment and many other related factors. For example, FIT can be selected as 10 ^-7 hours.

According to the exemplary embodiment described above in conjunction with FIG. 1 and FIG. 2 , the present invention realizes the estimation of the residual failure rate of an element whose failure mode and failure rate are unknown by using the PPM value. This approach helps to simplify the assessment process and reduce the difficulty of assessment. By using the PPM information to replace the failure mode and failure rate information of each relevant component in the signal chain required in the calculation, the approximate estimation of the residual failure rate of the signal chain is completed. Considering that the residual failure rate is an important index for evaluating the safety integrity level of the signal chain, the scheme proposed by the present invention obviously alleviates the bottleneck in the existing evaluation method.

The foregoing description is exemplary rather than restrictive in nature. For those skilled in the art, any variations and modifications to the disclosed examples to adapt to specific circumstances, requirements and other factors are feasible. Moreover, the specific operation steps of the method are disclosed above in a certain order. However, this does not mean that the order in which the text is presented represents the order in which the steps are performed. Therefore, those skilled in the art can understand that the specific operation steps of the method can be changed on the premise that the present invention can still be implemented, for example, the steps of the above method are combined or further split, and the order is changed. In any case, the protection scope of the present invention is determined by the contents of the appended claims and their equivalents.

Claims (8)

1. A method for determining the maximum residual failure rate of signal chain in the evaluation of automobile safety integrity level, wherein, said signal chain refers to the path through which signal flows in the evaluation, and determines its maximum residual failure rate by the following steps: For the component whose failure mode and corresponding failure rate cannot be known, obtain its corresponding PPM value, where the PPM value is the number of bad parts in the specified quantity of the component within the specified period; Using the obtained PPM value of the component to obtain the count failure rate of the component; For each of the above components, obtain the minimum diagnostic recognition rate among all safety-related failure modes, and then obtain the maximum diagnostic non-recognition rate of the component; Obtaining the maximum residual failure rate of the component related to safety based on the counted failure rate of the component and its maximum diagnostic non-recognition rate; For the remaining components with known failure modes and failure rates, obtain their safety-related residual failure rates; Combining the maximum residual failure rate of the above components with the residual failure rate of the remaining components, the maximum value of the residual failure rate of the entire signal chain is obtained. 2. The method for determining the maximum residual failure rate of a signal chain in an automobile safety integrity level assessment according to claim 1, said signal chain comprising a sensor and an electronic control unit receiving a sensor signal, wherein said sensor's The failure modes and corresponding failure rates are unknown. 3. The method for determining the maximum residual failure rate of the signal chain in the automotive safety integrity level assessment according to claim 1, wherein the counted failure rate of each failure mode and the corresponding failure rate unknown element and The product of the maximum diagnostic non-recognition rate is taken as the maximum safety-related residual failure rate of the component, and the maximum diagnostic non-recognition rate is the difference of the integer 1 and the previously obtained minimum diagnostic recognition rate associated with the component. 4. The method for determining the maximum residual failure rate of the signal chain in the vehicle safety integrity level assessment according to claim 2, wherein the electronic control unit is an electronic braking system. 5. The method for determining the maximum residual failure rate of the signal chain in the vehicle safety integrity level assessment according to claim 4, wherein the sensor is a wheel speed sensor, a steering wheel angle sensor and/or a vacuum sensor, so The electronic braking system described above is an electronic stability control system. 6. The method for determining the maximum residual failure rate of the signal chain in the vehicle safety integrity level assessment according to claim 4, wherein the sensor is a wheel speed sensor, and the electronic braking system is an anti-lock braking system moving system. 7. The method for determining the maximum residual failure rate of the signal chain in the vehicle safety integrity level assessment according to claim 1, the remaining safety-related residual failure rates of the remaining components are calculated in the following manner: For each of the remaining components, the failure rate and diagnostic recognition rate in each failure mode are obtained, and the difference between the integer 1 and the recognition rate is used as the diagnostic non-recognition rate of the component, and the failure rate in each failure mode is The product of the failure rate of the failure mode and the failure rate of diagnosis is taken as the residual failure rate of the failure mode; The residual failure rates for each failure mode of each component are summed to obtain the safety-related residual failure rate for that component. 8. The method for determining the maximum residual failure rate of the signal chain in the automotive safety integrity level assessment according to claim 1, wherein the PPM value is the number of defective parts per million pieces per year of the component, so The stated failure rate