DE102005015443A1 - Mass misalignment determining method for vehicles involves determining quality of mass binding of line strands based on comparison between supply voltages across controllers - Google Patents

Abstract

Two controllers (SG1,SG2) having the same operating voltage are connected to the same ground (MP1) of a vehicle. The supply voltages (Usg1,Usg2) of the controllers are measured. The quality of the mass binding of line strands are determined based on the comparison between the measured supply voltages.

Description

The The invention relates to a method and a device according to the preamble of the claims 1, 11 and 12.

at increasing proportion of vehicle electronics with a variety of electronic Control units, sensors and actuator technology increases the cost of vehicle wiring steadily at. For this wiring is largely no closed ground line laid in order to keep the cost of wiring low. In the vehicle individual mass points are defined, with different control units and consumers connected by means of individual earth straps to these ground points become. The connection to the individual ground points is however badly buggy. Due to the occurring during operation of the vehicle environmental influences Is it possible, that the devices connected to different ground points are theirs Reference masses have different contact resistance. There is a so-called mass offset, in which different Control devices or Consumers are at different ground potential. by virtue of These different potentials can cause it to malfunction Control of the consumer come, also be measuring signals misinterpreted due to the different reference potentials.

current Practice in vehicle service is at a suspected mass offset problem the earthbands individually unscrew, clean and where possible restore a common reference potential. This method is time consuming and due to the sometimes difficult installation position consuming. It is therefore desirable the re his contact resistance to determine the critical mass point and possibly even before it occurs of the masenrersatzproblems with a diagnosis to recognize and measures to avoid.

Previously known from the DE 100 28 765 C2 a device for determining the potential offset in a motor vehicle. Here, in two identically controlled by a controller loads, which are at different potential points, the flowing current or the falling voltage is measured. From the difference, a problematic ground point is detected. With the devices described, only critical mass points can be detected when a driving controller drives the loads of different mass points. A detection of which the ground points is faulty can not be made from a comparison.

Of the Invention is based on the object, a method and a device to carry out to create the method by which the strands of a Vehicle with regard to the quality of their ground connection and individual faulty ground points can be detected specifically.

These Task is in generic method according to the invention the characterizing features of claim 1 and for generic devices according to the features the claims 11 and 12 solved.

According to the invention advantageous the procedure for the diagnosis of electrical line strands in Vehicles for Line configurations in which at least two control devices with the same supply voltage operated and with one and the same mass point of the vehicle are connected. The invention makes use of the possibility of modern control devices their own supply voltage to measure and transmitted as measurement data to be able to. The controllers have their own ground reference, usually with the same Ground points like theirs Loads are connected. For the diagnosis of the strands of the Vehicle will be the supply voltage of the control devices that are on working at the same mass point, read out by comparing the measured values of the supply voltages a statement about the quality of the ground connection can be done. Advantageously, this statement is without one Intervention in the line structure of the vehicle possible, so that made a statement about the mass quality with little effort can be. The method uses the possibility of measuring the supply voltage through the control unit itself, thereby dispensing with further means of measurement can.

According to the invention the supply voltage of the control units is read out at a time, on which only one of the two to a common ground point connected control units a load is driving. This has the advantage that on the unloaded control unit the supply voltage remains the same while a drop in the measured value the supply voltage to the load driving the control unit observable is. In contrast, decreases in the unloaded controller, the supply voltage also with, is closed to a faulty ground point.

For verification of the self-diagnosis another control unit can be used. According to the invention, this is advantageously connected to another ground point. The from the comparison of the Supply voltages of the control units, working at the same mass point, obtained statement of a faulty ground point, when driving a load by only one control unit, the supply voltage of both control units decreases, is verified by the supply voltage of the control unit, which is connected to another ground point measured becomes. If the measured supply voltage is almost constant and the supply voltages of the other two control units are reduced, then a faulty ground point MP1 is detected. The approach here is that the used for verification control unit is connected to a fault-free ground point. It can be ruled out that the operating voltage has broken through the control of the load and thus the cause of the drop in the supply voltage of the two control units, which are connected to a common ground point is.

With Knowing the wiring of the vehicle, it is possible gradually to check the mass points of the vehicle. There will be one after the other Mass points selected, to which two controllers are connected on the ground side, this being their supply voltage while measure the activation of an actuator and make these measurement data available. This can successively individually for each ground point, the quality of the ground connection the control units be determined. Vehicle specific can be such an algorithm for Test of the ground points set up and processed in a diagnostic routine become.

With the method according to the invention can the individual faulty ground points are detected. It is advantageous to mark these mass points suitable - z. By numbering - and this Marking in the fault memory to deposit the respective control unit. In an extension of the invention, an evaluation may take place to what extent the mass point deviates from the norm. Dependent on from this review can different measures be taken, for. B. only the generation of an error entry, the next Reading out the fault memory in the workshop would be noticed. at serious, the functionality debilitating Mass offset can be issued information to the driver.

According to the invention advantageous is a vehicle control unit designed so that the procedure for self - diagnosis on this expires and through the controller the measurement data of the supply voltage from the other control units can be read out are, at the same time the information for controlling the actuators the control unit is applied. It can thus in-vehicle, starting from a control unit, in which is stored as a schedule of the test algorithm, the self-diagnosis of the vehicle with error messages regarding erroneous mass points can be generated.

In A development of the invention is the diagnostic algorithm in a vehicle test device, which for example workshops is used, integrated. The vehicle tester then individually speaks the ECUs to measure their supply voltage and generates a drive command for the Actuatorics, by comparing the measured supply voltages to judge the mass point tested and an information about the Goodness of Output earth point. The mass point can be assessed discreetly or by means of a stepless assessment criterion, which a sliding assessment between good and bad allowed to the need to repair or improve the ground connection too mark.

In A training of the procedure may not just be a mass point be checked by driving an actuator. Another possibility is a current pulse during to give an ongoing measurement to a mass point. By an appropriate Height of test current can even minor changes the contact resistance the mass points are easily identified. The test current must be fed in such a way that the current flows over the ground point to be tested. In a advantageous embodiment, the feed directly on the cable lug before the mass point to be tested, in order to obtain larger current values to protect the supply lines. Due to the high current, due to the external feed over the mass point flows, can even with little change the contact resistance of the earth point over the control units measurable voltage drop arise. In an education of the procedure can the measuring process in which the control units their operating voltages be triggered by the vehicle test device and during the Measurement is temporarily applied an external test current. The test current can For example, be generated by an external power source.

following the invention will be described in more detail with reference to an embodiment.

1 shows the ideal case in which all control units have the same reference potential, although they work on different mass points.

2 shows an equivalent circuit of line strands in a vehicle having a ground point with an increased contact resistance.

3 shows a flow chart for a possible implementation of the diagnostic procedure.

In 1 a part of a vehicle wiring is shown symbolically with 3 controllers SG1, SG2 and SG3 and 3 loads L1, L2 and L3. The loads L1-3 controlled by the control units SG1-SG3 are shown here symbolically as controllable resistors. The control units SG1-3 and the loads L1-3 are supplied by a power supply with the operating voltage Ub. The control units SG1 and SG2 are connected on the ground side to a ground point MP1, while the control unit SG3 is connected to a ground point MP3. The ground points are located on the vehicle and are intended to ensure the same reference potential for all loads and control units. The controllers SG1-3 are provided with means for measuring their supply voltage U _SG1-3 . In one possible embodiment, the measured value of the supply voltage is digitized by an A / D converter and provided as a measured value in the control unit or on a data bus. The core of the subsequent method is that the control units have their own reference _ground , against which the supply voltages U _{SG1-3 are} measured. This mass is usually routed to the same ground point as the loads L1-3 controlled by the respective control unit SG1-3. If now a load, for example L1 driven by the control unit SG1 and low impedance, while the load L2 is not controlled by the control unit SG2 and thus remains high impedance, so flows through the load L1, a current. The measured by the control unit SG1 supply voltage U _SG1 drops due to the voltage drop across L1 during the driving of the load. The voltage measured by the control unit SG2 remains constant.

In 2 an identical vehicle wiring is shown, which, however, at the ground point MP1 has an increased contact resistance, which is typical for a faulty ground point. The increased contact resistance is symbolized by the fault resistance R _error . Will now, as already 1 described, at an instant t = 1 an actuator controlled, which is symbolically represented here by the controllable load L1, the branch with L1 and SG1 becomes lower impedance. A current flows from SG1 through L1 and R _errors . Due to the voltage drop across the fault resistance, the supply voltage U _SG2 measured by the control unit SG2 also decreases. The reduction of the supply voltage U _SG1 and U _SG2 during runtime of an actuator t = 1, which results in a change of the load L1 in the direction of low impedance, characterizes the ground point MP1 as faulty. For a verification of the assessment of the ground point MP1, the supply voltage U _{SG3 of} the control unit SG3 can be measured at the same time. If this shows no change at the time t = 1 at which the load L1 is actuated with respect to the time t = 0 before activation of the load, then a faulty ground point MP1 can be assumed. If a break in the supply voltage U _SG3 also occurs when the load L1 is _triggered , then this is not due to a faulty ground point MP1, which is subject to increased contact resistance, because the control unit SG3 is opposite to a ground point MP2 different from the ground point MP1 Supply voltage U _SG3 measures.

In 3 an exemplary embodiment of the method according to the invention is illustrated with reference to a program flowchart. The self-diagnosis algorithm starts when the ignition is switched on. At time t = 0, the supply voltages U _{SG1-3 of} the three control units SG1-3 are read. At time t = 1, the load L1 is controlled by the control unit SG1 and thus low-resistance. During the activation of the load L1, the supply voltages U _{SG1-3 of} the three control units SG1-3 are read repeatedly. The reading of the supply voltages can be repeated at a selected clock rate. The individual time t = 1 is chosen here only as an example. Subsequently, the supply voltage U _{SG1 of} the control unit SG1 and the supply voltage U _{SG2 of} the control unit SG2 at the times t = 0 and t = 1 are compared. If these supply voltages U _SG1 and U _SG2 are both significantly lower at time t = 1 than at time t = 0, a faulty ground point MP1 is assumed. In a next step, the verification is carried out with the measured value of the supply voltage U _{SG3 of} the control unit SG3. If this measured value at time t = 0 is almost equal to that measured at time t = 1, a fluctuation of the operating voltage can be excluded and the ground point MP1 is marked as having an error.

In the event that only the supply voltage U _SG1 at the time t = 1 is significantly reduced compared to the time t = 0, while the supply voltage U _SG2 at time t = 1 is almost equal to the measured value at time t = 0, so is fault-free ground point MP1 closed. In the event that MP1 is rated as faulty due to the break in the supply voltages U _SG1 and U _SG2 at the time t = 1, but the verification with the measured value of the supply voltage U _{SG3 of} the control unit SG3 shows a collapse of the entire operating voltage, the ground point assumed to be faultless. It would also be possible to do no evaluation here and repeat the measurement or define another state of the mass point.

In an embodiment of the method, not shown, a current flow is generated externally instead of the current flow caused by the controlled loads to the ground point. This happens, for example, by an external power source. The current must be impressed so that it flows from a supply line to a ground point (MP1). One possibility is to impress the test current on the cable lug of the supply line directly in front of the ground point to be assessed (MP1). At high test currents, the feed directly in front of the ground point protects the supply line to this. The feeding of an external test current generates the already described for the power generation by a connected load effect that reduce at a faulty ground point, the operating voltages U _SG1 , and U _{S G2 of} the two connected to the common ground point MP1 control units, although only in one of Supply lines a test current is impressed. This is caused by the voltage drop across the fault resistance. On the basis of the evaluation of the operating voltages U _SG1 and U _{SG2 of} the control devices SG1 and SG2 connected to the common ground point MP1, the evaluation of the ground point takes place with regard to its contact resistance.

SG1

Control unit 1

SG2

Control unit 2 (SG1 u. SG2 are masseside to one

common Ground point connected)

SG3

Control unit 3

R _error

fault resistance of earth bond to earth point

MP1

ground point 1

MP2

ground point 2

L1

load 1 driven by SG1

L2

load 2 driven by SG2

L3

load 3 driven by SG3

ub

operating voltage

U _SG1-3

supply voltage the control units SG1-3 against the

ground point of the control unit measured

Claims (17)

Method for the diagnosis of electrical wiring harnesses in vehicles, in which at least two control units (SG1, SG2) are operated with the same operating voltage (Ub), wherein the control units (SG1, SG2) are connected to a ground point (MP1) of the vehicle, wherein the control units have a means for reading their supply voltage (U _SG1 , U _SG2 ), characterized in that the supply voltages (U _SG1 , U _SG2 ) of the control units (SG1, SG2) connected to the same ground point (MP1 ) and read out a statement about the quality of the ground connection of the line strands by comparing the measured values of the supply voltages. Method according to claim 1, characterized in that that the supply voltages of the control units are read out at a time t = 0, on which none of the control units (SG1, SG2) drives a load (L1, L2) and at least at one time t = 1 the supply voltages of the control devices (SG1, SG2) are read out, on which only one of the two to a common ground point connected control units (SG1, SG2) drives a load. A method according to claim 2, characterized in that a critical ground point (MP1) is detected when at both at a common ground point (MP1) connected control devices (SG1, SG2), the measured supply voltage (U _SG1 , U _SG2 ) is lower, although only one of the two control devices (SG1) connected to a common ground point (MP1) drives a load (L1). A method according to claim 1-3, characterized in that for verification of the self-diagnosis, the supply voltage (U _SG3 ) of another control device (SG3), which is connected to another ground point (MP2), is read out. A method according to claim 4, characterized in that a critical ground point (MP1) is detected when at both the common ground point (MP1) connected control devices (SG1, SG2), the measured supply voltage (U _SG1 , U _SG2 ) is lower, although only one of the two control devices (SG1) connected to a common ground point (MP1) drives a load (L1) and the supply voltage (U _SG3 ) measured by the control device (SG3) operating on a different ground point (MP2) remains constant. Process according to claims 1-5, characterized in that that successively selected ECUs (SG1, SG2, SG3 ...) are tested to gradually increase the quality of the mass points (MP1, MP2 ...) of the vehicle to determine. Method according to claim 1-6, characterized in that the load (L1 o. L2.) Controlled by the respective control device (SG1 or SG2 or SG3 o. L ...) are each connected to the same ground point as the associated control unit (SG1 o. SG2 o. SG3 ...). Method according to claims 1-7, characterized that the method for self-diagnosis preferably before starting the vehicle is started with the signal "Ignition ON". A method according to claim 1, characterized in that for the diagnosis of the line strands of the vehicle, the supply voltages (U _SG1 , _SG2 U) of the control units (SG1, SG2), which are connected to the same ground point (MP1), are read out at times an external test current is impressed in one of the leads to the ground point (MP1). A method according to claim 9, characterized in that the supply voltages of the control devices are read out at a time t = 0, on which in none of the control units (SG1, SG2) to the ground point (MP1) leading leads an external test current imprinted is and still at least at a time t = 1, the supply voltages the control units (SG1, SG2) are read, in which at least one of both from the control unit (SG1, SG2) to the common ground point (MP1) leading leads an external Test current imprinted becomes. Method according to claim 9 and 10, characterized in that a critical ground point (MP1) is detected when at both at a common ground point (MP1) connected control devices (SG1, SG2), the measured supply voltage (U _SG1 , U _SG2 ) when impressing an external test current in only one the supply to the common ground point (MP1) is lower. A method according to claim 9-11, characterized in that for verification of the self-diagnosis, the supply voltage (U _SG3 ) of another control device (SG3), which is connected to another ground point (MP2), is read out. Method according to claims 1-12, characterized in that in that at least one mass point recognized as critical (MP1) an entry in the error memory of the control unit (SG1) takes place, wherein the as critically recognized ground point (MP1) is suitably characterized. Method according to claim 13, characterized in that in that at least one mass point recognized as critical (MP1) a signal is sent to the driver. Vehicle control unit on which a method for diagnosis according to claim 1-14 runs, wherein the control unit (SG1) is connected via a data bus with the other control units (SG2, SG3 ...) of the vehicle and measured by all control units supply voltages (U _SG1 , _SG2 U, Us _G3 ...) by the control unit (SG1) are readable and further information about the control of the loads (L1, L2, L3 ...) by the respective control units (SG1, SG2, SG3 ... ) is applied to this and the control unit (SG1) on the basis of the comparison of the measured supply voltages (U _SG1 , U _SG2 ...) upon actuation of at least one of the loads (L1, L2, L3), an assessment of the mass points with respect to the contact resistance and at a as incorrectly detected ground point (MP1) generates an error signal. Diagnostic device on which runs a method for the diagnosis according to claim 1-14, wherein the diagnostic device via a data bus to the vehicle is connectable and measured by the control units (SG1, SG2, SG3 ...) supply voltages (U _SG1 , U _SG2 , U _SG3 ...) are readable by the diagnostic device and further information about the control of the loads (L1, L2, L3) by the respective control devices abut this and the diagnostic device due to the comparison of the measured supply voltages (U _SG1 , U _SG2 , U _SG3 ...) upon actuation of at least one of the loads (L1, L2, L3), an evaluation of the ground points with respect to the contact resistance takes place and an error signal is detected at a ground point (MP1) identified as faulty with which subsequently the ground point (MP1) recognized as critical is suitable is marked. Diagnostic device on which runs a method for the diagnosis according to claim 1-14, wherein the diagnostic device via a data bus to the vehicle is connectable and measured by the control units (SG1, SG2, SG3 ...) supply voltages (U _SG1 , U _SG2 , U _SG3 ...) are readable by the diagnostic device and further information about the impressing of an external test current applied to the diagnostic device and the diagnostic device due to the comparison of the measured supply voltages (U _SG1 , U _SG2 , U _SG3 ...) before and during the impressing of the external test current, the ground point (MP1) is evaluated with regard to its contact resistance and generates an error signal at a ground point (MP1) recognized as critical, in which case the ground point (MP1) recognized as critical is suitably identified.