METHOD FOR DETERMINING THE ELECTRICAL RESISTANCE OF AN ELECTRIC SUPPLY LINE

Abstract

A method for determining an electrical resistance of an electrical supply lead of an electrical system. The system is connected to a first and a second electrically conductive supply lead, which are electrically conductively connected on the current-source side. The system is configured to electrically connect an electrical load of the system selectably to the first or to the second supply lead. The method includes: configuring an electrical connection between the first supply lead and the load; configuring an electrical interruption between the second supply lead and electrical loads of the system; impressing a current in the first supply lead; determining a first voltage at the input of the first supply lead; determining a second voltage at the input of the second supply lead; determining a first resistance value of the first supply lead using the first and the second voltage and the impressed current.

Claims

1-15. (canceled)

16. A method for determining at least one electrical resistance of an electrical supply lead of an electrical system, the system being connected to at least a first electrically conductive lead and a second electrically conductive supply lead, the first and second supply leads being electrically conductively connected on a current-source side, and the system being configured to electrically connect an electrical load of the system selectably to the first supply lead or to the second supply lead, the method comprising the following steps: configuring an electrical connection between the first supply lead and the load; configuring an electrical interruption between the second supply lead and electrical loads of the system; impressing a current in the first supply lead; determining a first voltage at an input of the first supply lead of the system, with the current impressed in the first supply lead; determining a second voltage at an input of the second supply lead, with the current impressed in the first supply lead; and determining a first resistance value of the first supply lead of the system by way of the first and the second voltage and the impressed current.

17. The method as recited in claim 16, further comprising the following steps: determining a no-load voltage at the input of the second supply lead of the system, with no current being impressed in the first supply lead; determining a second resistance value that is effective between a current-source-side contact point of the first and second supply leads and a ground contact, using a zero-load voltage, the no-load voltage, and the impressed current.

18. The method as recited in claim 17, wherein the no-load voltage is determined when, during the determination of the no-load voltage, no further changes in current are impressed in a connection of the current-source-side contact point of the first and second supply leads and the ground connection.

19. The method as recited in claim 16, wherein the current is impressed using the load of the system, and control is applied to the load in a test mode using pulsed currents, without causing an external effect other than impression of the current.

20. The method as recited in claim 17, wherein at least one calibrated value, of the first and second voltages or of the impressed current, is used to determine the first or the second resistance value.

21. The method as recited in claim 17, wherein for determination of the first or of the second resistance value, at least one of the first or second voltages or the impressed current is corrected in such a way that systematic deviations are reduced before at least one resistance determination is carried out.

22. The method as recited in claim 16, in which at least one of the determined first and second resistance values is corrected in such a way that systematic deviations of the first or second resistance value is reduced.

23. The method as recited in claim 16, where at least one of the first or second voltages, or the impressed current, or the ascertained first or second resistance values, has associated with it a respective quality value that characterizes a quality of a respective determination.

24. The method as recited in claim 23, wherein the quality value of at least one of the first or second voltages, or of the impressed current, or of the ascertained first or second resistance values, is determined by way of at least one absolute condition of a result, of a measured value, of a ripple of the measured value, of a duration of the measurement, or of a temperature of individual components during the measurement.

25. The method as recited in claim 16, wherein before the current is impressed in the first supply lead, a check is made as to whether a special state of a vehicle that possesses such the system exists, before a current outside a regular operating mode is impressed in the first supply lead.

26. A method for predicting a voltage drop across at least one electrical resistance of a electrical supply lead of the electrical system, the system being connected to at least a first electrically conductive lead and a second electrically conductive supply lead, the first and second supply leads being electrically conductively connected on a current-source side, and the system being configured to electrically connect an electrical load of the system selectably to the first supply lead or to the second supply lead, the method comprising the following steps: configuring an electrical connection between the first supply lead and the load; configuring an electrical interruption between the second supply lead and electrical loads of the system; impressing a current in the first supply lead; determining a first voltage at an input of the first supply lead of the system, with the current impressed in the first supply lead; determining a second voltage at an input of the second supply lead, with the current impressed in the first supply lead; determining a first resistance value of the first supply lead of the system by way of the first and the second voltage and the impressed current; and predicting the voltage drop using the first resistance value and: (i) a limit current, and/or (ii) a least one of the first and second voltages, and/or (iii) the impressed current.

27. The method as recited in claim 26, wherein a control application signal for applying control to an at least semiautomated vehicle, and/or a warning signal to warn a vehicle occupant, is emitted depending on the predicted voltage drop.

28. An apparatus configured to determine at least one electrical resistance of an electrical supply lead of an electrical system, the system being connected to at least a first electrically conductive lead and a second electrically conductive supply lead, the first and second supply leads being electrically conductively connected on a current-source side, and the system being configured to electrically connect an electrical load of the system selectably to the first supply lead or to the second supply lead, the apparatus configured to: configure an electrical connection between the first supply lead and the load; configure an electrical interruption between the second supply lead and electrical loads of the system; impress a current in the first supply lead; determine a first voltage at an input of the first supply lead of the system, with the current impressed in the first supply lead; determine a second voltage at an input of the second supply lead, with the current impressed in the first supply lead; and determine a first resistance value of the first supply lead of the system by way of the first and the second voltage and the impressed current.

29. A non-transitory machine-readable storage medium on which is stored a computer program including instructions for determining at least one electrical resistance of an electrical supply lead of an electrical system, the system being connected to at least a first electrically conductive lead and a second electrically conductive supply lead, the first and second supply leads being electrically conductively connected on a current-source side, and the system being configured to electrically connect an electrical load of the system selectably to the first supply lead or to the second supply lead, the instructions, when executed by a computer, causing the computer to perform the following steps: configuring an electrical connection between the first supply lead and the load; configuring an electrical interruption between the second supply lead and electrical loads of the system; impressing a current in the first supply lead; determining a first voltage at an input of the first supply lead of the system, with the current impressed in the first supply lead; determining a second voltage at an input of the second supply lead, with the current impressed in the first supply lead; and determining a first resistance value of the first supply lead of the system by way of the first and the second voltage and the impressed current.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Exemplifying embodiments of the present invention are depicted in FIGS. 1 and 4 and are explained in further detail below.

[0066] FIG. 1 shows an electrical system having a first and a second electrically conductive supply lead, a current source, and a ground connection of the current source.

[0067] FIGS. 2A to 2D show systematic deviations of a resistance determination.

[0068] FIGS. 3A to 3D show systematic deviations of a resistance determination.

[0069] FIG. 4 shows steps of a method for determining an electrical resistance, in accordance with an example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0070] The method for determining the first electrical resistance of electrical supply lead 131 of system 140 will be described with reference to FIG. 1 and FIG. 4.

[0071] FIG. 1 schematically shows an electrical system 140 that is connected with a first electrically conducting supply lead 131 to a first terminal 140a of the system, and with a second electrically conducting supply lead 132 to a second terminal 140b of the system, the two supply leads 131, 132 being connected to one another on the current-source side at a star point or connection 123.

[0072] Star point 123 is connected, by way of a first terminal 110a, to current source 110. A second terminal 110b of the current source is connected via two parallel-connected ground connections 133, 134 to ground terminal 148 of the system. The two parallel-connected ground connections 133, 134 are connected to one another on the current-source side via a ground star point 124.

[0073] In FIG. 1, the ground connection is designed redundantly with the two ground connections; 133, 134 this ground connection between current source 140 and ground 148 of system 140 can, however, also be designed as one lead or, for example, as an electrically conductive chassis.

[0074] Electrical system 140 has a first switch 143 that is disposed between first terminal 140a and a first load 141 in such a way that a conducting connection can be selectably established between first load 141 and first terminal 140a of system 140.

[0075] Electrical system 140 has a second switch 145 that is disposed between second terminal 140b and further subassembly 142 of system 140 in such a way that a conducting connection can be selectably established between further subassembly 142 and second terminal 140b of system 140.

[0076] First switch 143 and second switch 145 can be electrically connected to one another selectably by way of a third switch 144 that is contacted to first switch 143 and to second switch 145 respectively on the side located oppositely from terminals 140a, 140b. Load 141 of system 140 is connected by way of a ground connection 146 to second contact 110b of current source 110. Further subassembly 142 of system 140 is connected by way of a ground connection 147 to second contact 110b of current source 110. Current source 110 can be described by an ideal current source 111 that is connected via its respective internal resistances 112, 113 with its first terminal 110a and its second terminal 110b of current source 110.

[0077] For the determination of electrical resistance 131 of the first electrical supply lead of electrical system 140, an electrical connection is configured S1 between first supply lead 131 and load 141 by the fact that first switch 143 is closed. An electrical interruption between second supply lead 132 and electrical loads 141, 142 of system 140 is configured S2 by the fact that second switch 145 of system 140 is opened. With this connection to current source 110 by way of first switch 143 and load 141 of system 140, a current is impressed S3 in first supply lead 131, since load 141 is also connected via its ground connection 146 to second pole 110b of current source 110. For the case in which load 141 of system 140 does not represent a passive electrical load, load 141 must have control applied to it by a control circuit (not shown in system 140 of FIG. 1) for impression of a current.

[0078] The method described here can be applied analogously in order to ascertain the resistance of the second supply lead, by impressing the current of load 141 on second supply lead 132 by the fact that second switch 145 and third switch 144 are closed and first switch 143 is opened. The voltages and currents, and the resistance of second supply lead 132, are determined analogously to what has been described above.

[0079] The first voltage is determined S4 at input 140a of first supply lead 131 of system 140 using a voltage sensor or a voltage measuring device (not shown in FIG. 1). A current is impressed in first supply lead 131 as a result of the connection of load 141 to current source 110 by way of the closed switch 143.

[0080] The second voltage is determined S5 at input 140b of second supply lead 132 of system 140 using a voltage sensor or voltage measuring device (not shown in FIG. 1). First resistance value 131 of the first supply lead is determined S6 by way of the first and the second voltage and the impressed current, in accordance with Ohm's law, by dividing the difference between the two voltages by the impressed current. With a passive load 141 of system 140, the impressed current is obtained using Ohm's law when the applied voltage is known. Load 141 can, however, also have a current sensor or current measuring device that determines the current that is being impressed in first supply lead 131.

[0081] The no-load voltage can be determined at input 140b of second supply lead 132 of system 140, using the voltage sensor described above, without impressing the current in first supply lead 131, for example by opening S7 switch 143 of system 140.

[0082] The second resistance value, which acts between the current-source-side contact point 123, i.e. the star point of the two supply leads 131, 132 and ground contact 148 of system 140, can be determined S8 by way of the zero-load voltage, the no-load voltage, and the impressed current.

[0083] FIGS. 2A to 2D show how electrical resistance 131, 132 is determined systematically at different magnitudes, depending on the magnitude of the system voltage, by way of a load 141 of system 140, for example an electronically commutated electric motor. The target value of the measurement of electrical resistance 131, 132 which is depicted in the diagram of FIG. 2A is equal to 35 mOhm. As is evident from the diagram of FIG. 2A, at higher system voltages the measured value systematically deviates toward an excessively high determined value for the resistance. FIGS. 2B to 2D show, in corresponding diagrams, that with additionally introduced target resistance values of 33 mOhm, 50 mOhm, or 100 mOhm, this effect becomes systematically intensified as the effective resistance values become higher.

[0084] FIGS. 3A to 3D show measurements, corresponding to the measurements of FIGS. 2A to 2D, that were measured at lower impressed currents and with the same measurement duration as the measurement of FIGS. 2A to 2D, in which the above-described effect of the systematic deviation of measured values from the target value is even more pronounced.