Method for determining an electrical variable

Abstract

A method for determining an electrical variable of a component of part of a vehicle electrical system including at least one external current and an electrical impedance unit. A measuring unit is configured to generate a plurality of current and voltage values for each of at least two different operating points of the impedance unit. The method includes: providing the current values of the impedance unit at a first operating point and at least one second operating point; providing the voltage values of the impedance unit at a first operating point and at least one second operating point; corresponding current and voltage values being associated with one another; determining the at least one electrical variable of the component based on a parameter estimation method and an electrical model of the part of the vehicle electrical system and at least part of the corresponding current and voltage values.

Claims

1. A method for determining an electrical variable of at least one component of a part of a vehicle electrical system of a vehicle, the part of the vehicle electrical system including at least one external current and an electrical impedance unit, and a measuring unit for the part of the vehicle electrical system is configured to generate a plurality of current and voltage values for each of at least two different operating points of the impedance unit, the method comprising the following steps: activating the impedance unit to operate at each of the at least two different operating points of the impedance unit; providing a respective plurality of current values of current flowing through the impedance unit measured at each of a first operating point of the at least two different operating points and at least one second operating point of the at least two different operating points; providing a respective plurality of voltage values of voltages at the impedance unit measured at the first operating point and the at least one second operating point; associating corresponding current values and voltage values of the respective pluralities of current values and the respective pluralities of voltage values with one another; and determining the at least one electrical variable of the at least one component based on a parameter estimation method and an electrical model of the part of the vehicle electrical system and at least a part of the corresponding current and voltage values of the first and the second operating points of the impedance unit; wherein the impedance unit is part of a brake system and/or part of a power steering system.

2. A method for determining an electrical variable of at least one component of at least one part of a vehicle electrical system, wherein the vehicle electrical system includes at least a first part and a second part including respective electrical components, and at least one electrical component is associated with both the first part and the second part of the vehicle electrical system, and each of the first part and the second part of the vehicle electrical system includes a respective measuring unit, which generates a plurality of current and voltage values of the electrical impedance unit at each of at least three different operating points of the impedance unit at the respective measuring unit, the method comprising: activating the impedance unit to operate at each of the at least three different operating points of the impedance unit; providing a respective plurality of current values of current flowing through the impedance unit measured at each of a first operating point of the at least three operating points, a second operating point of the at least three operating points, and at least a third operating point, at each of the respective measuring units; providing a respective plurality of voltage values of voltages at the impedance unit measured at each of the first operating point, the second operating point, and the at least third operating point, at each of the respective measuring units; associating corresponding current and voltage values of the respective pluralities of current values and the respective pluralities of voltage values with one another; and determining the electrical variable of the at least one component in the at least one part of the vehicle electrical system based on a modified parameter estimation method, and a modified electrical model of the parts of the vehicle electrical system, and at least a part of the corresponding current and voltage values of the at least three operating points; wherein the impedance unit is part of a brake system and/or part of a power steering system.

3. The method as recited in claim 1, wherein the parameter estimation method is based on a Kalman filter, or an extended Kalman filter, or an unscented Kalman filter, or a recursive least-squares method, or a particle filter.

4. The method as recited in claim 1, wherein the at least one component is a supply line resistivity of the impedance unit.

5. The method as recited in claim 1, wherein the impedance unit is an electrical load of the vehicle electrical system.

6. The method as recited in claim 1, wherein the impedance unit is controlled in each of the first and second operating point to determine the electrical variable of the at least one component of the part of the vehicle electrical system.

7. The method as recited in claim 1, wherein the electrical variable of the vehicle electrical system is transmitted to a central evaluation unit including a computer for monitoring the at least one component.

8. The method as recited in claim 1, wherein: (i) a control signal for activating an at least semi-automated vehicle is provided based on the electrical variable of the at least one component, and/or (ii) a warning signal for warning a vehicle occupant is provided based on the electrical variable of the at least one component.

9. An evaluation unit including a computer configured to determine an electrical variable of at least one component of a part of a vehicle electrical system of a vehicle, the part of the vehicle electrical system including at least one external current and an electrical impedance unit, and a measuring unit for the part of the vehicle electrical system is configured to generate a plurality of current and voltage values for each of at least two different operating points of the impedance unit, the evaluation unit configured to: activate the impedance unit to operate at each of the at least two different operating points of the impedance unit; receive a respective plurality of current values of current flowing through the impedance unit measured at each of a first operating point of the at least two different operating points and at least one second operating point of the at least two different operating points; receive a respective plurality of voltage values of voltages at the impedance unit measured at the first operating point and the at least one second operating point; associate corresponding current values and voltage values of the respective pluralities of current values and the respective pluralities of voltage values with one another; and determine the at least one electrical variable of the at least one component based on a parameter estimation method and an electrical model of the part of the vehicle electrical system and at least a part of the corresponding current and voltage values of the first and the second operating points of the impedance unit; wherein the impedance unit is part of a brake system and/or part of a power steering system.

10. A device, comprising: a measuring unit; an electrical impedance unit; and an evaluation unit evaluation unit including a computer configured to determine an electrical variable of at least one component of a part of a vehicle electrical system of a vehicle, the part of the vehicle electrical system including at least one external current and the electrical impedance unit, wherein the measuring unit is configured to generate a plurality of current and voltage values for each of at least two different operating points of the impedance unit, the evaluation unit configured to: activate the impedance unit to operate at each of the at least two different operating points of the impedance unit; receive a respective plurality of current values of current flowing through the impedance unit measured at each of a first operating point of the at least two different operating points and at least one second operating point of the at least two different operating points; receive a respective plurality of voltage values of voltages at the impedance unit measured at the first operating point and the at least one second operating point; associate corresponding current values and voltage values of the respective pluralities of current values and the respective pluralities of voltage values with one another; and determine the at least one electrical variable of the at least one component based on a parameter estimation method and an electrical model of the part of the vehicle electrical system and at least a part of the corresponding current and voltage values of the first and the second operating points of the impedance unit; wherein the impedance unit is part of a brake system and/or part of a power steering system.

11. The device as recited in claim 10, wherein the device is part of a control unit, or a braking unit, or an electrical power steering.

12. A non-transitory machine-readable storage medium on which is stored a computer program for determining an electrical variable of at least one component of a part of a vehicle electrical system of a vehicle, the part of the vehicle electrical system including at least one external current and an electrical impedance unit, and a measuring unit for the part of the vehicle electrical system is configured to generate a plurality of current and voltage values for each of at least two different operating points of the impedance unit, the computer program, when executed by a computer, causing the computer to perform the following steps: activating the impedance unit to operate at each of the at least three different operating points of the impedance unit; providing a respective plurality of current values of current flowing through the impedance unit measured at each of a first operating point of the at least two different operating points and at least one second operating point of the at least two different operating points; providing a respective plurality of voltage values of voltages at the impedance unit measured at the first operating point and the at least one second operating point; associating corresponding current values and voltage values of the respective pluralities of current values and the respective pluralities of voltage values with one another; and determining the at least one electrical variable of the at least one component based on a parameter estimation method and an electrical model of the part of the vehicle electrical system and at least a part of the corresponding current and voltage values of the first and the second operating points of the impedance unit; wherein the impedance unit is part of a brake system and/or part of a power steering system.

13. The method as recited in claim 1, wherein the impedance unit is a service brake of the vehicle.

14. The method as recited in claim 2, wherein the impedance unit is a service brake of the vehicle.

15. The method as recited in claim 1, wherein, the activating step including activating the impedance unit using pulsed current.

16. The method as recited in claim 2, wherein, the activating step including activating the impedance unit using pulsed current.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the present invention are described with reference to FIG. 1 and explained in greater detail hereinafter.

(2) FIG. 1 shows a part of a vehicle electrical system including a supply line and an assembly.

(3) FIG. 2 shows an outline of a method for parameter estimation in accordance with an example embodiment of the present invention.

(4) FIG. 3 shows two parts of a vehicle electrical system including shared components, in accordance with an example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(5) The method for determining an electrical variable of at least one component of a part of the vehicle electrical system is described with reference to FIGS. 1, 2, and 3.

(6) FIG. 1 outlines a part of a vehicle electrical system 100, using which a control unit 140 of an intelligent brake (IB) is supplied with electrical power at its terminals 142, 144. Power source 110, which has a source voltage U.sub.0, including its internal resistance 111 connected in series, is directly electrically connected at a first output terminal 114 to second terminal 144 of control unit 140. Second output terminal 112 of power source 110 is connected via a first supply line resistivity 120 at a neutral point 129 including a second supply line resistivity 130 to first terminal 142 of control unit 140. Control unit 140 represents the impedance unit. The power source may be designed in the form of an energy accumulator, for example a battery.

(7) The value of supply resistance 120 includes all resistors which are active in the corresponding vehicle electrical system branch. Supply line resistivity 120 includes in particular the supply line resistivities including the contact resistances in the plug, the resistances of the cables themselves, and also ground-side supply line resistivities.

(8) An unknown external current I.sub.x 146 also occurs at neutral point 129, which is not measured in the described method for determining an electrical variable of at least one component of the part of the vehicle electrical system. A measuring unit (not shown here) is configured to determine a plurality of voltage values between terminals 142 and 144 of control unit 140. Furthermore, the measuring unit is configured to determine a plurality of current values I.sub.L which flow through control unit 140 or impedance unit 140. Control unit 140 is configured to have at least two different operating points, for example due to brake applications of different strengths.

(9) Electrical external current I.sub.x may flow into other control units or other components of the entire vehicle electrical system.

(10) According to the method for determining the value of the resistance as an electrical variable of the supply line of at least one component, in the form of the sum of Ri, R1, and R2, of a part of a vehicle electrical system, a measuring unit generates a plurality of current and voltage values for each of at least two different operating points of control unit 140 and provides them to the method. Control unit 140 is controlled in such a way that it assumes these at least two different operating points. If the corresponding current and voltage values are not automatically associated with one another by the measuring unit, this takes place in an optional step of the method.

(11) The value of the sum of Ri, R1, and R2 of the supply line is determined as follows based on a parameter estimation method and an electrical model of the part of the vehicle electrical system and at least a part of the plurality of the corresponding current and voltage values of at least two operating points of the impedance unit.

(12) For the electrical model of the part of the vehicle electrical system, the following equation for computing a terminal voltage U.sub.2 at the control unit may be formulated for the functional description:
U.sub.2=U.sub.0−I.sub.x.Math.(R.sub.1+R.sub.i)−I.sub.L.Math.(R.sub.1+R.sub.2+R.sub.i)

(13) The unknown variables of the equation at point in time k may be compiled in a vector x.sub.k.

(14) $x_k=\left[\begin{array}{c}{R}_1+R_2+R_i\\ U_0-I_x.Math.\left(R_1+R_i\right)\end{array}\right]$

(15) Measured variable z.sub.k at point in time k is defined as follows:
z.sub.k=U.sub.2

(16) Unknown variables x.sub.k are estimated by an online parameter estimation method, for example, a Kalman filter, by iterative model-measured variable comparison at each point in time k.

(17) The corresponding equations for estimating x.sub.k are represented here, for example, in the form of an extended Kalman filter (EKF):

(18) With reference to FIG. 2, an initial estimation first takes place: {circumflex over (x)}.sub.0, P.sub.0

(19) This value is used as the first input value for time update (prediction) 210:

(20) with the state prediction:
{circumflex over (x)}.sub.k=f({circumflex over (x)}.sub.k-1,u.sub.k) and the prediction of the error covariance:
P.sub.k=A.sub.kP.sub.k-1A.sub.k.sup.T+W.sub.kQ.sub.k-1W.sub.k.sup.T
=> The result: {circumflex over (x)}.sub.k, P.sub.k is used for measurement update (correction) 220 as the input variable: the calculation of the Kalman gain follows therefrom:
K.sub.k=P.sub.kH.sub.k(H.sub.kP.sub.k.sup.TH.sub.k.sup.T+V.sub.kR.sub.kV.sub.k.sup.T) and thus: the estimation update with measurement:
{circumflex over (x)}_k={circumflex over (x)}.sub.k+K.sub.k[z.sub.k−h({circumflex over (x)}.sub.k)]) and the update of the error covariance:
P.sub.k=(I−K.sub.kH.sub.k)P.sub.k
=> The result: {circumflex over (x)}.sub.k, P.sub.k is given recursively 230 to time update (prediction) 210 (see above).

(21) In these equations:

(22) x.sub.k: parameter vector (variables to be estimated)

(23) P.sub.k: covariance matrix of the estimated variables (is determined iteratively by EKF, specification of an initial matrix including high starting values).

(24) W.sub.kQ.sub.k-1W.sub.k.sup.T: system noise matrix (parameters)

(25) V.sub.kR.sub.kV.sub.k.sup.T: measurement noise matrix (parameters)

(26) A.sub.k: system matrix

(27) H.sub.k: Jacobi matrix of the output function hk

(28) Z.sub.k: measured variable vector

(29) K.sub.k: Kalman filter gain

(30) $x_k=\left[\begin{array}{c}{R}_1+R_2+R_i\\ U_0-I_x.Math.\left(R_1+R_i\right)\end{array}\right],f\left({\hat{x}}_{k-1},u_k\right)={\hat{x}}_{k-1},z_k=\left[U_{\mathrm{IB}}\right]h\left({\hat{x}}_k^{-}\right)=\left[U_0-I_x.Math.\left(R_1+R_i\right)-I_{\mathrm{IB}}.Math.\left(R_1+R_2+R_i\right)\right]A_k=\left[\begin{array}{cc}1& 0\\ 0& 1\end{array}\right],H_k=\frac{\partial h\left({\hat{x}}_k^{-}\right)}{\partial x_k}$

(31) The above-described method steps of the parameter estimation are carried out iteratively until an abortion criterion is met. One possible abortion criterion is to compare the values of one or more diagonal elements of the covariance matrix to a set threshold and to abort the parameter estimation when the set threshold is fallen below. A certain estimate accuracy of the parameter estimation may be read off with the aid of the covariance matrix, a suitable abortion condition may therefore be defined using the values of the covariance matrix. Value {circumflex over (x)}.sub.k determined by the described parameter estimation represents the sought-after sum of Ri, R1, and R2 of the resistances of the supply line.

(32) The performance of the vehicle electrical system at the present point in time may be ascertained from the variables estimated via the Kalman filter. The smaller the sum of the Ri, R1, and R2 resistances of the supply line is, the higher is the performance.

(33) Estimated parameter R.sub.1+R.sub.2+R.sub.i stands directly for the internal resistance of the control unit supply. If an upper limiting value is exceeded, a reaction of the system may take place, for example, derating the power consumption or driver warning.

(34) The estimation of U.sub.0−I.sub.x.Math.(R.sub.1+R.sub.i) approximately supplies the source voltage of battery U0 at minor current Ix. This may be used, in consideration of various boundary conditions (Ix low, DC-DC converter or generator inactive, consideration of the measuring tolerances) to assess the battery charge level, i.e., at low charge level, an action may take place, for example, a driver warning.

(35) A reliable determination of parameters xk may only take place if at least two independent operating points were detected during operation. To ensure this, an induced current pulse may be generated in the control unit.

(36) FIG. 3 outlines a vehicle electrical system 300, which includes a first part and a second part each having electrical components, and at least one electrical component is associated with both the first part and the second part of vehicle electrical system 300. The components which are associated with both the first and the second part of vehicle electrical system 300 are power supply 310 having voltage source 310 and internal resistance 311 in series connection and a part of supply line resistivity R3 356.

(37) Vehicle electrical system 300 schematically outlined in FIG. 3 shows an assembly 320, which is connected to an electrically conductive supply line 352 at a first terminal 321 of assembly 320 and to a second electrically conductive supply line 351 at a second terminal 322 of assembly 320, the two supply lines 351, 352 being connected to one another at a neutral point or connection 359 on the power source side within vehicle electrical system 300.

(38) Neutral point 359 is connected via a first terminal 310a to power source 310. A second terminal 310b of the power source is connected via two ground connections 357, 358 connected in parallel to a ground terminal of assembly 320. The ground connection is designed redundantly in FIG. 3 using the two ground connections 357, 358.

(39) Electrical assembly 320 includes a first switch 324, which is situated between first terminal 321 of assembly 320 and a load 340 of the assembly in such a way that a conductive connection may optionally be established between load 340 and first terminal 321 of assembly 320.

(40) Electrical assembly 320 includes a second switch 326, which may establish a conductive connection between second terminal 322 and a third switch 323.

(41) First switch 324 and second switch 326 may optionally be electrically connected to one another with the aid of third switch 323, which is contacted with first switch 324 and second switch 326 in each case on the side opposite to terminals 321, 322. Load 340 of assembly 320 is connected to second contact 310b of power source 310 with the aid of a ground connection 342. Power source 310 may be described by an ideal voltage source 312, which is connected in series via its internal resistance 311 to its first terminal 310a and its second terminal 310b of power source 310.

(42) For the determination of a plurality of current and voltage values of the first part of the vehicle electrical system including first electrical supply line 352, an electrical connection is set up between first supply line 352 and load 340, in that first switch 324 is closed.

(43) An electrical interruption between second supply line 351 and load 340 of assembly 320 is set up in that second switch 326 of assembly 320 is opened.

(44) Using this connection, with the aid of first switch 324 and load 340 of assembly 320, a current is applied to first supply line 352 using power source 310, since load 340 is also connected via its ground connection 342 to second pole 310b of power source 310. Load 340 of assembly 320 has to be activated with the aid of a control circuit in order to occupy the at least three different operating points.

(45) The example method described here may be used correspondingly to determine a plurality of current and voltage values of the second part of the vehicle electrical system, in that the current of load 340 is applied to second supply line 351, second switch 326 and third switch 323 being closed and first switch 324 being opened. The determination of the voltages and currents of second supply line 351 takes place analogously as described above.

(46) The loaded terminal voltage of the impedance unit is determined at input 321 of first supply line 352 of assembly 320 using a voltage sensor or a voltage meter 334. At least one current is applied to first supply line 352 by the connection of load 340 with the aid of closed first switch 324 to power source 310.

(47) An unloaded terminal voltage may be determined, for example, at input 322 of second supply line 351 of assembly 320 using a voltage sensor or voltage meter 332.

(48) The unloaded terminal voltage may be determined at input 322 of second supply line 351 of assembly 320 using the above-described voltage sensor if a current is not applied to first supply line 352, for example, in that first switch 324 of assembly 320 is opened.

(49) For the determination of the current, load 340 may include a current sensor or an ammeter, which determines the current applied to first supply line 352.

(50) Both the first part of vehicle electrical system 300 includes a measuring unit 334 for the voltage and second part of vehicle electrical system 300 includes a measuring unit 332 for the voltage. Current I.sub.Mot in the first part of vehicle electrical system 300 and current I.sub.Vent in the second part of the power network may be provided either by a correspondingly designed measuring unit (not shown here) or by particular connected impedance unit Z.sub.L 340. The measurement of I.sub.Mot and I.sub.Vent may be carried out directly via a shunt or may be calculated by back-calculation from the phase currents of the EC motor used for the excitation. The one plurality of current and voltage values of electrical impedance unit Z.sub.L 340 is generated at each of at least three different operating points at the particular measuring unit and provided for the method.

(51) The corresponding current and voltage values are associated with one another as in the above-described exemplary embodiment.

(52) The determination of the electrical variables of the components in the parts of the vehicle electrical system is based on a modified parameter estimation method and modified electrical model of the parts of the vehicle electrical system and at least a part of the plurality of the corresponding current and voltage values of the at least three operating points. The parameter estimation method corresponds to that described above and the required modifications of the electrical model as well are described in the following.

(53) Two equations for computing terminal voltage U.sub.Mot and U.sub.Vent at the control unit may be formulated from the electrical circuit diagram of FIG. 3:
U.sub.Mot=U.sub.0−(I.sub.x+I.sub.Vent).Math.(R.sub.3+R.sub.i)−I.sub.Mot.Math.(R.sub.1+R.sub.3+R.sub.4∥R.sub.5+R.sub.i)
U.sub.Vent=U.sub.0−(I.sub.x+I.sub.Mot).Math.(R.sub.3+R.sub.i)−I.sub.Vent.Math.(R.sub.2+R.sub.3+R.sub.4∥R.sub.5+R.sub.i)

(54) The unknown variables of the equation at point in time k result here in vector xk:

(55) $x_k=\left[\begin{array}{c}{R}_1\\ R_2\\ R_3+R_4.Math.R_5+R_i\\ U_0-I_x.Math.\left(R_3+R_i\right)\end{array}\right]$

(56) Measured variable z.sub.k at point in time k is defined as follows:

(57) $z_k=\left[\begin{array}{c}{U}_{\mathrm{Mot}}\\ U_{\mathrm{Vent}}\end{array}\right]$

(58) Output matrix h.sub.k at point in time k is defined as follows:

(59) $h\left({\hat{x}}_k^{-}\right)=\left[\begin{array}{c}{U}_0-\left(I_x+I_{\mathrm{Vent}}\right).Math.\left(R_3+R_i\right)-I_{\mathrm{Mot}}.Math.(R_1+R_3+R_4.Math.R_5+R_i)\\ U_0-\left(I_x+I_{\mathrm{Mot}}\right).Math.\left(R_3+R_i\right)-I_{\mathrm{Vent}}.Math.(R_1+R_3+R_4.Math.R_5+R_i)\end{array}\right]$

(60) Furthermore, Jacobi matrices A.sub.k and H.sub.k result as follows:

(61) $A_k=\left[\begin{array}{c}1,0,0,0\\ 0,1,0,0\\ 0,0,1,0,\\ 0,0,0,1,\end{array}\right],H_k=\frac{\partial h\left({\hat{x}}_k^{-}\right)}{\partial x_k}$

(62) Therefore, the partial wiring harnesses including resistors R1, R2 and the partial wiring harness including R3+Ri+R4∥R5 may be diagnosed separately from one another with the aid of the additional measured variable.

(63) At least 3 linearly independent operating points are required for this purpose, which may be achieved by corresponding activation of the internal actuators. The measurement of I.sub.Mot and I.sub.Vent may be carried out directly via a shunt or may be calculated by back-calculation from the phase currents of the EC motor used for the excitation.