Method and device for error-compensated current measurement of an electrical accumulator

• US 20120283970A1
• Filed: 11/19/2009
• Published: 11/08/2012
• Est. Priority Date: 11/19/2009
• Status: Abandoned Application

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Boehm, Andre
• Application Number:
  US13/510,682
• Publication Number:
  US 20120283970A1
• Time in Patent Office: Days
• US Class Current: 702/64
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3828 using current integration
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

A method for error-compensated current measurement of an electrical accumulator, including: providing a time window-related estimated charge ascertained by a model-based estimator from operating variables of the accumulator and reflecting the estimated charge that has been withdrawn from the accumulator and supplied to the accumulator within the time window; and detecting the accumulator current supplied to the accumulator and withdrawn from the accumulator during the time window, with a current detection sensor. A zero crossing point in time (estimated charge is essentially zero) and a maximum point in time (the absolute value of the estimated charge essentially has a relative maximum or has a value which is greater than a minimum charge difference) are detected. A current measurement offset error is ascertained at the zero crossing point in time by comparing the estimated charge to the detected accumulator current. The accumulator current is ascertained according to the current measurement offset error, and a current measurement scaling error is ascertained at the maximum point in time by comparing the estimated charge to the detected accumulator current. The ascertained current measurement offset error is subtracted from the comparison result thus obtained, and the accumulator current is compensated for based on the current measurement scaling error. A related device for error-compensated current measurement is also described.

Claims

1-10. -10. (canceled)

11. A method for providing error-compensated current measurement of an electrical accumulator, the method comprising:

providing a time window-related estimated charge, which is ascertained by a model-based estimator from operating variables of the accumulator and which reflects the estimated charge that has been withdrawn from the accumulator and has been supplied to the accumulator within the time window;

detecting the accumulator current supplied to the accumulator and withdrawn from the accumulator during the time window, with a current detection sensor;

detecting a zero crossing point in time at which the absolute value of the estimated charge or the accumulator current is less than a maximum value;

detecting a maximum point in time at which the absolute value of the estimated charge or the accumulator current essentially has a relative maximum or has a value which is greater than a minimum value;

ascertaining a current measurement offset error at the zero crossing point in time by comparing the estimated charge to the detected accumulator current;

compensating for the accumulator current according to the current measurement offset error;

ascertaining a current measuring scaling error at the maximum point in time by comparing the estimated charge to the detected accumulator current;

subtracting the ascertained current measurement offset error from the comparison result thus obtained; and

compensating for the accumulator current based on the current measurement scaling error.

12. The method of claim 11, wherein the estimated charge is provided by ascertaining the estimated charge using an estimator which includes a physical model of the accumulator, the operating variables of the accumulator including the accumulator current and at least one further operating variable of the accumulator which is not directly dependent on the detected accumulator current and which influences the estimated charge, the at least one further operating variable including an accumulator terminal voltage, an accumulator temperature, at least one further operating variable of the accumulator which is different from the accumulator current, or a combination thereof.

13. The method of claim 11, wherein at least one of the compensation of the current measurement scaling error and the compensation of the current measurement offset error includes:

detecting a temperature of the current detection sensor or a temperature of an accumulator current measuring device which is connected to the current detection sensor;

ascertaining a temperature error component for the current measurement offset error and for the current measurement scaling error as a linear function of the temperature, the linear dependency being predetermined by a temperature characteristic of at least one component of the accumulator current measuring device, which includes the current detection sensor and detects the accumulator current; and

adding the particular temperature error component to the current measurement offset error and to the current measurement scaling error.

14. The method of claim 11, wherein the compensation includes one of:

subtracting the current measurement offset error, the current measurement scaling error, or both errors from the accumulator current;

multiplying a reciprocal value of the current measurement offset error, a reciprocal value of the current measurement scaling error, or a reciprocal value of both errors by the accumulator current; and

providing a correction error on the basis of which the detected accumulator current is corrected, the correction error being used as a control variable of a PI controller which has the current measurement offset error, the current measurement scaling error, or a sum thereof as the setpoint value, to continuously advance the correction error to the current measurement offset error, the current measurement scaling error, or a combination of both errors, according to the control response of the PI controller, the accumulator current being corrected according to the correction error provided by the PI controller.

15. The method of claim 11, wherein providing the estimated charge includes:

providing the time window as one of a plurality of successive or contiguous time windows, either all time windows having an associated length and the estimated charge being normalized to the associated length, or not being normalized, or time windows of the plurality of time windows of various lengths and the estimated charge being normalized to the particular length of the associated time window, and in addition, during the entire time window either the estimated charge or the measured accumulator current is essentially zero, the absolute value of the estimated charge or the measured accumulator current essentially has a relative maximum or a value which is greater than a minimum value, or the estimated charge which is linked to the time window is not used either for ascertaining the current measurement offset error or for ascertaining the current measurement scaling error.

16. A device for providing error-compensated current measurement of an electrical accumulator, comprising:

a model-based estimator configured to provide an estimated charge which is related to a time window, and which is connected to the operating variable input;

a current signal input configured for connection to an accumulator current measuring device which outputs a current signal which represents the accumulator current during the time window, which is supplied to the accumulator and is withdrawn from the accumulator;

an operating variable input for at least one operating variable of the accumulator;

a zero crossing comparator, connected to the estimator, which compares the estimated charge or the accumulator current to a maximum value in order to ascertain a zero crossing point in time;

a maximum comparator, connected to the estimator, which compares the absolute value of the estimated charge or the accumulator current to a minimum value, or which compares estimated charges or detected accumulator currents of two, three, or more than three successive time windows to one another to determine a point in time of a scaling error detection based on the difference;

an offset error ascertainment unit which includes an offset error subtraction unit which is configured to subtract the estimated charge, provided by the estimator, from the accumulator current at the zero crossing point in time which is provided by the zero crossing comparator, to provide the current measurement offset error as the result of the subtraction;

a scaling error ascertainment unit which includes an offset error subtraction unit which is configured to subtract the current measurement offset error, provided by the offset error ascertainment unit, from the accumulator current or from the time integral of the accumulator current to compensate for the offset error of the accumulator current, the scaling error ascertainment unit also including a ratio unit which is configured to provide a ratio of the compensated accumulator current to the estimated charge as the scaling error; and

a compensation unit configured to compensate for the provided offset error of the accumulator current, and to compensate for the scaling error of the accumulator current which has been compensated for with regard to the offset error.

17. The device of claim 16, wherein the estimator includes a physical model of the accumulator, the operating variable input being configured to receive an accumulator terminal voltage, an accumulator temperature, at least one further operating variable of the accumulator which is different from the accumulator current, or a combination thereof, the operating variable not being directly dependent on the detected accumulator current, and which influences the estimated charge.

18. The device of claim 16, further comprising:

an interpolator and a temperature input connected thereto for temperatures of the current detection sensor or an accumulator current-measuring device which is connected to the current detection sensor, the interpolator interpolating a temperature error component of the provided offset error, of the provided scaling error, or of both errors, according to a predetermined linear temperature characteristic, provided by the interpolator, of at least one component of the accumulator current measuring device, which includes the current detection sensor, the interpolator being configured to add the particular temperature error component to the current measurement offset error, to the current measurement scaling error, or to both errors for additional temperature compensation.

19. The device of claim 16, wherein the compensation unit includes one of:

a subtraction unit configured to subtract the current measurement offset error, the current measurement scaling error, or both errors from the accumulator current;

a multiplication unit configured to multiply a reciprocal value of the current measurement offset error, a reciprocal value of the current measurement scaling error, or a reciprocal value of both errors by the accumulator current; and

a correction error generator configured to generate a correction error and to correct the detected accumulator current based on the correction error, the correction error generator including a PI controller which uses the correction error as a control variable, and the PI controller receives the current measurement offset error, the current measurement scaling error, or a sum thereof as the setpoint value, and has a control response according to which the correction error is continuously advanced to the current measurement offset error, to the current measurement scaling error, or to a combination of both errors, and the compensation unit is configured to correct the accumulator current according to the correction error which is provided according to the correction error generator.

20. The device of claim 16, further comprising:

a time window generator which sets a start and an end of the time window, the start of a directly subsequent time window coinciding with the end of the preceding time interval or following same, and all time windows having the same length or having different lengths, and the device including a normalizer which is configured to normalize the estimated charge to the length of the time window or to 1 for time windows of the same length, and is configured for time windows of different lengths to normalize the estimated charge to the length of the time window, the time window generator being set up so that the offset error ascertainment unit, the scaling error ascertainment unit, the compensation unit, or a combination thereof is/are connected to the time window generator, and ascertaining, subtracting, or compensating for the offset error only when the zero crossing comparator ascertains that the absolute value of the estimated charge or of the accumulator current is less than a maximum value for the entire duration of the time window, or at least one of the scaling error ascertainment unit and the compensation unit being connected to the time window generator, and ascertaining or compensating for the scaling error only when the maximum comparator ascertains an absolute value of the estimated charge or of the accumulator current which is greater than the provided minimum value for the entire duration of the time window, or when the point in time of the scaling error detection is within the time window.