BATTERY SYSTEM IDENTIFICATION THROUGH IMPULSE INJECTION

• US 20160018471A1
• Filed: 07/17/2014
• Published: 01/21/2016
• Est. Priority Date: 07/17/2014
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: LEE, Tae-Kyung
• Granted Patent: US 10,451,678 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 31/007 using microprocessors or computers
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/385 Arrangements for measuring battery or accumulator variables for monitoring G01R31/382

Abstract

Vehicle systems and methods can include a traction battery and a controller to operate the traction battery according to current limits of a battery model identified from a battery response to a pulse of current injected into the battery while the battery is not being discharged to propel the vehicle or being charged. The pulse can have a sampling time and magnitude. The response is battery terminal voltages measurements at every sampling time during a set duration. The controller can implement a state estimator configured to output battery state uses a battery impulse response. The pulse input into the battery can be a current signal and the measured battery response can be a voltage. The controller can select a time period for the pulse input and battery measurement response to be when the controller is not charging the battery or drawing current from the battery to propel the vehicle.

Claims

1. A vehicle comprising:

a traction battery including a plurality of cells; and

at least one controller configured to operate the traction battery according to battery current limits of a battery model identified from a response of the battery to a pulse of current injected into the battery while the battery is not being discharged to propel the vehicle or being charged.

2. The vehicle of claim 1 wherein the pulse has an associated predetermined sampling time and magnitude, and the response is a collection of battery terminal voltages measured at every sampling time during a set duration.

3. The vehicle of claim 2 wherein the set duration is long enough to gather a number of voltage measurements that are used to identify the battery model.

4. The vehicle of claim 1 wherein the controller is configured to produce a discrete space model of the traction battery and to convert the discrete space model to a continuous state space model.

5. The vehicle of claim 4 wherein the current limits are based on the continuous state space model.

6. The vehicle of claim 5 wherein the controller is configured to use Eigendecomposition to transform the continuous state space model to derive mathematical expressions to estimate the battery current limits.

7. The vehicle of claim 1 wherein the controller is configured to construct a Hankel matrix using the response, to decompose the Hankel matrix into a singular value, to identify discrete state space matrices from the singular value, to convert the discrete state space matrices into continuous state space matrices, to perform Eigendecomposition on the continuous state space matrices to derive mathematical expressions, and to compute the battery current limits using the mathematical expressions.

8. A vehicle comprising:

a traction battery including a plurality of cells; and

at least one controller programmed to

inject an impulse of electric current with a duration and a magnitude to the traction battery while the controller is not charging the battery or drawing current from the battery to propel the vehicle and while output voltage of the traction battery is stabilized,

measure impulse responses of voltage outputs at a set time step during a time period,

identify a battery dynamics model from the impulse responses,

transform the battery dynamics model to a state space model,

estimate battery current limits and available power limits based on the state space model, and

operate the traction battery according to the battery current limits and available power limits.

9. The vehicle of claim 8 wherein the battery dynamics model is identified in a discrete state space model, and the discrete state space model is converted to a continuous state space model.

10. The vehicle of claim 8 wherein the state space model has a diagonal system matrix including system Eigenvalues and wherein the battery dynamics model is transformed through Eigendecomposition.

11. The vehicle of claim 8 wherein the set time step is short enough to resolve battery system dynamics information.

12. The vehicle of claim 8 wherein the time period is long enough to identify battery system dynamics information.

13. The vehicle of claim 8 wherein the controller is configured to:

construct a Hankel matrix from the impulse responses,

decompose the Hankel matrix into a singular value,

identify state space matrices based on the singular value,

convert the state space matrices into continuous forms of the state matrices,

perform Eigendecomposition on the continuous forms of the state matrices, and

compute the battery current limits using Eigendecomposed forms of the state matrices.

14. A method for battery state estimation comprising:

injecting a signal pulse into a traction battery while the battery is not being discharged to propel a vehicle or being charged;

sensing a response of the traction battery to the pulse; and

operating the traction battery according to battery current limits of a battery model identified from the response.

15. The method of claim 14 wherein sensing the response includes:

measuring impulse responses of voltage outputs at every time step during a time period,

identifying a battery dynamics model from the measured impulse responses,

transforming the battery dynamics model to a state space model having a diagonal system matrix including system Eigenvalues through Eigendecomposition, and

estimating the battery current limits and available power limits from a transformed system dynamics model.