Battery State of charge estimation using Unscented Kalman filter

Hi,

I built a 2RC battery equivalent circuit model in Matlab to find out State of charge (SOC) using Unscented Kalman filter. When I simulated I got the following error

An error occurred while running the simulation and the simulation was terminated

Caused by:

• Sigma points calculation failed because the state covariance is not positive semi-definite. One potential reason is a small Alpha parameter.

Component:Simulink | Category:Block error

The below picture is my Unscented kalman filter block

I think the problem is in the Covariance value.How to choose the covariance value and how to make it as a positive semi-definite .Kindly help me in this.

[hua peng]

Hi. Samy.. I want to know ,Have you solved this problem yet?

Answer 1

[Monowar Hossain]

Hi. Samy..

You shoud tune the covarience. It's is random.