I see that you wish to design an anti-lock regenerative braking system by integrating regenerative braking capabilities into an existing ABS system.
You can refer to the following MATLAB Answers post which contains several useful implementations and fruitful discussions on the same topic: https://www.mathworks.com/matlabcentral/answers/404664-simulink-model-of-regenerative-braking
I hope this answer will lead you to solving your issue.
