Solving Steering Equations for Vehicle Control

[johngeo]

Hi,
I am new to control system and coding.my problem is suppose we have a steering value and know we need to turn the vehile. I facing difficulty in understanding some equations.

       phi=T*st. %here st. is steering value and 'T' is some constant , 
but I am facing difficulty to understand what it is? whether it is time constant or something else.
           % radius of curvature (ICC)
            R=L/tan(phi);
            str.=30*(V/R);% cann't understand what the use of this equation. here 'v' is some constant.
            theta new=theta+str.; %theta is vehicle angle.
            %centre of curvature(ICC)
            A=X-R*sin(theta);
            B=Y+R*cos(theta);
            %new position of rear axle mid point
            X=A+R*sin(theta new);
            Y=B-R*cos(theta new);

 

[johngeo]

str.=30*(V/R);% cann't understand what the use of this equation. here 'v' is forward velocity of vehicle.

please help me in understanding the concept of this equation.
How can we get an angle from R (ICC) and V (velocity)