simple PID Controller tunning using ZN - 'S' curve method

Function which gives Kp, Ki , Kd, Ti & Td values using 'S' curve method. (open loop tuning method)

ZN_PI_PID(S,Set value, Settling Value, T1, T2)

S- 1 for PI, 2 for PID

T1 - Time taken to reach 23.8% of set value
T2 - Time taken to reach 63.2% of set value