want to find RUL or prediction of 'degradation level' when i have Transfer Funtion of healthy system and TF of degraded system

Please can anybody help me in finding RUL or degradation level of my machine when i have transfer function of healthy system and degraded transfer function. Now i want to know how much degradation already occured and after how much time machine need refurbishing if degradation TF bandwidth reduce to 50% to original 100%.

regards,

[arsalan khan]

or anomaly detection