A method for monitoring health of a hydraulic fluid subsystem comprising: determining a plurality of forces acting on an actuator of the hydraulic fluid subsystem ; determining a plurality of parameters based on at least one of an actuator inlet flow rate (q 3 ), an actuator outlet flow rate (q 3 '), an area of a cylinder of the actuator , a volume of the cylinder , a damping coefficient of the cylinder , a stiffness of a spring in the cylinder , and the plurality of forces acting on the actuator ; receiving a valve inlet pressure (p 6 ) of at least one of oil and gas flowing through a pipe while entering a valve operationally coupled to the actuator and a valve outlet pressure (p 7 ) of the at least one of the oil and the gas flowing through the pipe while flowing out of the valve ; and monitoring the health of the hydraulic fluid subsystem based on at least one of the plurality of parameters, the valve inlet pressure (p 6 ), and the valve outlet pressure (p 7 ); characterized in that determining the plurality of parameters comprises: generating a plurality of dynamic equations based on the plurality of forces and at least one of the actuator inlet flow rate (q3), the actuator outlet flow rate (q 3 '), the area of the cylinder of the actuator , the volume of the cylinder , the damping coefficient of the cylinder , the stiffness of the spring in the cylinder , and the plurality of forces acting on the actuator ; and solving the plurality of dynamic equations to determine the plurality of parameters. determining a plurality of forces acting on an actuator of the hydraulic fluid subsystem ; determining a plurality of parameters based on at least one of an actuator inlet flow rate (q 3 ), an actuator outlet flow rate (q 3 '), an area of a cylinder of the actuator , a volume of the cylinder , a damping coefficient of the cylinder , a stiffness of a spring in the cylinder , and the plurality of forces acting on the actuator ; receiving a valve inlet pressure (p 6 ) of at least one of oil and gas flowing through a pipe while entering a valve operationally coupled to the actuator and a valve outlet pressure (p 7 ) of the at least one of the oil and the gas flowing through the pipe while flowing out of the valve ; and monitoring the health of the hydraulic fluid subsystem based on at least one of the plurality of parameters, the valve inlet pressure (p 6 ), and the valve outlet pressure (p 7 ); characterized in that determining the plurality of parameters comprises: generating a plurality of dynamic equations based on the plurality of forces and at least one of the actuator inlet flow rate (q3), the actuator outlet flow rate (q 3 '), the area of the cylinder of the actuator , the volume of the cylinder , the damping coefficient of the cylinder , the stiffness of the spring in the cylinder , and the plurality of forces acting on the actuator ; and solving the plurality of dynamic equations to determine the plurality of parameters. generating a plurality of dynamic equations based on the plurality of forces and at least one of the actuator inlet flow rate (q3), the actuator outlet flow rate (q 3 '), the area of the cylinder of the actuator , the volume of the cylinder , the damping coefficient of the cylinder , the stiffness of the spring in the cylinder , and the plurality of forces acting on the actuator ; and solving the plurality of dynamic equations to determine the plurality of parameters. <EOS>