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, 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, 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, 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.