NESTED-LOOP MODEL-FOLLOWING CONTROL LAW
Embodiments are directed to systems and methods for utilizing a two-degree-of-freedom model-following control law within an architecture of nested loop functions. This allows for the separation of command and feedback path requirements and enables the restrictions of the inner loops to be applied to the outer loop feedbacks. This method of restriction allows a better allocation of coordinated authority between the loops.
1 . A method for controlling an aircraft effector, comprising:
applying a reference command to a command model;
translating at least one output of the command model to a forward path signal using a transform;
combining the forward path signal with an outer loop feedback signal to create an inner loop command;
applying the inner loop command to an inner loop controller; and
generating an effector command using the inner loop controller, wherein the effector command is used to control the aircraft effector.
2 . The method of claim 1 , further comprising:
generating at least one aircraft feedback signal representing an aircraft parameter; and
combining the at least one aircraft feedback signal with a corresponding output of the command model to create the outer loop feedback signal.
3 . The method of claim 2 , further comprising:
generating at least one additional aircraft feedback signal representing an aircraft parameter; and
providing the at least one additional aircraft feedback signal to the inner loop controller as an inner loop feedback signal.
4 . The method of claim 1 , wherein the reference command is selected from one of: a translational rate command (TRC), a heading, a position, an altitude, a velocity, a flight path angle, a vertical velocity, a load factor, a pitch rate, a roll rate, and an angle of attack.
5 . The method of claim 1 , further comprising:
receiving the reference command from a flight control system, a flight control computer, flight director, waypoint navigator, navigation computer, or an autopilot.
6 . The method of claim 1 , wherein the reference command is received from a second outer loop, and wherein the reference command corresponds to a second inner loop command generated in the second outer loop.
7 . The method of claim 1 , wherein the at least one output of the command model corresponds to one or more of a filtered version of the reference command and a derivative of the filtered reference command.
8 . The method of claim 5 , wherein the outer loop feedback signal is created in a proportional, integral, and derivative (PID) loop.
9 . The method of claim 1 , wherein the aircraft effector is a control surface, a propellor, or an actuator configured to control the position of the control surface or propellor.
10 . The method of claim 1 , wherein the inner loop command is an attitude, rate, load factor, or angle of attack command.
11 . The method of claim 1 , wherein the command model represents desired dynamics of an aircraft.
12 . A flight control system for an aircraft, comprising:
a flight control computer configured to control aircraft effectors in response to a control law, the flight control computer comprising one or more processors and a memory, wherein the memory stores instructions for executing the control law, the instructions causing the flight control computer to perform the steps of:
applying a reference command to a command model;
applying one or more command model outputs to a transform to create a forward path signal;
combining the forward path signal with a feedback signal to create an inner loop command;
applying the inner loop command to an inner loop controller;
generating an aircraft effector command using the inner loop controller;
receiving at least one aircraft feedback signal representing an aircraft parameter;
combining the at least one aircraft feedback signal with the one or more command model outputs a to create the feedback signal.
13 . The flight control system of claim 12 , wherein the instructions further causing the flight control computer to perform the steps of:
receiving at least one additional aircraft feedback signal representing an aircraft parameter; and
providing the at least one additional aircraft feedback signal to the inner loop controller as an inner loop feedback signal.
14 . The flight control system of claim 12 , wherein the reference command is selected from one of: a translational rate command (TRC), a heading, a position, an altitude, a velocity, a flight path angle, a vertical velocity, a load factor, a pitch rate, a roll rate, and an angle of attack.
15 . The flight control system of claim 12 , wherein the instructions further causing the flight control computer to perform the steps of:
receiving the reference command from a flight control system, a flight control computer, flight director, waypoint navigator, navigation computer, or an autopilot.
16 . The flight control system of claim 12 , wherein the instructions further causing the flight control computer to perform the steps of:
generating the reference command in a nested outer loop, and wherein the reference command corresponds to a second inner loop command generated in the nested outer loop.
17 . The flight control system of claim 12 , wherein the at least one output of the command model corresponds to one or more of a filtered version of the reference command and a derivative of the filtered reference command.
18 . The flight control system of claim 12 , wherein the outer loop feedback signal is created in a filtered proportional, integral, and derivative (PID) loop.
19 . The flight control system of claim 12 , wherein the aircraft effector is a rotor cyclic control, a rotor/propellor collective control, an electric motor speed, torque, or current command, a control surface, a propellor, or an actuator configured to control the position of the control surface or propellor.
20 . The flight control system of claim 12 , wherein the inner loop command is an attitude, rate, load factor, or angle of attack command.