Flight control system
A system and method for controlling an aircraft with flight control surfaces that are controlled both manually and by a computing device is disclosed. The present invention improves overall flight control operation by reducing the mechanical flight control surface components while providing sufficient back-up control capability in the event of either a mechanical or power-related failure. Through the present invention, natural feedback is provided to the operator from the mechanical flight control surface which operates independent of computer-aided flight control surfaces. Further, through the present invention, force input signals received from the pilot are filtered to improve the operation of the computer-aided flight control surfaces.
1. A process for positioning the powered control surfaces of an aircraft having both powered and unpowered control surfaces comprising the steps of:
measuring a force signal received from the pilot of the aircraft in response to the aerodynamic forces on the unpowered control surfaces;
converting the force signal into a torque signal;
applying a filter to the torque signal to calculate a control signal;
providing the control signal to the aircraft for positioning the powered control surfaces of the aircraft;
wherein the step of applying a filter to the torque signal further comprises the steps of:
converting the torque signal into an angular acceleration value;
converting the angular acceleration value into an angular velocity value;
calculating a frictional torque value for the angular velocity;
calculating a damping torque value for the angular velocity;
converting the angular velocity value into an angular position value;
calculating a stiffness torque for the angular position value;
calculating a control signal for the powered control surfaces from the angular position value;
subtracting the frictional torque value, the damping torque value, and the stiffness torque value from the torque signal.
2. The process of claim 1 wherein the step of applying a filter to the torque signal further comprises the steps of:
calculating a frictional torque value for the torque signal;
converting the torque signal into an angular acceleration value;
converting the angular acceleration value into an angular velocity value;
calculating a damping torque value for the angular velocity;
converting the angular velocity value into an angular position value;
calculating a stiffness torque for the angular position value;
calculating a control signal for the powered control surfaces from the angular position value;
subtracting the frictional torque value, the damping torque value, and the stiffness torque value from the torque signal.
3. The process of claim 1 wherein the step of converting the torque signal into an angular acceleration value comprises integrating the torque signal over a period of time and the step of converting the angular acceleration value into an angular velocity value comprises integrating the angular acceleration value over a period of time.
4. The process of claim 3 wherein the step of calculating a frictional torque value for the angular velocity value comprises applying a frictional deadband model to the angular velocity value.
5. The process of claim 3 wherein the step of calculating a damping torque value for the angular velocity value comprises multiplying the angular velocity value by a damping coefficient value selected from a schedule of values measured in wind tunnel and test flights.
6. The process of claim 3 wherein the step of converting the angular velocity value into an angular position value comprises integrating the angular velocity value over a period of time.
7. The process of claim 3 wherein the step of calculating a stiffness torque for the angular position value further comprises selecting a hinge moment as a function of the angular position value from a schedule of values measured in wind tunnel and test flights.
8. The process of claim 1 wherein the step of providing the control signal to the aircraft further comprises the steps of:
applying a gain factor to the angular position value to calculate a powered surface angular position estimated value;
applying a lag compensator to the powered surface angular position estimated value to calculate a control signal.
9. The process of claim 8 wherein the step of calculating a stiffness torque for the angular position value further comprises the step of selecting a hinge moment as a function of the angular position value and of the powered surface angular position estimated value from a schedule of values measured in wind tunnel and test flights.
10. The process of claim 8 further comprising the steps of:
measuring the actual angular position of the unpowered control surfaces;
subtracting the angular position value from the actual angular position to calculate a position difference value;
multiplying the position difference value by a time constant to produce an adjusted position difference value;
subtracting the adjusted position difference value from the torque signal.
11. The process of claim 1 wherein the aircraft has a control means for inputting a force signal, and the step of converting the force signal into a torque value comprises multiplying the force signal by the moment of inertia of the control means.