Variable gain control nose wheel steering system

1. A method for determining a target steering angle for nose landing gear of an aircraft, the method comprising:

receiving rudder pedal input data into a steering control unit;

receiving aircraft speed data into the steering control unit;

calculating a normal gain which is a positive quantity in all aircraft speed and pedal stroke ranges in the steering control unit;

calculating a parking gain which is a positive quantity in parking and taxiing speed ranges in the steering control unit;

adding the normal gain and the parking gain to determine a target steering angle in the steering control unit; and

controlling the nose landing gear direction based on the determined target steering angle.

2. The method of claim 1 , wherein a maximum steering angle for the nose landing gear is constant at a maximum value in the parking speed range and the maximum steering angle decreases continuously from a maximum parking speed to a maximum critical speed.

3. The method of claim 2 , wherein the maximum steering angle is zero at the maximum critical speed.

4. The method of claim 1 , wherein in take-off speed range, the target steering angle is directly proportional to rudder pedal input.

5. The method of claim 4 , wherein in the take-off speed range, a gradient of a line, which depicts the target steering angle versus the rudder pedal input, decreases as the aircraft speed increases.

6. The method of claim 1 , wherein in the parking speed and the taxiing speed ranges, the target steering angle is directly proportional to the rudder pedal input in a taxiing pedal range.

7. The method of claim 6 , wherein the target steering angle exponentially increases according to the rudder pedal input for pedal inputs greater than the taxiing pedal range.

8. The method of claim 7 , wherein the target steering angle gradually decreases according to the speed of the aircraft for pedal inputs greater than the taxiing pedal range.

9. The method of claim 1 , wherein the normal gain is calculated by multiplication of gain K and gain A, wherein the parking gain is calculated by multiplication of gain C and gain B, wherein gain K and gain C are calculated according to the rudder pedal input, wherein gain A and gain B are calculated according to the aircraft speed.

10. A method for determining a target steering angle for nose landing gear of an aircraft, the method including:

receiving rudder pedal input data into a steering control unit, wherein the rudder pedal input data corresponds to a percentage of an input stroke of a rudder pedal on an aircraft;

receiving aircraft speed data into the steering control unit;

calculating a gain K based on the received rudder pedal input data in the steering control unit;

calculating a gain A based on the received aircraft speed in the steering control unit;

calculating a gain C based on the received rudder pedal input data in the steering control unit;

calculating a gain B based on the received aircraft speed in the steering control unit;

determining a target steering angle for a nose landing gear in the steering control unit, wherein the target steering angle is a summation of normal gain and parking gain, wherein the normal gain is a product of the gain K and the gain A and the parking gain is a product of the gain C and the gain B; and

controlling the nose landing gear direction based on the determined target steering angle.

11. The method of claim 10 , wherein the gain K is a linearly related to the rudder pedal input of the aircraft.

12. The method of claim 10 , wherein the gain A is exponentially related to the received aircraft speed for received aircraft speeds greater than a maximum taxiing speed, and the gain A is constant for received aircraft speeds less than the maximum taxiing speed.

13. The method of claim 10 , wherein the gain B is a constant in a parking speed range, the gain B is exponentially related to the received air craft speed in a taxiing speed range, and the gain B is zero in a take off speed range.

14. The method of claim 10 , wherein the gain C is zero in a taxiing pedal range, and the gain C is exponentially related to the rudder pedal input for rudder pedal inputs greater than a maximum taxiing pedal range stroke.

15. A steering control unit (“SCU”) for a nose wheel steering system for an aircraft, the SCU comprising:

a normal gain calculation module, wherein the normal gain calculation module calculates a normal gain, which is a positive quantity in all aircraft speed and pedal stroke ranges;

a parking gain calculation module, wherein the parking gain calculation module calculates a parking gain, which is a positive quantity in parking and taxiing speed ranges;

a target steering calculation module that adds the normal gain and the parking gain to determine a target steering angle; and

a control signal output for controlling a nose wheel steering direction based on the determined target steering angle.