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Aircraft on ground path following

Aircraft on ground path following

(OP)
Hi Everyone,

I am new here but I need some guidance for my project which involves having an Airbus A320 following a pre-defined path around an airport.

Now, I have a set of X-Y coordinates which describe a 180 degree U-turn type of path and I have managed to calculate steering angles for the nose wheel of the plane using the wheel base and 3 consecutive points along the path. However, I am struggling to solve how the control logic would dictate which point on the path is the desired/target point if the plane is say... in a random position which is not on the path, but close to the path.

The aircraft assumes 3 degrees of freedom

Has anyone done anything like this before?

LS

RE: Aircraft on ground path following

Look at agricultural solutions. A problem working large fields with very wide implements (seeders, spreading fertilizer, spreading chemical treatments etc.) is to avoid overlapping and to avoid missed sections.
Some systems, after programing, will automatically steer a tractor and implement to cover hundreds or thousands of acres with-out overlap, missed sections or contact with fences or water holes.
With the basic system, at the end of a row, the driver takes control and turns the rig around under human control. When the rig crosses the next path to be followed, the automatic system takes over steering the rig.
Take a look at some of these systems. It may be helpful to see how others have solved similar problems.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Aircraft on ground path following

Either the predefined path is the centerline of the available taxiway (and you have to assume it's wide enough for the landing gear) - so program the center of the gear pattern to stay on the centerline, or it's two "paths" defining the boundary and you need to program so the wheels stay inside the lines.

RE: Aircraft on ground path following

There are a couple of ways to do this.
One is to use super imposed moves as a function of the motion of a virtual target position.
The other is to compute a polynomial that gears to the virtual target. This polynomial keeps track of the actual position, gear ratio and gear ratio rate as function of the virtual target's position, velocity and acceleration. The polynomial must end up at the same position as the target position with gear ratios set to 1 and gear ratio rates set to 0 so the plane's actual position, velocity and acceleration match the virtual position velocity and acceleration.
There is a lot of calculus using the chain and product rule.

Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
http://forum.deltamotion.com/

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