High accuracy bank-to-turn autopilot
First Claim
1. A method of controlling a guided weapon comprising the steps of:
- determining a line-of-sight rotation rate between said guided weapon and a target in terms of first body pitch and yaw components relative to a body of said guided weapon;
transforming said pitch and yaw components into inertial pitch and yaw components relative to an inertial reference framefiltering said inertial pitch and yaw components;
transforming said inertial pitch and yaw components, after said filtering, back into second body pitch and yaw components; and
commanding a pitch control channel with said second body pitch component and commanding a roll control channel with said second body yaw component.
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Accused Products
Abstract
In a bank-to-turn autopilot, increased accuracy and insensitivity to tracking noise and glint are achieved by using a yaw LOS rate to drive the roll rate loop and by sending only a body coordinate pitch LOS rate to a pitch channel so as to not introduce errors in the cross plane. By uncoupling the pitch and roll loops, pitch/yaw/roll coupling, large roll transients, and cross plane maneuvers can be minimized. Additionally, body LOS rates are transformed to inertial LOS rates and subsequently back to body LOS rates such that guidance filtering may be performed in a non-rolling frame of reference. This allows the guidance filtering to be separately optimized without regard to destabilizing effects of such filtering due to roll-to-yaw coupling path lags. In other words, servo dynamic path lags are reduced since the guidance filters do not have to track the high frequency roll rates. They only need to process a slowly varying inertial pitch and yaw rates which are then mathematically resolved back to body coordinates. Thus heavier filtering may be performed by the guidance filters while maintaining the same phase margin obtainable using simpler guidance filters in a rolling reference frame. Finally, a minimum-roll implementation is obtained by correcting the sign of the roll rate command with the pitch acceleration command. Roll is thereby constrained within ±90° as opposed to ±180° otherwise.
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Citations
13 Claims
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1. A method of controlling a guided weapon comprising the steps of:
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determining a line-of-sight rotation rate between said guided weapon and a target in terms of first body pitch and yaw components relative to a body of said guided weapon; transforming said pitch and yaw components into inertial pitch and yaw components relative to an inertial reference frame filtering said inertial pitch and yaw components; transforming said inertial pitch and yaw components, after said filtering, back into second body pitch and yaw components; and commanding a pitch control channel with said second body pitch component and commanding a roll control channel with said second body yaw component. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A bank-to-turn guided weapon control system comprising:
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line-of-sight rate determining means for determining a line-of-sight rate between said guided weapon and a target; a roll command channel; and means for coupling only a yaw rate portion of an output of said line-of-sight rate determining means to said roll command channel. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A bank-to-turn guided weapon, comprising
a pitch control surface for changing a pitch attitude of said guided weapon; -
a roll control surface for changing a roll attitude of said guided weapon; and a bank-to-turn autopilot for changing a yaw attitude of said guided weapon through a combination of changes in said pitch attitude and said roll attitude, said bank-to-turn autopilot comprising yaw rate determining means and pitch rate determining means and a roll command channel, said yaw rate determining means commanding said roll command channel exclusive of any contribution in magnitude from said pitch determining means.
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Specification