# US 10,480,904 B2 · Gbias for rate based autopilot

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- Number: US 10,480,904 B2
- Document ID: US10480904B2
- Status: Granted
- Kind: B2
- Application number: 16/333,860
- Filed: 2017-08-17
- Published: 2019-08-29
- Granted: 2019-11-19
- Earliest claimed: 2017-08-17
- Assignees: BAE Systems Information and Electronic Systems Integration Inc.
- Applicants: BAE Systems Information and Electronic Systems Integration Inc.
- Inventors: David J. Schorr; Jeremy B. Gibson; James H. Steenson
- Web page: https://patentgrep.com/patent/US10480904B2

## CPC

- F41G 7/22: Homing guidance systems
- F41G 7/2213: {maintaining the axis of an orientable seeking head pointed at the target, e.g. target seeking gyro}
- F41G 7/36: using inertial references
- F42B 15/01: Arrangements thereon for guidance or control ({steering arrangements F42B10/60}; aircraft flight control B64C; guidance systems other than those installed aboard F41G7/00, F41G9/00; locating by use of radio or other waves G01S; flight control in general G05D1/00; computer aspects G06])
- F42B 15/10: Missiles having a trajectory only in the air
- G05D 1/10: Simultaneous control of position or course in three dimensions (G05D1/12 takes precedence)
- G05D 1/107: {specially adapted for missiles}
- G05D 1/108: {animated with a rolling movement}
- F41G 7/2246: {Active homing systems, i.e. comprising both a transmitter and a receiver}
- F41G 7/226: {Semi-active homing systems, i.e. comprising a receiver and involving auxiliary illuminating means, e.g. using auxiliary guiding missiles}
- F41G 7/2293: {using electromagnetic waves other than radio waves}
- G06F 17/11: for solving equations {, e.g. nonlinear equations, general mathematical optimization problems (optimization specially adapted for a specific administrative, business or logistic context G06Q10/04)}
- F41G: WEAPON SIGHTS; AIMING (optical aspects thereof G02B)
- F42B: EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION (explosive compositions C06B; fuzes F42C; blasting F42D)
- G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

A device, system, and method for shaping the trajectory of a projectile employing a Gravity bias, Gbias. The system includes a seeker, a guidance filter, a pitch rate filter, an actuator, pitch/yaw/roll coupled aerodynamics, and lateral rate sensors. It receives roll orientation input to a guidance and control autopilot; it applies Additional Gbias to that produced by the null rate command to the lateral control loops of the guidance and control autopilot device. The lateral rate command is equal to the desired Additional Gbias divided by an estimate of the projectile velocity. The Additional Gbias is translated to a rate command and incorporated into guidance loop commands to boost an Inherent Gbias to shape the trajectory of the projectile to the target.

## Claims

### Claim 1

A method for shaping a trajectory of a projectile comprising:
obtaining input to a guidance and control autopilot system of the projectile, wherein the input comprises roll orientation with respect to gravity, and an estimate of a velocity of the projectile, and providing the input to at least one processor of the guidance and control autopilot system;
applying an Additional gravity bias (Gbias) to an Inherent Gbias;
determining a total rate command by the at least one processor of the guidance and control autopilot system, wherein an additional rate command is determined by dividing the Additional Gbias by the estimate of the velocity of the projectile; and
whereby the guidance and control autopilot system is configured to guide the projectile to a target using the total rate command of the guidance and control autopilot system.

### Claim 2 (depends on 1)

The method of claim 1, comprising:
determining the Inherent Gbias amount produced by null guidance and control lateral rate control loops of the guidance and control autopilot system.

### Claim 3 (depends on 1)

The method of claim 1, comprising:
determining a Desired Gbias amount; and
determining the Additional Gbias amount.

### Claim 4 (depends on 3)

The method of claim 3, wherein an orientation of a roll inertial guidance coordinate frame with respect to gravity is utilized to partition the Desired Gbias into pitch and yaw control loops.

### Claim 5 (depends on 3)

The method of claim 3, wherein the Desired Gbias magnitude balances guidance errors with trajectory lofting to produce a near 0 G airframe in an end game.

### Claim 6 (depends on 3)

The method of claim 3, wherein the Desired Gbias lofts the trajectory after a seeker laser acquisition.

### Claim 7 (depends on 1)

The method of claim 1,
where
γ
.
c
=
a
m
V
m
=
Gbias
V
m
wherein {dot over (γ)}c comprises the additional rate command for use by lateral control loops, am comprises an estimate of an additional lateral acceleration of the projectile, Vm comprises the estimate of the velocity of the projectile, and Gbias comprises the Additional Gbias.

### Claim 8 (depends on 1)

The method of claim 1, wherein the guidance and control autopilot system does not comprise an accelerometer, whereby complexity and cost of the projectile is reduced.

### Claim 9 (depends on 1)

The method of claim 1, wherein terminal lateral G requirements of an airframe are ballistic, near 0 G, and residual airframe lateral Gs are available to absorb other endgame guidance errors;
the other endgame guidance errors comprising rate sensor errors and seeker errors that have a random orientation with respect to gravity.

### Claim 10

A system for shaping a trajectory of a projectile comprising:
a guidance and control autopilot;
at least one processor of the guidance and control autopilot executing a program performing as follows:
processing a roll orientation with respect to gravity and an estimate of a velocity of the projectile;
determining an Inherent Gbias amount produced by null guidance and control lateral rate control loops of the guidance and control autopilot;
determining a Desired Gbias amount;
determining an Additional Gbias amount;
applying the Additional Gbias to the Inherent Gbias;
determining a total rate command by the at least one processor of the guidance and control autopilot system, wherein the total rate command is determined by dividing the Desired Gbias by the estimate of the velocity of the projectile; and
guiding the projectile to a target using the total rate command from the guidance and control autopilot.

### Claim 11 (depends on 10)

The system of claim 10 wherein the guidance and control autopilot comprises:
lateral acceleration sensors;
lateral turn rate sensors;
velocity sensors; and
an orientation determination system, wherein the orientation determination system receives input from the lateral acceleration sensors, the lateral turn rate sensors, and the velocity sensors.

### Claim 12 (depends on 10)

The system of claim 10, wherein the roll orientation is input after launch.

### Claim 13 (depends on 10)

The system of claim 10,
where
γ
.
c
=
a
m
V
m
=
Gbias
V
m
wherein {dot over (γ)}c comprises the additional rate command for use by the lateral control loops, am comprises an estimate of an additional lateral acceleration of the projectile, Vm comprises the estimate of the velocity of the projectile, and Gbias comprises the Additional Gbias.

### Claim 14 (depends on 10)

The system of claim 10, wherein determination of the roll orientation with respect to gravity comprises a magnetometer.

### Claim 15 (depends on 10)

The system of claim 10, wherein determination of the roll orientation with respect to gravity comprises an initialized inertial measurement unit (IMU).

### Claim 16 (depends on 10)

The system of claim 10, wherein sensors of the guidance and control autopilot comprise only rate sensors.

### Claim 17 (depends on 10)

The system of claim 10, wherein the guidance and control autopilot comprises a seeker.

### Claim 18 (depends on 10)

The system of claim 10, wherein the guidance and control autopilot is an angular rate based autopilot.

### Claim 19 (depends on 10)

The system of claim 10, wherein the system does not comprise an accelerometer, whereby complexity and cost of the projectile is reduced.

### Claim 20

A guidance and control autopilot device for shaping a trajectory of a projectile comprising:
a feed forward section;
a guidance filter;
pitch/yaw/roll coupled aerodynamics;
a feed forward section;
a pitch rate sensor;
wherein at least one processor determines a total rate command equal to an Additional Gbias divided by an estimate of a velocity of the projectile, combined with guidance loop commands, incorporating a roll orientation with respect to gravity; and
whereby the guidance and control autopilot device is configured to guide the projectile to a target.