Gyroless platform stabilization techniques
First Claim
1. Apparatus for stabilizing an object around at least first and second object axes of rotation with respect to an inertial frame of reference, said object being carried by a vehicle subjected to rotational movement around at least first and second vehicle axes of rotation corresponding to said at least first and second object axes of rotation, said apparatus comprising in combination:
- means for generating vehicle rotation signals corresponding to the rotational movement of said vehicle around at least said first and second vehicle axes of rotation with respect to said inertial frame of reference;
feedback means for generating feedback signals corresponding to the movement of said object around at least said first and second object axes of rotation independent of said inertial frame of reference;
control system means responsive to said vehicle rotation signals and responsive to said feedback signals for generating movement signals; and
movement means responsive to said movement signals for rotatably moving said object around at least said first and second object axes, whereby said object is stabilized around at least said first and second object axes with respect to said frame of reference without the use of a gyroscope as said vehicle undergoes rotation relative to said inertial frame of reference.
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Abstract
A method and apparatus for platform stabilization. The apparatus uses linear and/or angular accelerometers to derive the roll, pitch, and yaw components of the angular velocity of the vehicle the apparatus is mounted on. Based on the calculation of angular velocity or acceleration of the vehicle and the current rate and angle of rotation of the device to be stabilized, the apparatus generates setpoint and movement commands for servo motors that rotate the sensing device such that the line of sight of the sensing device is stabilized. A control system implements a velocity control system, or, alternatively, an acceleration control system. In one embodiment of the invention, the accelerometers are positioned on a mounting base along axes corresponding to the roll, pitch and yaw axes of the vehicle in a location adjacent to the sensing device. In an alternative embodiment, the accelerometers are positioned on the stabilized element itself, with the command strategy being to force gimbal rotations so that the output of the accelerometers is urged towards a null value.
216 Citations
42 Claims
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1. Apparatus for stabilizing an object around at least first and second object axes of rotation with respect to an inertial frame of reference, said object being carried by a vehicle subjected to rotational movement around at least first and second vehicle axes of rotation corresponding to said at least first and second object axes of rotation, said apparatus comprising in combination:
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means for generating vehicle rotation signals corresponding to the rotational movement of said vehicle around at least said first and second vehicle axes of rotation with respect to said inertial frame of reference; feedback means for generating feedback signals corresponding to the movement of said object around at least said first and second object axes of rotation independent of said inertial frame of reference; control system means responsive to said vehicle rotation signals and responsive to said feedback signals for generating movement signals; and movement means responsive to said movement signals for rotatably moving said object around at least said first and second object axes, whereby said object is stabilized around at least said first and second object axes with respect to said frame of reference without the use of a gyroscope as said vehicle undergoes rotation relative to said inertial frame of reference. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
- 14. Apparatus, as claimed in claim 9, wherein said apparatus is operated in a scanning mode and wherein said third movement signal is responsive to a third setpoint signal, G3, corresponding to the desired angular velocity of said object around said third gimbal axis and proportional to
- space="preserve" listing-type="equation">(-W.sub.1 -W.sub.2 tan G.sub.1)/( cos G.sub.2 cos G.sub.1 +tan G.sub.1 cos G.sub.2 sin G.sub.1)
wherein said second movement signal is responsive to a second setpoint signal corresponding to the desired angular velocity of said object around said second gimbal axis and proportional to
space="preserve" listing-type="equation">(-W.sub.2 -G.sub.3 cos G.sub.2 sin G.sub.1)/( cos G.sub.1),and wherein said first movement signal is responsive to a first setpoint signal corresponding to the desired angular velocity of said object around said first gimbal axis and proportional to
space="preserve" listing-type="equation">(-W.sub.3 +G.sub.3 sin G.sub.2)where W1, W2 and W3 correspond to the difference between the base angular velocities in roll, pitch, and yaw, respectively and the desired angular scanning velocities of said object and where G1 and G2 are the angles of rotation around said first and second gimbal axes, respectively.
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- 15. Apparatus, as claimed in claim 9, wherein said third movement signal is responsive to a third setpoint signal, G3, corresponding to the desired angular acceleration of said object around said third gimbal axis and proportional to
- space="preserve" listing-type="equation">(-W.sub.1 -W.sub.2 tan G.sub.1)/( cos G.sub.2 cos G.sub.1 +tan G.sub.1 cos G.sub.2 sin G.sub.1),
wherein said second movement signal is responsive to a second setpoint signal corresponding to the desired angular acceleration of said object around said second gimbal axis and proportional to
space="preserve" listing-type="equation">(-W.sub.2 -G.sub.3 cos G.sub.2 sin G.sub.1)/( cos G.sub.1),and wherein said first movement signal is responsive to a setpoint signal corresponding to the desired angular acceleration of said object around said first gimbal axis and proportional to
space="preserve" listing-type="equation">(-W.sub.3 +G.sub.3 sin G.sub.2)where W1, W2 and W3 correspond to the angular accelerations of said vehicle around said first, second and third vehicle axes, respectively and where G1 and G2 are the angles of rotation around said first and second gimbal axes, respectively.
- space="preserve" listing-type="equation">(-W.sub.1 -W.sub.2 tan G.sub.1)/( cos G.sub.2 cos G.sub.1 +tan G.sub.1 cos G.sub.2 sin G.sub.1),
space="preserve" listing-type="equation">(-W.sub.2 -G.sub.3 cos G.sub.2 sin G.sub.1)/( cos G.sub.1),
space="preserve" listing-type="equation">(-W.sub.3 +G.sub.3 sin G.sub.2)
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17. A method for stabilizing an object around at least first and second object axes of rotation with respect to an inertial frame of reference, said object being carried by a vehicle subjected to rotational movement around at least first and second vehicle axes of rotation corresponding to said at least first and second object axes of rotation, said method comprising the steps of:
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generating vehicle rotation signals corresponding to the rotational movement of said vehicle around at least said first and second vehicle axes of rotation with respect to said inertial frame of reference; generating feedback signals corresponding to the movement of said object around at least said first and second object axes of rotation independent of said inertial frame of reference; generating movement signals responsive to said one or more vehicle rotation signals and responsive to said feedback signals; and rotatably moving said object around at least said first and second object axes responsive to said movement signals, whereby said object is stabilized around at least said first and second object axes with respect to said inertial frame of reference without the use of a gyroscope as said vehicle undergoes rotation relative to said inertial frame of reference. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
- 25. A method, as claimed in claim 17, wherein said vehicle axes of rotation comprise orthogonal vehicle axes of rotation, wherein said object is moved in a scanning mode relative to said vehicle by rotation around first, second and third orthogonal object axes of rotation and said movement signals comprise first, second and third movement signals for rotation around said first, second and third orthogonal object axes of rotation, respectively, and wherein said third movement signal is responsive to a third setpoint signal, S3, proportional to
- space="preserve" listing-type="equation">(-W.sub.1 -W.sub.2 tan Y)/( cos P cos Y+tan Y cos P sin Y),
said second movement is responsive to a second setpoint signal proportional to
space="preserve" listing-type="equation">(-W.sub.2 -S.sub.3 cos P sin Y)/ cos Y,and said first movement signal is responsive to a first setpoint signal proportional to
space="preserve" listing-type="equation">-W.sub.3 +S.sub.3 sin P,wherein W1, W2 and W3 correspond to the differences between the measurements of the angular accelerations of said vehicle around said orthogonal vehicle axes of rotation and the desired angular scanning accelerations of said object, and Y and P are the angles of rotation around said first and second object axes of rotation.
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- 26. A method, as claimed in claim 17, wherein said vehicle axes of rotation are orthogonal vehicle axes of rotation, wherein said object is moved relative to said vehicle by rotation around first, second and third orthogonal object axes of rotation and said movement signals comprise first, second, and third movement signals for rotation around said first, second, and third orthogonal object axes of rotation, respectively, and wherein said third movement signal is responsive to a third setpoint signal, S3 proportional to
- space="preserve" listing-type="equation">(-W.sub.1 -W.sub.2 tan Y)/( cos P cos Y+tan Y cos P sin Y),
said second movement signal is responsive to a second setpoint signal proportional to
space="preserve" listing-type="equation">(-W.sub.2 -S.sub.3 cos P sin Y)/ cos Y,and said first movement signal is responsive to a first setpoint signal proportional to
space="preserve" listing-type="equation">-W.sub.3 +S.sub.3 sin P,wherein W1, W2 and W3 are the measurements of the angular velocities of said vehicle around said orthogonal vehicle axes of rotation and Y and P are the angles of rotation around said first and second object axes of rotation.
- space="preserve" listing-type="equation">(-W.sub.1 -W.sub.2 tan Y)/( cos P cos Y+tan Y cos P sin Y),
space="preserve" listing-type="equation">(-W.sub.2 -S.sub.3 cos P sin Y)/ cos Y,
space="preserve" listing-type="equation">-W.sub.3 +S.sub.3 sin P,
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28. Apparatus for stabilizing an object capable of being rotated in three degrees of freedom with respect to an inertial frame of reference, said object being carried in a vehicle subject to rotational movement around first, second and third vehicle axes of rotation with respect to said inertial frame of reference, said object defining three object axes corresponding to said first, second and third vehicle axes of rotation, said apparatus comprising in combination:
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linear accelerometer means carried by said object for measuring the net linear accelerations of said object and said vehicle in said three degrees of freedom; processor means for calculating the net angular accelerations of said object and said vehicle in said three degrees of freedom in response to said linear accelerometer means; control system means responsive to said calculating of said net angular accelerations by said processor means for generating movement signals; and movement means responsive to said movement signals for rotatably moving said object in said three degrees of freedom, whereby said object is stabilized in said three degrees of freedom with respect to said inertial frame of reference without the use of a gyroscope as said vehicle undergoes rotation relative to said inertial frame of reference. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36)
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37. A method of stabilizing an object capable of being rotated in three degrees of freedom with respect to an inertial frame of reference, said object being carried in a vehicle subject to rotational movement around first, second and third vehicle axes of rotation with respect to said inertial frame of reference, said object defining three object axes corresponding to said first, second and third vehicle axes of rotation, said method comprising the steps of:
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measuring the net linear accelerations of said object and said vehicle in said three degrees of freedom; calculating the net angular accelerations of said object and said vehicle in said three degrees of freedom in response to said measurement of net linear accelerations; generating movement signals responsive to said calculating of said net angular accelerations; and rotatably moving said object in said three degrees of freedom responsive to said movement signals, whereby said object is stabilized in said three degrees of freedom with respect to said inertial frame of reference without the use of a gyroscope as said vehicle undergoes rotation relative to said inertial frame of reference. - View Dependent Claims (38, 39, 40, 41, 42)
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Specification