Motion-tracking
CAFCFirst Claim
1. A system for tracking the motion of an object relative to a moving reference frame, comprising:
- a first inertial sensor mounted on the tracked object;
a second inertial sensor mounted on the moving reference frame; and
an element adapted to receive signals from said first and second inertial sensors and configured to determine an orientation of the object relative to the moving reference frame based on the signals received from the first and second inertial sensors.
5 Assignments
1 Petition
Accused Products
Abstract
Inertial trackers have been successfully applied to a wide range of head mounted display (HMD) applications including virtual environment training, VR gaming and even fixed-base vehicle simulation, in which they have gained widespread acceptance due to their superior resolution and low latency. Until now, inertial trackers have not been used in applications which require tracking motion relative to a moving platform, such as motion-base simulators, virtual environment trainers deployed on board ships, and live vehicular applications including helmet-mounted cueing systems and enhanced vision or situational awareness displays. to the invention enables the use of inertial head-tracking systems on-board moving platforms by computing the motion of a “tracking” Inertial Measurement Unit (IMU) mounted on the HMD relative to a “reference” IMU rigidly attached to the moving platform.
275 Citations
42 Claims
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1. A system for tracking the motion of an object relative to a moving reference frame, comprising:
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a first inertial sensor mounted on the tracked object;
a second inertial sensor mounted on the moving reference frame; and
an element adapted to receive signals from said first and second inertial sensors and configured to determine an orientation of the object relative to the moving reference frame based on the signals received from the first and second inertial sensors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
computing the orientation of the object with respect to a fixed inertial reference frame using the signals from the first inertial sensor, computing the orientation of the moving reference frame with respect to the same fixed inertial reference frame using the signals from the second inertial sensor. and computing the relative orientation based on the two orientations. -
7. The system of claim 6, further comprising a drift corrector for correcting inertial drift in the determined orientation of the object with respect to the inertial reference frame or of the moving reference frame with respect to the inertial reference frame.
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8. The system of claim 7, in which said drift corrector includes sensors for determining tilt with respect to earth'"'"'s gravitational field.
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9. The system of claim 7, where said drift corrector includes sensors for determining heading with respect to earth'"'"'s magnetic field.
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10. The system of claim 6, further comprising a drift corrector for correcting inertial drift in the determined orientation of the object with respect to the moving reference frame by using non-inertial sensors to independently measure the relative orientation.
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11. The system of claim 2, in which the first and second inertial sensors each further comprises three linear accelerometers.
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12. The system of claim 11, further comprising an element for calculating the position of the object relative to the moving reference frame.
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13. The system of claim 12, in which the calculating element double-integrates a relative linear acceleration signal computed from the linear accelerometer signals measured by the first and second inertial sensors.
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14. The system of claim 13, in which the moving reference frame has an angular velocity and an angular acceleration, and wherein calculation of said relative linear acceleration signal includes compensation for tangential, Coriolis and centripetal acceleration effects caused by the angular velocity and angular acceleration of the moving reference frame.
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15. The system of claim 14, in which the compensation for tangential, Coriolis and centripetal acceleration effects is calculated using the angular velocity or angular acceleration of the moving reference frame measured by the second inertial sensor.
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16. The system of claim 13, in which no compensation for the effect of gravity on the accelerometers is made.
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17. The system of claim 12, in which the calculation of the position of the object relative to the moving reference frame includes:
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computing the position of the object with respect to a fixed inertial reference frame using the signals from the first inertial sensor, computing the position of the moving reference frame with respect to the same fixed inertial reference frame using the signals from the second inertial sensor, and computing the relative position based on the position of the object and the position of the moving reference frame.
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18. The system of claim 17, further comprising a drift corrector for correcting inertial drift in the determined position of the object with respect to the inertial reference frame or of the moving reference frame with respect to the inertial reference frame.
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19. The system of claim 18, in which the drift corrector includes sensors for measuring position of both the object and the moving reference frame with respect to landmarks fixed in common inertial reference frame.
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20. The system of claim 1, in which the moving reference frame is associated with a vehicle, and the second inertial sensor comprises a pre-existing inertial measurement unit on a vehicle that was installed for the purpose of navigation.
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21. The system of claim 1, in which the first and second inertial sensors each comprises at least six linear accelerometers and associated processors to extract three angular inertial signals and three linear accelerations.
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- 22. A method comprising determining an orientation of an object relative to a moving reference frame based on signals from two inertial sensors mounted respectively on the object and on the moving reference frame.
Specification