Inclinometer measurement system and method providing correction for movement induced acceleration errors
First Claim
1. A system for sensing the inclination of element with respect to gravity, said element defining orthogonal X and Y axes, and a Z axis orthogonal to both said X and Y axes, said element being rotatable about an axis of rotation extending parallel to said Z axis, said element being supported by and rotatable with a platform, comprising:
- an inclinometer, mounted on said element at a location spaced from said axis of rotation by a distance r, for providing inclinometer outputs indicating acceleration in the X and Y directions, designated as Ix and Iy, respectively, a line from said axis of rotation to said inclinometer forming an included angle B with said X axis,a sensor, mounted on said platform, for sensing the rotational speed w of the element about said axis of rotation and providing a sensor output indicating said rotational speed W,a circuit for differentiating said sensor output to determine the angular acceleration of said element dw/dt,a circuit for multiplying said angular acceleration by the value r to determine the tangential acceleration of said element at said point where said inclinometer is mounted r(dw/dt),a circuit for resolving the tangential acceleration of said element at said point where said inclinometer is mounted to determine the X axis component thereof, and for resolving the tangential acceleration of said platform at said point where said inclinometer is mounted to determine the Y axis component thereof, anda circuit for subtracting said X axis component of said tangential acceleration of said element at said point where said inclinometer is mounted from said acceleration Ix sensed in a direction parallel to said X axis, and for subtracting said Y axis component of said tangential acceleration of said element at said point where said inclinometer is mounted from said acceleration Iy sensed in a direction parallel to said Y axis, whereby said inclinometer outputs Ix and Iy are corrected for errors that would otherwise result from tangential acceleration.
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Accused Products
Abstract
A system and a method sense the inclination of a machine element, such as a platform, and eliminate tangential and radial acceleration errors. The platform defines orthogonal X and Y axes, and is rotatable about a Z axis. An inclinometer, mounted on the platform at a location spaced from the axis of rotation by a distance r, provides inclinometer outputs indicating acceleration in the X and Y directions, Ix and Iy, respectively. A rate gyro on the platform senses the rotational speed w of the platform. The rate gyro output w is differentiated and multiplied by r to determined tangential acceleration at the inclinometer. A circuit resolves the tangential acceleration into X axis and Y axis components, which are used to correct the inclinometer outputs Ix and Iy for errors that would otherwise result from tangential acceleration.
39 Citations
16 Claims
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1. A system for sensing the inclination of element with respect to gravity, said element defining orthogonal X and Y axes, and a Z axis orthogonal to both said X and Y axes, said element being rotatable about an axis of rotation extending parallel to said Z axis, said element being supported by and rotatable with a platform, comprising:
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an inclinometer, mounted on said element at a location spaced from said axis of rotation by a distance r, for providing inclinometer outputs indicating acceleration in the X and Y directions, designated as Ix and Iy, respectively, a line from said axis of rotation to said inclinometer forming an included angle B with said X axis, a sensor, mounted on said platform, for sensing the rotational speed w of the element about said axis of rotation and providing a sensor output indicating said rotational speed W, a circuit for differentiating said sensor output to determine the angular acceleration of said element dw/dt, a circuit for multiplying said angular acceleration by the value r to determine the tangential acceleration of said element at said point where said inclinometer is mounted r(dw/dt), a circuit for resolving the tangential acceleration of said element at said point where said inclinometer is mounted to determine the X axis component thereof, and for resolving the tangential acceleration of said platform at said point where said inclinometer is mounted to determine the Y axis component thereof, and a circuit for subtracting said X axis component of said tangential acceleration of said element at said point where said inclinometer is mounted from said acceleration Ix sensed in a direction parallel to said X axis, and for subtracting said Y axis component of said tangential acceleration of said element at said point where said inclinometer is mounted from said acceleration Iy sensed in a direction parallel to said Y axis, whereby said inclinometer outputs Ix and Iy are corrected for errors that would otherwise result from tangential acceleration. - View Dependent Claims (2, 3, 4)
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5. A method for sensing the inclination of an element with respect to gravity, said element defining orthogonal X and Y axes, and a Z axis orthogonal to both said X and Y axes, said element being rotatable about an axis of rotation extending parallel to said Z axis, comprising the steps of:
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sensing acceleration in the X and Y directions, designated as Ix and Iy, respectively, from an inclinometer mounted on said element at a location spaced from said axis of rotation by a distance r, and providing inclinometer outputs indicating acceleration in the X and Y directions, sensing the rotational speed w of the element about said axis of rotation and providing an output indicating said rotational speed w, differentiating said rotational speed w to determine the angular acceleration of said element dw/dt, multiplying said angular acceleration by the value r to determine the tangential acceleration of said element at said point where said inclinometer is mounted r(dw/dt), resolving the tangential acceleration of said element at said point where said inclinometer is mounted to determine the X axis component thereof, resolving the tangential acceleration of said element at said point where said inclinometer is mounted to determine the Y axis component thereof, subtracting said X axis component of said tangential acceleration of said element at said point where said inclinometer is mounted from said acceleration IX sensed in a direction parallel to said X axis, and subtracting said Y axis component of said tangential acceleration of said element at said point where said inclinometer is mounted from said acceleration IY sensed in a direction parallel to said Y axis, whereby said inclinometer outputs Ix and Iy are corrected for errors that would otherwise result from tangential acceleration. - View Dependent Claims (6, 7, 8)
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9. A system for sensing the inclination of a platform with respect to gravity, said platform defining orthogonal X and Y axes, and a Z axis orthogonal to both said X and Y axes, said platform being rotatable about an axis of rotation extending parallel to said Z axis, comprising:
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an inclinometer, mounted on said platform at a location spaced from said axis of rotation by a distance r, for providing inclinometer outputs indicating acceleration in the X and Y directions, designated as Ix and Iy, respectively, a line from said axis of rotation to said inclinometer forming an included angle B with said X axis, a rate gyro, mounted on the platform, for sensing the rotational speed w of the platform about said axis of rotation and providing a rate gyro output indicating said rotational speed w, a circuit for differentiating said rate gyro output to determine the angular acceleration of said platform dw/dt, a circuit for multiplying said angular acceleration by the value r to determine the tangential acceleration of said platform at said point where said inclinometer is mounted r(dw/dt), a circuit for resolving the tangential acceleration of said platform at said point where said inclinometer is mounted to determine the X axis component thereof, and for resolving the tangential acceleration of said platform at said point where said inclinometer is mounted to determine the Y axis component thereof, and a circuit for subtracting said X axis component of said tangential acceleration of said platform at said point where said inclinometer is mounted from said acceleration IX sensed in a direction parallel to said X axis, and for subtracting said Y axis component of said tangential acceleration of said platform at said point where said inclinometer is mounted from said acceleration IY sensed in a direction parallel to said Y axis, whereby said inclinometer outputs Ix and Iy are corrected for errors that would otherwise result from tangential acceleration. - View Dependent Claims (10, 11, 12)
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13. A method for sensing the inclination of a platform with respect to gravity, said platform defining orthogonal X and Y axes, and a Z axis orthogonal to both said X and Y axes, said platform being rotatable about an axis of rotation extending parallel to said Z axis, comprising the steps of:
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sensing acceleration in the X and Y directions, designated as Ix and Iy, respectively, from an inclinometer mounted on said platform at a location spaced from said axis of rotation by a distance r, and providing inclinometer outputs indicating acceleration in the X and Y directions, sensing the rotational speed w of the platform about said axis of rotation and providing an output indicating said rotational speed w, differentiating said rotational speed w to determine the angular acceleration of said platform dw/dt, multiplying said angular acceleration by the value r to determine the tangential acceleration of said platform at said point where said inclinometer is mounted r(dw/dt), resolving the tangential acceleration of said platform at said point where said inclinometer is mounted to determine the X axis component thereof, resolving the tangential acceleration of said platform at said point where said inclinometer is mounted to determine the Y axis component thereof, subtracting said X axis component of said tangential acceleration of said platform at said point where said inclinometer is mounted from said acceleration IX sensed in a direction parallel to said X axis, and subtracting said Y axis component of said tangential acceleration of said platform at said point where said inclinometer is mounted from said acceleration IY sensed in a direction parallel to said Y axis, whereby said inclinometer outputs Ix and Iy are corrected for errors that would otherwise result from tangential acceleration. - View Dependent Claims (14, 15, 16)
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Specification