Angular accelerometer stabilized pendulum
First Claim
1. In a vertical indicating device having a Schuler-tuned pendulum, the pendulum having a rotational degree of freedom about a horizontal axis, the improvement comprising:
- an angular accelerometer having an axis parallel to the rotational axis of said pendulum;
torsional coupling means between said angular accelerometer and said pendulum;
means for generating an electrical signal representative of the relative angular velocity between said angular accelerometer and said pendulum; and
means responsive to said signal for applying a restoring torque to said pendulum proportional to an acceleration associated to said relative angular velocity;
whereby said pendulum has an effective moment of inertia substantially greater than its actual physical moment of inertia, such that its period of oscillation is that of a simple pendulum having a length equal to the earth'"'"'s radius, whereby said pendulum maintains its alignment with the local gravity vector independently of horizontal acceleration.
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Abstract
A gyroless vertical indicating device which tracks the local gravity vector independent of horizontal acceleration. A compound pendulum and an angular accelerometer each has a single rotational degree of freedom about a common axis. Rotational motion of the pendulum and of the angular accelerometer about the axis is coupled by a quartz fiber suspension therealong. A signal representative of the relative angular velocity between the pendulum and the angular accelerometer is fed back to a torquing system which maintains the pendulum'"'"'s orientation along the local gravity vector.
16 Citations
15 Claims
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1. In a vertical indicating device having a Schuler-tuned pendulum, the pendulum having a rotational degree of freedom about a horizontal axis, the improvement comprising:
- an angular accelerometer having an axis parallel to the rotational axis of said pendulum;
torsional coupling means between said angular accelerometer and said pendulum;
means for generating an electrical signal representative of the relative angular velocity between said angular accelerometer and said pendulum; and
means responsive to said signal for applying a restoring torque to said pendulum proportional to an acceleration associated to said relative angular velocity;
whereby said pendulum has an effective moment of inertia substantially greater than its actual physical moment of inertia, such that its period of oscillation is that of a simple pendulum having a length equal to the earth'"'"'s radius, whereby said pendulum maintains its alignment with the local gravity vector independently of horizontal acceleration. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- an angular accelerometer having an axis parallel to the rotational axis of said pendulum;
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11. A device for maintaining a stable vertical in two dimensions thereby defining a horizontal plane, comprising:
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a frame; a platform member to be maintained in a fixed relationship to said plane; a plurality of gimbals mounting said platform to said frame wherein said platform is free to assume any angular orientation in space relative to said frame; first and second stabilized pendula mounted to said platform, each stabilized pendulum including a pendulum having a rotational degree of freedom about a horizontal axis, an angular accelerometer having an axis parallel to the rotational axis of the associated pendulum, torsional coupling means between said angular accelerometer and said associated pendulum, means for generating an electrical signal representative of the angular velocity between said angular accelerometer and said associated pendulum, and means responsive to said signal for applying a restoring torque to said associated pendulum proportional to an acceleration associated to said relative angular velocity, whereby said associated pendulum is Schuler tuned with respect to its axis of rotation; the axis of the first stabilized pendulum being parallel to said plane; the axis of the second stabilized pendulum being parallel to said plane and perpendicular to the axis of said first stabilized pendulum; first and second means for generating an electrical signal representative of relative angular motion between said platform and said first and second pendula respectively; and first and second means responsive to said first and second signals representative of relative angular motion between said platform and said first and second pendula, respectively, for applying a torque to said platform in order to slave said platform to said first and second pendula respectively; whereby said platform is maintained in fixed relationship to the horizontal plane. - View Dependent Claims (12)
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13. A device for maintaining a stable vertical in two dimensions thereby defining a horizontal plane comprising:
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a frame; a pendulum assembly having a first rotational degree of freedom about a first horizontal pitch axis and having a second rotational degree of freedom around a second horizontal roll axis; a plurality of gimbals mounting said pendulum assembly to said frame whereby said pendulum assembly is free to assume any angular orientation relative to said frame; first and second angular motion sensors, each including an angular accelerometer having a rotational degree of freedom about an axis, torsional coupling means between said angular accelerometer and the associated pendulum along the angular accelerometer axis, means for generating an electrical signal representative of the relative angular velocity between said angular accelerometer and said associated pendulum, and means responsive to said signal representative of the relative angular velocity for applying a restoring torque to said associated pendulum proportional to an acceleration associated to said relative angular velocity, whereby said associated pendulum is Schuler tuned with respect to the corresponding angular accelerometer axis; the first angular accelerometer having its axis aligned with said pitch axis; the second angular accelerometer having its axis aligned with said roll axis; whereby said pendulum assembly is Schuler tuned with respect to both the pitch and the roll axis. - View Dependent Claims (14, 15)
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Specification