Angular position sensing and control system, apparatus and method
First Claim
1. In apparatus for sensing the attitude relative to a local horizontal reference of a part on a machine having a framework supporting said part while said framework is free to move relative to the local horizontal reference, a linear accelerometer adapted to be mounted on said part having a sensitive axis for detecting departure thereof from the local horizontal reference and for producing a first signal representing a slow response angular displacement of said part, means for summing connected to receive said first signal and producing a summed output, means for receiving said summed output and for attenuating high frequencies therein, said last named means providing an error compensation signal, means adapted to be mounted on said part for sensing rotational motion thereof, said last named means producing a second signal representing a fast response indication of angular displacement of said part, means for combining said error compensation signal and said second signal and for providing a combined signal, means for feeding back said combined signal to said means for summing, said first signal and said combined signal having opposing sense for the same motion sense, whereby steady state errors in said second signal are compensated in said combined signal by said error compensation signal and transients in said second signal appear in said combined signal.
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Abstract
A structural body is monitored in angular position about at least one axis by utilizing a level sensor and a sensor responsive to angular motion of the body about the axis being monitored. An output indicative of long term angular variations of the body about the axis is provided by the level sensor and short term angular variations are indicated by the output from the sensor responsive to angular motion about the axis. The signals indicative of long term and short term angular variations are combined to provide a broad band output signal indicative of angular position which is immune to high frequency translational variations appearing at the level sensor output, but which is responsive to high frequency angular inputs. The fast response angular sensor output is compared with the slow response level sensor output and an error signal is produced which drives the angular sensor output signal into coincidence with the level sensor output signal. The combined broad band angular output indication may be utilized for angular position monitoring for controlling one part of a machine relative to a predetermined external angular position reference for driving a stable platform to assume a predetermined angle about the axis.
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Citations
13 Claims
- 1. In apparatus for sensing the attitude relative to a local horizontal reference of a part on a machine having a framework supporting said part while said framework is free to move relative to the local horizontal reference, a linear accelerometer adapted to be mounted on said part having a sensitive axis for detecting departure thereof from the local horizontal reference and for producing a first signal representing a slow response angular displacement of said part, means for summing connected to receive said first signal and producing a summed output, means for receiving said summed output and for attenuating high frequencies therein, said last named means providing an error compensation signal, means adapted to be mounted on said part for sensing rotational motion thereof, said last named means producing a second signal representing a fast response indication of angular displacement of said part, means for combining said error compensation signal and said second signal and for providing a combined signal, means for feeding back said combined signal to said means for summing, said first signal and said combined signal having opposing sense for the same motion sense, whereby steady state errors in said second signal are compensated in said combined signal by said error compensation signal and transients in said second signal appear in said combined signal.
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4. In a sensing apparatus a linear accelerometer for producing a first signal, an angular accelerometer for producing a second signal, means for receiving said first signal, said means for receiving operating to pass steady state signals, to attenuate transient signals, and to provide a compensation signal, means for combining said compensation signal and said second signal and for providing a combined output signal, said combined output signal containing components resulting from said second signal having a sense opposite to said first signal for the same motion sense, means for coupling said combined output signal to said means for receiving, said combined output signal thereby being substantially free of the effects of spurious linear acceleration in said first signal and being substantially free of steady state errors in said second signal.
- 5. In an angular position sensing system for broad band detection of the angular position of a structural body referenced to earth'"'"'s coordinates about at least one axis, a level sensor mounted to detect angular position of the structural body about said one axis and producing an angular position output related thereto, means for attenuating short term components in said angular position output and providing a long term angular position output, means for detecting angular motion about said one axis substantially solely sensitive to angular motion and producing an angular motion output related thereto, means for combining said long term angular position and motion outputs, said means for combining including means for converting said angular motion output to a second angular position output, whereby a combined angular position output is produced, said combined angular position output being coupled to said means for attenuating, whereby short term second angular position output is present in said combined angular position output thereby providing a continuous broad band combined angular position output containing long and short term outputs related to angular position.
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10. The method of sensing the angular position of a structural body relative to a predetermined angular position about at least one axis referenced to earth'"'"'s coordinates, comprising the steps of sensing the deviation from local horizontal of a plane in the body about said one axis, sensing the angular acceleration of the body about said one axis, rejecting the high frequency components in the sensed deviation from local horizontal, integrating the sensed angular acceleration twice, rejecting the low frequency components in the twice integrated signal, and combining the remaining low and high frequency components in the sensed deviation and twice integrated signals respectively, thereby providing a broad band signal indicative of angular position.
- 11. Apparatus for sensing angular position of a structure about an axis wherein the structure is free to move about the axis comprising a level sensor for monitoring angular position of the structure relative to a level reference and providing a level indicative output, an angular motion sensor for monitoring angular motion of the structure about the axis and providing an angular motion indicative output, a compound amplifier, first and second means for summing included in said compound amplifier, said level indicative output being coupled to said first means for summing, and said angular motion indicative output being coupled to said second means for summing, said compound amplifier operating to convert said angular motion indicative output to an angular position indicative output and to provide a combined angular position indicative output including components related to said angular position and level indicative outputs, means for feeding back said combined angular position indicative output to said first means for summing, said compound amplifier further operating to remove long term angular position indicative outputs and short term level indicative outputs from said combined angular position indicative output, thereby providing said last named output free of errors induced by steady state angular motion indicative output and transient level indication output.
Specification