US3634682A
Expired / Lapsed
US
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Laser interferometer-type servo-positioning system comprising velocity control network and phase-lock network
Assignee: Polaroid Corp
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Filing: 1970-02-13
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Granted: 1972-01-11
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Expires: 1990-02-13
Abstract
Abstract A precision servo-positioning system is provided for moving a stable platform to a predetermined position with extremely fine accuracy. Basically, a laser interferometer is utilized to detect changes in the position of the stable platform and provides output signals to an electronic control network which in turn provides input signals to a motor used to drive the platform. The electronic control network includes a velocity control network, a phase-lock network, and a velocity feedback network. The velocity control network provides a DC level input signal to the motor driving the platform such that the platform will be caused to attain a predetermined velocity and includes means for monitoring the output signals from the laser interferometer and determining velocity information therefrom. The velocity control network converts this velocity information into a DC level which is negatively fed back to the motor so as to null the input thereto when the platform has achieved a predetermined velocity. Once the platform has achieved such predetermined velocity, it continues to move under its own momentum. As the moving platform approaches a predetermined position, at its predetermined velocity, the velocity control network is switched off and a phase-lock network is switched on to bring the moving platform to rest at such predetermined position. The phase-lock network incorporates a reference signal source and compares the output signals from the laser interferometer with the signal from said reference to generate an error signal indicative of the phase difference between the setting of said reference signal source and said laser output signals. When the phase difference between the reference signal source setting and the signals from the laser interferometer is a predetermined amount the error signal will be 0. This error signal is fed back to the motor, which drives the stable platform, and is polarity sensitive to the phase difference between the laser interferometer output signals and the reference signal source setting. Thus, the phase-lock network will provide signals to the motor tending to drive the platform toward the predetermined position at which the error signal will be 0. A velocity feedback network is used in conjunction with the phase-lock and provides negative feedback signals to the motor so as to oppose the velocity of the platform. Thus, the velocity feedback network serves to prevent the platform from overshooting the predetermined position and entering a cogging mode.
Inventors
- 👤 Nathan Gold
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 05:56
CPC Classifications
G; G05; G05D; G05D3/00; G05D3/12; G05D3/14; G05D3/1445; G01; G01B; G01B9/00; G01B9/02; G01B9/02055; G01B9/02075; G01B9/02078; G01B9/02079; G01B9/02081; G01B2290/00; G01B2290/70
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
198 words
Apparatus for precisely positioning a slideable platform, including: motor means connected to said platform for effecting movement thereof; a laser interferometer operatively connected to said platform for detecting changes in the position thereof and providing an output signal as a function of such changes in position; means connected to said laser interferometer for receiving said output signal and generating a signal indicative of the average velocity of said platform in response thereto; means for providing a reference signal corresponding to a predetermined position of said platform; means for providing a reference signal corresponding to a predetermined velocity of said platform; means for comparing said output signal with said position reference signal and generating an error signal indicative of the deviation of said platform from a predetermined position; means for comparing said average velocity signal and said velocity reference signal and generating a velocity error signal corresponding to the deviation of said platform from said predetermined velocity; means for coupling said velocity error signal to said motor means for causing said platform to seek said predetermined velocity; and means for coupling said position error signal to said motor means whereby said platform will be driven to said predetermined position.
Claim 2
Dependent Claim
198 words
Apparatus for precisely positioning a slideable platform, including: motor means connected to said platform for effecting movement thereof; a laser interferometer operatively connected to said platform for detecting changes in the position thereof and providing an output signal as a function of such changes in position; means connected to said laser interferometer for receiving said output signal and generating a signal indicative of the average velocity of said platform in response thereto; means for providing a reference signal corresponding to a predetermined position of said platform; means for providing a reference signal corresponding to a predetermined velocity of said platform; means for comparing said output signal with said position reference signal and generating an error signal indicative of the deviation of said platform from a predetermined position; means for comparing said average velocity signal and said velocity reference signal and generating a velocity error signal corresponding to the deviation of said platform from said predetermined velocity; means for coupling said velocity error signal to said motor means for causing said platform to seek said predetermined velocity; and means for coupling said position error signal to said motor means whereby said platform will be driven to said predetermined position.
Claim 3
Dependent Claim
42 words
The invention as related in claim 1, further including switch means connected to said position error signal coupling means and said velocity error signal coupling means for alternately uncoupling said position error signal and said velocity error signal from said motor means.
Claim 4
Dependent Claim
34 words
The invention of claim 2, further including means connected to said laser interferometer for receiving said position output signals, deriving the instantaneous velocity of said platform therefrom, and providing an output signal indicative thereof.
Claim 5
Dependent Claim
32 words
The invention as related in claim 3, additionally including means for coupling said instantaneous velocity signal to said motor means so as to accelerate said platform in a direction opposite its velocity.
Claim 6
Dependent Claim
27 words
The invention as recited in claim 4, wherein said instantaneous velocity signal coupling means includes means for combining said instantaneous velocity signals with said position error signals.
Claim 7
Dependent Claim
24 words
The invention of claim 5, wherein said means for deriving the instantaneous velocity of said platform includes means for differentiating said position output signals.
Claim 8
Dependent Claim
21 words
The invention as related in claim 6, wherein said position reference signals and said velocity reference signals are DC level signals.
Claim 9
Dependent Claim
61 words
The invention as recited in claim 7, additionally including: means for generating a pair of phase-displaced pulsed output signals in synchronism with said position output signals; and means adapted to receive said pulsed output signals for detecting the direction of travel of said platform therefrom and providing a pulsed output signal polarity dependent upon the direction of travel of said platform.
Claim 10
Dependent Claim
41 words
The invention of claim 8, further including means for receiving said polarity-dependent pulsed output signal and generating a DC signal responsive thereto of a level dependent upon the frequency and polarity thereof and corresponding to the average velocity of said platform.
Claim 11
Dependent Claim
125 words
In apparatus for accurately positioning a sliding platform, the combination including: motor means for moving said platform; means for detecting changes in the position of said platform and generating a pair of cyclical output signals phase dependent upon the position of said platform and phase displaced from each other by a predetermined amount; means for generating a pair of amplitude displaced position reference signals; means for combining one of said pair of position reference signals with one of said phase displaced cyclical signals; means for combining the other of said position reference signals with the other of said phase displaced cyclical signals; and means responsive to said combined signals for providing an output signal indicative of the deviation of said platform from a predetermined position.
Claim 12
Dependent Claim
125 words
In apparatus for accurately positioning a sliding platform, the combination including: motor means for moving said platform; means for detecting changes in the position of said platform and generating a pair of cyclical output signals phase dependent upon the position of said platform and phase displaced from each other by a predetermined amount; means for generating a pair of amplitude displaced position reference signals; means for combining one of said pair of position reference signals with one of said phase displaced cyclical signals; means for combining the other of said position reference signals with the other of said phase displaced cyclical signals; and means responsive to said combined signals for providing an output signal indicative of the deviation of said platform from a predetermined position.
Claim 13
Dependent Claim
28 words
The invention as related in claim 10, further comprising means for coupling said position deviation signal to said motor means for moving said platform to a predetermined position.
Claim 14
Dependent Claim
42 words
The invention as set forth in claim 11, wherein said position reference signals are DC level signals whose amplitudes may be varied as a function of the phase angle of said cyclical output signals corresponding to a predetermined position of said platform.
Claim 15
Dependent Claim
55 words
The invention as described in claim 12, wherein said combining means includes: means for multiplying one of said phase-dependent cyclical output signals with one of said position reference signals; and means for multiplying the other of said pair of phase-dependent cyclical output signals with the other of said pair of phase displaced position reference signals.
Claim 16
Dependent Claim
45 words
The invention as related in claim 13, wherein said phase-dependent dependent cyclical output signals are sinusoidal and are phase displaced pi /2 radians and wherein said position reference signals are amplitude displaced such that the sum of said multiplied signals will provide a sinusoidal function.
Claim 17
Dependent Claim
28 words
The invention as set forth in claim 14, further including means adapted to receive said phase-dependent cyclical output signals and determine the instantaneous velocity of said platform therefrom.
Claim 18
Dependent Claim
49 words
The invention as described in claim 15 further including means connected to said instantaneous velocity determining means, and adapted to receive said multiplied signals, for providing an output signal to said motor means having a velocity component tending to accelerate said platform in a direction opposite to its velocity.
Claim 19
Dependent Claim
38 words
The invention of claim 16, wherein said velocity determining means includes means for subtracting one of said cyclical output signals from the other of said cyclical output signals and means for summing both of said cyclical output signals.
Claim 20
Dependent Claim
103 words
The invention as recited in claim 17, further including: means for differentiating the difference of said cyclical output signals; means for inverting a portion of the output of said differentiating means so as to provide plural output signals indicative of the derivative of both the difference of said cyclical output signals and the inverse thereof; means for differentiating the sum of said cyclical output signals; and means for inverting a portion of the output of said sum differentiating means so as to yield plural output signals indicative of both the derivative of the sum of said cyclical output signals and the inverse thereof.
Claim 21
Dependent Claim
37 words
The invention as recited in claim 18, further including means for selectively gating one of said differentiated signals or its inverse to said means connected to said velocity determining means depending on the position of said platform.
Claim 22
Dependent Claim
36 words
The invention as described in claim 19, further including means for generating a pair of pulsed output signals phase displaced by pi /2 radians and in synchronism with said pair of phased dependent cyclical output signals.
Claim 23
Dependent Claim
50 words
The invention as set forth in claim 19, wherein the output of said subtracting means is a first cyclicAl signal varying sinusoidally about a voltage level of zero and the sum of said phase-dependent cyclical output signals is a second cyclical signal varying sinusoidally about a voltage level of zero.
Claim 24
Dependent Claim
42 words
The invention as specified in claim 21, wherein said gating means includes means for selectively passing only such portions of said first and second cyclical sinusoidal output signals occuring within + or - pi /4 radians of their respective zero crossover points.
Claim 25
Dependent Claim
36 words
The invention as related in claim 20, wherein said gating means includes means for receiving said pulsed output signals and determining the quadrant of said phase-dependent cyclical output signals corresponding to the position of said platform.
Claim 26
Dependent Claim
41 words
The invention as related in claim 23, wherein said quadrant detecting means provides four outputs; each of said four outputs corresponding to positioning of said platform in a different one of four quadrants with respect to said phase-dependent cyclical output signals.
Claim 27
Dependent Claim
18 words
The invention of claim 24, wherein said means for providing said position reference signals comprises a sine-cosine potentiometer.
Claim 28
Dependent Claim
21 words
The invention of claim 25, further including means connected to said motor means for imparting a predetermined velocity of said platform.
Claim 29
Dependent Claim
84 words
The invention as recited in claim 26, wherein said means for imparting a predetermined velocity to said platform includes: means for generating a reference signal corresponding to a predetermined velocity of said platform; means for determining the average velocity of said platform; means for comparing said average velocity with said predetermined velocity and generating an error signal corresponding to the difference therebetween; and means for coupling said velocity error signal to said motor means for bringing the velocity of said platform to that predetermined.
Claim 30
Dependent Claim
56 words
The invention as stated in claim 27, wherein said means for determining the average velocity of said platform incorporates means for generating a pulse train of a frequency corresponding to the sum of the zero crossovers of said pair of pulsed output signals and of a polarity corresponding to the direction of travel of said platform.
Claim 31
Dependent Claim
48 words
The invention as portrayed in claim 28, further including means for receiving said pulsed train and generating a DC output signal of a polarity corresponding to the average polarity of the pulses comprising said pulse train and of a level corresponding to the average velocity of said platform.
Claim 32
Dependent Claim
27 words
The invention as set forth in claim 29, wherein said means for providing output signals phase dependent on the position of said platform comprises a laser interferometer.
Claim 33
Dependent Claim
134 words
In apparatus for precisely positioning a movable platform, the combination including: means operatively connected to said platform to provide sine and cosine output signals phase dependent on the position of said platform; means for providing a pair of DC level reference signals corresponding to the sine and cosine, respectively, of a predetermined phase angle with respect to said phase-dependent sine and cosine signals; means for multiplying one of said DC level reference signals and one of said sine and cosine phase-dependent signals; means for multiplying the other of said reference signals and the other of said sine and cosine phase-dependent signals; and means for summing said multiplied signals to yield an output signal indicative of the difference between said predetermined phase angle and the instantaneous phase angle of said phase-dependent sine and cosine signals.
Claim 34
Dependent Claim
134 words
In apparatus for precisely positioning a movable platform, the combination including: means operatively connected to said platform to provide sine and cosine output signals phase dependent on the position of said platform; means for providing a pair of DC level reference signals corresponding to the sine and cosine, respectively, of a predetermined phase angle with respect to said phase-dependent sine and cosine signals; means for multiplying one of said DC level reference signals and one of said sine and cosine phase-dependent signals; means for multiplying the other of said reference signals and the other of said sine and cosine phase-dependent signals; and means for summing said multiplied signals to yield an output signal indicative of the difference between said predetermined phase angle and the instantaneous phase angle of said phase-dependent sine and cosine signals.
Claim 35
Dependent Claim
20 words
The invention as set forth in claim 31, wherein said means for providing said reference signals comprises a sine-cosine potentiometer.
Claim 36
Dependent Claim
43 words
The invention of claim 22, further including: motor means for moving said platform; means coupling said motor means and said phase angle difference output signal, whereby said platform will seek a position such that said phase angle difference output signal will be nulled.
Claim 37
Dependent Claim
55 words
The invention as cited in claim 33, wherein said means for providing position dependent sine and cosine signals comprises a laser interferometer; and further including means responsive to said sine and cosine position dependent signals for determining the instantaneous velocity of said platform therefrom and providing a feedback signal to said coupling means indicative thereof.
Claim 38
Dependent Claim
133 words
The invention of claim 34, additionally including: means connected to said laser interferometer for generating a first sinusoidal signal phase displaced from one of said sine and cosine position dependent signals by pi /4 radians and a second sinusoidal signal displaced from the other of said sine and cosine position dependent signals by pi /4 radians; said first and second sinusoidal signals being phase displaced from each other by pi /2 radians and cyclically varying about a DC reference level; and means for providing said velocity feedback signal by differentiating said first and second sinusoidal signals and selectively passing only such portions of said differentiated signals as occur in the region + or - pi /4 radians with respect to the reference level crossover points of said first and second sinusoidal signals, respectively.
Claim 39
Dependent Claim
60 words
The invention as described in claim 35, wherein said means for providing said first sinusoidal signal includes means for subtracting one of said sine and cosine position dependent signals from the other of said sine and cosine position dependent signals; and said means for providing said second sinusoidal signal includes means for summing said sine and cosine position dependent signals.
Claim 40
Dependent Claim
66 words
The invention as set forth in claim 36, wherein said cosine corresponding reference signal is multiplied by said cosine position dependent signal and said sine corresponding reference signal is multiplied by said sine position dependent signal, whereby said sum of said multiplied signals will be a cosine function of the difference in phase between said sine and cosine position dependent signals and said predetermined phase angle.
Claim 41
Dependent Claim
74 words
The invention as cited in claim 37, wherein said means for subtracting one of said sine and cosine position dependent signals from the other of said sine and cosine position dependent signals includes means for inverting one of said sine and cosine position dependent signals and means for summing said inverted signal with other of said sine and cosine position dependent signals; and wherein said means for driving said platform comprises a linear motor.
Claim 42
Dependent Claim
81 words
The invention as related in claim 38, wherein said sine position dependent signal is subtracted from said cosine position dependent signal to yield a sinusoidal signal corresponding to said cosine position dependent signal, but advanced in phase pi /4 radians with respect thereto; and wherein said sine position dependent signal is summed with said cosine position dependent signal to yield a sinusoidal output signal corresponding to said sine position dependent signal but advanced in phase pi /4 radians with respect thereto.
References Cited (Backward Citations)
US3539256A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-01-10 | 1975-07-12 | 1976-01-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-10 | 1979-07-12 | 1980-01-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-10 | 1983-07-12 | 1984-01-11 | $7700.00 | Window Closed / Lapsed |