US4263527A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Charge control of piezoelectric actuators to reduce hysteresis effects
Assignee: Charles Stark Draper Laboratory Inc
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Filing: 1979-05-17
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Granted: 1981-04-21
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Expires: 1999-05-17
Abstract
Abstract A piezoelectric actuator and a control circuit therefor to apply a charge to the actuator proportional to an input signal magnitude. The charge controlled actuator achieves a more linear input-displacement response with reduced hysteresis.
Inventors
- 👤 Robert H. Comstock
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 13:55
CPC Classifications
H; H02; H02N; H02N2/00; H02N2/02; H02N2/06; H02N2/062
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
103 words
Piezoelectric apparatus for controllably displacing one object with respect to another in response to an electrical input signal comprising: piezoelectric actuator means for displacing such object and electrically charging in response to an applied electrical signal; first circuit means responsive to the level of charge on said piezoelectric actuator means for producing a feedback signal in substantial proportion to said level of charge; and second circuit means jointly responsive to said electrical input signal and said feedback signal for applying to said actuator means said applied electrical signal for producing on said actuator a level of charge substantially proportional to said input signal.
Claim 2
Dependent Claim
103 words
Piezoelectric apparatus for controllably displacing one object with respect to another in response to an electrical input signal comprising: piezoelectric actuator means for displacing such object and electrically charging in response to an applied electrical signal; first circuit means responsive to the level of charge on said piezoelectric actuator means for producing a feedback signal in substantial proportion to said level of charge; and second circuit means jointly responsive to said electrical input signal and said feedback signal for applying to said actuator means said applied electrical signal for producing on said actuator a level of charge substantially proportional to said input signal.
Claim 3
Dependent Claim
24 words
A piezoelectric apparatus according to claim 1 wherein said piezoelectric actuator comprises one or more high gain piezoelectric wafers of the type exhibiting hysteresis.
Claim 4
Dependent Claim
18 words
A piezoelectric apparatus according to claim 2 wherein said piezoelectric actuator includes wafers exhibiting a strong ferroelectric effect.
Claim 5
Dependent Claim
55 words
A piezoelectric apparatus according to claim 1 wherein: said second circuit means comprises circuit means for driving said piezoelectric actuator by a signal proportioned in accordance with the difference between said input signal and said feedback signal in such a manner as to drive said level of charge toward the level of said input signal.
Claim 6
Dependent Claim
40 words
A piezoelectric apparatus according to claim 1 wherein: said second circuit means comprises amplifying means responsive to said input signal and said feedback signal for amplifying the difference between said signals and applying the amplified difference to said piezoelectric actuator.
Claim 7
Dependent Claim
90 words
A piezoelectric apparatus according to claim 5 wherein: said input signal is a voltage signal; said means for generating a signal proportional to said level of charge comprises capacitor means serially coupled to said piezoelectric actuator for producing a voltage proportional to said charge; and said amplifying means comprises a differential amplifier having a non-inverting input terminal for receiving said input signal, an inverting terminal for receiving said signal proportional to said charge, and an output terminal for driving said piezoelectric actuator in accordance with the difference between said signals.
Claim 8
Dependent Claim
23 words
A piezoelectric apparatus according to claim 6 including initialization circuit means for correlating a nominal input signal with mid-range displacement of the actuator.
Claim 9
Dependent Claim
20 words
A piezoelectric apparatus according to claim 7 wherein said initialization circuit means includes means for selectively by-passing said capacitor means.
Claim 10
Dependent Claim
39 words
A piezoelectric apparatus according to claim 8 wherein said initialization circuit means includes means for replacing the charge proportional signal at the inverting terminal of said amplifying means with a signal derived from the output of said amplifying means.
Claim 11
Dependent Claim
23 words
The piezoelectric apparatus according to claim 9 wherein said initialization circuit means includes means for applying a down-ramped sinusoid to said amplifying means.
Claim 12
Dependent Claim
23 words
A piezoelectric apparatus according to claim 1 including initialization circuit means for correlating a nominal input signal with mid-range displacement of the actuator.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-04-20 | 1984-10-20 | 1985-04-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-04-20 | 1988-10-20 | 1989-04-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-04-20 | 1992-10-20 | 1993-04-21 | $7700.00 | Window Closed / Lapsed |