Brushless DC tachometer
First Claim
1. A brushless tachometer for providing a DC output voltage indicative of the speed of a rotatable shaft comprising:
- a multi-pole brushless resolver connected to the shaft to be instrumented for providing modulated sine and cosine position indications;
an oscillator providing a modulating input signal to said resolver;
a side band splitting circuit connected to receive the modulated sine and cosine position indications and providing two output signals whose frequencies difference is representative of shaft speed;
frequency to voltage converting means connected to receive the two output signals from said side band splitter circuit and providing two output voltage signals wherein each voltage output signal is a function of the frequency of one of the two input signals; and
,a comparator for comparing the two output signals from said frequency to voltage converting means and providing a different signal whose magnitude is indicative of shaft speed and whose sign is indicative of the direction of shaft rotation.
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Accused Products
Abstract
A brushless tachometer is disclosed which provides a DC output voltage which is a direct function of an instrumented shaft'"'"'s rotational velocity. The DC voltage is bi-directional, changing sign when the shafts direction of rotation is reversed. The disclosed tachometer preferably utilizes a brushless printed circuit resolver having a large number of poles. The sine and cosine outputs from the resolver are fed to a phase shifting circuit which provides two output signals whose frequencies are related to the speed of rotation of the shaft being instrumented. The frequency of one of the signals increases as the shaft speed increases while the frequency of the other signal decreases as the shaft speed increases. These two signals having frequencies related to shaft speed are fed to frequency to voltage converters. The outputs from the frequency to voltage converters are fed to a differential amplifier whose output is the DC signal which is indicative of the direction and the speed of rotation of the shaft.
25 Citations
8 Claims
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1. A brushless tachometer for providing a DC output voltage indicative of the speed of a rotatable shaft comprising:
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a multi-pole brushless resolver connected to the shaft to be instrumented for providing modulated sine and cosine position indications; an oscillator providing a modulating input signal to said resolver; a side band splitting circuit connected to receive the modulated sine and cosine position indications and providing two output signals whose frequencies difference is representative of shaft speed; frequency to voltage converting means connected to receive the two output signals from said side band splitter circuit and providing two output voltage signals wherein each voltage output signal is a function of the frequency of one of the two input signals; and
,a comparator for comparing the two output signals from said frequency to voltage converting means and providing a different signal whose magnitude is indicative of shaft speed and whose sign is indicative of the direction of shaft rotation. - View Dependent Claims (2, 3)
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4. A brushless tachometer for indicating shaft speed comprising:
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a multi-pole resolver having a mechanical connection to the shaft and providing a first voltage signal V1 and a second voltage signal V2 ; an oscillator electrically connected to said multi-pole resolver for providing a carrier frequency; said first voltage signal V1 being a sine position indication defined by the envelope of the carrier; said second voltage signal V2 being a cosine position indication defined by the envelope of the carrier; a phase shifting circuit connected to receive said first signal V1 and said second signal V2 and providing a third signal output V3 and a fourth output signal V4 ; said third signal V3 having a frequency which is a function of the carrier frequency the number of resolver poles, and the shaft angular frequency; said fourth signal V4 having a frequency which is a function of the carrier frequency, the number of resolver poles, and the shaft angular frequency; a first frequency to voltage converter means for connected said third voltage signal, V3, to a fifth voltage signal, V5, whose magnitude is determined by the frequency of the fourth voltage signal V4 ; and
,a second frequency to voltage converter means for converting said fourth voltage signal, V4, to a sixth voltage signal V6 whose magnitude is determined by the frequency of the fourth voltage signal V4 ; and
,comparator means for differentially combining the fifth voltage signal and the sixth voltage signal to provide an output signal V0 which is a DC signal whose magnitude indicates shaft speed. - View Dependent Claims (5)
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6. A tachometer for providing a DC signal which is indicative of the direction and speed of rotation of a shaft comprising:
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an oscillator; a multi-pole resolver receiving an input modulating signal from said oscillator and having a mechanical connection to the shaft and providing output modulated sine and cosine position indications; phase shifting circuit means connected to receive as inputs the modulated sine and cosine position indications for providing two output signals one of whose frequency increases with shaft speed and the others whose frequency decreases with shaft speed; frequency to voltage converting means for converting the two output signals from said phase shifting circuit to two voltage signals one of whose DC voltage level increase with shaft speed and the other whose DC voltage level decreases with shaft speed; and
,combining means for combining the two voltage signals from the frequency to voltage converting means for providing a DC signal whose magnitude is indicative of shaft speed and whose sign is indicative of the direction of rotation. - View Dependent Claims (7, 8)
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Specification