Coded data generation or conversion – Phase or time of phase change – Synchro or resolver signal
Reexamination Certificate
1999-12-23
2001-11-20
Young, Brian (Department: 2819)
Coded data generation or conversion
Phase or time of phase change
Synchro or resolver signal
C318S632000
Reexamination Certificate
active
06320524
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a converter for digitizing the output of a resolver (hereinafter referred to as R/D converter).
2. Description of the Related Art
A resolver is a kind of rotary transformer, and includes two stator windings and one rotor winding. The two stator windings are mechanically disposed at an angle of 90 degrees. The amplitude of a signal obtained by magnetic coupling to the stator windings becomes a function of relative position between the position of the rotor (shaft) and the stator. Thus, two kinds of output voltages (S
3
−S
1
, S
4
−S
2
), which are modulated by a sine (sine wave) and a cosine (cosine wave) of a shaft angle and are expressed by the following equations (1) and (2), are obtained. Although equation (5) indicates a signal of a resolver format, the signal of the resolver format is based on a signal [output voltages (S
3
−S
1
) and (S
4
−S
2
)] obtained from the resolver output.
S
3
−
S
1
=
E
0
sin&ohgr;
t
sin&thgr; (1)
S
4
−
S
2
=
E
0
sin&ohgr;
t
cos&thgr; (2)
Where, &thgr; is an axial angle, &ohgr; is an angular velocity corresponding to a rotor excitation frequency (f), and E
0
is an rotor excitation amplitude.
Here, using AD2S90 of Analog Device Company as an example, a conventional resolver digital converter (R/D converter
1
) of a tracking system will be described.
FIG. 5
is a functional block diagram of the AD2S90.
In
FIG. 5
, when a transducer (rotor of the resolver) (not shown) passes through a position equivalent to a least significant bit, the output (output of a serial interface) is renewed by one LSB. Renewal of CLKOUT corresponds to increase of one LSB.
When the present word state of an up down counter
2
is made &phgr;, the output voltage (S
3
−S
1
) is multiplied by cos &phgr; through a sine cosine multiplier
3
, and the output voltage (S
4
−S
2
) is multiplied by sin&phgr;, whereby signals expressed by the following equations (3) and (4) are obtained.
E
0
sin&ohgr;
t
sin&thgr; cos&phgr; (3)
E
0
sin&ohgr;
t
cos&thgr; sin&phgr; (4)
The signals expressed by the equations (3) and (4) are subtracted through an error amplifier
4
, whereby a signal expressed by the following equation (5) is obtained.
E
0
sin&ohgr;
t
(sin&thgr;cos&phgr;−cos&thgr;sin&phgr;)=
E
0
sin&ohgr;
t
sin(&thgr;−&phgr;) (5)
Where, (&thgr;−&phgr;) is an angular error.
A demodulator circuit
5
and an integrator
6
are connected to an output side of the error amplifier
4
, and a voltage controlled oscillator (VCO)
7
is connected to the demodulator circuit
5
and the integrator
6
. Then, the demodulator circuit
5
, the integrator
6
, and the VCO
7
form a close loop, which operates in such a manner that sin(&thgr;−&phgr;) [see the equation (5)] is made zero. When this operation is realized, the word state &phgr; of the up and down counter
2
connected to the sine cosine multiplier
3
becomes equal to the resolver shaft angle &thgr;.
However, in the foregoing R/D converter
1
of the tracking system shown in
FIG. 5
, attention has not been paid in the following points.
(a) Since it is a kind of PLL control, response speed is low. Particularly, as resolution becomes high, the response speed becomes low.
(b) It is necessary to compensate temperature drift of the analog operating circuit (the sine cosine multiplier
3
, the demodulator circuit
5
and the like), so that its IC circuit becomes complicated and expensive.
(c) If an interface cable between the resolver (not shown) and the R/D converter
1
becomes long, a phase becomes large because of delay between the exciting sine wave and the sine-wave output and cosine-wave output of the resolver, and an angular error becomes large.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances, and an object of the invention is to provide an R/D converter which enables high speed response. Another object of the invention is to eliminate temperature drift compensation and to make an apparatus inexpensive.
According to a first aspect of the invention, an R/D converter includes a gate array to which data obtained through AD conversion of sine-wave output and cosine-wave output of a resolver are inputted and has logical operation capability, and the gate array obtains a rotor shaft angle of the resolver by digital operation on the basis of the digital input data.
According to a second aspect of the invention, in the structure of the first aspect, the gate array inputs digital data for an excitation sine wave of the resolver to a DA converter, and the DA converter obtains the excitation sine wave of the resolver on the basis of the input data from the gate array.
According to a third aspect of the invention, in the structure of the second aspect, at a specific phase time of the excitation sine wave of the resolver, a sine-wave output signal and a cosine-wave output signal of the resolver are subjected to AD conversion, and the rotor shaft angle is calculated.
According to a fourth aspect of the invention, in the structure of any one of the first to third aspects, a quadrant to be formed by dividing an angular space of the resolver into two equal parts is obtained, the rotor shaft angle of the resolver in the quadrant is obtained on the basis of polarities of the sine-wave output and the cosine-wave output of the resolver, and an initial angle of a rotor shaft angle for calculating VCO is set at the center of the divided quadrant.
According to a fifth aspect of the invention, in the structure of the fourth aspect, a sine value corresponding to a difference between the rotor shaft angle of the resolver and an angle corresponding to an address of a sine-wave table is calculated, and an angle of the VCO is increased or decreased on the basis of size relation between the rotor shaft angle of the resolver and the angle of the VCO.
According to a sixth aspect of the invention, in the structure of the fifth aspect, the quadrant is set such that a value in the angular space becomes large from the left to the right, and in the quadrant, if the rotor shaft angle of the resolver exists right as compared with the angle of the VCO, the angle of the VCO is made to increment.
According to a seventh aspect of the invention, in the structure of the fifth aspect, the quadrant is set such that a value in the angular space becomes large from the left to the right, and in the quadrant, if the rotor shaft angle of the resolver exists left as compared with the angle of the VCO, the angle of the VCO is made to decrement.
According to an eighth aspect of the invention, in the structure of any one of the aspects
5
to
7
, an AD conversion value of the sine-wave output of the resolver and a sine value of the angle of the VCO are compared with each other, an address corresponding to an angle of the sine-wave table is increased or decreased by one bit according to the rotor shaft angle in the quadrant, and an angle corresponding to the address is made to approach the rotor shaft angle.
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patent: 4857926 (1989-08-01), Neglia et al.
patent: 4933674 (1990-06-01), Gasperi et al.
patent: 4989001 (1991-01-01), Serev
patent: 5162798 (1992-11-01), Yundt
patent: 5455498 (1995-10-01), Kakimoto et al.
patent: 5646496 (1997-07-01), Woodland et al.
patent: 5796231 (1998-08-01), Kyodo
Minebea Co. Ltd.
Nguyen John
Oliff & Berridg,e PLC
Young Brian
LandOfFree
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