Resolver, resolver fault detection circuit, and resolver...

Details Resolver, resolver fault detection circuit, and resolver... Resolver, resolver fault detection circuit, and resolver...

2001-05-23

2004-10-12

Pert, Evan (Department: 2829)

Electricity: measuring and testing

Impedance, admittance or other quantities representative of...

Lumped type parameters

C318S661000, C310S06800R

Reexamination Certificate

active

06803781

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resolver, and more particularly, a resolver having a structure in which a fault can be rapidly detected even when windings are short-circuited. Furthermore, the present invention relates to a method for detecting a fault by means of provision of a fault detection circuit for detecting such an accident.
2. Description of the Related Art
A resolver is one kind of synchronous transmitter which provides from its output windings an output signal that has an amplitude modulated in accordance with X and Y components of a rotation angle of its rotor. Conventionally, the resolver is typically used as a detection system or for triangulation calculation in a servomechanism.
For example, a resolver as shown in
FIG. 14
includes a rotor, a stator and two pairs of orthogonal windings, i.e., excitation windings
111
and output windings
112
. Two of such resolvers make a pair, in which the stators or rotors of the respective resolvers are coupled to each other. One phase of either the stator or the rotor of the resolver functioning as a transmitter is excited by AC power. Thus, an AC output in accordance with a difference between a rotation position of the transmitter resolver and that of the receiver resolver can be obtained at the corresponding orthogonal phase of the transmitter resolver.
An alternative structure of the resolver is known as a variable reluctance resolver. In this structure, a rotor has a shape of a rectangle or the like and no winding is provided around the rotor. A stator is provided with a plurality of poles with an excitation winding and an output winding being wound around the same pole of the stator. A sum of outputs from the plurality of output windings at the different poles is provided as a single output from the output windings.
FIG. 16
shows an example of the winding structure of the above-mentioned resolver. The relationship between the excitation winding
111
and the output winding
112
to be wound around any one of the poles is defined as follows. The respective excitation windings
111
are wound around the poles so that an N pole and an S pole of the resultant magnetization appear alternatively at the adjacent poles, while the respective output windings
112
are wound around the poles so that an N pole and an S pole of the resultant magnetization appear alternatively at every two poles. More specifically, when the excitation winding
111
at the first pole provides an N pole, N poles are generated by the output windings
112
at the first and second poles, while S poles are generated by the output windings
112
at the third and fourth poles, and such a configuration will appear in the repeated manner.
In the resolver having the above-mentioned construction, a fault such as short-circuit between the windings may occur. Thus, fault detection is necessary for improving the reliability of an apparatus incorporating therein a resolver.
FIG. 15
shows an example of a conventional resolver and a fault detection circuit utilizing the same. The configuration in
FIG. 15
includes a resolver
10
and a resolver fault detection circuit
11
. The resolver
10
has output windings
112
X and
112
Y for respectively outputting an X direction component and a Y direction component of a rotor of a resolver
10
. The resolver fault detection circuit
11
includes square calculators
121
X and
121
Y respectively connected to the output windings
112
X and
112
Y, an adder
123
for calculating a sum of outputs from both of the square calculators
121
X and
121
Y, a rectifier circuit
124
for rectifying an output VE from the adder
123
, and a comparator circuit
125
for comparing an output from the rectifier circuit
124
with a reference voltage.
In order to facilitate understandings of the invention, the variable reluctance resolver is taken as an example which has a structure in which a stator is provided with a plurality of poles. The same pole of the stator is provided with an excitation winding
111
, an output winding
112
X for outputting an X direction component of a rotor, and an output winding
112
Y for outputting a Y direction component of the rotor, that are wound therearound. A sum of outputs of the output windings wound around the respective poles is provided as a single output from the output windings. With respect to such a variable reluctance resolver, the relationship of phases among the excitation winding
111
and the output windings
112
X and
112
Y for respectively outputting the X direction component and the Y direction component of the rotor will be described with reference to FIG.
16
.
In the case where the direction of magnetization generated by a voltage induced by the excitation winding
111
in the output winding
112
X for outputting the X direction component of the rotor is the same as the direction of magnetization of the excitation winding
111
, a voltage ENS induced at any one of the poles can be expressed by Equation 1 when an AC voltage VP as expressed in E sin &ohgr;t is applied to the excitation winding
111
, where &ohgr; represents an angular frequency which is expressed as 2&pgr;f, f represents a frequency, a and b are constants defined by characteristics of the excitation winding
111
, the output winding
112
X, the rotor and the stator.
ENS
=(
a+b
sin &thgr;)·
E
sin &ohgr;
t
  (Eq. 1)
On the other hand, in the case where the direction of magnetization generated by the voltage induced by the excitation winding
111
in the output winding
112
X is different from the direction of magnetization of the excitation winding
111
, a voltage ENN induced at any one of the poles can be expressed by Equation 2.
ENN
=(−
a+b
sin &thgr;)·
E
sin &ohgr;
t
  (Eq. 2)
The relationship between the excitation winding and the output winding to be wound around any one of the poles is defined as illustrated in FIG.
16
. In the case where the windings wound around the first pole and the second pole in such a structure are connected in series, the resultant voltage V
12
can be expressed by Equation 3 below in view of the above-mentioned Equations 1 and 2.
V
12=(
a+b
sin &thgr;)·
E
sin &ohgr;
t
+(−
a+b
sin &thgr;)·
E
sin &ohgr;
t
  (Eq. 3)
Similarly, a voltage V
34
expressed in Equation 4 is generated by the third and fourth poles.
V
34=(−
a+b
sin &thgr;)·
E
sin &ohgr;
t
+(
a+b
sin &thgr;)·
E
sin &ohgr;
t
  (Eq. 4)
From Equations 3 and 4, the terms with the constant a are eliminated in the case where the adjacent poles are connected in series, so that voltages V
12
and V
34
as expressed in Equation 5 can be obtained.
V
12=2
b
sin &thgr;·
E
sin &ohgr;
t=V
34  (Eq. 5)
Accordingly, when the output windings of all of the poles are connected in series in the case where the number of the poles is a multiple of 2, the terms with the constant a are eliminated so that an output voltage VS from the output winding
112
X can be expressed by Equation 6.
VS=K
sin &thgr;·
E
sin &ohgr;
t
  (Eq. 6)
In the equation, K is a constant defined in accordance with the constant b and the number of poles, and is expressed by Equation 7 where N represents the number of poles.
K=N·B
  (Eq. 7)
Similarly, an output from the output winding
112
Y for outputting the Y direction component of the rotor can be expressed by Equation 8, since the output winding
112
Y is wound around so that the phase thereof is shifted by 90° with respect to the rotor.
VC=K
cos &thgr;·
E
sin &ohgr;
t
  (Eq. 8)
When output voltages from the above-mentioned resolver are applied to the square calculators
121
X and
121
Y in
FIG. 15
, the square calculators
121
X and
121
Y respectively provide voltage outputs as expressed in Equations 9 and 10.
VSX=VS
2
=K
2
·sin &thgr;
2
·E
2
sin
2
&ohgr;t
  (Eq. 9)
VCY=VC
2
=K
2
·cos &thgr;
2
·E
2
sin
2
&ohgr;

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