Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
2000-05-08
2002-05-14
Chapman, John E. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
C073S001370, C073S504160
Reexamination Certificate
active
06386034
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an angular rate sensor.
BACKGROUND OF THE INVENTION
FIG. 4
shows an example of angular rate sensors that have been proposed in the past. In
FIG. 4
, a support pin
101
made of metal is press-fitted perpendicularly and secured in a weight plate (not shown in the figure), and one end of another support pin
102
made of metal is press-fitted and secured in the support pin
101
in an orthogonal direction to it. A block
103
also made of metal is fixed at the other end of the support pin
102
by soldering. Vibration plates
104
and
105
are fixed at both ends of the metal block
103
. A piezoelectric element
106
is bonded on the vibration plate
104
to constitute a vibration exciter
150
, and another piezoelectric element
107
is bonded on the vibration plate
105
to constitute a means
160
for detecting a level of vibrations. A tip of the vibration plate
104
is extended in a manner to form a right angle with the piezoelectric element
106
to become a detecting plate
108
. A tip of the vibration plate
105
is also extended in the same manner to form a right angle with the piezoelectric element
107
to become another detecting plate
109
. Piezoelectric elements
110
and
111
are bonded on the detecting plates
108
and
109
respectively, to constitute detecting means
170
and
180
for detecting a Coriolis' force generated in proportion to an angular rate. All of the above complete an element unit
112
of a tuning-fork type angular rate sensor.
A structure of
FIG. 4
further comprises;
(a) a current amplifier
120
for amplifying an output signal from the piezoelectric element
107
provided on the vibration plate
105
to detect a level of vibrations of the vibration plate
105
, which vibrates in a tuning-fork phenomenon in concert with vibrations of the vibration plate
104
;
(b) a full-wave rectifier circuit
122
for producing a D.C. voltage by rectifying an output signal of a band-pass filter (hereinafter referred to as “BPF”)
121
, wherein an output signal of the current amplifier
120
is input;
(c) an automatic gain control circuit (hereinafter referred to as “AGC”)
123
whose amplification factor for the output signal of the BPF
121
varies according to a magnitude of an output signal of the full-wave rectifier circuit
122
;
(d) a driver
124
for driving the piezoelectric element
106
bonded on the vibration plate
104
in accordance with a magnitude of an output signal of the AGC
123
;
(e) a charge amplifier
125
for inputting and amplifying output signals of the piezoelectric elements
110
and
111
, which detect a Coriolis' force generated in proportion to an angular rate;
(f) a synchronous detection circuit
127
for detecting an output signal of a BPF
126
, wherein an output signal of the charge amplifier
125
is input;
(g) a sensor output terminal
129
for outputting an output signal of a low-pass filter (hereinafter referred to as “LPF”)
128
, wherein an output signal of the synchronous detection circuit
127
is input;
(h) a determination circuit
130
for inputting the output signal (an amplitude of signal at a point “A”) of the full-wave rectifier circuit
122
and the output signal (an amplitude of signal at a point “B”) after amplified by the charge amplifier
125
, and determining an abnormality; and
(i) an abnormality diagnosis terminal
131
for communicating an abnormality to an outside from the determination circuit
130
, when it determines the abnormality. A reference numeral
132
represents a power supply connection terminal, and a reference numeral
133
represents a grounding terminal. The elements described above constitute a driving circuit
134
.
The angular rate sensor is completed by having the above element unit
112
of a tuning-fork type angular rate sensor and the driving circuit
134
.
In addition, a voltage E is supplied from a power source
135
to the power supply connection terminal
132
of the driving circuit
134
. A load resistor
136
is connected to the sensor output terminal
129
, and an output signal C is supplied toward a controller side (not shown in the figure). In the like manner, a load resistor
137
is connected to the abnormality diagnosis terminal
131
, and an output signal D is supplied toward another controller side (not shown in the figure).
FIG. 5
shows changes in voltage of the output signal C, the output signal D and a voltage of the grounding terminal
133
in the angular rate sensor, that occur when a circuit opens, for an instance, at a point “X” between the grounding terminal
133
of the driving circuit
134
and the earth ground.
In the prior art technique described above, it is possible to make a determination that an opening has taken place in the circuit, since the output signal D of the abnormality diagnosis terminal,
131
changes quickly from a high voltage level to a low voltage level as shown in
FIG. 5
, if the circuit opens at the point “X” between the grounding terminal
133
of the driving circuit
134
and the earth ground.
However, the output signal C of the sensor output terminal
129
shows a phenomenon, in which the voltage increases gradually toward a level of power source voltage E, as shown by a dashed line in
FIG. 5
, due to a combined impedance of the driving circuit
134
and the load resistors
136
and
137
. Therefore, it is not possible to determine whether the angular rate sensor is normal or abnormal, with the output signal C alone.
In addition, a voltage of the grounding terminal
133
shows only a phenomenon of increasing gradually to the level of power source voltage E, it is not possible to distinguish between normality and abnormality of the sensor with this signal.
However, there are controllers, depending on their types, that are not capable of taking an output signal D of the abnormality diagnosis terminal
131
due to a limitation in number of input signals. Or, there are other cases wherein a system distributes and inputs only an output signal C of the sensor output terminal
129
into a plurality of controllers to serve for their individual control functions. It is desirable for a system of these types to instantly determine whether the angular rate sensor is normal or abnormal, only with the output signal C of the sensor output terminal
129
.
SUMMARY OF THE INVENTION
The angular rate sensor of the present invention comprises:
(a) a vibration exciter for providing a vibration body with vibrations;
(b) a means for detecting a level of vibrations of the vibration body;
(c) a detecting means for detecting a Coriolis' force produced in proportion to an angular rate;
(d) a current amplifier for amplifying an output signal of the means of detecting a level of vibrations;
(e) a full-wave rectifier circuit for producing a D.C. voltage by rectifying an output signal of a band-pass filter, wherein an output signal of the current amplifier is input;
(f) an automatic gain control circuit whose amplification factor for the output signal of the band-pass filter varies according to a magnitude of an output signal of the full-wave rectifier circuit;
(g) a driver for driving the vibration exciter according to a magnitude of an output signal of the automatic gain control circuit;
(h) a charge amplifier for inputting and amplifying a signal detected by the detecting means for detecting a Coriolis' force;
(i) a synchronous detection circuit for detecting an output signal of a bandpass filter, wherein an output signal of the charge amplifier is input;
(j) a sensor output terminal for outputting an output signal of a low-pass filter, wherein an output signal of the synchronous detection circuit is input;
(k) a determination circuit for inputting the output signal of the full-wave rectifier circuit and the output signal after amplified by the charge amplifier, and for determining an abnormality; and
(l) an output clamping circuit activated by an output signal of the determination circuit, when the determination circuit makes a determination of abnormality, for clamping
Chapman John E.
Matsushita Electric - Industrial Co., Ltd.
Ratner & Prestia
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