25-07-2012, 12:45 PM
Quartz rate gyro sensor for automotive control
[attachment=28864]
Introduction
The precession, the Sagnac effect, and the Coriolis effect
are used for the detection of angular rate. Generally, the precession
type sensors are used for ships and the Sagnac type
sensors are used for airplanes. Sensors of the Coriolis effect
type are suitable for compact applications, because the
sensors are small in size, resistant to shock, and inexpensive
[1–3]. Gas rate gyros and simple vibration type sensors
are used for automotive navigation systems. There were
many studies for vibration type angular rate sensors. They
were grouped into several types by materials.
Principle
We used quartz crystal for the rate gyro sensor material.
This is because the quartz is stable in the wide temperature
range and works in long operation time. The quartz has
toughness in mechanical stress due to a single crystal. The
quartz itself shows the piezoelectric effect. Also, the quartz
is good material for micro-machining with mask etching like
crystal silicon.
Structure and design
We have designed a new sensor element for the quartz
rate gyro sensor. The element consists of an H shape vibrator,
a support stem, and a fixed part as shown in Fig. 2. The
upper tuning fork works as an excitation part and the lower
Structure of the sensor electrodes and their connections.
tuning fork works as a detection part. With no angular rate,
only the upper tuning fork vibrates by the excitation in the
direction of X. When angular rates in the direction of Y are
applied to the sensor, the lower tuning fork vibrates in the direction
of Z, perpendicular to the exciting vibration direction
of X.
Experimental results
The quartz sensor element was made using the bulk
micro-machining technology by means of a wet etching
process with NH4F +HF solution. The process is shown in
Fig. 11. At first, a metal mask was deposited on a quartz
wafer. A photoresist on the metal mask was patterned by
the photolithography (a). The metal mask was patterned
with the photoresist (b). The quartz wafer was etched with
the NH4F + HF solution ©. The masks were removed and
the shape of element was formed (d). Electrodes on the
element were deposited (e). The element was covered with
the photoresist (f).
[attachment=28864]
Introduction
The precession, the Sagnac effect, and the Coriolis effect
are used for the detection of angular rate. Generally, the precession
type sensors are used for ships and the Sagnac type
sensors are used for airplanes. Sensors of the Coriolis effect
type are suitable for compact applications, because the
sensors are small in size, resistant to shock, and inexpensive
[1–3]. Gas rate gyros and simple vibration type sensors
are used for automotive navigation systems. There were
many studies for vibration type angular rate sensors. They
were grouped into several types by materials.
Principle
We used quartz crystal for the rate gyro sensor material.
This is because the quartz is stable in the wide temperature
range and works in long operation time. The quartz has
toughness in mechanical stress due to a single crystal. The
quartz itself shows the piezoelectric effect. Also, the quartz
is good material for micro-machining with mask etching like
crystal silicon.
Structure and design
We have designed a new sensor element for the quartz
rate gyro sensor. The element consists of an H shape vibrator,
a support stem, and a fixed part as shown in Fig. 2. The
upper tuning fork works as an excitation part and the lower
Structure of the sensor electrodes and their connections.
tuning fork works as a detection part. With no angular rate,
only the upper tuning fork vibrates by the excitation in the
direction of X. When angular rates in the direction of Y are
applied to the sensor, the lower tuning fork vibrates in the direction
of Z, perpendicular to the exciting vibration direction
of X.
Experimental results
The quartz sensor element was made using the bulk
micro-machining technology by means of a wet etching
process with NH4F +HF solution. The process is shown in
Fig. 11. At first, a metal mask was deposited on a quartz
wafer. A photoresist on the metal mask was patterned by
the photolithography (a). The metal mask was patterned
with the photoresist (b). The quartz wafer was etched with
the NH4F + HF solution ©. The masks were removed and
the shape of element was formed (d). Electrodes on the
element were deposited (e). The element was covered with
the photoresist (f).