174

L. Parayitam et al.

Fig. 13.6 Principle of

Sagnac effect

of optical gyroscope depends on the intensity of light and size of the instrument

[6]. The salient features of these gyroscopes are less power consumption with

light weight, low cost, reliability and wide dynamic range.

b.

Ring Laser Gyroscopes (RLG) is also working based on the Sagnac effect.

RLG uses laser beam and mirrors rather than light and optical fiber coil as

compared to the FOG as shown in Fig. 13.7. The laser beam separated as a two

beams, and these beams travel in opposite directions in the mirror loop.

One travels in clock wise (CW) direction, and other travels in Counter Clock Wise

(CCW) direction. These two beams are recombined and given to the detector.

The detector will find the path difference between two beams. If the path difference

of the two beams are same, then it means there is no rotation in the device. If rotation

occurs, there will be a path difference between two beams and result in a net phase

difference and destructive interference. The amplitude changing in accordance to the

phase shift, therefore the amplitude outcome is a measurement of the rotation rate.

The main advantage of RLG is no moving coil means no friction, hence there is no

inherent drift, compact in size, light weight and virtually everlasting device.

c.

MEMS Gyroscopes: MEMS based inertial sensor technology is a fast growing

and became a ubiquitous with their adoption in many applications like smart

phones, gaming systems, TV remotes, wearable sensors and in MAVs for navi-

gation purpose. The MEMS sensors are manufactured with very small in size and

light weight using the latest advanced technologies. MEMS based gyroscope

operates on the principle of Coriolis effect, which states that in a reference frame,

an object with mass m, rotating with angular velocity ω and velocity V which

experience a force Fc.

Fc = −2m(ωxV )

(13.1)