Inertial navigation systems (INS) used gyroscopes and accelerometers to evaluate the position, velocity, acceleration, angles and angular velocities.
Typical INS consists of the following elements:
- Module inertial sensors;
- Support electronics equipment;
- Computing unit.
In general, there are many kinds of construction INS, but all systems can be divided into two groups - the platform INS and INS without platform.
Platform INS using a special platform suspended in Cardan suspension that provides free rotation in three spaces (Fig. 60). On the platform is placed a group of three accelerometers to measure acceleration components along the axes X, Y, Z and a group of three gyroscopes to measure angular velocity. In Cardan joints suspension placed motors that rotate the platform.
Fig.60. Stabilized Platform in Cardan suspension
Gyroscopes follow the rotations and platforms involve motors hold the platform in a fixed orientation relative to the selected coordinate system. Stabilized and put in some coordinate system corresponding accelerometers measure acceleration. Example INS platform is shown in Fig. 61
Fig. 61. Module platform of inertial sensors
By integrating the measured acceleration (аx(t), аy(t), аz(t)) at a particular time (t) with the known initial values of the parameters (Vx(t0), Vy(t0), Vz(t0)), assess speed:
According to the obtained velocity component assess position coordinates, given the known position of the previous time (X(t0), Y(t0),Z(t0)).
A large number of PCs equipped at present without platform INS. In such systems, accelerometers and gyroscopes are rigidly fixed to each other and are attached directly to the PC case (Fig. 62).
Fig. 62. INS without platform (Marconi FIN 3110)
In without platform INS acceleration measured in the reference frame PC. The measured values of angles gyroscopes are used to convert the measurement results of acceleration (аx, аy) in the navigation coordinate system (аxn, аyn).
One of the major advantages of the use of INS is its autonomy and independence from external factors. However INS characteristic accumulation of errors.