FIELD OF THE INVENTION
North alignment of Turn tables and Thermal chambers are required for testing
of articles related to Navigation and mainly for inertial navigation systems (INS) since
these systems contain inertial sensors such as gyroscopes and accelerometers. INS
is used in many different moving objects, including vehicles such as aircraft,
submarines, spacecraft, and guided missiles.
BACKGROUND OF THE INVENTION
Gyroscopes measure the angular velocity of the system in the inertial reference
frame. By using the original orientation of the system in the inertial reference frame
as the initial condition and integrating the angular velocity, the system's current
orientation is known at all times. These sensors provide the key navigation
parameters such as position, velocity and attitude. A critical factor governing the
level of accuracy achievable in such a system is the alignment and calibration of the
sensors so the sensors are calibrated at the meridian aligned turn tables and
temperature compensation of drifts of gyroscope is carried out in the meridian
aligned thermal chamber.
Conventional method for meridian alignment is the polar alignment technique with
the help of theodolites. Present invention is concerned with the process of meridian
alignment of turn tables and thermal chambers with the help of calibrated INS like
Attitude and Heading Reference System (AHRS) and an existing aligned turn table.
SUMMARY OF PRESENT INVENTION
In accordance with one aspect of present invention is to provide an alternate process
for meridian alignment of turn tables and thermal chambers without using theodolite
and its accessories as required in conventional polar alignment technique.
Annexure‐II
In accordance with second aspect of present invention is to provide an alternate
process with the help of a calibrated INS like Attitude & Heading Reference System
(AHRS) along with its set of apparatus for checking its performance and an aligned
turn table at the work place.
In accordance with another aspect of present invention is to provide an alternate
process which is far less time consuming and requires very less resources than the
polar alignment technique.
In accordance with yet another aspect of present invention is to provide an alternate
process which provides the accuracy of the meridian alignment comparable to that of
INS like AHRS.
In accordance with yet another aspect of present invention is to provide an alternate
process which can be performed by lesser skilled individual than the polar alignment
technique.
In accordance with yet another aspect of present invention is to provide an alternate
process which can be performed at the work place with in the area covered by the
specified cable length of set of apparatus for checking the performance of INS like
AHRS.
BRIEF DESCRIPTION OF THE DRAWING
The features and advantages of the present invention will become more
apparent and descriptive in the description when considering together with Block
Diagram and flow chart referred for this alternate process of Meridian/North
alignment.
1. Fig. 1 is the Block diagram
2. Fig. 2 is the Flow diagram
DETAILED DESCRIPTION
Present invention is to provide an alternate process for meridian alignment of turn
tables and thermal chambers without using theodolite and its accessories as
required in conventional polar alignment technique. It utilizes the main feature of INS
Annexure‐II
like AHRS. The feature of serviceable INS like Attitude and Heading Reference
System (AHRS) is that once it is switched ON it reads zero as its initial position for
heading and if the unit position is changed accordingly it reads the angle by which
the position is shifted. This feature is utilized for north alignment of Turn tables and
thermal chambers by switching ON the INS at the existing aligned Turn Table and
shifting the unit in switched ON condition to the turn table to be north aligned.
Thereafter, the turn table is moved in such a direction that the heading read by INS
is about zero and within the accuracy defined for north alignment of the turn table.
Referring to the Block Diagram and the flow diagram, the present invention is
an alternate process of Meridian/North alignment of Turn table with the help of an
INS.
Figure 1 is the Block Diagram
Block diagram includes the power supply, one calibrated INS at the existing aligned
turn table and the PC attached with the set of apparatus for checking the
performance of another INS.
The dark line represents the connection when the INS is placed at the existing
meridian aligned turn table and the dotted line represents the connection after the
INS is shifted to the turn table/thermal chamber to be meridian aligned.
Figure 2 is the Flow Diagram for the alternate process.
The process includes the following steps as described in the flow diagram.
1. Calibrated INS is switched ON at its existing aligned turn table with the
required power supply and the set of apparatus required for the performance
check of INS..Once it is switched ON, it reads zero as its initial position for
heading and as it is placed on the existing aligned turn table the reading is
accurate.
2. INS is then moved from the existing aligned turn table to the turn table/thermal
chamber to be aligned with in the area covered by the specified cable length
attached with the set of apparatus for checking the performance of INS.
3. Heading reading on the screen of the PC attached with the set of apparatus
for checking the performance of INS is observed and analyzed.
Annexure‐II
4. If the reading of heading is with in the accuracy defined for the turn table or
thermal chamber to be aligned then the Meridian/North alignment is complete
for the turn table or thermal chamber.
5. If the reading of heading is not with in the accuracy defined for the turn table
or thermal chamber to be aligned then the turn table or thermal chamber is
moved in such a direction that the error is reduced.
6. After each movement of the turn table/thermal chamber the heading reading
on the screen of the PC is observed and analyzed and the process is
continued till the reading of heading is with in the accuracy defined for the turn
table or thermal chamber to be aligned.
7. Meridian/North alignment is complete for the turn table or thermal chamber.
Meridian alignment of Turn tables and Thermal chambers are required for testing
of articles related to Navigation and mainly for inertial navigation systems (INS) since
these systems contain inertial sensors such as gyroscopes and accelerometers.
Conventional approach for meridian alignment is the Polar alignment technique
which requires theodolite and its accessories. It makes it bulky and this technique
proves to be costly as well as very much time consuming. The Alternate process
described above requires far less resources and very much less time consuming.
The accuracy of the meridian alignment is comparable to that of the performance of
the INS. Polar alignment technique requires highly skilled individual for its completion
however the alternate process can be done by lesser skilled individual.

WE CLAIMS:-
Accordingly, the description of the present invention is to be considered as illustrative only and is for the purpose of teaching those skilled in the art of the best mode of carrying out the invention.The details may be varied substantially without departing from the spirit of the invention, and exclusive use of all modifications which are within the scope of the appended claims is reserved. We Claim

1. A system comprises:
- Calibrated Inertial Navigation System (INS) like Attitude & Heading Reference System (AHRS)
- Meridian Aligned Turn table
- Check Apparatus for Checking performance of INS

2. The System of Claim 1 wherein, is used for meridian/north alignment of turn table/Thermal chamber without using Theodolite as used in conventional polar technique for meridian/north alignment.

3. The System of Claim 1 wherein, is used with in the specified Supply cable length for the INS at the work Place.

4. The System of Claim 1 wherein, is used for meridian/north alignment of turn table/Thermal chamber with in the accuracy similar to that of INS.

5. The System of Claim 1 wherein, is far less time consuming than the Conventional Polar alignment technique.

6. The System of Claim 1 wherein, is required much less resources than the Conventional Polar alignment technique.

7. The System of Claim 1 wherein, requires no special training for meridian/north alignment as compared to conventional method which is done by specialists. ,TagSPECI:As per Annexure-II