The present invention relates to generation of test inputs for gyros.
BACKGROUND OF THE INVENTION
The gyros are installed on the platform, which is used to provide information
pertaining to the angle at which aircraft is flying. The gyros are meant for stabilizing the
platform (Zero position). Once the platform is stabilized, the electrical force applied to the
gyro is used to calculate the angle at which the aircraft is flying. Two gyros are used, one
meant for X-axis and the other one for Y-axis.
The automatic test bench for gyros (ATP) is meant for carrying out the final
acceptance test for the gyros in the stand-alone mode. It is a PC based test set up
incorporating standard and custom built test and measuring instruments interfaced by
GPIB bus.
SUMMARY OF PRESENT INVENTION
In accordance with one aspect of present invention is the Servo tray is the heart of
the Gyro Test Bench. It receives input from the Gyro and the outputs are viewed through
instruments like the DMM, DAVM, Oscilloscope and the Industrial PC. This tray consists
of nine cards. The Servo Tray also consists of the motherboard which acts as an
interface between the below mentioned cards, to the external connectors made available
at the rear end of the tray and also to the test points and LED’s in the front panel of the
Servo tray.
In accordance with one aspect of present invention is to provide capabilities to the
gyros system as installed on the platform, which is used to generate trajectories
pertaining to the angle at which aircraft is flying.
In accordance with second aspect of present invention is to provide the automatic
test bench for gyros (ATP) for carrying out the final acceptance test for the gyros in the
stand-alone mode. It is a PC based test set-up incorporating standard and custom built
test and measuring instruments interfaced by GPIB bus.
In accordance with another aspect of present invention is to maintain the
temperature of the Gyro base, the Gyro cover and the Gyro at around 80 deg C, two
transformers installed in the heating tray provide voltages for the heating elements.
In accordance with yet another aspect of present invention, the subject invention
is easy to repair & maintain.
Annexure‐II
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention will become more apparent
and descriptive in the description when considered together with figures presented:
Fig. 1 is a System Level Block Diagram
Fig. 2 is a Block diagram of Servitude card-I
Fig. 3 is a Block diagram of Servitude card-II
Fig. 4 is a Block diagram of Channel Card X & Y
Fig. 5 is a Block diagram of Demodulator Filter Card
Fig. 6 is a Block diagram of Measuring Filter Card
Fig. 7 is a Block diagram of Relay Card-I
Fig. 8 is a Block diagram of Relay Card-II
Fig. 9 (a) is a Block diagram of Relay Card-III
Fig. 9 (b) is a Block diagram of Relay Card-III
Fig. 10 is a Block diagram of Mother Board
DETAILED DESCRIPTION
The Servo tray takes the inputs like X- axis and Y- axis current sources and
provides X–axis and Y--axis outputs to the Channel Card X and Y as Pickoff X and
Pickoff Y. The Channel cards demodulate the signal from the Gyro and the outputs are
filtered. The detailed description of each card used in the servo tray is explained below.
The current sources are required to provide current compensation to the gyro. The
instruments like oscilloscope, DMM, are connected to PC through GPIB bus. (Refer
Fig.1)
FUNCTIONAL DESCRIPTION
1. Servitude card I: This card basically generates the following outputs:
a) 355.5 Hz (Three phase wheel supply pulses separated by 120 deg phase. Phase to
phase voltage is 7.5 V). (Refer Fig. 2)
b) 355.5 Hz + 10 Hz pulses
c) 355.5 Hz – 10 Hz pulses
d) 355.5 Hz + 30 Hz pulses
e) 355.5 Hz – 30 Hz pulses
f) 19.2 KHz
2. Servitude card II: This card gets an input of 19.2KHz square wave from servitude
card 1. This square wave is converted to 19.2 KHz sine wave with the help of wave
shaping circuits with tuned PI filter, amplifier and drive circuitry to generate the excitation
voltage which is 19.2KHz sine wave of amplitude 5V RMS as well as reference excitation
voltages for the channel cards, which is 19.2KHz sine wave of amplitude 1V RMS.
Feedback mechanism is employed to maintain the amplitude of the sine wave. (Refer
Fig. 3)
Annexure‐II
3. X and Y Channel Cards: The excitation voltage is modulated with 19.2KHZ signal in
the GYRO. The modulated signal is available as X pick-off and Y pick-off from the
detector coils in the gyro. The X and Y channel cards are similar in hardware and are
meant for processing X pick-off and Y pick-off output from the Gyro. The channel card
demodulates the modulated signal (modulated with 19.2 KHZ) from the gyro with the
help of the reference excitation of 19.2 KHz generated from the Servitude card 2. (Refer
Fig. 4)
4. Demodulator Filter Card: Tuned filters for 177.7Hz, 355.5Hz and 533.3Hz are
incorporated in this card. This card receives demodulated output from both the Channel
Cards X & Y and the filters are tuned to receive the main output frequency of 355.5 Hz
and harmonics of 177.7 Hz and 533.3 Hz. (Refer Fig. 5)
5. Measuring Filter Card: The Measuring Filter Card is used to measure the outputs at
the time constants of 6 seconds. To achieve this, the card has two sections as shown in
the block diagram below. The relay card 2 selects either the 1K, 10K, 100E resistor for a
given input and through the capacitor bank the signal is amplified and passed on to the
Digital Multi-meter (DMM). This card is mainly used at the time of calibrating the unit
during which the output of this card is expected to reach the 2/3rd value of the maximum
by 6 sec which indicates the time constant is maintained. (Refer Fig. 6)
6. Relay card 1: This card has relays, which are activated in a pre-determined series.
The relays are arranged such that there are thirteen stages and each stage has a driver
circuit which receives commands from pc as to which stage is switched on first and so
on. The output from the relay card is routed to the measuring instruments like DAVM,
DAU card and the Oscilloscope. The block diagram below shows the thirteen different
stages with their input signals and the output instrument to which the signals are routed.
(Refer Fig. 7)
Relay card 2: The relay card 2 is divided into nine sections. These sections have inputs
signals from different cards like the Measuring filter card and Channel card. Sections one
to four have inputs from Measuring filter card and through different sequence of
switching it selects the 1k, 10k and 100E resistors in the Measuring filter card for time
period of 6s. (Refer Fig. 8)
Relay card 3: Relay card 3 also has relays, which are activated through commands from
the IPC. This card acts as an interface to the signals that enter and leave the servo tray.
The signals that need to go to the front panel and also to the Gyro from Servo Tray pass
on through this card. (Refer Fig. 9a &9b)
7. Mother Board: All the above described cards are interconnected through the
motherboard. The connections to the front panel is through the two D type connectors on
the front side of the board and the connections to the external system is through the
three D type connectors placed on the rear end of the board. These connectors are
connected to 50 pin circular connectors placed at the rear end of the servo tray. (Refer
Fig. 10)

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. The Servo Tray, comprising
- Servitude card I,
- Servitude card II,
- X and Y Channel Cards,
- Demodulator Filter Card,
- Measuring Filter Card,
- Relay card 1,
- Relay card 2,
- Relay card 3,
- Mother Board,
- Generic equipments capable of monitoring of waveforms, frequency, voltage etc. &
- Looms & Cables for interconnecting Unit under test and various equipments of the said bench as well as the generic computing device.

and as described earlier in the detailed description.

2. The system as per claim 1, capable of generating different frequencies upto 400KHz with different amplitudes and shapes.

3. The system as per claim 1, capable of selection of different relay components based on the type of input fed by user using generic computing device or automatically in case a trajectory is selected.

4. The system as per claim 1, capable to measure the outputs at the time constants of 6 seconds.

5. The system as per claim 1, servo tray takes the inputs like X- axis and Y- axis current sources and provides X–axis and Y--axis outputs to the Channel Card X and Y as Pickoff X and Pickoff Y.

6. The system as per claim 1, mounted with atleast one display system capable of displaying various parameters of importance like voltage, current etc., further capable to monitor atleast one control point with respective indicators.

7. The system as per claim 1, wherein, the Servo Tray also consists of the motherboard which acts as an interface between the below mentioned cards, to the external connectors made available at the rear end of the tray and also to the test points and LED’s in the front panel of the Servo tray.

8. The system as per claim 1, wherein, modules are used along with the standard equipments, which are capable to perform all test in same type applications.
,TagSPECI:As per Annexure-II