1.Title of the invention
Tool for in-situ loading of Harmonization Parameters into Inertial Sensor Units.
2.Field of invention
This invention provides a tool for in-situ loading of harmonization parameters into inertial sensor unit on aircraft (or carrier) and verification.
3.Use of invention
The harmonization of an inertial sensor unit, i.e. inertial measurement unit (IMU) or attitude & heading reference-unit (AHRU) is required to be performed as part of the sensor unit's installation on aircraft (or carrier). The platform on which the inertial sensor unit is mounted, needs to be harmonized with respect to carrier axes. This invention provides a tool for in-situ loading of harmonization parameters (loaded into the inertial sensor unit) on aircraft or carrier and verification of harmonization parameters and sensor parameters, with an intention to reduce time and effort.
4.Aim of the invention
The principal aim of this invention is to reduce the time and effort for loading the harmonization parameters into inertial sensor unit (i.e., IMU, AHRU etc.), by developing a tool for in-situ loading of harmonization parameters into the inertial sensor unit. The methodology also involves in-situ verification of the harmonization parameters entered into the memory of the inertial sensor unit and verification of sensor parameters.
5.Summary of the present invention
The invention provides an innovative tool for in-situ loading of harmonization parameters into inertial sensor unit on aircraft (or carrier) and verification of the harmonization and sensor parameters. The tool consists of a portable computer and an electrical loom with switch selections and end connectors to interface with sensor unit and the computer. The application software for the data exchange pertaining to harmonization parameter loading, verification of the loaded parameters, and verification of the sensor parameters is resident in the portable computer.
6.Statement of invention
This invention provides a tool for in-situ loading of harmonization parameters into inertial sensor unit (i.e., IMU, AHRU etc.) on aircraft. The methodology also involves in-situ verification

of the harmonization parameters loaded into the memory of the inertial sensor unit and verification of sensor parameters.
7. Detailed description of invention Background:
The harmonization of an inertial sensor unit, i.e. inertial measurement unit (IMU) or attitude & heading reference unit (AHRU) is required to be performed as part of the unit's installation on aircraft (or carrier). The platform, on which the inertial sensor unit is mounted, needs to be harmonized with respect to carrier axes. This can be done by measuring angular deviations (pitch angle error, roll angle error, and yaw angle error) of the sensor mounting platform (under sensor installed condition) with respect to carrier axes, loading the angular deviations into the sensor memory module, and then correcting the sensor parameters for the angular deviations in the installation. Also, sensor mounting orientations with respect to carrier axis reference and the arm distance between the sensor's centre of gravity and centre of gravity of the carrier need to be loaded into the sensor memory module for necessary harmonization. These parameters being loaded into memory module of inertial sensor unit, for the harmonization, are called as harmonization parameters.
The harmonization parameters are stored in the removable memory module of the inertial sensor unit. This invention provides a tool for in-situ loading of harmonization parameters into inertial sensor unit without removing the sensor from the carrier for saving time and effort. This also aids the verification of the sensor parameters after loading the harmonization parameters.
In the earlier method for loading of harmonization parameters, the inertial sensor unit to be removed from the carrier and to be integrated in a test bench for loading the parameters after measuring the angular deviations. Then the sensor to be integrated again on the carrier. This is a time consuming process. In order to reduce the time taken, an innovative tool for in-situ loading of harmonization parameters is invented. The tool also helps in post harmonization verification of the sensor parameters and confirms the correctness of angular deviation measurement and loading.
Methodology & Apparatus:
Prior to the loading of harmonization parameters into the memory module of the inertial sensor unit, the carrier is levelled in longitudinal and lateral axes. Pitch angle, roll angle, and yaw angle deviations are measured, i.e. the angular deviations on all three axes are measured for the sensor witKresoect to carrier axes. An electrical loom is developed, as Dart of the tool, which is
interfaced the carrier maintenance connector at one end, and the other end is connected to serial interface (RS232 port) and data bus connector (avionics data bus protocol) of the portable computer. The electrical loom also consists of switches for setting the installation discrete signal inputs to the inertial sensor unit to configure the inertial sensor unit into harmonization mode. The portable computer, part of the tool, hosts the application software for data exchange with inertial sensor unit for loading of harmonization parameters and post-harmonization verification. The harmonization parameters include, angular deviation parameters (i.e., pitch angle error, roll angle error, and yaw angle error) measured on aircraft, sensor mounting orientations with respect to carrier axes, and arm distance between sensor centre of gravity and carrier centre of gravity. The test set-up is shown in Fig 1.0 & Fig 2.0.
The carrier and inertial sensor unit are powered ON and the harmonization parameters are loaded into the memory module of the sensor unit through portable computer. The application software for the data exchange with the inertial sensor unit is resident in the portable computer. The parameter loaded into the memory module of the sensor unit can also be read back using the same tool.
After entering the required parameters into the memory module of inertial sensor unit, post-harmonization verification is performed. The discrete signal to the sensor unit needs to be set for operational mode (instead of harmonization mode as done earlier) and apply power reset to the sensor unit. The operational parameters from sensor unit pertaining to pitch angle, roll angle, and yaw angle can be accessed by the computer through avionics data bus protocol interface and verification can be done under carrier levelled condition. For qualitative verification, the pitch and roll indication are also viewed on cockpit displays for attitude indication (Refer Fig 3.0).

Claims
We claim that
1.The invention establishes a methodology and apparatus for in-situ loading of harmonization parameters into inertial sensor unit on aircraft and verification of the harmonization and sensor parameters.
2. The invention reduces the time and efforts involved in loading of the harmonization parameters into inertial sensor unit and verification.
3.The invention verifies the angular deviation of the inertial sensor unit after loading the harmonization parameters, by acquiring the computed data of the unit on a portable computer, to ensure correctness of the loaded harmonization parameters. s
4.The invention can be used across various platforms for loading harmonization parameters into Inertial Measurement Unit (IMU), Attitude and Heading Reference Unit (AHRU), Gyro Reference Unit (GRU), Standby Flight Instrument (SFI) etc., with appropriate adaptations.