Inertial Measurement Test Request
Inertial Sensor Laboratory serves to provide testing and calibration of Inertial Measurement Unit (IMU), accelerometers and gyroscopes used for navigation and guidance systems. Inertial Sensor Laboratory (AÖL) has been in service since founded in 1994. We have been collaborated with many companies in country and performed tests of various kinds of inertial sensors and inertial measurement units in the laboratory.
Laboratory work has been carried out according to ISO 9001:2000 Quality Management System. Some Standards used in these tests given below:
- IEEE Std. 528 - 2001: Standard for Inertial Sensor Terminology.
- IEEE Std. 1293 - 1998: Standard Specification Format Guide and Test Procedure for Linear Single-Axis, Nongyroscopic Accelerometers.
- IEEE Std. 836 - 2001: Recommended Practice for Precision Centrifuge Testing of Linear Accelerometers.
- IEEE Std. 952 - 1997 (R2002): IEEE Standard Specification Format Guide and Test Procedure for Single-Axis Interferometric Fiber Optic Gyros.
Accelerometer Tests
Technical specifications of accelerometer can be verified and calibration parameters can be found by accelerometer tests. Stability and temperature dependency of calibration parameters can be calculated also. These tests are divided into two parts. First part is Allan variance tests and second part is calibration tests.
Allan Variance Tests
Data should be taken for long time (for hours) without giving input to the IMU. Allan variance is the average of the variance of adjacent pairs of elements in a contiguous time series of data versus the averaging time used to generate the elements. Allan variance results are related to basic sensor noise terms given below:
- Quantization Noise
- Rate Random Walk
- Bias Instability
- Rate Ramp
Allan variance tests can be performed using the index table, three-axis motion simulator, two-axis motion simulator.
Calibration Tests
Each accelerometer is calibrated separately by these tests. Calibration tests can be performed by using index table, centrifuge, two axis/three axis motion simulator. Highly sensitive inputs can be given to the accelerometer using that equipment. Calibration tests are divided into two parts as position tests and centrifuge tests. Position tests can be performed by using index table, two axis/three axis motion simulator. Table is tumbled through a series of positions to apply components of local gravity vector in the range of ±1 g.
Bias, scale factor and misalignments can be calculated as a result of position tests. Scale factor can be calculated during centrifuge tests for all measurement range of the accelerometer. Accelerometer calibration matrix is constituted with these calculated parameters and this matrix is used by navigation process and IMU software. Calibration tests can be repeated to find the temperature dependence of the calibration parameters.
Test Sample Requirements and Delivery Conditions
Accelerometer tests can be applied to quartz pendulum type and MEMs (Micro-Electro- Mechanical Systems) type accelerometers.
Suitable test setup for accelerometer testing should be selected and configured. This test setup should mainly include sensor mounting fixture, software and electronic equipment required to operate accelerometer and measure its output. After the test setup is complete, test plan is prepared and the results of all measurements are reported.
Basic Devices Used in These Tests and Their Technical Specifications
| 2-Axis Motion Simulator | |
|---|---|
| Positioning resolution | 0.00001 ° |
| Positioning accuracy | <1 arcsec |
| Rate resolution | 0.0001 °/s |
| Rate stability |
±% 0.0002 < 400 °/s ±% 0.0005 < 1,000 °/s |
| Max. rate |
1,000 °/s (inner axis) 400 °/s (outer axis) |
| Max. acceleration |
2,700 °/s² (inner axis) 260 °/s² (outer axis) |
| Payload capacity | 40 kg |
| Temperature range | -60 to +90 °C |
| Index Table | |
|---|---|
| Positioning accuracy | 0.25 arcsec |
| Repeatability | 0.05 arcsec |
| Position stability | 0.025 arcsec |
| Orthogonality | 2 arcsec |
| Positioning resolution | 1.0 deg |
| Payload | 10 lbs |
| Height x Width x Diameter | 2,620 x 1,755 x 1,219 mm |
| Weight | 310 lbs |
| Centrifuge | |
|---|---|
| Positioning resolution | 0.00001 ° |
| Positioning accuracy | <1 arcsec |
| Rate resolution | 0.00001 °/s |
| Rate stability | % 0,0001 |
| Rate range | 4,000 °/s |
| Linear acceleration range | 0.5 - 200 g |
| Payload capacity | 10 kg |
| Test chamber temperature range | -60 to +125 °C |
Gyroscope Tests
Allan Variance Tests
Data should be taken for long time (for hours) without giving input to the gyroscope. Allan variance is the average of the variance of adjacent pairs of elements in a contiguous time series of data versus the averaging time used to generate the elements.
Allan variance results are related to basic sensor noise terms given below:
- Quantization Noise
- Angle Random Walk
- Bias Instability
- Rate Ramp
Allan variance tests are performed by using indexing table (or dividing head), two axis position/rate table, three axis motion simulator.
Calibration Tests
Each gyroscope is calibrated separately by these tests. Calibration tests can be performed by using two axis position / rate table or three axis motion simulator Highly sensitive rate inputs can be given to the gyroscope using this equipment. Measurement range of the gyroscopes has been considered for the test inputs. Gyroscopes scale factor, misalignments and errors can be calculated as a result of rate inputs in all measurement range of gyroscope. Bias value is calculated by precision positioning of gyroscopes. Gyroscope calibration matrix is constituted with these calculated parameters and this matrix can be used during navigation process and IMU software. Calibration tests can be repeated to find the temperature dependence of the calibration parameters.
Test Sample Requirements and Delivery Conditions
These tests can be applied to fiber-optic, laser and MEMs (Micro-Electro-Mechanical Systems) and vibrating types of gyroscopes. Suitable test setup for gyroscope testing should be selected and configured. This test setup mainly includes sensor mounting fixture, software and electronic equipment required to operate gyroscope and measure its output. After the test setup is complete, test plan is prepared and the results of all measurements are reported.
Basic Devices Used in These Tests and Their Technical Specifications
| 2-Axis Motion Simulator | |
|---|---|
| Positioning resolution | 0.00001 ° |
| Positioning accuracy | <1 arcsec |
| Rate resolution | 0.0001 °/s |
| Rate stability |
±% 0.0002 < 400 °/s ±% 0.0005 < 1,000 °/s |
| Max. rate |
1,000 °/s (inner axis) 400 °/s (outer axis) |
| Max. acceleration |
2,700 °/s² (inner axis) 260 °/s² (outer axis) |
| Payload capacity | 40 kg |
| Temperature range | -60 to +90 °C |
| 3-Axis Motion Simulator | |
|---|---|
| Positioning resolution | 0.00001 ° |
| Positioning accuracy | <1 arcsec |
| Rate resolution | 0.00001 °/s |
| Rate stability | % 0,0001 |
| Highest Speed |
1,000 °/s (inner axis) 750 °/s (middle axis) 500 °/s (outer axis) |
| Max. Acceleration |
1,660 °/s² (internal axis) 590 °/s² (middle axis) 660 °/s² (outer axis) |
| Temperature Range | 55 to +85 °C |
Inertial Measurement Unit Tests
IMUs can be tested in detail which is necessary during the design and development stage of navigation systems. At first, Allan Variance tests are performed and investigated for understanding general performance of sensors. Later, accelerometers and gyroscopes calibration parameters are found with the calibration tests.
Allan Variance Tests
Data should be taken for long time (for hours) without giving input to the IMU. Allan variance is the average of the variance of adjacent pairs of elements in a contiguous time series of data versus the averaging time used to generate the elements. Allan variance results are related to basic sensor noise terms given below:
- Quantization noise
- Angle Random Walk
- Bias Instability
- Rate Ramp
Calibration Tests
Error models of inertial sensors used in IMU are calculated with calibration tests. Each IMU is calibrated separately. Calibration tests can be performed by using two axes position/rate table or three axes motion simulator. Highly sensitive rate and acceleration inputs can be given to the IMUs using this equipment. As a result of position tests, bias, scale factor and misalignments of accelerometer and bias of gyroscopes are calculated. Gyroscope and accelerometer calibration matrix are constituted with these calculated parameters and this matrix can be used during navigation process and IMU software. Calibration tests can be repeated to find the temperature dependence of the calibration parameters.
Test Sample Requirements and Delivery Conditions
Suitable test setup for testing IMU should be selected and configured. This test setup mainly includes IMU mounting fixture, software and electronic equipment required to operate IMU and measure its sensors output. After the test setup is complete, test plan will be prepared and all measurements results will be reported.
Basic Devices Used in These Tests and Their Technical Specifications
| 2-Axis Motion Simulator | |
|---|---|
| Positioning resolution | 0.00001 ° |
| Positioning accuracy | <1 arcsec |
| Rate resolution | 0.0001 °/s |
| Rate stability |
±% 0.0002 < 400 °/s ±% 0.0005 < 1,000 °/s |
| Max. rate |
1,000 °/s (inner axis) 400 °/s (outer axis) |
| Max. acceleration |
2,700 °/s² (inner axis) 260 °/s² (outer axis) |
| Payload capacity | 40 kg |
| Temperature range | -60 to +90 °C |
| Index Table | |
|---|---|
| Positioning accuracy | 0.25 arcsec |
| Repeatability | 0.05 arcsec |
| Position stability | 0.025 arcsec |
| Orthogonality | 2 arcsec |
| Positioning resolution | 1.0 deg |
| Payload | 10 lbs |
| Height x Width x Diameter | 2,620 x 1,755 x 1,219 mm |
| Weight | 310 lbs |
| 3-Axis Motion Simulator | |
|---|---|
| Positioning resolution | 0.00001 ° |
| Positioning accuracy | <1 arcsec |
| Rate resolution | 0.00001 °/s |
| Rate stability | % 0,0001 |
| Highest Speed |
1,000 °/s (inner axis) 750 °/s (middle axis) 500 °/s (outer axis) |
| Max. Acceleration |
1,660 °/s² (internal axis) 590 °/s² (middle axis) 660 °/s² (outer axis) |
| Temperature Range | 55 to +85 °C |
