I. Overview of the Test Plan

1.1 Test Purpose

The unmanned aerial vehicle (UAV) inertial measurement unit (IMU), as the core component for UAV attitude perception and position calculation, directly determines the reliability and safety of UAV flight control through its measurement accuracy, stability, and dynamic response characteristics. This test plan aims to systematically verify the performance indicators of the UAV IMU under different working conditions such as static and dynamic states in a controllable laboratory environment, comprehensively identify potential performance defects, and provide precise and reliable test data support for IMU selection, optimized design, and UAV flight control system debugging, ensuring that the IMU meets the performance requirements of the UAV's intended flight mission.

1.2 Test Scope

This plan covers laboratory testing of the core performance parameters of the UAV IMU, mainly including: static accuracy tests (bias, scale factor error, installation error), dynamic response tests (angular rate tracking accuracy, acceleration tracking accuracy), environmental adaptability tests (temperature, humidity effects), stability tests (long-term operation performance), and data output consistency tests. The test object is the IMU module for a certain model of UAV. The test environment is limited to a controlled professional laboratory setting and does not involve outdoor real-flight condition testing.

1.3 Reference Standards and Basis

The formulation of this test plan mainly refers to the following standards and bases:

JJF 1535-2015 Calibration Specification for Micro-Electro-Mechanical System (MEMS) Gyroscopes

JJF 1427-2013 Calibration Specification for Micro-Electro-Mechanical System (MEMS) Linear Accelerometers

GB/T 28587-2012 "Inertial Measurement Unit for Mobile Mapping Systems"

GB/T 38996-2020 "General Requirements for Flight Control Systems of Civil Light and Small Fixed-Wing UAVs"

GJB 2426A-2015 "Test Methods for Fiber Optic Gyroscopes"

IMU Module Product Technical Manual and UAV Flight Control System Design Requirements

Relevant Aerospace Inertial Navigation Equipment Test Specifications

II. Test Environment and Equipment

2.1 Laboratory Environmental Requirements

To ensure the accuracy and stability of test data, the laboratory environment must meet the following conditions:

Temperature: (20±5)°C

Relative Humidity: ≤85%RH, no condensation

Vibration: ≤0.1g, avoiding external vibration interference

Electromagnetic Environment: Complies with GB/T 17618-2015 requirements, away from strong electromagnetic interference sources

Power Supply: Stable AC 220V±10%, frequency 50Hz±1Hz, equipped with an uninterruptible power supply (UPS)

2.2 Core Test Equipment List

Test equipment must be calibrated and within the validity period. The specific list and purposes are shown in the table below:

III. Test Content and Procedures

3.1 Pre-test Preparation

1.  Equipment Check: Confirm all test equipment is powered normally, calibrated, and within the validity period; check the operation status of equipment like the turntable and vibration table to ensure no abnormal noise or jamming. 2.  Environment Confirmation: Adjust laboratory temperature and relative humidity to the required test range, ensuring no significant vibration or electromagnetic interference. 3.  IMU Installation and Connection: Precisely fix the IMU to the test platform using the mounting fixture; connect the IMU power and data cables, ensuring firm connections and good contact; establish communication between the data acquisition card and the PC test software, completing parameter configuration (sampling rate, data format, etc.). 4.  Warm-up and Initialization: Power on the IMU for warm-up for no less than 30 minutes; start the IMU initialization program, and after self-calibration, confirm the IMU output data is stable (no jumps or abnormal values).

3.2 Static Accuracy Test

The static accuracy test aims to verify the measurement error of the IMU in a stationary state. Core test parameters include gyro bias, accelerometer bias, scale factor error, and installation error.

3.2.1 Gyro Bias Test

1.  Fix the IMU on a horizontal test bench, ensuring the IMU sensitive axes are parallel to the horizontal plane with no angular displacement excitation. 2.  Start the data acquisition system, set the sampling rate to 100Hz, and continuously collect IMU three-axis gyro output data for 2 hours. 3.  After collection, process the data: remove outliers (using the 3σ criterion), calculate the mean and standard deviation of the three-axis gyro output data. The mean value is the gyro bias error. 4.  Record test data and compare with the bias index specified in the product technical manual to determine compliance.

3.2.2 Accelerometer Bias Test

1.  Keep the IMU stationary. Adjust the IMU attitude so that the three-axis accelerometers are in horizontal, vertical upward, and vertical downward orientations (stabilize the IMU for 5 minutes in each orientation). 2.  In each orientation, continuously collect IMU three-axis accelerometer output data at a 100Hz sampling rate for 30 minutes per orientation. 3.  Data processing: After removing outliers, calculate the mean value of the accelerometer output data for each orientation; based on the standard gravity value (9.80665 m/s²), calculate the accelerometer bias error (deviation between measured and theoretical values). 4.  Record bias data for each orientation and verify compliance with index requirements.

3.2.3 Scale Factor Error Test

1.  Gyro Scale Factor Test: Fix the IMU on a high-precision turntable, aligning the turntable rotation axis with one IMU gyro sensitive axis. Set the turntable to rotate at different angular rates (e.g., 5°/s, 10°/s, 20°/s, 50°/s, 100°/s) uniformly. Use no fewer than 11 angular rate points within the positive and negative input angular rate ranges. Each angular rate operates stably for 1 minute while collecting IMU gyro output data. Repeat the test for the other two sensitive axes. 2.  Accelerometer Scale Factor Test: Fix the IMU on the turntable, aligning the turntable rotation axis with one IMU accelerometer sensitive axis. Rotate the turntable in positive and negative directions with angle increments θ=360/n, recording the accelerometer output at each angular position. Repeat for the other two axes. 3.  Data processing: Based on the standard excitation value set by the turntable and the actual IMU output value, use the least squares method to fit the scale factor curve and calculate the scale factor error (deviation between fitted value and theoretical scale factor). 4.  Record the scale factor error for each axis and determine compliance with index requirements.

3.2.4 Installation Error Test

1.  Fix the IMU on the turntable, using the mounting fixture to ensure initial alignment of the IMU coordinate system with the turntable coordinate system. Set the turntable to perform small-angle (±5°) step rotations around the X, Y, and Z axes separately, pausing for 30 seconds at each step, and collect IMU three-axis gyro output data. 2.  Based on the turntable's actual rotation angles and IMU output angle data, establish an installation error model and solve for the installation error angles using the least squares method. 3.  Record installation error data. If the error exceeds the allowable range, readjust the mounting fixture and retest.

3.3 Dynamic Response Test

The dynamic response test aims to verify the IMU's tracking accuracy and response speed under dynamic excitation. Core test parameters include angular rate tracking error, acceleration tracking error, and dynamic response time.

3.3.1 Gyro Dynamic Tracking Test

1.  Fix the IMU on the turntable, aligning the turntable rotation axis with one IMU gyro sensitive axis. Start the turntable to run according to a preset dynamic excitation curve (e.g., step, sine, triangular wave). Step angular rate range: 0~100°/s, sine angular rate amplitude: 0~50°/s, frequency: 0.1~10Hz. 2.  Synchronously start the data acquisition system to collect turntable reference angular rate data and IMU gyro output data, with a sampling rate set to 1kHz. 3.  Data processing: Compare IMU output data with turntable reference data to calculate dynamic tracking error (peak error, root mean square error); calculate dynamic response parameters like rise time and settling time from the step response curve. 4.  Repeat the test for the other two sensitive axes and record dynamic performance data for each axis.

3.3.2 Accelerometer Dynamic Tracking Test

1.  Fix the IMU on the vibration table, with the input reference axis (IRA) direction parallel to the vibration direction. Start the vibration table to run according to a preset dynamic excitation curve (step, sine). Step acceleration range: 0~20g, sine acceleration amplitude: 0~10g, frequency: 0.1~50Hz. 2.  Synchronously collect vibration table reference acceleration data and IMU accelerometer output data, with a sampling rate set to 1kHz. 3.  Data processing: Compare the two sets of data to calculate dynamic tracking error (peak error, root mean square error); calculate dynamic response parameters like rise time and settling time for the accelerometer from the step response curve. 4.  Repeat the test for the other two sensitive axes and record dynamic performance data for each axis.

3.4 Environmental Adaptability Test

The environmental adaptability test aims to verify the IMU's performance stability under different temperature and humidity environments, focusing on the impact of temperature on IMU accuracy.

3.4.1 Low-Temperature Environment Test

1.  Place the test fixture with the IMU installed into the temperature and humidity chamber, connecting the power and data cables (ensure cables can function normally with the chamber door closed). 2.  Set the chamber temperature to the IMU's lower operating temperature limit and maintain until IMU output stabilizes. 3.  In the low-temperature environment, repeat core items from sections 3.2 (static accuracy test) and 3.3 (dynamic response test) (gyro bias, accelerometer bias, step tracking error), collect and record test data. 4.  After testing, restore the chamber temperature to room temperature, hold for 30 minutes, and observe if IMU output data returns to normal.

3.4.2 High-Temperature Environment Test

1.  Set the chamber temperature to the IMU's upper operating temperature limit and maintain until IMU output stabilizes. 2.  In the high-temperature environment, repeat core items from sections 3.2 and 3.3, collect and record test data. 3.  After testing, restore the chamber temperature to room temperature, hold for 30 minutes, and observe if IMU output data returns to normal.

3.5 Stability Test (Long-Term Operation Test)

1.  Place the IMU in a standard laboratory environment (20℃±5℃，≤85%RH), fixed on a horizontal test bench, ensuring stable power supply and normal data transmission. 2.  Power on the IMU and warm up for 30 minutes. Set the data acquisition system to continuously collect IMU output data at a 100Hz sampling rate for 12 hours. 3.  Data processing: Extract gyro bias and accelerometer bias data every 30 minutes to analyze the trend over time; calculate the maximum fluctuation range of the data over 12 hours to verify the IMU's stability during long-term operation.

3.6 Data Output Consistency Test

1.  Select 3 samples of the same IMU model. Under identical laboratory conditions, using the same test equipment and parameters, conduct the static accuracy tests from section 3.2 separately. 2.  Collect and record core data (gyro bias, accelerometer bias, scale factor error, etc.) for all 3 IMUs. 3.  Calculate the coefficient of variation (standard deviation/mean) for the same parameter across the 3 IMUs to verify the output consistency of the same model product.

IV. Data Processing and Acceptance Criteria

4.1 Data Processing Methods

Outlier Removal: Use the 3σ criterion to remove outliers from test data, ensuring data validity. Accuracy Indicator Calculation: Bias error is calculated using the mean value method; scale factor error is calculated using the least squares fitting method; tracking error is calculated using peak error and root mean square error (RMSE). Data Visualization: Use test software to plot data curves (e.g., bias vs. time curve, dynamic tracking comparison curve) to visually present IMU performance trends. Repeatability Verification: Perform 3 repeat tests for the same test item, calculate the repeatability error of the test results to ensure test data reliability.

4.2 Acceptance Criteria

Based on the IMU product technical manual and UAV flight control system design requirements, the following core performance indicator acceptance criteria are established (adjustable based on actual product parameters):

If all test data meet the above index requirements, the IMU laboratory test is judged qualified. If any single index fails to meet the requirement, analyze the cause (e.g., installation error, equipment interference, IMU defect) and retest for verification.

V. Test Safety and Precautions

Equipment Operation Safety: Operators must be familiar with the operating specifications of each test device and strictly follow procedures to start/run equipment. During turntable/vibration table operation, keep clear of rotating/vibrating parts to avoid mechanical injury. Electrical Safety: Ensure all test equipment is properly grounded to prevent electric shock. Before connecting/disconnecting cables, cut off power to prevent short circuits damaging equipment or the IMU module. Temperature/Humidity Test Safety: Do not open the chamber door during operation to avoid burns/frostbite from rapid temperature changes. After testing, wait for the internal temperature to return to room temperature before removing the test sample. Data Safety: Save test data in real-time during testing and back up data files regularly. After testing, categorize and organize data to ensure traceability. Equipment Maintenance: After testing, power off all test equipment and clean surfaces. Regularly lubricate and calibrate equipment like turntables and vibration tables to ensure long-term stable operation.

VI. Test Report Preparation

After testing completion, a detailed UAV IMU laboratory test report must be prepared. The report should include:

Test Overview: Including test purpose, scope, basis, environment, etc. Test Equipment: List the model, specifications, and calibration status of all test equipment. Test Process: Describe in detail the test steps and parameter settings for each test item. Test Data: Organize and present raw data, processed data, and data curves for each test item. Result Analysis: Compare test data with qualification requirements, analyze IMU performance; for issues found, provide cause analysis and improvement suggestions. Test Conclusion: Clearly state whether the IMU laboratory test is qualified or not. Appendices: Include raw test data, test equipment calibration certificates, test site photos, etc.