Doppler Radar Airspeed Measurement for Inertial Navigation Drift Correction
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Solution Overview
Problem
Inertial-based location systems on airborne platforms are susceptible to sensor errors such as drift, leading to inaccurate location information over time, especially when satellite-based location systems are unavailable due to hardware failures or jamming.
Innovation Solution
A radar system provides an airspeed measurement to the inertial-based location system by determining the falling edge of the Doppler signature of radar reflections, allowing for sensor bias correction and improved accuracy through sensor adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If satellite-based location systems are used to provide airspeed measurements, then navigation accuracy is improved, but the system becomes vulnerable to hardware failures and radio jamming
Solution Approach 1:
The patent transitions from satellite-based positioning to radar-based velocity measurement by changing the measurement parameter from position (GPS) to velocity (Doppler shift). This allows the system to obtain accurate airspeed measurements through frequency shift analysis of radar reflections, bypassing satellite dependency while maintaining measurement precision.
Solution Approach 2:
The patent introduces radar reflections from ground objects as an intermediary medium to obtain velocity information. Instead of directly relying on satellite signals, the system uses reflected radar waves from the ground environment to derive airspeed through Doppler frequency analysis, providing a reliable alternative measurement path.
2Reliability
If inertial-based location systems are used when satellite systems are unavailable, then location information can be provided, but sensor drift causes accuracy to deteriorate over time
Solution Approach 1:
The patent implements a feedback mechanism where radar-derived velocity measurements continuously correct inertial navigation system (INS) drift. The Doppler velocity measurements serve as reference feedback to adjust and recalibrate INS sensor biases, preventing accuracy deterioration over time while maintaining system availability during satellite outages.
Solution Approach 2:
The system performs preliminary velocity measurements using radar Doppler effects to establish accurate reference data before relying on inertial navigation. By obtaining precise velocity information through radar reflections in advance, the system can pre-correct inertial sensor drift, improving subsequent location accuracy during satellite-denied operations.
3Measurement precision
If radar systems use traditional frequency analysis methods, then velocity information can be obtained, but the falling edge detection of Doppler signature is required for accurate airspeed measurement
Solution Approach 1:
The patent extracts the falling edge characteristic from the complete Doppler signature spectrum to obtain airspeed information. By focusing only on the falling edge portion of the Doppler frequency distribution rather than analyzing the entire spectrum, the system simplifies signal processing while maintaining accurate velocity measurement capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The radar system enhances the accuracy of inertial-based location systems by providing a reference measurement to correct for sensor errors, ensuring reliable velocity and location information even without satellite-based navigation.
Implementation Method 1
Some systems may also estimate the relative motion of objects causing radar reflections based on Doppler frequency shifts in the received reflected signals
Data Source
AI summary
Methods and systems for a precision Doppler-based airborne platform velocity measurement system are presently disclosed. An example method comprises transmitting a radar signal with an antenna of an airborne platform. The method also includes receiving at least one radar reflection with the antenna. As part of the method, one or more processors may be configured to determine (i) a falling edge of a Doppler signature of the received radar reflection and (ii) a signal representative of an airspeed based on the falling edge of the Doppler signature. Additionally, the method includes providing the determined signal to an inertial measurement system. Further, the method includes determining location parameters of the airborne platform by the inertial measurement system, including determining at least one sensor adjustment for the inertial measurement unit based on the determined signal. Finally, the method includes operating the inertial measurement system with the sensor adjustment.