Baro-Inertial Vertical Speed Correction Under Rapid Altitude Changes
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Solution Overview
Problem
Existing baro-inertial loops in airborne systems experience transient errors in vertical velocity due to rapid changes in barometric altitude, particularly when approaching the ground or flying over cliffs, leading to inaccurate vertical velocity calculations.
Innovation Solution
A method to limit baro-inertial velocity corrections by modifying the vertical position correction gain based on the difference between barometric altitude and baro-inertial position, using a processor to adjust gains K1, K2, and K3 when the altitude difference exceeds a threshold, thereby reducing the impact of transient altitude errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If baro-inertial loops continuously correct vertical velocity using barometric altitude measurements, then vertical positioning accuracy is improved, but transient errors occur during rapid pressure changes such as when approaching ground or flying over cliffs
Solution Approach 1:
The patent applies dynamics by making the position correction gain variable rather than fixed. The gain is dynamically adjusted based on the vertical velocity magnitude - reduced when vertical velocity exceeds a threshold and increased when it remains below the threshold. This dynamic adaptation allows the system to maintain reliability during rapid pressure changes while preserving measurement precision during normal operation
Solution Approach 2:
The patent changes the parameter of position correction gain based on operating conditions. By monitoring vertical velocity and adjusting the gain parameter accordingly (reducing it during high vertical velocity conditions associated with rapid pressure changes), the system resolves the contradiction between maintaining continuous correction accuracy and avoiding transient errors during adverse conditions
2Speed
If position correction gain is increased to quickly correct barometric altitude errors, then convergence speed is improved, but vertical velocity transient errors are amplified
Solution Approach 1:
The patent uses dynamic gain adjustment to resolve this contradiction. The position correction gain is not fixed but varies with vertical velocity conditions. During rapid pressure changes with high vertical velocity, the gain is reduced to prevent amplification of transient errors. During normal conditions with low vertical velocity, the gain is increased to achieve faster convergence of altitude correction
Solution Approach 2:
The system changes the correction gain parameter based on real-time vertical velocity measurements. This parameter adaptation allows the system to optimize convergence speed under normal conditions while preventing velocity transient errors during adverse pressure change conditions
3Measurement precision
If continuous velocity correction is applied in baro-inertial loops, then altitude accuracy is improved, but acceleration errors accumulate causing permanent velocity bias
Solution Approach 1:
The patent applies local quality by treating velocity correction differently based on local conditions (vertical velocity magnitude). Instead of uniform continuous correction, the system applies reduced correction during high vertical velocity periods and normal correction during low vertical velocity periods. This localized adjustment prevents acceleration error accumulation while maintaining altitude accuracy where conditions permit
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 method effectively limits transient baro-inertial velocity errors, maintaining accurate vertical velocity calculations even in conditions of rapid pressure changes, improving system robustness and reducing startup time for vertical position accuracy.
Implementation Method 1
The baro-inertial loop taking as input at least one vertical acceleration from at least one measurement of the accelerometer A and at least one barometric altitude from at least one measurement of the baro-altimeter BA
Implementation Method 2
An IMS includes at least acceleration and rotation sensors to determine the motion of the system in which it is mounted relative to Earth
Implementation Method 3
This vertical acceleration information γZ is integrated first by integrator I1 to obtain a vertical velocity Vzbi, then a second time by integrator I2 to obtain a vertical position (altitude) Zbi
Data Source
Figure 1~2B
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Figure 5~6
AI summary
The invention relates to a method for limiting baro-inertial vertical speed correction, baro-inertial vertical speed being calculated by a baro-inertial loop implemented by a processor included in an airborne system further comprising an accelerometer and a barometric altimeter, the loop taking a vertical acceleration and a barometric altitude as input and being configured so as: - to provide at least one altitude and the vertical speed; - to correct the altitude and the vertical speed on the basis of the barometric altitude, a position correction gain, a vertical speed correction gain and a vertical acceleration correction gain. The method comprises a step of limiting vertical speed correction when the absolute value of the difference between the barometric altitude and the altitude exceeds a predetermined threshold, said step of limiting vertical speed correction comprising modification of the position correction gain.