Blended Altitude Rate via Complementary Filter
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Solution Overview
Problem
Air data systems in aircraft face challenges in accurately determining altitude rate due to the amplification of high-frequency components in pressure-based measurements, leading to decreased dynamic response caused by low-pass filtering techniques that rely on past data and introduce lag.
Innovation Solution
An air data computer is configured with an inertial sensor assembly, air data parameter module, and altitude rate blending module, which uses a complementary filter to blend vertical acceleration from inertial sensors with pressure altitude to produce a blended altitude rate, enhancing accuracy and dynamic response by combining low-frequency pressure-based components with high-frequency accelerometer-based components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low-pass filtering techniques are used to process altitude rate, then high-frequency noise is attenuated, but dynamic response decreases due to lag introduced by relying on past data
Solution Approach 1:
The patent combines pressure-based altitude measurements with accelerometer-based vertical acceleration measurements to produce a blended altitude rate output. The complementary filter merges these two different measurement approaches, allowing the system to benefit from both the accuracy of pressure measurements and the fast response of accelerometer measurements, thereby resolving the contradiction between measurement precision and dynamic response
Solution Approach 2:
The system changes the parameter being measured by using two different physical quantities: static pressure for altitude and dynamic acceleration for vertical motion. By transforming acceleration data into vertical velocity through integration and combining it with pressure-derived altitude rate, the system achieves both accuracy and fast response without relying solely on filtered past data
2Productivity
If numerical differentiation is used to generate altitude rate from pressure altitude, then altitude rate can be derived, but high-frequency components are amplified causing noise
Solution Approach 1:
The patent merges the differentiated pressure altitude signal with integrated accelerometer vertical acceleration signal using a complementary filter. This combination allows the system to generate altitude rate productively while the filter suppresses the high-frequency noise that would otherwise be amplified by numerical differentiation
Solution Approach 2:
The complementary filter acts as an intermediary that processes both the differentiated pressure signal and the integrated acceleration signal. It mediates between these two signals, allowing the productive aspect of differentiation to continue while filtering out the harmful high-frequency amplification through its low-pass filtering characteristics
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 solution increases the accuracy and bandwidth of altitude rate outputs, improving the dynamic response and maintaining the accuracy of pressure-based measurements while correcting for errors in inertial sensor outputs, resulting in more precise operational control for aircraft systems.
Implementation Method 1
blend the vertical acceleration and the pressure altitude using a complementary filter to produce a blended altitude rate
Data Source
AI summary
An air data computer configured to be installed on an aircraft includes an inertial sensor assembly having a plurality of accelerometers and a plurality of rate gyroscopes. The air data computer is configured to: determine a pressure altitude of the aircraft based on measured pressure of the airflow about the exterior of the aircraft; determine an estimated attitude of the aircraft based on rotational rate sensed by the plurality of rate gyroscopes; and determine a vertical acceleration of the aircraft based on the estimated attitude of the aircraft and the acceleration sensed by the plurality of accelerometers. The air data computer is further configured to blend the vertical acceleration and the pressure altitude using a complementary filter to produce a blended altitude rate that is output to consuming systems.