Movable Notch Filtering for eVTOL Flight Control Vibrations
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electric propulsion systems in aircraft, such as tilt-rotor aircraft, experience significant propeller vibrations that corrupt state estimates and lead to high-frequency commands, increasing power consumption, temperature, and noise, and compromising controllability and safety.
Innovation Solution
Implementing a filtering system that adjusts based on propeller speed and edgewise airflow to reduce the influence of propeller vibrations on aircraft state measurements, using notch filters to attenuate specific frequencies and ensure accurate state estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If propeller vibrations are filtered using a fixed-frequency notch filter, then high-frequency commands are reduced, but the filter becomes inaccurate when propeller speed varies
Solution Approach 1:
The patent implements a movable notch filter where the center frequency is dynamically adjusted based on measured propeller speed. The filter transitions from a fixed-frequency design to a dynamic system that continuously adapts its parameters, allowing the center frequency to track the propeller vibration frequency as speed changes, thereby maintaining filtering accuracy across varying operating conditions
Solution Approach 2:
The system uses feedback from propeller speed sensors to continuously update the notch filter parameters. The measured propeller speed feeds into the filter adjustment mechanism, creating a closed-loop system that automatically compensates for speed variations and maintains optimal filtering performance without manual intervention
2Measurement precision
If a notch filter is applied to reduce propeller vibration influence, then state estimation accuracy improves, but the system complexity increases
Solution Approach 1:
The patent introduces an intermediary processing layer between the raw IMU measurements and the flight control system. This intermediary notch filter acts as a mediator that selectively removes vibration frequencies before the data reaches the state estimation algorithm, improving accuracy without requiring changes to the core estimation methodology or sensor hardware
Solution Approach 2:
The system replaces complex mechanical vibration isolation mechanisms with an electronic/software-based filtering approach. Instead of physically isolating sensors from propeller vibrations through complex mechanical mounting systems, the patent uses digital signal processing to electronically remove vibration effects, reducing mechanical complexity while achieving the same goal
3Speed
If high-frequency commands are generated from corrupted state estimates, then flight control responsiveness is maintained, but power consumption and noise increase
Solution Approach 1:
The patent applies vibration filtering as a preliminary action before state estimation and control command generation. By removing propeller vibration effects from the measurements in advance, the system prevents the generation of high-frequency correction commands that would otherwise be needed to compensate for vibration-induced estimation errors, thereby reducing overall control activity and power consumption
Data Source
AI summary
An electrical system for an aircraft is disclosed, comprising: at least one processor configured to: receive first sensor data from at least one inertial sensor of the aircraft, wherein the first sensor data is indicative of a state of the aircraft, receive second sensor data from at least one of an airspeed sensor indicating an airspeed of the aircraft or a propeller speed sensor indicating a propeller speed of at least one propeller of the aircraft, and determine the state of the aircraft based on the first sensor data, wherein determining the state of the aircraft comprises filtering aircraft state measurements based on the second sensor data to lessen influence of propeller vibrations on at least one aircraft signal. The at least one processor is further configured to control the aircraft based on a pilot input command and the determined state of the aircraft.