Acoustic Airspeed Sensor Boundary Layer Compensation
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Solution Overview
Problem
Conventional airspeed measurement methods, such as pitot probes and ultrasonic anemometers, face inaccuracies due to blockages like ice and neglect the boundary layer, leading to unreliable airspeed readings crucial for aircraft operation.
Innovation Solution
An acoustic airspeed sensor system that uses a computation unit with propagation measurement modules, wind angle, and airspeed modules to determine airspeed and wind angle without obstructing airflow, employing beamforming algorithms to account for the boundary layer and shadowing effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pitot probes are used to measure airspeed, then airspeed can be determined through pressure differential, but the probes may become blocked by ice making readings inaccurate
Solution Approach 1:
The patent replaces the mechanical pitot probe system with an acoustic measurement system using ultrasonic transducers. The ultrasonic transducers emit and receive sound waves through the aircraft surface to measure airspeed based on acoustic propagation time differences, eliminating the mechanical components that are susceptible to ice blockage while maintaining measurement capability under icing conditions
Solution Approach 2:
The patent introduces acoustic waves as an intermediary medium to measure airspeed indirectly. Instead of directly measuring pressure differentials with exposed probes, the system uses sound wave propagation through the aircraft structure as a mediator to obtain airspeed data without exposing measurement components to the external environment where ice accumulation occurs
2Reliability
If ultrasonic anemometers are built flush with the aircraft surface, then they avoid blockages, but they neglect the boundary layer reducing measurement accuracy
Solution Approach 1:
The patent applies local quality by positioning ultrasonic transducers at specific locations on the aircraft surface where the boundary layer effects are minimized or characterized. The system uses multiple transducer pairs at different positions to capture local flow variations and compensates for boundary layer effects through computational algorithms that account for the specific aerodynamic environment at each measurement location
Solution Approach 2:
The patent implements feedback through computational algorithms that process acoustic propagation data and iteratively refine airspeed measurements by accounting for boundary layer effects. The system uses measured acoustic propagation times to infer flow conditions and applies correction factors based on the relationship between acoustic wave propagation and the boundary layer, continuously improving measurement accuracy
3Device complexity
If conventional calculation methods are used for ultrasonic anemometers, then computations are simple, but they do not accurately consider the boundary layer reducing airspeed accuracy
Solution Approach 1:
The patent changes the computational parameters by incorporating boundary layer characteristics into the acoustic propagation model. Instead of using simple straight-line propagation assumptions, the system modifies the calculation to account for refractive effects, absorption variations, and path deviations caused by the boundary layer, using adjusted propagation speed parameters and path length calculations that reflect actual atmospheric conditions
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
Provides accurate, high-bandwidth measurements of airspeed and wind angle without mechanical moving parts, reducing icing risks and airflow disturbance, and improving measurement precision by considering the boundary layer effects.
Implementation Method 1
measuring the time of flight of an acoustic pulse from the acoustic transmitter to each of the plurality of acoustic receivers
Implementation Method 2
the calculations used to determine air speed do not accurately consider the boundary layer (i.e., the speed of air in the immediate vicinity of the surface of the aircraft)
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
An acoustic airspeed sensor system can include at least one acoustic transmitter (12) configured to provide an acoustic pulse, a plurality of acoustic receivers (14A - 14L) including at least a first acoustic receiver, a second acoustic, receiver, and a third acoustic receiver, each positioned at a first radial distance from the at least one acoustic transmitter. The first acoustic receiver, the second acoustic receiver, and the third acoustic receiver are each configured to receive the acoustic pulse at a first time, a second time, and a third time, respectively, and output a first receiver signal, a second receiver signal, and a third receiver signal respectively. The system can include a computation unit (507) operatively connected to the acoustic receivers and configured to generate a propagation function. The computation unit is further configured to determine true air speed based upon a receiver signals and the propagation function.