Pseudo-Random Acoustic Modulation for Drone Range Finding
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Solution Overview
Problem
Existing unmanned aerial systems (UAS) face challenges in range finding due to acoustic transducers that are only resonant at a single frequency or a narrow range of frequencies, limiting their ability to perform frequency modulation, which is necessary for accurate distance measurement and navigation, especially in complex residential environments.
Innovation Solution
The use of piezoelectric acoustic transducers that modulate transmitted data using pseudo-random sequences of bits for on-off modulation, allowing identification of reflections without frequency change, enabling distance determination and three-dimensional sound navigation and ranging (SONAR) without frequency modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If acoustic transducers operate at a single resonant frequency, then device complexity is reduced, but measurement precision deteriorates due to inability to perform frequency modulation
Solution Approach 1:
The patent replaces frequency modulation (a mechanical/physical parameter change) with pseudo-random binary sequence modulation (a digital signal processing approach). Instead of varying the frequency of the acoustic transducer, the system modulates the amplitude of a fixed-frequency carrier wave using a pseudo-random binary sequence, allowing unique identification of transmitted signals and their reflections without requiring the transducer to operate across multiple frequencies.
2Measurement precision
If frequency modulation is used for range finding, then measurement precision improves, but device complexity increases due to transducer frequency requirements
Solution Approach 1:
The patent substitutes mechanical frequency modulation with digital pseudo-random sequence modulation. The acoustic transducer operates at a fixed resonant frequency, while the information is encoded in the amplitude modulation using pseudo-random binary sequences. This digital approach achieves unique signal identification and accurate range finding without requiring the transducer to physically operate across multiple frequencies.
Solution Approach 2:
The patent changes the modulation parameter from frequency variation to amplitude variation using pseudo-random sequences. Instead of changing the frequency parameter of the acoustic signal, the system varies the amplitude of a fixed-frequency carrier wave according to a pseudo-random binary sequence, enabling signal identification and range measurement through temporal correlation rather than frequency discrimination.
3Measurement precision
If pseudo-random sequences are used for modulation, then measurement precision improves through reflection identification, but device complexity increases due to signal processing requirements
Solution Approach 1:
The patent employs autocorrelation processing of the received signal against the known transmitted pseudo-random sequence to identify reflections. This feedback mechanism allows the system to distinguish between direct signals and reflected signals by detecting the characteristic time delay and correlation pattern, enabling accurate range finding even in complex acoustic environments with multiple reflections.
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
This solution allows UAS to accurately determine distances and navigate through residential areas by identifying reflections using pseudo-random sequences, enhancing safety and delivery precision by avoiding obstacles like trees and houses.
Implementation Method 1
an acoustic actuator to transmit acoustic data, the acoustic actuator having the resonant frequency
Implementation Method 2
transmit acoustic data from the acoustic actuator; receive acoustic data with an acoustic sensor
Implementation Method 3
receive acoustic data with an acoustic sensor, the acoustic sensor having the resonant frequency
Implementation Method 4
determine a delay time between the transmitting and the receiving of the modulated wave sequence
Implementation Method 5
receive a reflected wave sequence including a reflection of the modulated wave sequence
Data Source
AI summary
Techniques for range finding for an unmanned aerial system are described. As one example, an unmanned aerial system includes at least one motor to provide propulsion, a piezoelectric acoustic actuator having a resonant frequency, a piezoelectric acoustic sensor having the resonant frequency, and a controller to modulate a fixed amplitude and fixed frequency, at the resonant frequency, carrier wave according to a pseudo-random sequence of bits to produce a modulated wave sequence having a respective section of the carrier wave for each bit of the bits of the pseudo-random sequence having a first value, and a respective section of the carrier wave for each bit of the bits of the pseudo-random sequence having a second value, transmit the modulated wave sequence from the piezoelectric acoustic actuator, receive a reflected wave sequence including a reflection of the modulated wave sequence with the piezoelectric acoustic sensor, determine a delay time between the transmit and the receive of the modulated wave sequence based on the reflected wave sequence received by the piezoelectric acoustic sensor and the modulated wave sequence transmitted by the piezoelectric acoustic actuator, and modify power provided to the at least one motor based on the delay time.