Ultrasonic Object Location via Time-Shifted Signal Templates
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Solution Overview
Problem
Existing ultrasonic tracking systems face limitations in update frequency and signal-to-noise ratio due to interference from echoes from fixed objects, leading to inaccurate distance measurement and motion detection, particularly when tracking objects with weaker reflections like fingers amidst stronger reflections from walls or torsos.
Innovation Solution
Applying a time-shift function to the initial signal to produce the transmit signal, allowing for the calculation of impulse responses that distinguish between reflections from objects at different ranges, thereby enhancing the signal-to-noise ratio and improving echo discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transmit signal is made more frequent to improve update frequency, then the frame rate increases, but echoes from previous transmissions interfere with current transmissions causing measurement precision to deteriorate
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing impulse response templates for known distances before actual measurement. When measuring, the system compares received echoes against these pre-stored templates to identify and filter out unwanted reflections, enabling high update frequency while maintaining precision through template-matching rather than raw signal analysis
Solution Approach 2:
The patent introduces an intermediary approach by using a digital signal processor as a mediator between the ultrasonic transducer and the measurement system. The DSP performs complex template-matching and interference filtering operations, allowing the system to operate at high frequencies while the intermediary processor handles the complexity of separating desired echoes from unwanted reflections
2Speed
If short pulses are used to improve response time, then the update frequency increases, but the signal-to-noise ratio deteriorates due to reduced energy content
Solution Approach 1:
The patent applies periodic action by transmitting repeated ultrasonic pulses at high frequency and using template-matching to identify echoes. The system accumulates information across multiple periodic transmissions, effectively compensating for the reduced energy of individual short pulses through temporal integration and pattern recognition
Solution Approach 2:
The patent changes the parameter approach by transitioning from analyzing raw signal amplitude to analyzing temporal patterns and echo signatures. By characterizing echoes based on their time-profile and comparing against stored templates rather than relying solely on signal strength, the system maintains measurement quality despite using lower-energy short pulses
3Object-affected harmful factors
If dithering the interval between pulses to overcome around-the-timebase echoes, then interference from fixed objects is reduced, but the complexity of the system increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating impulse response templates for various distances and storing them in memory before actual measurement. This eliminates the need for complex real-time signal processing and dithering operations, reducing system complexity while maintaining the ability to filter unwanted reflections through simple template comparison
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 approach enables more accurate and reliable tracking of objects by confining unwanted echoes to specific impulse response taps, making them easier to detect and disregard, and providing a better signal-to-noise ratio compared to prior methods, especially in scenarios where unwanted echoes have greater energy than the object of interest.
Implementation Method 1
emit an ultrasonic burst of energy from a transducer, receive the echo bouncing off an object using one or more sensors
Implementation Method 2
receive the echo bouncing off an object
Implementation Method 3
compute the time-delay between emission and reception
Implementation Method 4
the channel impulse response can be calculated from the received signal, using knowledge of the actual emitted signal
Data Source
AI summary
Estimating the impulse response of a channel by providing an initial signal (20); applying a time-shift function to the initial signal (20) to produce a transmit signal (36); transmitting the transmit signal (36); receiving a received signal; calculating an impulse response from the received signal as if the received signal had been produced by the initial signal; and using the impulse response to distinguish between received signals arising from reflections from objects (6) at different ranges.