Pseudo-Random Ultrasonic Position Detection for Multi-Body Tracking
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Solution Overview
Problem
Existing ultrasonic position detection systems struggle to accurately and stably detect the positions of multiple moving bodies, especially when the propagation distance is long, due to interference between direct and reflected waves, and the inability to distinguish between multiple transmitters.
Innovation Solution
A position detection system that uses pseudo-random sequence modulation for ultrasonic signals, with high self-correlativity and low cross-correlativity, and employs multiple ultrasonic reception units to calculate the propagation time and position of each moving body by filtering and correlating the received signals with model waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the ultrasonic detection range is increased to cover larger drawing areas, then the propagation time of ultrasonic increases, but the detection interval T must be set longer which reduces the number of moving bodies that can be detected simultaneously
Solution Approach 1:
The patent changes the parameter of ultrasonic signal waveform from a simple burst shape to a pseudo-random sequence modulated waveform. This parameter change allows the use of correlation processing which dramatically improves the precision of arrival time detection, enabling accurate position detection even when multiple ultrasonic signals overlap in time, thus allowing more moving bodies to be detected simultaneously in large detection ranges.
Solution Approach 2:
The patent introduces correlation processing as an intermediary method between signal reception and position calculation. By using correlation between the received ultrasonic signal and a reference pseudo-random sequence, the system can precisely identify signal arrival times even in the presence of multiple simultaneous transmissions, effectively mediating the conflict between large detection range and multi-target capability.
2Length of stationary object
If the propagation distance is long, then the propagation time increases requiring longer detection intervals, but this prevents accurate detection of multiple moving bodies at the same time
Solution Approach 1:
The patent applies parameter change by transforming the ultrasonic signal from a simple burst waveform to a pseudo-random sequence modulated waveform. This enables the use of correlation processing which provides precise arrival time detection even over long propagation distances where multiple signals may overlap, thereby maintaining measurement precision despite increased propagation time.
Solution Approach 2:
The patent implements preliminary action by pre-modulating the ultrasonic signal with a pseudo-random sequence before transmission. This preliminary modulation embeds unique identification characteristics in each transmitter's signal, allowing the receiver to distinguish and accurately measure signals from multiple transmitters even when they arrive simultaneously after long propagation distances.
3Quantity of substance
If multiple moving bodies transmit ultrasonic signals simultaneously, then the detection of direct waves becomes difficult due to interference with reflected waves and signals from other transmitters
Solution Approach 1:
The patent changes the waveform parameter from a simple burst signal to a pseudo-random sequence modulated signal. This parameter change enables correlation processing which can distinguish direct waves from reflected waves and signals from other transmitters by comparing the received signal with the known transmitted pseudo-random sequence, thereby maintaining detection stability when multiple moving bodies transmit simultaneously.
Solution Approach 2:
The patent applies segmentation by assigning different pseudo-random sequences to different transmitters. This segments the overall signal environment into distinguishable components, allowing the receiver to separately identify and process signals from each transmitter even when they transmit simultaneously, thus preventing interference and maintaining reliable detection.
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
Enables precise and stable detection of multiple moving bodies' positions even at long propagation distances, avoiding interference and ensuring accurate identification of direct waves.
Implementation Method 1
an ultrasonic signal transmitted from an electronic pen to a receiver will be about 2 m at the maximum and a propagation time will be on the order of 7 ms
Implementation Method 2
a matched filter obtains correlation between a reception signal and a transmission signal to detect a peak of an output of the matched filter and calculate a propagation time of a sound wave by a peak time
Data Source
AI summary
A position detection system, includes at least one moving body (MB) including a transmission device simultaneously emitting a trigger signal indicating transmission timing and an ultrasonic signal obtained by modulating a signal of a frequency as a reference by pseudo random sequence data having high self-correlativity, and a reception device detecting MB position. The reception device includes ultrasonic reception units, a unit calculating a correlation value between a waveform of the ultrasonic signal and a model waveform of the pseudo random sequence, a unit subjecting the waveform of the ultrasonic signal and the model waveform to calculate a correlation value between the two waveforms, a unit calculating a propagation time of each ultrasonic to arrive at each of the ultrasonic reception units from trigger signal reception to correlation peak detection, and a unit calculating MB position from the ultrasonic propagation time and the interval length between the ultrasonic reception units.