Time-of-flight sensor ambiguity resolution with coded pulses
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Solution Overview
Problem
Existing distance measurement technologies face challenges in resolving ambiguities caused by multiple targets, distance jumps, and overlapping pulses, leading to difficulties in accurately determining the propagation time and distance in environments with complex scenarios.
Innovation Solution
A distance measuring device with a transmitter, receiver, counter unit, and control and evaluation unit that employs coded transmission signals, direct decoding of received signals, and a data buffer to calculate transit time, using techniques such as interval modulation, amplitude modulation, and burst modulation to enhance signal robustness and resolve ambiguities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pulse spacing is reduced to increase measuring rate, then productivity is improved, but ambiguity occurs when multiple pulses are on their way simultaneously
Solution Approach 1:
The patent applies preliminary action by assigning a unique code to each transmitted pulse before it is sent. This coding is done in advance using a code generator that creates distinct identification sequences for each pulse. When pulses are received, the code assignment unit matches the received code with the transmitted code to determine which received pulse corresponds to which transmitted pulse, thereby resolving ambiguity even when multiple pulses are simultaneously in flight.
2Productivity
If transmission frequency is increased to improve measuring rate, then productivity is improved, but pulse wrapping occurs causing pulse order changes
Solution Approach 1:
The patent assigns unique codes to transmitted pulses in advance before transmission. This preliminary coding allows the system to handle high transmission frequencies without pulse wrapping issues, as each received pulse can be unambiguously identified by its unique code regardless of arrival order.
Solution Approach 2:
The patent implements feedback by having the code assignment unit continuously monitor received pulses and match them with transmitted pulse codes. This feedback mechanism detects pulse wrapping conditions and corrects the pulse order identification by comparing received codes with the sequence of transmitted codes, ensuring accurate distance measurement even at high transmission rates.
3Measurement precision
If unambiguous distance measurement is achieved through coding methods, then measurement precision is improved, but latency time increases
Solution Approach 1:
The patent applies preliminary action by pre-generating and storing unique codes for each pulse in a code generator. This preparation is done in advance, allowing the system to quickly match received pulses with transmitted pulses using simple code comparison rather than complex post-processing, thereby reducing latency while maintaining unambiguous identification.
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
The solution provides robust evaluation of signals, enabling accurate distance measurement even in complex scenarios with multiple targets and distance jumps, by directly decoding received pulses and associating them with transmission pulses, thus calculating absolute distances without relying on coding-dependent tables or prior assumptions.
Implementation Method 1
sending pulsed electromagnetic radiation, such as laser light, onto a target to be measured
Implementation Method 2
receiving the reflection coming back from the target
Implementation Method 3
the distance to the target being determined based on the propagation time of the pulses
Data Source
Figure 1~2
Figure 3a~3b
Figure 3c~3d
AI summary
The invention relates to a distance measuring device for measuring the transit time of electromagnetic signals, comprising at least: a transmitter (2) for sending coded transmission signals (6) according to a pattern specified by an encoder (8), a receiver (3) for detecting the signals reflected by at least one object (12) as received signals (7), a counter unit (17) with a time counter for writing time counter values generated by the transmission of the transmission signals (6) and the reception of the received signals (7) into at least one register, and a control and evaluation unit (9) for calculating the transit time by decoding the received signals (7) and reading the register of the counter unit (17).