FMCW Lidar Chirp Segmentation for Variable Range Resolution
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Solution Overview
Problem
Conventional lidar systems in autonomous vehicles require multiple sensor systems to achieve different range resolutions, increasing complexity and cost, as the resolution is invariant across the entire sensing range, making it inefficient for varying object distances.
Innovation Solution
A lidar system employing a piecewise linear modulation scheme with a frequency-modulated continuous wave (FMCW) signal, featuring an up-chirp and down-chirp with multiple linear segments of different slopes, allowing for distance computation with resolutions dependent on the object's distance from the system, enabling granular resolution for close objects and coarse resolution for distant objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional FMCW lidar system uses a single linear modulation scheme, then the system structure is simple, but the resolution is invariant across the entire sensing range, which is inefficient for varying object distances
Solution Approach 1:
The patent divides the sensing range into multiple segments with different resolution requirements. The modulation scheme is segmented into multiple linear segments with different slopes, where each segment corresponds to a specific range interval. This allows the system to apply high resolution (steep slope) for close objects and low resolution (shallow slope) for distant objects, optimizing measurement precision across varying distances while maintaining a single sensor system.
Solution Approach 2:
The patent implements a dynamic modulation scheme where the chirp slope changes over time according to the object distance. The control circuitry dynamically adjusts the modulation parameters based on detected range information, switching between different linear segments with different slopes. This dynamic adaptation allows the system to optimize resolution for the current sensing range, improving measurement precision without requiring multiple fixed sensor systems.
2Measurement precision
If multiple sensor systems are used to achieve different range resolutions, then measurement precision for different distances is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes a single FMCW lidar system multi-functional by enabling it to perform both high-resolution close-range detection and low-resolution far-range detection using different segments of the piecewise linear modulation scheme. The same sensor system adapts its resolution characteristics based on the object distance, eliminating the need for multiple specialized sensor systems while maintaining measurement precision across different ranges.
Solution Approach 2:
The patent changes the modulation parameter (chirp slope) dynamically based on the sensing range. By adjusting the slope parameter of the linear modulation segments, the system achieves different range resolutions with a single sensor. The control circuitry modifies the modulation parameters in real-time, allowing one sensor system to perform the work of multiple sensor systems with fixed resolution characteristics.
3Device complexity
If a single FMCW lidar system is used with invariant resolution, then device complexity is reduced, but measurement precision is insufficient for both close and distant objects
Solution Approach 1:
The sensing range is segmented into multiple intervals, each associated with a specific linear segment of the modulation scheme. The patent divides the overall range into close-range and far-range segments, with each having optimized resolution characteristics. This segmentation allows the single sensor system to achieve high measurement precision for both close and distant objects by applying the appropriate segment resolution to each distance interval.
Solution Approach 2:
The system dynamically adapts its resolution characteristics based on the detected object distance. The control circuitry monitors the range and dynamically switches between different modulation segments with different slopes, ensuring that the appropriate resolution is applied for the current sensing scenario. This dynamic parameter adjustment enables a single sensor system to achieve variable measurement precision optimized for different distances.
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 efficient computation of distances with varying resolutions based on object proximity, reducing the need for multiple sensor systems and enhancing the lidar system's performance in autonomous vehicles by adapting resolution according to the object's range.
Implementation Method 1
frequency modulating and/or phase modulating continuous wave light to form a modulated signal beam
Implementation Method 2
detecting light back-scattered by the collection of scatterers
Implementation Method 3
the FMCW lidar system employs a coherent detection method
Data Source
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AI summary
A lidar system is described herein. The lidar system includes a transmitter that is configured to emit a frequency-modulated lidar signal. The lidar system further includes processing circuitry that is configured to compute a distance between the lidar system and an object based upon the frequency -modulated lidar signal, the processing circuitry configured to compute the distance with a first resolution when the distance is at or beneath a predefined threshold, the processing circuitry configured to compute the distance with a second resolution when the distance is above the predefined threshold, wherein the first resolution is different from the second resolution.