Optimized vehicle radar operation based on echo signal characteristics

Abstract

The invention discloses a navigation system for a vehicle. The system includes a radar antenna array and a radar operating system. The radar antenna array transmits and receives radar signals and includes a plurality of channels, each channel including transmit and receive functionality. The radar operating system drives the antenna to transmit a radar signal and to receive a reflected signal at least partially from below the vehicle. The radar operating system (i) evaluates the complexity of the signal received through each channel, reduces an operating parameter associated with the channel if the complexity of the signal associated with the channel falls below a threshold, and (ii) periodically locates the vehicle based at least in part on the received radar signal.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 415,826, filed on October 13, 2022, and entitled “Optimized Vehicle-Borne Radar Operation Based on Return-Signal Character,” which is incorporated herein by reference in its entirety. Technical Field

[0002] The present invention relates generally to the operation of vehicle-mounted radar equipment, such as for navigation, and more particularly to optimizing radar systems that use radar reflections from the ground or other surfaces to locate a position. Summary of the invention

[0003] In certain embodiments, a navigation system for a vehicle may include: a radar antenna array configured to transmit and receive radar signals, the radar antenna array may include a plurality of channels, each channel including transmit and receive functions; and a radar operating system for driving the antenna to transmit the radar signal and at least partially receive reflected signals from under the vehicle. The radar operating system may be configured to (i) evaluate the complexity of the signal received through each channel, if the signal complexity associated with the channel decreases below a threshold, reduce an operating parameter associated with the channel, and (ii) periodically locate the vehicle based at least in part on the received radar signals.

[0004] In some embodiments, a signal is identified as complex if it exhibits a signal-to-noise ratio (SNR) that exceeds a threshold. In some embodiments, the threshold is 20 dB. In some embodiments, a channel signal is identified as complex if the overall number of signals received through all channels includes more than a threshold number of unique features, and the channel signals have features whose average or peak value does not exceed a threshold level below the average or peak value of the overall signal. In some embodiments, the threshold level is 3 dB.

[0005] In some embodiments, the operating parameter is a duty cycle. In some embodiments, the duty cycle has a period determined at least in part by signal complexity. In some embodiments, the duty cycle has intervals of full power and no power, and the relative duration of the intervals is determined at least in part by signal complexity. In some embodiments, the radar operating system is configured to close a channel whose signal complexity decreases below a threshold and periodically reopen the channel to evaluate the signal complexity associated with the channel. In some embodiments, if the signal complexity associated with the channel is above the threshold, the operating parameter associated with the channel is increased.

[0006] In certain embodiments, a vehicle navigation method may include the following steps: using a radar antenna array including multiple channels to transmit radar signals to a driving surface and receive radar signals reflected from the driving surface; using a radar operating system to computationally evaluate the complexity of radar signals received through each channel, and if the signal complexity associated with the channel is below a threshold, reducing an operating parameter associated with the channel; and periodically locating the vehicle based at least in part on the received radar signals. In some embodiments, a signal is identified as complex if it exhibits a signal-to-noise ratio (SNR) that exceeds a threshold. In some embodiments, the threshold is 20 dB.

[0007] In certain embodiments, the method may further include the step of identifying unique features associated with the radar signal received from each channel and the overall signal received from all channels, wherein a channel signal is identified as complex if the radar signals received from all channels overall include more than a threshold number of unique features and the channel signal has features with an average or peak value that does not exceed a threshold level below the average or peak value of the overall signal.

[0008] In some embodiments, the step of identifying the unique signature is performed by feature extraction. In some embodiments, the threshold level is 3 dB. In some embodiments, the operating parameter is a duty cycle. In some embodiments, the duty cycle has a period determined at least in part by signal complexity. In some embodiments, the duty cycle includes intervals of full power and no power, and the relative duration of the intervals is determined at least in part by signal complexity.

[0009] In some embodiments, the radar operating system is configured to close a channel whose signal complexity decreases below a threshold and periodically reopen the channel to evaluate the signal complexity associated with the channel. In some embodiments, if the signal complexity associated with the channel is above the threshold, an operating parameter associated with the channel is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The foregoing summary, as well as the following detailed description of the present system, will be better understood when read in conjunction with the appended drawings of exemplary embodiments. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

[0011] In the attached picture: Figure 1 schematically depicts an exemplary surface penetrating radar (SPR) system according to an embodiment of the present invention; Figure 2 Yes Figure 1 Front view of a vehicle with an SPR system. DETAILED DESCRIPTION

[0012] Vehicle navigation can be performed using surface penetrating radar (SPR). This approach provides accurate vehicle positioning regardless of poor weather or visibility, obscured road markings, or other common challenges faced by advanced driver assistance systems. SPR systems can locate a vehicle to within a few centimeters. A typical SPR navigation system includes an array of antenna elements that can be pointed downward toward the ground. Each antenna element has transmit and receive capabilities and corresponds to a separate channel. The channels operate independently, and the surface and subsurface information obtained from all channels is integrated into an SPR image used to locate the vehicle, for example by comparison with a position-indexed reference SPR image.

[0013] In a typical implementation, each channel transmits continuously at full power during part of its transmission cycle. This may not be efficient because not all antenna elements contribute equally to the composite image; for example, the outer channels may not cover ground areas that produce meaningful reflections. The result is excessive power consumption and unnecessary computational burden because low-information signals are processed despite their small contribution to the SPR image and localization.

[0014] Therefore, there is a need for an adaptive approach to operating a vehicle SPR system that customizes the power and computational resources allocated to individual SPR channels based on their contribution to vehicle localization.

[0015] According to an embodiment of the present invention, received signal complexity is used as a criterion for determining the amount of power and / or computing resources used to operate each channel in the SPR array. For example, if the signal complexity is so low that a channel does not contribute meaningfully to vehicle positioning, it can be completely turned off (e.g., for a preset time).

[0016] As used herein, the term "complex signal" refers to a signal that meets a complexity threshold specified by an objective formula or function. For example, a complex signal can be a signal with an average amplitude that exceeds the noise floor or meets a minimum signal-to-noise ratio (SNR). If the signal contains significant spectral content with unique characteristics, the complexity threshold can be set to, for example, 3 dB below the average or peak value in that spectral region. This will be discussed in further detail below.

[0017] Reference Figure 1, a representative mobile SPR system 100 includes an SPR antenna array 102, as described in detail below, which can be installed on the bottom of a vehicle. The SPR antenna array 102 includes one or more antenna elements for transmitting and receiving radar signals. An SPR processor 104 controls the transmission operation of the SPR antenna array 102, receives return radar signals for analysis, and monitors the return signals of the complexity in the SPR antenna array 102, as described below. In various embodiments, the detected SPR signals are processed to generate one or more SPR images of the surface and / or subsurface area along the trajectory of the vehicle on which the antenna array 102 is installed. Suitable SPR antenna configurations and systems for processing SPR signals have been described, for example, in U.S. Patent No. 8,949,024, the entire disclosure of which is incorporated herein by reference.

[0018] For navigation, the SPR image is compared with a previously acquired and stored SPR reference image of a subsurface area that at least partially overlaps a subsurface area of ​​a defined route. The image comparison may be based on a registration process such as correlation, see U.S. Patent No. 8,786,485, the entire disclosure of which is incorporated herein by reference. The position of the vehicle and / or the terrain conditions of the route may then be determined based on the comparison.

[0019] Reference Figure 2 A and attached Figure 2 B, a vehicle 200 which may be any mobile platform or structure includes an SPR system 202, such as Figure 2 B, SPR system 202 transmits SPR signal 204 from multiple SPR transmitting elements. Antenna array 208 illustratively includes 12 linear configurations of spatially invariant transmitting and receiving antenna elements a to 1 for transmitting and receiving radar signals. 12 antenna elements can form 11 channels 1-11. Each channel includes a transmitting and receiving element or a transmitting and receiving pair. In some embodiments, antenna elements are also installed on the front bumper of vehicle 200 to detect guide elements.

[0020] The SPR antenna array 208 may be nominally or substantially parallel to the ground surface 206 and may extend parallel or perpendicular to the direction of travel. The SPR signals 204 may propagate downward from the transmit antenna elements to and / or through the road surface 206 below the vehicle 202. The SPR signals are backscattered upward from the surface 206 or below the surface of the road and may be detected by the receive antenna elements.

[0021] According to various embodiments of the present invention, the SPR processor 104 continuously or periodically analyzes the return signals received through the channels 1-11 and evaluates them according to the complexity criteria. If the criteria are met, the transmission function operates normally and the return signals are processed as described above. However, if the criteria are not met, the SPR processor 104 can allocate less power and computational processing to the weak channels by changing its duty cycle, i.e., cyclically opening and closing at fixed intervals. The absolute and relative duration of the on / off interval can be determined by the degree of gap with the complexity threshold, for example, the larger the gap, the longer the duration of the "off" state relative to the "on" state and / or the longer the cycle period. Optionally, the distance between the points where the complexity criteria are met can be used to control the conversion between the on and off states. For example, the distance between the points can be a function of speed. If the signal complexity associated with the channel is higher than the threshold, the operating parameters associated with the channel can be increased. When the unused channel becomes the "off" state, the channel in the "on" state can have an increased scan rate. Increasing the scan rate of each "on" channel can allow more data to be collected from the surface and / or subsurface area. In some embodiments, a state machine handles the transition of a channel between on and off states.

[0022] In other embodiments, the channel power is proportionally reduced rather than cyclically turned on and off. The total power can be reduced, or the reduction can be applied to a specific frequency or frequency band. When the vehicle 202 stops, the SPR signal 204 can be propagated downward from the transmitting antenna element to and / or through the road surface 206 below the vehicle 202 with a bandwidth of, for example, 100 Hz, and when the vehicle 202 is traveling at a maximum speed (e.g., 100 miles / hour), the bandwidth can be increased to 200 Hz. In some embodiments, the bandwidth can be proportionally changed between 100-200 Hz, between 110-190 Hz, between 120-180 Hz, between 130-170 Hz, and between 140-160 Hz based on the speed of the vehicle 202. Increasing the bandwidth and shortening the interval can allow more data to be collected from the surface and / or subsurface area.

[0023] As mentioned above, a complex signal can be a signal with an average amplitude that exceeds the noise floor or meets a minimum SNR. In decibels (dB), SNR can be defined as 20log 10 (Signal Amplitude / Noise Amplitude). The signal is the reflected echo from an object or set of objects. The noise is the average background amplitude excluding the signal. For example, the thermal noise at the receiver can be given by N=kTB, where N is the power in Watts and k is the Boltzmann constant (1.38x10 -23 J / K), T is the absolute temperature in Kelvin, and B is the transmission bandwidth in Hertz. The minimum SNR can be, for example, 20 dB or higher.

[0024] As previously described, the threshold may alternatively be based on spectral content having unique features. The uniqueness of features may be assessed using conventional feature extraction algorithms (e.g., wavelet-based feature extraction, frequency domain feature search based on genetic algorithms, etc.) to identify high-value features. If the number of high-value features in the map or current SPR image (or both) exceeds a minimum value, the complexity threshold may be set to a value (e.g., 3 dB) below the mean or peak value of the high-value features. In the absence of a sufficient number of high-value features, an SNR criterion may be used, or a decision may be made that the overall signal lacks sufficient features to determine when any specific channel is not contributing enough.

[0025] Other suitable metrics include coefficient of variation, dynamic range, and average power. The coefficient of variation is defined as the ratio of the standard deviation of the signal for each channel to the mean of the signal. The coefficient of variation for each channel should be within minimum / maximum thresholds established based on the expected operating domain and / or similarity to other channels, for example, the thresholds could be set at one or two standard deviations from the mean of all channels combined. Dynamic range is defined as the ratio of the maximum to minimum signal value for each channel. Average power is defined as the average of the absolute values ​​of the channel signals. These metrics should also be within expected minimum / maximum thresholds (e.g., set to one or two standard deviations from the mean of all channels combined) and / or close to expected similarity for other channels.

[0026] The SPR processor 104 may include one or more modules implemented in hardware, software, or a combination of hardware and software. For embodiments where the functionality is provided as one or more software programs, the programs may be written in any of a variety of high-level languages, such as PYTHON, FORTRAN, PASCAL, JAVA, C, C++, C#, BASIC, various scripting languages, and / or HTML. In addition, the software may be implemented in assembly language for a microprocessor resident on a target computer; for example, if the software is configured to run on an IBM PC or PC clone, the software may be implemented in Intel 80x86 assembly language. The software may be included on an article of manufacture, including but not limited to a floppy disk, a jump drive, a hard disk, an optical disk, a tape, a PROM, an EPROM, an EEPROM, a field programmable gate array, or a CD-ROM. Embodiments using hardware circuits may be implemented using, for example, one or more FPGA, CPLD, or ASIC processors. The term "about" or "approximately" is used herein to provide textual support for the exact number following it and the number following the term that is close to or approximate to the number. When determining whether a number is close to or approximates a specifically listed number, a number that is close to or approximates an unlisted number can be a number that provides a substantial equivalent of the specifically listed number in the context in which it is presented. It should be understood that all numerical values ​​and ranges disclosed herein are approximate values ​​and ranges, whether or not "about" is used with it. It should also be understood that, as used herein, the term "about" in combination with a number refers to a value that can be ±0.01% (including the end value), ±0.1% (including the end value), ±0.5% (including the end value), ±1% (including the end value), ±2% (including the end value), ±3% (including the end value), ±5% (including the end value), ±10% (including the end value), or ±15% (including the end value) of the number. It should also be understood that when a numerical range is disclosed herein, any numerical value within the range is also specifically disclosed.

[0027] Those skilled in the art will appreciate that changes may be made to the exemplary embodiments shown and described above without departing from the broad inventive concepts thereof. It should be understood that the embodiments and claims disclosed herein are not limited in their application to the details of the constructions and arrangements of components described in the specification and shown in the drawings. Rather, the specification and drawings provide examples of contemplated embodiments. The embodiments and claims disclosed herein are also capable of implementing other embodiments and can be practiced and executed in various ways.

[0028] Specific features of the exemplary embodiments may or may not be part of the claimed invention, and various features of the disclosed embodiments may be combined. Unless specifically set forth herein, the terms "a", "an", and "the" are not limited to one element, but should be understood to mean "at least one". Finally, unless specifically set forth herein, the disclosed or claimed methods should not be limited to performing their steps in the order written, and those skilled in the art can readily appreciate that the steps may be performed in any practical order.

Claims

1. A navigation system for a vehicle, the system comprising: a radar antenna array configured to transmit and receive radar signals, the radar antenna array comprising a plurality of channels, each channel comprising transmit and receive functions; as well as A radar operating system is configured to drive an antenna to transmit a radar signal and receive a reflected signal at least partially from below the vehicle, wherein the radar operating system is configured to (i) evaluate the complexity of the signal received through each channel, reduce an operating parameter associated with the channel if the signal complexity associated with the channel decreases below a threshold, and (ii) periodically locate the vehicle based at least in part on the received radar signal.

2. The system according to claim 1, wherein: A signal is identified as complex if it exhibits a signal-to-noise ratio (SNR) exceeding a threshold.

3. The system according to claim 2, wherein: The threshold is 20 dB.

4. The system according to claim 1, wherein: A channel signal is identified as complex if the signal received through all channels collectively includes more than a threshold number of unique features and the channel signal has features whose average or peak value does not exceed a threshold level below the average or peak value of the overall signal.

5. The system according to claim 4, wherein: The threshold level is 3dB.

6. The system according to claim 1, wherein: The operating parameter is the duty cycle.

7. The system according to claim 6, wherein: The duty cycle has a period determined at least in part by the signal complexity.

8. The system according to claim 6, wherein: The duty cycle has full power and no power intervals, the relative durations of the intervals being determined at least in part by the signal complexity.

9. The system according to claim 1, wherein: The radar operating system is configured to close a channel whose signal complexity decreases below a threshold and to periodically reopen the channel to evaluate the signal complexity associated with the channel.

10. The system according to claim 1, wherein: The radar operating system is further configured to increase an operating parameter associated with the channel when a signal complexity associated with the channel is above a threshold.

11. A vehicle navigation method, the method comprising the following steps: transmitting radar signals toward a driving surface and receiving radar signals reflected from the driving surface using a radar antenna array including a plurality of channels; computationally evaluating, using a radar operating system, a complexity of radar signals received through each of the channels, and reducing an operating parameter associated with a channel if the signal complexity associated with the channel is below a threshold; and The vehicle is periodically located based at least in part on the received radar signals.

12. The method according to claim 11, wherein: A signal is identified as complex if it exhibits a signal-to-noise ratio (SNR) exceeding a threshold.

13. The method according to claim 12, wherein: The threshold is 20 dB.

14. The method of claim 11, further comprising the step of identifying unique features associated with the radar signal received from each channel and the overall signal received from all channels, wherein a channel signal is identified as complex if the overall received signals from all channels contain more than a threshold number of unique features and the channel signal has features with an average or peak value not exceeding a threshold level below the average or peak value of the overall signal.

15. The method of claim 14, wherein the step of identifying unique features is performed by feature extraction.

16. The method according to claim 14, wherein: The threshold level is 3dB.

17. The method according to claim 11, wherein: The operating parameter is the duty cycle.

18. The method according to claim 17, wherein: The duty cycle has a period determined at least in part by the signal complexity.

19. The method according to claim 17, wherein: The duty cycle has full power and no power intervals, the relative durations of the intervals being determined at least in part by the signal complexity.

20. The method according to claim 11, wherein: The radar operating system is configured to close a channel whose signal complexity decreases below a threshold and to periodically reopen the channel to evaluate the signal complexity associated with the channel.

21. The method according to claim 11, further comprising: An operating parameter associated with the channel is increased when a signal complexity associated with the channel is above a threshold.

Images