Multi-geomagnetic sensor speed measurement system and a speed measurement method using the same

Patent metadata

Field	Value
Publication number	US-11908319-B2
Application number	US-202017427573-A
Country	US
Kind code	B2
Filing date	Jul 30, 2020
Priority date	Jun 11, 2020
Publication date	Feb 20, 2024
Grant date	Feb 20, 2024

Abstract

A multi-geomagnetic sensor speed measurement system comprises a geomagnetic vehicle detection module, a data transmission module, a data reception module and a backend data processing module. When measuring, the geomagnetic vehicle detection module collects the geomagnetic data when the vehicle passes and processes it to obtain temporal data; the backend processing module receives the data for data cleaning; the backend processing module selects the reference sensors and opens individual time windows; the backend processing module processes the temporal data based on the number of temporal data in the time window; in the case of duplicate-detection, a measurement threshold δ is set and the temporal data is merged based on the threshold δ; in the case of mis-detection, the data is interpolated to make up for the mis-detection; based on the alignment result, a minimum variance method is used to estimate the speed of the vehicle.

First claim

The invention claimed is:

1. A speed measurement method using a multi-geomagnetic sensor speed measurement system,
wherein the multi-geomagnetic sensor speed measurement system comprises a geomagnetic vehicle detection module, a data transmission module, a data reception module, and a backend data processor,
wherein the geomagnetic vehicle detection module is wired to the data transmission module, the data transmission module is wirelessly connected to the data reception module, and the data reception module is wired to the backend data processor,
wherein the multi-geomagnetic sensor speed measurement system comprises number M of the geomagnetic vehicle detection modules, and the geomagnetic vehicle detection modules are deployed in groups along a roadside, wherein every two or more of the geomagnetic vehicle detection modules are grouped together,
wherein each geomagnetic vehicle detection module comprises a group of geomagnetic sensors and a controller, the geomagnetic sensors are used to collect magnetic field data on a road surface, adjacent geomagnetic sensors are spaced by d meters, the controller is used to receive data collected by the geomagnetic sensors in order to analyze temporal data used by vehicles passing the geomagnetic vehicle detection module and to transmit the temporal data to the data transmission module at intervals, the intervals being set to x seconds or y minutes based on an actual demand,
wherein the data transmission module receives the temporal data using a wireless transmitter and sends it to the data reception module in wireless communication,
wherein the data reception module receives the temporal data reported by the data transmission module using the wireless transmitter and transmits it to the backend data processor,
wherein the backend data processor is used to process the temporal data, the processing comprising aligning acquired data, corresponding the temporal data to a corresponding vehicle and calculating a speed of the vehicle as it passes the group of the geomagnetic sensors based on the aligned data, and
wherein, the speed measurement method comprises:
1) collecting geomagnetic data as the vehicle passes using the geomagnetic vehicle detection module for threshold detection processing to obtain temporal data which comprises data on a time spent for the vehicle to approach and leave the geomagnetic sensor, the step of collecting geomagnetic data as the vehicle passes using the geomagnetic vehicle detection module for threshold detection processing comprising:
1a) collecting corresponding geomagnetic data in real time using the geomagnetic sensors in the geomagnetic vehicle detection module to send to the controller in the geomagnetic vehicle detection module; and
1b) comparing the collected data with a set threshold value using the controller of the geomagnetic vehicle detection module to determine whether the vehicle is approaching or leaving the geomagnetic sensor and to obtain the temporal data for the vehicle approaching or leaving the geomagnetic sensor;
2) merging the temporal data into a group of data using the geomagnetic vehicle detection module, the merged temporal data is sent to the data reception module by means of the data transmission module which sends the temporal data to the backend processor;
3) performing data cleaning of the received temporal data using the backend processor, the step of performing data cleaning of the received temporal data using the backend processor comprising:
3a) removing data that is clearly abnormal based on an upper limit threshold Th 3 , a lower data limit threshold Th 4 , and a data increase threshold Th using the backend processor; and
3b) determining whether there is a situation where multiple data are generated when a single vehicle passes, i.e. duplicate-detection, based on a data increase threshold Th (b) using the backend processor for every two adjacent temporal data, and deleting this part of the data when duplicate-detection occur;
4) regrouping of temporal data after data cleaning using the backend processing module processor;
5) selecting a reference sensor for a same group of temporal data using the backend processor and creating individual time windows;
6) processing the temporal data accordingly based on the number of temporal data in the time window using the backend processor;
7) setting a measurement threshold δ when there are multiple temporal data corresponding in the time window, and merging the temporal data based on the measurement threshold δ;
8) confirming that a mis-detection has occurred when there is no temporal data corresponding in the time window, i.e. the vehicle has passed by but not been detected, and compensating the mis-detection data by interpolation;
9) determining that the data is correct at this time when there is a temporal data correspondence in the time window, and determining whether each group of data has been data aligned after getting a data alignment result according to step 5) to step 8), if yes, executing step 10), if not, executing step 5); and
10) estimating the speed of vehicle based on alignment results using a minimum variance method to calculate the speed of the vehicle.

2. The speed measurement method according to claim 1 , wherein, in step 1a), real-time collection of corresponding geomagnetic data using the geomagnetic sensor in the geomagnetic vehicle detection module comprises collecting the geomagnetic data caused by changes in magnetic flux output to the controller of the geomagnetic vehicle detection module when a vehicle passes the geomagnetic sensor corresponding increase or decrease in value.

3. The speed measurement method according to claim 1 , wherein, in step 1b) the controller of the geomagnetic vehicle detection module is used to compare the collected data with a set threshold value to determine whether the vehicle is approaching or leaving the geomagnetic sensor and to obtain the temporal data for the vehicle approaching or leaving the geomagnetic sensor, by the following steps:
1b1) comparing the geomagnetic data from the geomagnetic sensor with a high geomagnetic data threshold Th 1 ,
if the geomagnetic data from the geomagnetic sensor is above the high geomagnetic data threshold Th 1 , then it is continuously determined whether incoming data is above the high geomagnetic data threshold for a period of time Δt; if yes, it is recorded by a timer and then step 1.4) is performed, if not, it is determined to be interference from an adjacent reverse lane and no recording is performed; and
if the geomagnetic data from the geomagnetic sensor is below the high geomagnetic data threshold Th 1 , then it is determined that the vehicle is not close to the geomagnetic sensor and no processing is performed; and
1b2) comparing the geomagnetic data from the geomagnetic sensor with a low geomagnetic data threshold Th 2 ;
if the geomagnetic data from the geomagnetic sensor is below the low geomagnetic data threshold Th 2 , then continue to determine if the incoming data is below the low geomagnetic data threshold for a period of time Δt; if yes, it is recorded by a timer, if not, it is determined that the vehicle has not left a detection area of the geomagnetic sensor and no recording is performed; and
if the geomagnetic data from geomagnetic sensor is higher than the low geomagnetic data threshold Th 2 , the vehicle is considered to not having left the geomagnetic sensor and continues to wait until the geomagnetic data from the geomagnetic sensor is below the low geomagnetic data threshold Th 2 , and
wherein the high geomagnetic threshold Th 1 , the low geomagnetic threshold Th 2 and the time threshold Δt are based on the results of actual waveforms tested in the field.

4. The speed measurement method according to claim 1 , wherein, in step 3) the data cleaning of th

Assignees

• Univ Xidian

Inventors

• Li Changle
• Chen Zhiqiang
• Mao Guoqiang
• Hui Yilong
• Chen Yuexu

Classifications

• G08G1/052 Primary

  with provision for determining speed or overspeed {(speed measuring in general G01P)} · CPC title

• G08G1/042 Primary

  using inductive or magnetic detectors · CPC title