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

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 Th3, a lower data limit threshold Th4, 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.