Patent ID: 11908319
Assignee: XIDIAN UNIVERSITY
Field: Control (Instruments)
Classification: CPC G | IPC G

Claim 2:
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 Th1,
if the geomagnetic data from the geomagnetic sensor is above the high geomagnetic data threshold Th1, 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 Th1, 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 Th2;
if the geomagnetic data from the geomagnetic sensor is below the low geomagnetic data threshold Th2, 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 Th2, 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 Th2, and
wherein the high geomagnetic threshold Th1, the low geomagnetic threshold Th2 and the time threshold Δt are based on the results of actual waveforms tested in the field.