Parking space state judgment method of geomagnetic vehicle detector

Abstract

The invention discloses a parking space state judgment method of a geomagnetic vehicle detector. The method includes the following steps that: a three-axis (XYZ) magnetoresistive sensor with a temperature compensation function is adopted; when the sensor is installed, the Z axis of the sensor is perpendicular to the ground, the Y axis and X axis of the sensor point to the adjacent edges of a parking space respectively; two axial directions (i.e. horizontal axial directions) of the Y axis and X axis are set as auxiliary reference axes and are used for monitoring the dynamic perturbation value of a magnetic field; the axial direction (i.e. vertical axial direction) of the Z axis is set as a main reference axis and is used for judging the static variation amount of the magnetic field; and a horizontal surface magnetic field dynamic perturbation value monitoring and vertical axial direction magnetic field strength variation amount determination method is used in combination to judge whether the parking space is unoccupied or unoccupied. According to the method, whether vertical axial direction magnetic field strength variation amount is larger than an uplink threshold value or is smaller than a downlink threshold value is judged, and a Mealy state machine model is used to judge the current status of the parking space. With the method adopted, interference on parking space judgment of the geomagnetic vehicle detector caused by adjacent parking spaces, surrounding passing vehicles and sensor temperature drift and background magnetic field drift can be effectively inhibited, and the problem of frequently jump of the state of a parking space can be solved.

Description

technical field [0001] The invention relates to a parking space state judging method of a geomagnetic vehicle detector, belonging to the technical field of geomagnetic parking space detection. Background technique [0002] The geomagnetic vehicle detector is a device for determining the status of parking spaces by monitoring geomagnetic changes. Due to its high detection sensitivity, low power consumption, buried installation and wireless communication, it does not require wiring and is not easily damaged by vehicle rolling. , so it is currently the most popular parking space detection method applied to parking space state detection in open-air parking lots. However, in the actual use of geomagnetic parking space detection, there are often the following problems that affect the detection accuracy of the parking space state: [0003] The first is the temperature drift of the sensor. Due to the large temperature difference in the outdoor environment, there is a temperature dr...

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Problems solved by technology

[0004] The second is the problem of the geomagnetic disturbance of the adjacent parking space. Since the geomagnetic detector is extremely sensitive to the disturbance of the surrounding magnetic field, when the vehicle is parked, it will cause a certain disturbance to the magnetic field of the adjacent parking space. When the disturbance exceeds a certain threshold, the sensor may be damaged. Misjudgment, usually the means to solve this technical problem is to adopt a benchmark or threshold self-calibration scheme under the state of an empty parking space (such as Chinese patent CN104867355A). Carry out self-calibration, when the parking space is occupied, the magnetic field disturbance caused by parking in the surrounding parking spaces cannot be corrected; another method is to use the collaborative decision-making method of adjacent parking spaces, and synthesize the current parking space status by analyzing the parking status of the surrounding parking spaces Judgment (Chinese patent CN103544848A), this method needs to set up the topological relationship diagram of all adjacent detection vehicles in the parking lot, and combine the detection data of the detectors of the adjacent parking spaces for judgment, the algorithm is relatively complicated, and the practicability is not strong

[0005] Finally, there is the problem of frequent jumps in the determination results of the parking space status. There are two factors causing this problem: First, the vehicle passes the vehicle detector without stopping, causing the parking space status to change from "no car" → "vehicle" → "no car" Second, due to various reasons, the magnetic field near the vehicle detector changes, so that the magnetic field collection value oscillates near the judgment threshold, and frequent and continuous parking space state "jumps" occur

Usually the means to solve this technical problem is to use multiple judgments or window filtering algorithm. This algorithm can effectively solve the jump of the parking space state caused by the first phenomenon, but it cannot cure the jump of the parking space state caused by the second situation, and the number of judgments Or if the number of filters is set too small, the above problems cannot be solved, and if it is set too large, the real-time performance of the parking space status judgment will be reduced