Replacing Inductive Loop Vehicle Detectors at Entry Gates with 2D LiDAR Sensors
The Current State and Challenges of Inductive Loop Vehicle Detectors
Inductive loop vehicle detectors have been widely adopted by traffic management authorities. These detectors work by embedding a wire loop, generally rectangular in shape, beneath the road surface. The size of the loop can be customized according to application needs. This loop forms a detection zone, and as vehicles enter, remain in, or exit the zone, the ferromagnetic and metallic properties of the vehicle alter the inductance of the loop. The change in inductance can be easily detected using frequency or reactance methods, accurately reflecting the vehicle's presence and movement.
Inductive loop vehicle detectors are relatively easy to understand and use, and they offer a high level of accuracy in vehicle detection. This has ensured their continued importance in the market. However, after two to three years of installation, these detectors tend to fail more frequently, and the high cost of replacing them becomes a significant drawback. Additionally, after winter, the aging process of the loop accelerates, and there is no economically viable solution to this issue. The replacement of inductive loops requires substantial construction work, which can greatly disrupt traffic, prompting the exploration of alternative vehicle detection methods.
Entry Gate Vehicle Detection Solution: 2D LiDAR Sensors
A 2D LiDAR sensor system for gate control consists of two components: the "trigger radar" and the "anti-collision radar." The trigger radar is used to monitor the arrival of vehicles, activating the capture camera and raising the automatic gate arm. The anti-collision radar monitors the departure of vehicles, controlling the gate arm's movement to prevent incidents of the gate hitting vehicles or people.
Working Principle of 2D LiDAR for Lane Entry and Exit
Laser Scanning:
2D LiDAR emits laser pulses and calculates the distance to objects by measuring the time it takes for the pulses to reflect back to the sensor (known as time of flight). This scanning typically occurs within a single plane, allowing the LiDAR to capture a profile of the environment within that plane.Object Detection:
When a vehicle or pedestrian enters the laser’s scanning range, the LiDAR system detects the presence of the object and updates its position and distance information in real-time. Through continuous laser pulse scanning, the LiDAR can accurately track the movement of the target object.Data Processing:
The LiDAR system transmits the collected distance and position data to a control system, which can further process this information to identify the type of target object (e.g., vehicle or pedestrian) and determine its direction and speed.Triggering Control:
At lane entry and exit points, the LiDAR system can be used to control the gate operation. For example, when a vehicle is detected approaching the entry or exit, the LiDAR system triggers the appropriate action, such as raising the barrier or capturing the license plate. Similarly, after the vehicle passes through, the system ensures the barrier closes safely to prevent collisions.Environmental Adaptability:
Since LiDAR uses infrared lasers, the system can maintain high accuracy under various lighting conditions (e.g., day, night, strong light, or backlight). This makes the LiDAR system particularly effective in outdoor applications, such as parking lots and toll booths.Installation Recommendations for 2D LiDAR Sensors at Entry Gates
1. LiDAR sensor installation height: The lower edge should be 0.6 meters above the road surface.
2. "Anti-collision radar" installation: Install it on the side of the gate control box in the direction of the gate arm's movement, facing the lane, using a wall-mounted setup.
3. "Trigger radar" installation: Install it at a horizontal distance of about 4 meters from the license plate camera (the trigger distance can be adjusted between 3.5 and 5 meters as needed). It can be wall-mounted on the entry control box or installed on a dedicated post.
4. Mounting orientation: The anti-collision radar should be mounted longitudinally, while the trigger radar should be mounted transversely.
5. Barrier installation: If a barrier is installed on the outer side of the lane, ensure it is securely fixed. Avoid using movable or easily displaced devices like retractable belts or traffic cones.
Related Laser Scanning Radar
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Sensing range 20m, A technique that uses a laser beam to measure distance and create detailed maps of objects and environments.
LD-100R is mainly designed for reflector-based AGV navigation, also used for scene measurement applications.
