With the rapid development of the national economy, the logistics and freight transportation industry has penetrated into every corner of people's lives. Driven by commercial interests, the phenomenon of overloaded and over-length freight vehicles has become increasingly frequent, causing significant damage to road facilities, especially expressway facilities. In particular, the frequent occurrence of major traffic accidents is mostly attributed to the overloaded and over-length operation of freight vehicles. close. In order to effectively manage the overloading and oversize of trucks, dynamic highway vehicle automatic weighing equipment has been widely applied to both ordinary roads and expressways. Move
The dynamic vehicle automatic weighing equipment (hereinafter referred to as "dynamic vehicle scale") serves as the core equipment for highway over-limit control and freight weight-based toll collection. Its weighing accuracy and stability directly affect the efficiency of traffic management and social fairness and justice. Due to the influence of the working principle, different types of dynamic vehicle scales have differences in weighing accuracy. Depending on the different application scenarios, appropriate dynamic vehicle scale products should be selected.
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Classification of dynamic vehicle scales
Common dynamic vehicle scales are divided into the following types: whole vehicle dynamic vehicle scale, axle (axle group) weight dynamic vehicle scale, curved plate dynamic vehicle scale, quartz crystal dynamic vehicle scale, flat plate modular dynamic vehicle scale, modular dynamic vehicle scale, and narrow strip dynamic vehicle scale, etc.
Among many dynamic vehicle scales, according to the weighing principle, they can be classified into two major categories: one is whole vehicle weighing, represented by whole vehicle type, flat plate modular type, and modular type; the other is axle (axle group) weight weighing, represented by axle weight type, curved plate type, quartz crystal type, and narrow strip type.
Axle (axle group) weight weighing type dynamic vehicle scales have simple construction, short installation period, and lower project implementation costs. However, they have poor accuracy and low reliability, and most of the time cannot be used as the basis for highway law enforcement systems, resulting in significant law enforcement disputes. Whole vehicle weighing type scales have a larger construction engineering volume and longer period, but they have high weighing accuracy and good system stability, and are particularly suitable for use in law enforcement situations such as over-limit stations and off-site law enforcement.
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2.1 
Working principle and technical characteristics of dynamic vehicle scales
System composition 1
The typical dynamic vehicle scale system consists of: carrier (strain type/piezoelectric type/sapphire crystal type/bent plate type), vehicle type detection, vehicle separation device (grating/ coil), weighing system (data processing center), license plate recognition, image monitoring, outline detection, management computer, background server, LED display screen, sound and light alarm, and outdoor speakers, as shown in Figure 1. 2.2 
Dynamic weighing principle
When a vehicle passes over the carrier, the sensor is triggered, the vehicle type detection and vehicle separation device are activated, the weighing system begins waveform collection, and the vehicle axle weight (axle group weight) / vehicle total weight is calculated. Combined with the vehicle type information and vehicle separation device information, the vehicle total weight, speed and vehicle type are obtained, and the data is sent to the management computer. The computer matches the vehicle weight information with the license plate information, outline information and image information for this vehicle and uploads it to the background server. The computer simultaneously sends the processing results to the barrier machine, LED display screen, sound and light alarm and outdoor speakers to execute relevant commands. Throughout the process, the axle (axle group) weight type dynamic vehicle scale obtains the total weight of the vehicle by detecting the axle (axle group) weight and accumulating it, while the vehicle total weight type dynamic vehicle scale obtains the vehicle total weight by directly weighing the vehicle. 2.3 Technical features
During the dynamic weighing process, due to factors such as vehicle vibration, instrument vibration, installation quality of the instrument, and vehicle driving conditions, the instantaneous fluctuation of the dynamic load is significant. At the same time, there is also the interference of multi-axis coupled vibration. The accuracy of dynamic weighing is affected by multiple factors in combination. Therefore,
During the data processing, particular attention is paid to eliminating the influence of interfering factors on the data, ensuring the accuracy of weighing.
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3.1
Analysis of Common Problems
Large dynamic weighing error
Problem description: The weighing results of the same vehicle vary significantly, and the deviation from the actual static weighing value exceeds the allowable range.
Possible causes:
High vehicle speed: The vehicle does not travel at a constant speed (usually 5km/h to 10km/h) through the weighing area;
Uneven road surface: The uneven road surface in the weighing area causes vehicle vibration;
Vehicle vibration or sudden acceleration/braking: The vehicle's vibration or sudden acceleration/braking leads to abnormal distribution of axle weight;
Sensor response delay: The sampling rate of the weighing sensor is insufficient, unable to collect the original data that changes rapidly during weighing. Solution:
Install减速bumps or LED speed limit indicators to inform drivers to slow down and pass the scale platform at a constant speed；
Repair the road surface in the weighing area to ensure its smoothness (the recommended error should be ≤ 3mm/m)；
Optimize the algorithm and adopt multi-sensor data fusion technology to compensate for vibration interference；
Use high-speed sampling sensors (such as quartz sensors or high-speed strain gauges).
The problem of poor repeatability of dynamic vehicle scales is particularly manifested in the use of axle (axle group) weighing type dynamic vehicle scales. During the vehicle's movement， it is affected by road smoothness， vehicle acceleration and other factors， and the axle weight of the vehicle changes constantly and significantly， resulting in the inability to trace the source of the axle weight and poor repeatability after repeated weighing， with a large total weight error. This
The large error of the weighing equipment mainly depends on the weighing principle. Through other means (such as data processing), this error can only be reduced to a limited extent. The vehicle-scale type dynamic truck scale does not pay much attention to the axle weight of the vehicle. It obtains the vehicle data by packaging the axle weights. During the repeated weighing of the vehicle, the axle weights of the vehicle may vary, but the total weight will not have a large error, and the repeatability is good. This means that the axle (axle group) weight measurement type weighing equipment of the vehicle-scale type dynamic truck scale has more advantages in the total weight measurement of the vehicle.
3.2
Vehicle Separation and Axle Number Recognition Errors
Problem Description: The system misjudges the number of vehicle axles (such as identifying a trailer as two vehicles); it is unable to separate adjacent vehicles when the vehicle distance is too close.
Possible Causes:
Trigger Coil Fault: The ground sensing coil is damaged or has insufficient sensitivity;
Light/Wind Weather Interference: Strong light, rain, snow causing misjudgment of the light curtain or camera;
Software Logic Defect: The axle spacing algorithm does not consider special vehicle types (such as multi-axle trailers). Solution:
Regularly check the conductivity and insulation of the anti-theft coil, and replace the aging coils;
Replace traditional optical components with infrared light curtains or anti-interference radars;
Update the software algorithm and add a special vehicle database (such as long-wheelbase and suspended axle vehicles);
In terms of axle number recognition, if the vehicle weighing instrument with independent axle identifier has the same axle number recognition rate as the axle (axle group) weighing instrument, the axle number recognition rate of the vehicle weighing instrument using software to identify the axle number may be lower.
3.3 
Abnormal sensor signals
Problem manifestation: The instrument shows data jumps or no signal; some sensors' output values are significantly deviated from the normal range.
Possible causes:
Cable damage or oxidation of the connector: Line faults caused by vehicle rolling or rain erosion;
Electromagnetic interference (EMI): Interference from nearby high-voltage equipment or frequency converters in the signal transmission;
Sensor overload damage: Internal strain gauges of the sensor break due to the impact of overloaded vehicles. Solution:
Use armored shielded cables, and seal the connection points with waterproof sealant;
Install magnetic ring filters or isolation transformers, etc.;
Add buffering devices (such as rubber pads) to disperse the impact force, replace large range sensors;
Axle load type, flat panel modular type and modular type dynamic balancers only need to replace the damaged sensors when replacing the sensors, which is convenient and has a lower cost. The sensors of the bent plate type, quartz crystal type and narrow strip type dynamic balancers are mostly integrated modules, and the entire modular replacement is required, and the installation cost is higher. 3
At a higher level.
3.4 
Poor environmental adaptability
Problem manifestations: The sensor's sensitivity decreases in low-temperature environments; weighing data drifts in rainy and snowy weather.
Possible causes:
Temperature drift: Insufficient temperature compensation for the sensor, resulting in output deviations in low/ high temperatures;
Water accumulation and ice formation: Water accumulation in the scale platform gap freezes, affecting the smooth passage of vehicles;
Salt fog corrosion: In coastal areas, salt erosion of the sensor's housing or circuit. Solution:
Select sensors with a wider temperature range (such as 40℃ - 80℃) and enable the automatic temperature compensation function;
Design drainage channels or heating devices to prevent freezing. Use stainless steel housing sensors and regularly apply anti-rust agents.
3.5 
Data communication and system integration failures
Problem manifestations: Weighing data cannot be uploaded to the overload control platform;联动 failure with license plate recognition system and video surveillance.
Possible causes：
Incompatible communication protocols： (RS485/Ethernet interface protocols do not match the upper computer). Network delay or disconnection (affected by weather or distance in fiber optic/4G transmission)；
Software version conflicts： The weighing system is incompatible with the database version. Solution:
Configure protocol converters (such as Modbus to TCP/IP);
Employ dual-link redundant network (wired + wireless backup);
Maintain a unified software version and regularly upgrade system firmware.
3.6 
Mechanical structure damage
Problem manifestations: Scale body deformation or cracking; installation foundation subsidence leading to
tilting of the weighing area.
Possible causes:
Overloaded vehicle crushing: After the scale body is installed, it should frequently bear loads exceeding 25% of the maximum scale capacity (such as vehicles weighing over 100 tons);
Insufficient strength of the foundation concrete: Not poured with a grade above C40 or improperly maintained. Solution:
Add a dynamic weighing pre-check system to intercept overloaded vehicles in advance;
Re-lay the foundation and add steel mesh to enhance its compressive strength.
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Key points and precautions for daily maintenance
Weekly inspection: Clean the surface of the scale platform of mud and debris, check the sensor
Check if the cable protection layer is intact, check the sensitivity of the ground sensing coil and the light curtain
And the integrity of other ground-related devices.
Monthly maintenance: Calibrate the sensor zero point as needed, check the clearance of the limiters (1-3mm) as needed
Back up system parameters and vehicle type data base.
Annual overhaul: Conduct a comprehensive inspection of the foundation levelness, repair cracks, replace aged sensors or cables.
Overload control station: Need to be linked with license plate recognition and LED screen in real time to ensure rapid interception of overloaded vehicles.
Toll station: Need to match the ETC system to avoid a decrease in traffic efficiency due to weighing delays.
Mining area / port: For high dust environment, add air tightness protection and automatic dust cleaning devices.
5  Conclusion
Dynamic vehicle scales, as measurement equipment in the field of road transportation, their operational stability and weighing data accuracy directly affect over-limit control, logistics freight efficiency, and traffic safety. Through the analysis of common problems, it can be seen that the equipment performance is influenced by various external environmental factors, mechanical structures, weighing sensors, data communication, and system integration failures. In the future, continuous improvements are needed in the following aspects:
(1) Technological innovation. Develop sensors and weighing controllers with higher precision and good dynamic performance, so that they can adapt to various environmental factors, and apply new technologies such as dynamic weighing algorithms to improve the real-time and reliability of dynamic weighing.
(2) Standard improvement. Promote the update of industry norms, clearly defining the requirements for equipment installation, calibration, and usage cycles.
(3) Promotion of new product application. Promote the selection and use of dynamic weighing equipment with high accuracy, high throughput efficiency, and ease of maintenance.
With the deep integration of intelligent and digital technologies, the dynamic vehicle scale weighing system will develop towards higher integration and automation, providing solid support for the freight logistics industry and intelligent transportation.