1 Introduction
In northern my country, snowfall is common in winter, especially in some high-altitude and cold regions where the snowfall period can last for 5-6 months. Accumulated snow poses significant hazards to roads, airports, and people's travel, often causing traffic disruptions and accidents. Therefore, quickly and effectively clearing snow after it falls to ensure smooth road traffic has always been a challenging task.
There are two traditional methods of snow removal: one is manual removal. The biggest drawback of manual snow removal is its low efficiency and the fact that it must be done during the day, which seriously affects traffic and causes great inconvenience to passing vehicles and pedestrians. The other is spreading de-icing agents. Salt is the most economical and effective de-icing agent, but if the spreading operation is not properly controlled and excessive salt is spread, it will damage plants, pollute groundwater, harm the environment, waste resources, and increase economic losses[1].
With the development of society and the continuous improvement of mechanization technology, people urgently need a high-performance, highly automated machine to replace the traditional snow removal method. The development of multi-functional snow removal vehicle was proposed in this context. It adopts a vehicle speed navigation automatic spreading control system, which overcomes the shortcomings of the traditional snow melting spreading vehicle that uses single-level or multi-level speed adjustment, which is inaccurate and inefficient. The intelligent spreading system controller proposed in this paper can be said to be the "brain" of the multi-functional snow removal vehicle. It is under the control of this controller that the snow removal vehicle can automatically complete the spreading operation according to the regulations. Therefore, the intelligent spreading system controller plays an important role in promoting the development of new multi-functional snow removal vehicles [2].
2 Dispensing System
The spreading system uses a digital control chip as its core and electro-hydraulic controls the spreading mechanism, enabling the snowplow to evenly spread the material onto the road surface according to a preset spreading amount. The entire system consists of two parts: a controller and a hydraulic mechanism. The controller is responsible for the system's operation, while the hydraulic mechanism is the system's actuator, responsible for spreading the material.
The system has two operating modes: automatic and manual, each used for different work scenarios. In automatic mode, the control system automatically updates the parameters of the hydraulic motor based on changes in vehicle speed, spreading width, and other parameters to meet the set spreading volume requirements. This mode is used for normal spreading conditions. In manual mode, the control system operates at a constant speed set by the operator. This mode is used for testing, calibration, and special working conditions such as low-speed operations.
The system also allows the operator to set the current parameters of the hydraulic motors to meet the set spreading requirements, which is very useful when operating in special or hazardous areas. Furthermore, during the spreading operation, the operator can change the required spreading amount and width at any time according to the specific situation. Whenever new data is set, the system will update the current parameters of the two hydraulic motors to meet the new requirements.
3 Dispensing System Controller
The controller is the core part of the dispensing system and the implementer of various functions of the system. Its structure is shown in Figure 1. The control structure of the controller is divided into two parts: the main controller and the signal processor. The sensor transmits the external signal to the signal processor through the connection channel. The signal processor is responsible for detecting, collecting and processing the sensor signal, and analyzing and processing the control signal from the main controller. Then, it outputs two analog signals to drive the hydraulic mechanism and transmits the data to be displayed to the main controller. The main controller is mainly responsible for generating control information and transmitting the control command to the signal processor. At the same time, it realizes the functions of data display, sound and light alarm and so on. The controller uses the MSP430 microcontroller as the core processor and together with the peripheral functional module circuits, it forms a hardware system [3][4]. With the help of flexible software, it can complete the complex control tasks.
Figure 1. Block diagram of the dispensing system controller
4. Control Principle and Parameter Calibration
The output of the spreading system controller is two analog current signals, which are the currents driving the electro-hydraulic proportional flow control valves. The current is approximately proportional to the speed of the hydraulic motor [5], as shown in Figure 2. Therefore, the speed of the hydraulic motor can be adjusted by controlling the current parameters. The hydraulic mechanism consists of two electro-hydraulic proportional flow valves, one for controlling the hydraulic motor of the material conveyor belt and the other for controlling the hydraulic motor of the spreading disc. The conveyor belt is used to transport the spreading material. The conveying amount, i.e. the spreading amount, is controlled by adjusting the speed of the hydraulic motor. The faster the speed of the hydraulic motor, the more material is spread per unit time, and vice versa. The spreading disc is used to control the spreading width of the material. The faster the speed of the hydraulic motor, the wider the spreading width, and vice versa. In this way, the spreading amount and spreading width of the material can be controlled by changing the magnitude of the current signal output by the controller.
Figure 2. Schematic diagram of the relationship between hydraulic motor speed and proportional amplification current.
In summary, the key issue is how to calculate the value of the internal D/A converter of the microcontroller from parameters such as vehicle speed, spreading width, and spreading amount.
4.1 The calculation formula for the drive parameters of the control conveyor belt is as follows:
(1)
In the formula: V is the value in the DAC12_0DAT register; SL is the required spreading amount; SK is the spreading width; C is the vehicle speed; N is the material conveyor belt calibration parameter; a is the unit coefficient.
DAC12_0DAT is the data register in the internal D/A conversion module of the microcontroller, and its value is the value to be converted into current. In this system, the conversion accuracy is 12 bits, and the highest conversion value is 4095. As can be seen from equation (1), the spreading amount and spreading width are given parameters. We also need to know the vehicle speed and the conveyor belt calibration parameters to obtain the value of V.
The expression for calculating vehicle speed is as follows:
(2)
In the formula: C is the vehicle speed (unit: km/h); T is the number of pulses within the timing period; M is the calibration pulse number; b is the unit coefficient.
The calibration pulse count is recorded by counting the number of pulses in 100 meters of vehicle travel, and then the travel distance corresponding to a unit pulse can be calculated. The timer is set to 500ms, that is, the speed value is refreshed every 500ms.
The value of the unit coefficient b is calculated as follows:
(3)
The counter is started at the same time the timing begins. After the timer interrupt occurs, the vehicle speed is calculated by inputting equation (3) into equation (2) based on the count value read.
The conveyor belt calibration parameter N is a key coefficient that enables the system to obtain correct drive parameters. Its calibration principle is to record the material weight value obtained under full-scale current output (full-speed hydraulic motor) within a certain time period, with the unit being kg/s. However, the unit of the spreading amount required by equation (1) is g/m2, so it is necessary to unify the unit to kg/s so that the voltage conversion value can be calculated using the proportional relationship. The value of the unit coefficient a is calculated as follows:
(4)
Substituting equation (4) into equation (1), we can obtain the correct parameters for the proportional flow valve driving the conveyor belt.
4.2 The driving parameters of the spraying disc are determined directly through the calibration of the spraying disc.
The verification principle is as follows: While ensuring the conveyor belt motor is running normally and driving at full capacity, the current conversion value of the driving spray disc is manually changed. Once the correct width is obtained, the drive is stopped and the parameters are stored. Verification is performed sequentially from width values of 4m to 10m, and the values are stored in an array. After verification, the system can then call the corresponding current conversion value based on a given width to meet the spraying width requirements.
In this way, the system will automatically adjust the parameters of the proportional flow valve of the drive conveyor belt and the proportional flow valve of the spreading disc according to the changes in vehicle speed and spreading width, so as to ensure that the spreading amount and spreading width meet the requirements.
5. Conclusion
A novel vehicle speed-guided intelligent snow removal system controller is proposed. The hardware utilizes the MSP430F167 microcontroller as the processor, demonstrating excellent performance in both system processing speed and control precision. This controller is currently in use. Experiments have shown that snowplows equipped with the intelligent snow removal system controller can improve resource utilization by nearly 30%. Furthermore, the controller is inexpensive and easy to use, indicating a promising market prospect.
In addition, the development of this controller is of great significance to the development of multi-functional snowplows and the development of snowplow machinery in my country[6].
Name: Cui Shijie
Affiliation: School of Mechanical Engineering, Dalian University of Technology (116023)
Mailing Address: Room 218, School of Mechanical Engineering, Dalian University of Technology, Dalian, Liaoning Province
Contact number: 15941161942 Email: [email protected]
