Abstract : To address the bottlenecks of long retrieval times, high power consumption, and high management and maintenance costs in traditional parking garages, this paper proposes a multi-process automated parking garage scheme for simultaneous storage and retrieval of multiple vehicles, drawing inspiration from chain-driven pallet and elevator-type garage structures. The three-story structure of the garage features independent units that can work in conjunction with elevators. The garage control system is based on a Siemens S7-200 CPU, using a positioning module. Real-time management and control of the automated parking garage are achieved through a touchscreen and card reader. This paper introduces the system structure and control implementation method. Test results show that the maximum retrieval time of this garage is less than 90 seconds, which is superior to existing parking garages.
Keywords : multi-process; automated parking system; Siemens S7-200;
Chinese Classification Number : Document Identification Code:
0 Introduction
With the rapid development of my country's automobile industry and the economies of major cities, more and more families own private cars, leading to parking difficulties in many cities. Limited parking space is insufficient to cope with the increasing number of cars. Solving this parking problem is crucial for urban economic development. However, existing automated parking systems in the domestic market are mainly of the following types: lift-and-slide, vertical lift, and lane stacking. Lift-and-slide systems, in particular, have low land utilization rates, and the number of levels severely limits parking and retrieval time. Vertical lift systems require high precision in safety and manufacturing, resulting in high investment costs. Further analysis and research on automated parking systems revealed that independent unit management, and efficient, multi-process, and rational management of these independent units, are key to solving the related problems.
1. Structure and working principle of multi-process lifting parking garage
1.1 Structure of Lift-Type Multi-Process Automated Parking Garage
This automated parking system consists of two parts: mechanical and control. The mechanical part mainly comprises entrance and exit ramps and car elevators, trolleys for transporting vehicles, reinforced concrete parking spaces, and safety protection devices, primarily functioning to transfer and store vehicles. The studied automated parking system has three levels, each with six parking spaces, distributed on both sides of the car elevator system. The front and rear ramps for car entry and exit are located before and after the car elevator system, with a central elevator shaft for lifting vehicles. Each parking space is equipped with an independent transport trolley.
Figure 1. Three-dimensional model of the lifting multi-process stereo vehicle
1.2 Working Principle of Lift-Type Multi-Process Automated Parking Garage
When a user needs to park their car, they first swipe their card at the entrance and select a parking space via a display screen. If the selected space is on the second or third floor, the elevator starts. When the elevator reaches the selected space, the corresponding parking garage's photoelectric receiver receives the photoelectric signal emitted by the elevator. The control system then sends this information to the transport trolley built into the selected parking space via a wireless communication central control unit. The transport trolley moves along the horizontal track of the parking space and the longitudinal track of the transport passage to the elevator track. When the elevator returns to the entrance, the user drives their vehicle onto the transport trolley. Once the pre-stored vehicle is correctly parked, the parking position detection system detects the successful parking. The green indicator light illuminates, prompting the user to disembark. After pressing the elevator lift button on the touchscreen, the transport trolley and the pre-stored vehicle are transported to the pre-storage level by the elevator. The transport trolley, carrying the pre-stored vehicle, leaves the elevator and enters the longitudinal track of the transport channel on that level. The transport trolley determines its current position using a vehicle position detection sensor. When it reaches a parking space, the trolley stops moving forward and accurately stops at the turning position. Under the action of the trolley's steering mechanism, the trolley achieves a 90-degree turn and enters the parking space along the transverse track, completing one parking operation. If the user chooses to store the vehicle in the first-floor garage, the elevator lifting operation will be eliminated, and the transport trolley will be directly retrieved for the parking operation. The vehicle retrieval operation is the reverse of the storage operation. When a user needs to retrieve their vehicle, they swipe their card at the entrance. The user interface then displays their information, including card number, storage time, storage location, retrieval time, unit price, and total fee. After payment, the control system moves the lifting platform to the vehicle's location. A transport trolley carrying the vehicle moves onto the lifting platform, and the system then moves the lifting platform back to the entrance, completing one retrieval operation. This is the working principle of one type of elevator. This automated parking system has multiple elevators that can be operated simultaneously without interference. While one elevator is working, another idle elevator can be used to handle the next vehicle needing storage or retrieval, greatly improving parking efficiency.
2. Lift-type multi-process automated parking system
2.1 Design Scheme for Multi-Process Lift-Type Automated Parking Garage
The lifting multi-process three-dimensional parking garage control system is designed to consist of two parts: a control box installed inside the parking garage and a ground monitoring system.
The control box inside the garage includes the core controller of the control system, the parking elevator's operating position detection, motor control circuits, and wireless communication circuits. It can detect in real time whether the garage is in the parking, retrieval, or waiting period. Simultaneously, it can obtain the specific location and operating status of the parking elevator and transmit all this information to the ground monitoring system via communication.
The ground monitoring system includes a human-machine interface, a display of the elevator's operating status in the parking garage, and communication circuits. The communication circuits acquire, display, and analyze elevator operating data sent from the control box.
Figure 2. Scheme for the control system of the lifting multi-process automated parking garage.
2.2 Selection of the core of the control system
The selection of the control core for a multi-process vertical parking garage control system is crucial and must be based on the system requirements and operation.
The core control function of a multi-process automated parking system primarily involves using information from a ground monitoring system and feedback from position sensors to control the motors, thus enabling the parking and retrieval of vehicles via the elevators. This task can be effectively accomplished using a microcontroller, PLC, or a combination of microcontrollers and computers. However, the critical aspect is ensuring the stable, safe, and reliable operation of the entire system. PLCs are particularly advantageous due to their high reliability, strong anti-interference capabilities, and low power consumption.
It has the advantage of easy maintenance, and since the control system needs to control the motor, PLC control is more convenient.
Therefore, considering all the above points, we ultimately chose to use a PLC-based control system to complete the control task of the lifting multi-process automated parking garage.
2.3 Composition Framework of the Control System
Figure 3. Scheme for the lifting-type multi-process automated parking system
The PLC primarily controls the forward and reverse rotation of three sets of motors, processes proximity switch signals, and communicates with the host computer. The PLC waits for position information from the host computer before initiating actions; the proximity switches transmit the received position information back to the PLC. Path planning is implemented by an algorithm on the host computer. That is, when parking, the host computer plans the optimal path using an internal algorithm and transmits the path information to the PLC to execute motion commands. The position information from the proximity switches is used as nodes for motion commands and for monitoring and recording path data. This completes the motion process of the model test, providing a physical model and design reference for subsequent development.
3. Software Flow and Host Computer Software Design of the Control System
3.1 Software Flow of the Control System
According to the project plan requirements, the function implemented in this design is for the system to automatically perform the tasks of retrieving and storing vehicles in the multi-level parking garage, and to ensure the completion of the following indicators, including position accuracy and optimal time for parking and retrieving vehicles.
In the design of a multi-process automated parking system, motor control is divided into two parts. The first part includes the elevator car lifting control motor, the elevator movement motor, and the pallet control motor for parking or retrieving vehicles. The second part consists of the motors in the parking garage during parking or retrieval.
When controlling the first part of the motor, the PLC controls the forward and reverse rotation of the motor by controlling the on and off of the relays, thereby realizing the operation of the elevator and the operation of parking and retrieving the vehicle.
The second part, motor control, is achieved by controlling a photoelectric transmitter lamp and a photoelectric pair circuit, thereby enabling the motor to operate in the garage.
Figure 4. Control system program flowchart
3.2 Software Design for the Upper Computer System of a Lift-Type Multi-Process Automated Parking Garage
In this control system, VB will be used for the development of the host computer. Within the VB environment, a PC will communicate with the PLC via RS485 to issue commands to the slave computer and simultaneously acquire information from it. The collected data will be dynamically tracked, displayed, analyzed, plotted as curves, and stored. The host computer will primarily perform three functions: first, a real-time data display interface, showing the real-time status of the slave computer's vehicle storage and retrieval operations; second, the ability to query and process historical data; and third, the execution of user-required tasks.
During the communication process between the host computer (PC) and the PLC, the host computer needs to display the real-time operating status of the automated parking garage, including the current number of cars in the garage, the parking time of each car, and the information of the customers currently parking their cars.
Figure 5 Vehicle storage status display
In this design, the parking garage status is distinguished by color in the interface design. A gray car indicates that there is no car in the garage, while a colored car indicates that there is a car in the garage. This makes it easy to clearly distinguish the parking status of vehicles in the garage.
In the interface design, customer information for parking is displayed using only the card number, not the name. When a user needs to retrieve or park a car, they swipe their card on the card reader, and the user interface will display the user information, including the card number, parking time, parking location, retrieval time, unit price, and amount charged. The interface also includes parking records, which record information such as the most recent customer's parking and retrieval times.
Figure 6 Design Interface
4. Summary
As my country's socio-economic level continues to improve, people's demand for resources is constantly increasing, making parking problems increasingly difficult to manage. Multi-stage, lift-type automated parking systems offer a feasible solution to this problem.
Based on a detailed understanding of the project plan, this paper proposes its own solution through comparison and analysis with related technical fields both domestically and internationally. Employing multi-object group control technology, multiple parking units can be simultaneously and synchronously controlled during operation, providing parking services for multiple vehicles at the same time. Furthermore, a transport vehicle with running and steering functions, capable of wireless data interaction with the overall control system, has been developed, enriching the structural forms of the automated parking garage and enabling rapid vehicle storage and retrieval. By organically combining modern wireless communication technology, on-demand battery charging technology, multi-object group control technology, and related communication technologies, the paper improves the intelligence level of garage management and operation while optimizing the garage structure. This results in an automated parking garage with advantages such as small footprint, low manufacturing cost, high intelligence, and convenient and quick vehicle storage and retrieval.
The experiment theoretically verified the correctness of the control system, but this does not mean that problems will not arise in practical applications. Further practical experiments and extensive refinement of the system are needed to truly make it a control system that meets the design requirements.
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First author's biography : Tang Jie, born on November 30, 1994, male, native of Xinli Town, Zhong County, Chongqing, undergraduate student.
