“Dark Warehouse” in Shandong Iron and Steel Cold Rolling Plant

In the steel coil warehouse and finished product warehouse of the cold rolling mill of Shandong Iron and Steel Co., Ltd. in Rizhao, all running vehicles have been upgraded to unmanned intelligent vehicles. No one can be seen in the cab any more, and the entire workshop does not need lighting, making it a veritable ” “Dark Warehouse”, that is, a smart workshop, that does not require manual operation, so it can run with the lights turned off. In the past two years of operation, the unmanned operation rate has stabilized at more than 99%, achieving the expected results.


Dark Warehouse, steel mill warehouse


1. “Dark Warehouse” hardware system composition


The “Dark Warehouse” is mainly composed of unmanned driving and warehouse area management systems. The hardware system includes a ground station server, driving PLC, frequency conversion control system, warehouse management system, industrial wireless network positioning system, intelligent clamp system, anti-sway system, anti-rail gnawing system, anti-collision system, ground remote control, vehicle scanning and identification system, Video surveillance, safety guardrails, etc.

Unmanned driving uses the driving positioning system to automatically complete the collection of position information. By detecting the main hook position, steel coil quality and other information, it automatically determines the driving position and the lifting and unwinding status, and automatically combines the driving positioning information, lifting coil judgment information, and driving status. Information, driving execution information, etc. are sent to the reservoir area management system. The warehouse area management system issues lifting instructions in accordance with the rules and in line with on-site needs, and the driving vehicle automatically performs the lifting work according to the instructions. The driving positioning system feeds back location information in real-time, and at the same time, the vehicle-mounted terminal returns the operation execution results to the warehouse area management system.


2. Key technologies for autonomous driving


1) Car model scanning and identification technology


In order to safely hoist the materials (up/down) to the base of the transport vehicle or transport them to the designated steel coil position, the system generates the coordinates of the (up/down) hoisting, and the scanning recognition system checks and confirms the shape of the steel coil position at the base of the transport vehicle. , drive the vehicle and then perform lifting work.


2) Ground obstacle avoidance control


Ground obstacle avoidance control technology means that when there are ground obstacles in the unmanned driving range, the spreader moves to the target in the optimal path to achieve safe lifting and avoid collision with obstacles.

In order to prevent vehicles entering the reservoir area from colliding with other vehicles, vehicles are monitored in real-time at a certain height to achieve anti-collision control of driving vehicles. The system scans the vehicle’s moving channel at any time through a scanner and transmits real-time information to the ground station. After the unmanned vehicle hoists the steel coil, the ground station uses signal lights to indicate when entering the vehicle channel to control the vehicle’s entry. When the vehicle enters the channel, the ground station instructs the unmanned vehicle to stop temporarily.


3) On-road anti-collision system


The collision avoidance system between trains optimizes collision avoidance control between trains according to the priority of work instructions. The vehicle that receives the instruction first takes priority, and the vehicle behind it gives way to the vehicle in front. One for driving operation and the other for driving avoidance to improve driving efficiency.

In addition, the driving PLC is also equipped with an anti-collision function as a backup function after the ground station loses contact. A light barrier is installed on the driving vehicle. When the distance between the two vehicles is too close, the driving PLC will control the parking to avoid collision.


4) Driving positioning and spreader anti-sway control


Under the condition that the incoming products are not damaged, the steel coils are correctly hoisted up/down to the designated position through unmanned driving. During driving, the swing angle of the spreader is controlled within ±0.5°.

The position control error does not exceed ±25mm. The moving distance between the starting position and the target position received from the ground station is used to generate the driving mode (long distance: trapezoid, short distance: triangle), and the distance meter value is used to reflect the actual moving distance of the vehicle. , implement speed and swing control.


5) Intelligent spreader system


The action of the intelligent spreader is controlled by the driving automation system, which mainly completes functions such as clamping, loosening, lifting and rotating the spreader, and also has the function of transmitting signals from each sensor back to the onboard PLC system. Compared with ordinary clamp spreaders, the intelligent spreader adds the following equipment: equipment with rotation function, angle detection sensor, clamping in place sensor, releasing in place sensor, steel coil inner diameter induction sensor, lower object induction sensor, etc.

A material identification scanner is installed on the fixture, and the scanner scans downward. The driving terminal can receive the scanner signal, calculate the exact location and dimensions of the material through the software program, and send this information to the L2 system in the warehouse area, which passes signal analysis and makes effective lifting instructions, thereby effectively preventing the clamp from colliding with the material and improving the lifting position accuracy.

Using material identification technology, the location and size of the steel coil to be hoisted can be determined, improving the accuracy during the automatic hoisting process and reducing the probability of the clamp colliding with the steel coil. The steel coil inner diameter identification technology is adopted, that is, the steel coil inner diameter induction sensor and photoelectric sensor are installed on the spreader to prevent damage to the steel coil. The angle detection sensor on the spreader can assist in the anti-sway function of the spreader. Through clamp clamping force detection, excessive clamping force can be prevented and the steel coil can be protected.


6) Wireless network positioning and tracking system


The wireless network positioning and tracking system consists of a driving part, a ground part and a network communication part.

The vehicle travels through the Gray busbar for precise positioning, and the intelligent spreader is equipped with a laser sensor to determine the position of the clamp. The driving and clamp positioning signals are transmitted to the ground receiving station through wireless transmission. The ground receiving station server transmits the signals to the L2/L3 server through the optical fibre network to track and process the driving and clamp positioning signals.


7) Security fence system


For unmanned driving systems, safety management is necessary, so safety interlocks are designed between the safety fence settings and the fence gates and the driving system. Each set of safety fences contains a set of PLC remote stations, including door opening and closing request buttons, indicator lights, emergency stop buttons, safety door limits, electronically controlled locks, audible and visual alarms, etc., connected to the ground PLC system.


8) Driving digital intelligent anti-rail rail system,


The driving track digital intelligent adjustment system consists of a control cabinet, high-precision laser detection components, a programmable controller, a display screen, a power supply and a relay. The system has functions such as calculation and interface connection. The display screen displays the real-time parameters of the track gap, sets the system control menu, handles various alarm events, performs real-time calculation and control, adopts multiple redundant settings, digital and analogue quantities judge each other, and is equipped with Broken line detection, fault built-in and other prompt systems.


3. Warehouse management system


The warehouse management system is a key link in realizing the “black light warehouse”. It is equivalent to the brain of the entire operation activity, and all instructions are issued from here. The warehouse management system server adopts dual-machine hot standby mode, Linux operating system, supports AsiaInfo anti-virus software, and interacts with the industrial WiFi mode used by the driving system for data interaction.


Functions of the warehouse management system


(1) Steel coil tracking management


The storage area management system communicates with the driving PLC system and MES system to realize the tracking management of steel coils entering, leaving, and stacking in the storage area and updates the data in real-time.


(2) Task management


The types of tasks that can be performed by unmanned vehicles include packaging steel coils coming off the line and warehousing, steel coils being rolled into the warehouse on cross-over trucks, steel coil loading and shipping in the warehouse area, and steel coil stacking. Task management includes task generation, task scheduling, task tracking, current task query, historical task query and other functions.


(3) Driving route planning


After the warehouse management system assigns tasks to driving vehicles, the driving control system manages the driving actions. According to the constraints of the operation safety rules, the driving path is optimized, the executable dispatching instructions are generated, and the instructions are sent to the driving PLC system. When planning a driving path, it is necessary to consider all avoidance areas in the current warehouse to ensure that driving movement instructions are safe and effective.


(4) Monitoring of driving operation status


During the operation of the driving system, accurate tracking of the driving system and the steel coil is the basis for the stable operation of the unmanned driving system. The driving monitoring system processes the driving actions, status, position and loading status information sent in real-time by the driving PLC control system to realize real-time tracking of the driving operation in the warehouse area, as well as the real-time position and status of the steel coils in the warehouse area. Tracking and software-based identification of stack locations and steel coils in the warehouse area.


(5) Exception handling


Follow the instructions to try not to affect the execution of subsequent operations, handle them as automatically as possible, provide sufficiently flexible exception handling functions, and properly handle various abnormal situations in driving operations, including emergency stops, emergency command insertion, etc.


(6) Running status and tasks


Driving operation modes include manual operation mode, automatic operation mode and maintenance mode. The mode-switching function ensures that the switching of driving modes has minimal interference with the current work rhythm. The HMI system provides graphical monitoring and display and manual intervention functions for the entire unmanned driving system. Relevant information includes warehouse area information, driving location and status information, operation information, parking space information, and communication status information between various systems. The HMI system also provides alarm information that occurs during driving, including emergency stop and fault alarms during driving, discrepancies between steel coil and stack position tracking information, etc.


(7) Stacking position allocation


To achieve efficient operation of warehouse management, it is necessary to reasonably allocate the target stacking positions of steel coils in the warehouse according to the production plan and the current usage of the warehouse, so as to achieve the goal of rapid warehouse storage of steel coils. In addition, according to the stacking rules, the idle time of driving is used to stack steel coils, and the steel coils are stacked near the loading area to facilitate rapid loading.


(8) Multi-vehicle task allocation


The warehouse management system has built-in task allocation and avoidance rules, which can realize task allocation and avoidance functions for multiple vehicles within a span according to different situations.


(9) Communication management


It can realize communication between the warehouse management system and various external systems, including communication with the MES system, production line L1/L2 system, vehicle PLC system, ground PLC system, etc. The communication method uses TCP messages.


(10) Reports and information inquiry


Generate real-time inventory, driving operation performance and other reports, as well as other reports required by the owner. WMS can collect statistics on driving action information at various stages and adds a maintenance prediction function. The cause of driving faults can be clarified through a query, and the fault prediction can also be informed to maintenance personnel.


4. Advantages of “Dark Warehouse”


1) Flexible driving operation


The unmanned driving system has 3 operating modes, fully automatic mode, semi-automatic mode and manual operation mode. In the fully automatic mode, manual operation is not required for driving. The L2 system in the reservoir area needs to make the correct optimized path and give instructions. The driving control also needs to make specific operations or travelling functions based on the characteristics of the driving. In semi-automatic mode, the driving operator can make better use of the equipment and reduce equipment losses by operating accurately according to reasonable operating prompts. When a failure occurs in the warehouse management system, the manual mode can be used to manually operate and control the operation of the vehicle.


2) Safe, efficient and low cost


The black light warehouse does not require manual operation, can better exert driving performance, and is energy-saving and efficient. It not only saves expensive labour costs but more importantly, achieves the intrinsic safety of the factory.


3) Steel coils automatically enter and exit the warehouse


The MES system sends the warehousing information to the intelligent warehouse management system. The intelligent warehouse management system automatically generates instructions based on the steel coil information sent by the relevant L1 and L2 systems, and the crane automatically performs lifting and warehousing operations. At the same time, it can automatically determine whether the steel coil is out of the warehouse based on the weighing information and position detection information carried by the hook part on the crane. According to the MES command, the lifting instructions are automatically generated and the out-of-warehouse operation is automatically performed. The data and location information of steel coils entering and exiting the warehouse will be updated in the intelligent warehouse management system and MES system at the same time.


4) Traffic dispatch optimization


Reasonably allocate the traffic to work, avoid traffic road overlap, improve efficiency, reduce the number of lifting times, and reduce uneven traffic loads due to uneven distribution.


5) Real-time material tracking and management


The incoming, outgoing, reversing, and withdrawing actions of steel coils are recorded in detail, and the required data is transmitted to the MES system to update the information in the warehouse in real-time and track the movement of steel coils in real-time.


6) Essentialize safety interlocking management


When moving the lifting coil while driving, there is a safe operation interlock between the over-span vehicle carrying steel coils, transport saddles and other equipment in the same vehicle. Prevent conflicts between the driving action and the action of other related equipment, which may cause damage to the equipment or steel coils. It mainly includes the unloading saddle of the driving and acid rolling exit section, the coiling saddle of the CAL1 entrance section, the coiling saddle of the CAL2 entrance section, and the coiling saddle of the CGL entrance section. There is a safety locking link when lifting steel coils. Lock, the loading/unloading steel coil on the saddle is not allowed to move any more during crane lifting.


5. Benefit analysis of the “Dark Warehouse” project


After the cold rolling warehouse and pickling finished product warehouse of Shandong Iron and Steel Co., Ltd. Rizhao Company are put into use with intelligent functions, the economic benefit analysis is shown in the table.


  Classification Cost/10,000 yuan Total/10,000 yuan
Investment Intelligent upgrade of “Black Light Warehouse” 1861 1861
Annual cost reduction Human resources 860 1042
Reduced energy consumption 134
Reduce quality loss 48
Annual loss Annual equipment maintenance costs 62 392
Annual equipment discount 330

As can be seen from the table, the investment cost of the “Dark Warehouse” can be recovered within two years of successful operation. The return rate is high and the indirect and invisible benefits generated are immeasurable. Especially during the epidemic, it played a huge role.

The successful application of the “Dark warehouse” in the cold rolling mill not only reduces the number of operators but also makes inventory turnover faster and more efficient. It has greatly improved the intelligent manufacturing level of Shandong Rizhao Company and laid a good foundation for the next step of the intelligent dream factory.

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