A large enterprise needs to establish an automated three-dimensional warehouse consisting of 12 stackers, 18744 cargo positions and a pre-processing system consisting of 133 conveyors and 34 elevators. Its characteristics are: large storage capacity, high frequency of access and storage, complex pre-treatment process and large number of equipment. This is composed of a large number of equipment automated warehouse, the main problem to be solved is the stability of the system, the second is the efficiency of the warehouse. The following issues are mainly considered in the design of the project: convenient installation and debugging (to shorten the installation and debugging cycle), simple equipment control and stable and reliable control of the pre-processing system must be achieved. The control system needs to have the ability of equipment fault self-diagnosis and fault site protection.
Design of control hardware architecture
According to the preset system requirements, we boldly use the AS-interface bus as the underlying transmission bus for detection signals and control signals.
AS-I(Actuator-Sensor-Interface) is the English abbreviation of actuator-sensor-interface. It is a bus network used in the bidirectional exchange of information between the controller (master station) and the sensor/actuator (slave station). It belongs to the underlying monitoring network system under the field bus (Fieldbus). A AS-i bus system can be connected to PLC, gateway or upper field bus (Profibus, Interbus, DeviceNet, CAN, Modbus, Modbus, CCLink, Ethernet) through the gateway in its master station. AS-i master station can be used as a node server of the upper fieldbus, and a batch of AS-i slave stations can be attached to it. AS-i bus is mainly used in sensors and actuator systems with switching characteristics. Sensors can be position proximity switches of various principles, as well as temperature, pressure, flow, and liquid level switches. Actuators can be a variety of switch valves, electric/gas converter and sound, light alarm, can also be relays, contactors, buttons and other low-voltage switch electrical appliances. Of course, the AS-i bus can also be connected to analog equipment. It must be noted that in addition to transmitting signals, the two-core cable connecting the master station and the slave station also provides working power. Its network topology is flexible (linear, tree, bus, star, etc.), the data transmission rate is 167Kbit/s, the system is simple to install, debug and expand, with fault warning function, maintenance, diagnosis is simple and fast, and the downtime is short.
The length of each AS-bus is 300 meters, the number of slave stations is 31, and each slave station can be connected to 4 inputs and 4 outputs. In this program, we use a dual AS-i bus, the system from the electrical appliances into two, to ensure the convenience of electrical installation and debugging, but also for the control software to achieve equipment fault self-diagnosis function to lay a good hardware foundation.
Design of 2. Control Software Architecture
The control system of automated warehouse equipment has gone through several periods such as electrical control, electrical program control, and digital program control. At present, the warehouse pre-processing system of the three-dimensional warehouse is generally processed by conveyors, transmission trolleys, and cargo tables. For the pre-processing system composed of conveyors, there will be great differences in scale and arrangement with the requirements of users. Therefore, when designing its mechanical structure, it is necessary to consider the complexity of the conveyor control system and the difficulty of control implementation. In addition, in the field installation and commissioning, because the system is a new system customized for users, the characteristics of the detection signal, the characteristics of the control signal and the workflow are special. At present, the control system adopted by most manufacturers, by the program code to outline the equipment workflow, its control complexity is closely related to the scale of the system, this program structure is not only difficult to debug, in terms of its operational reliability, stability, will be with the debugging personnel's technical ability and psychological quality of different and have a great difference.
In order to meet the high standard requirements of the enterprise and meet the pre-design requirements of the system, we rely on the AS-i hardware foundation to design a control technology suitable for the pre-processing system of the three-dimensional warehouse composed of conveyor groups to overcome the bottleneck problem of the existing technology in the design and debugging, reduce the design complexity, improve the debugging efficiency, stable operation reliability, and improve the working performance of the overall conveyor group. This technology through the conveyor system tree star data structure processing, resulting from the equipment detection signal, equipment control signal, conveyor topology data, material running path data composed of data group. After the data group is processed by a common data engine, the control structure of the individual conveyor is controlled and dispatched by the execution control unit. The control technology that the conveyor control is independent of the data engine and the execution control unit is realized.
The logical model of the conveyor is established so that the conveyor can be controlled logically, that is, the conveyor of the logical model has the same function as the conveyor of the actual physical type. In the processing of detection signals, the logical model is designed with a perfect conveyor structure, that is, a conveyor model with functions such as arrival detection, cargo detection, speed change detection, and waiting detection. In the control signal processing, also uses a perfect conveyor structure design. After completion, the physical conveyor input signal and control output signal are connected with the data of the corresponding function of the logical conveyor to form a conveyor control entity. At the same time, in the same way, the construction of the elevator control entity.
First, the conveyor structure is layered, and the present control technique can control conveyor structures up to 200 layers. Secondly, the physical topology of the conveyor is classified. At present, the combined structure of the conveyor is generally linear, right-angle, ding-shaped, and cross-shaped. The latter three types of structures also need to work with elevators during transmission. This results in a data engine consisting of four control processes. In the control engine, through the analysis of the set path, the topology analysis obtains the combined structure of the transmission path of the goods on the conveyor, and calls the corresponding control process for processing.
Secondly, the topological structure description data of the conveyor and the elevator, and the coupling mechanism description data of the conveyor and the elevator are established.
Finally, set the possible running path data of the conveyor.
At this point, we can control the goods along the logical path of the conveyor in the physical conveyor handling. In the design of the conveyor system, there is no need to consider the control complexity that may occur with the conveyor. In debugging, as long as the physical conveyor input signal and control output signal are connected with the data of the corresponding function of the logical conveyor, a conveyor control entity is formed and the topological structure data of the conveyor group and the material handling path data are established according to the actual situation, the debugging work of the conveyor can be completed.
After the data model of the conveyor group is established, in order to make the system coordinate work, a common data processing engine composed of routing function module, path analysis module, process generation module and equipment monitoring module, equipment scheduling module, process control module, etc. is needed to complete the coordination of the conveyor group.
This control technology is a digital path optimization technology. The material handling of the management system is bound to the digital scheduling of the equipment through the pallet bar code, and the equipment monitoring module monitors the running state of the material. The equipment fault self-diagnosis and fault field protection are successfully realized, which lays a solid foundation for the stable and reliable operation of the pre-processing system.
Status of 3. field applications
First, the AS-i bus connects binary actuators and sensors in a simple and economical way. Because the acquisition points of all signal processing are very close to the processing unit, the installation and debugging of electrical appliances are extremely convenient; the hidden dangers of safety and failure are minimized.
Secondly, through the on-site optimization of the digital engine, the system can realize the design, installation and debugging of the library pre-processing system of any complex process. After nearly two years of operation, the stability and reliability of the system have been verified.
At present, the technology has been successfully applied to many large enterprises in the automated frozen warehouse and automated warehouse.
