I. Overview of the Crane Industry

Material handling has become an important part of human production activities, with a history of over 5,000 years. With the expansion of production scale and the improvement of automation, as important equipment for material handling, cranes are increasingly widely used in modern production processes, playing a greater role, and the requirements for cranes are also increasing. Cranes are undergoing a huge transformation.

Cranes belong to one category of construction machinery. The construction machinery industry can be mainly divided into the following sub-sectors: excavating machinery, lifting machinery, compaction machinery, piling machinery, road machinery, rock drilling machinery, earthmoving and transport machinery, reinforced concrete machinery, and other machinery.

As a branch of construction machinery, lifting machinery can be further subdivided into:

Lifting machinery is developing towards larger scale, specialization, modularization, combination, automation, intelligence, complete sets, systematization, new types, practicality, and clustering.

II. Overview of Cranes and Composition of Automation Systems

Cranes have a compact structure and are difficult to wire. In addition, complex signal wiring can also cause difficulties in crane maintenance. Therefore, wireless signal connection is a very good solution for cranes. When cranes operate on site, safety is extremely important. The application of modern electronic technology, IT communication technology, and radio technology in cranes has been experimented with and improved by various manufacturers. Wireless technology is increasingly recognized by practice, and remote monitoring and wireless control technologies have been fully applied and realized in the crane industry.

Stable signals, real-time speed response, strong anti-interference ability, strong diffraction ability, long distance, and support for multiple industrial network protocols are the prerequisites for cranes in wireless communication systems.

Saiyuan's industrial wireless communication products have all the above characteristics.

Saiyuan's industrial wireless communication modules can achieve a communication distance of up to ten kilometers, support protocols such as MODBUS, ASCII, and PPI, are safe and stable, have strong penetration and diffraction capabilities, and achieve millisecond-level real-time response. They are an excellent choice for mobile, rotating, and inconvenient wiring occasions in industries such as lifting.

In this crane linkage application, the wireless communication of 4 vehicles uses Saiyuan's SY-S72 product for communication, with one master station and three slave stations. The controllers all use Siemens S7-224, and wireless synchronization data is used for synchronous actions.

In this application, one master station monitors three slave stations. Each slave station needs to exchange 20 bytes of data. With 3 stations polling, using SY-S72 at a transmission rate of 9600 bps, through Saiyuan's wireless communication program, the cumulative acquisition time for the three stations is about 25 ms, meaning polling can be performed about 40 times per second.

Since Saiyuan's wireless communication module occupies a bandwidth of 15K, which is very small, the characteristic of radio is that different frequencies do not interfere, while the same frequency inevitably interferes. Therefore, in the program, preparations should be made. When instantaneous communication failure occurs on site due to co-channel interference, the master station can be set in the program to actively send polling instructions again within 1~50 ms to restore communication.

A fault at one station does not affect normal communication at other stations. The master station can be set to determine how to act when a single station fails and notify all slave stations. When communication fails, slave stations can take actions such as maintaining the current state or directly adopting an emergency state.III. Configuration List

Each on-site control station:

No. Name Model Quantity

1 Siemens PLC S7-224 1

2 Wireless communication module SY-S72 1

3 Large suction cup omnidirectional antenna SY-ANT-22 1

4 Bus connector 972-0BB41 1

5 Switching power supply SY-PW 1

IV. Characteristics of Wireless Communication on Cranes

For crane communication, the first consideration is wired communication. However, in actual use, because it is difficult to isolate wired communication cables from power cables at a distance, on-site electromagnetic interference often interferes with communication signals, making normal transmission and reception difficult. A better solution is to use optical fiber for communication, but due to the relatively complex production process, when the optical fiber breaks, on-site maintenance is very difficult. It requires re-laying optical fibers, which is a large workload and requires special equipment for on-site fusion splicing. The maintenance cycle is long and the impact is significant.

During design, many wireless solutions have also been used. Most products on the market use the 2.4G WIFI protocol for transmission. During debugging, when there is line of sight, normal communication can be established, with speeds up to 54 Mbps, and even video can be transmitted. However, during movement, if there are obstructions or rainy weather, it is difficult to ensure line-of-sight transmission. 2.4G signals are intermittent and very unstable when there are obstructions. And in rainy weather, the signal also becomes unstable. Whether well-known brands or common products on the market, they all have this problem.

After in-depth analysis, the diffraction ability of 2.4G products is mainly determined by their physical characteristics. The 2.4G frequency band has a wavelength of about 124 mm, and its signal attenuates quickly with weak diffraction ability. This is the characteristic of microwaves. No brand's product can change this physical characteristic. Therefore, when encountering obstructions, including rainy weather, water molecules become like walls, absorbing microwaves and preventing diffraction, causing the signal to be absorbed and distorted, leading to communication problems.

Therefore, in complex environments, low-frequency products with stronger diffraction ability must be selected for transmission, such as 433 MHz wireless communication products. Their wavelength is 692 mm, and signals with longer wavelengths have strong diffraction ability. Signals can be reflected and diffracted to reach the destination. Moreover, the transmission speed of radio is the same as the speed of light regardless of the frequency band, so there is no problem of speed reduction after multiple diffractions. The key lies in the processing speed and capability of the wireless communication module.

After on-site comparative experiments, Saiyuan's wireless communication module SY-S72, which has a national patent, was finally selected because the product showed stable signals in various complex on-site environment tests, and the wireless communication module has fast processing speed. The delay caused by the transmission and reception of the wireless communication module does not exceed 5 ms, far exceeding the performance of products on the market.V. On-site Application Effects of Crane Linkage

4-machine linkage crane

The wireless communication on each crane is installed at the top

During debugging, attention should be paid to selecting the location for installing the wireless communication antenna. Using omnidirectional antennas, especially high-gain fiberglass antennas or directional Yagi antennas, helps ensure stable signal transmission. In addition, for the switching power supply used by the PLC and wireless communication module, it is recommended to use a high-quality switching power supply with a small ripple coefficient. It is best to add a signal isolator between the PLC and the wireless communication module. Saiyuan's industrial wireless communication system, once debugged properly, works stably, which is what production units value most.

In the above system, Saiyuan's wireless communication products have been used in this crane linkage for 3 years, withstanding the tests of weather conditions, dust, and relatively harsh on-site electromagnetic interference, and working stably.