With the development of science and technology, people have higher and higher requirements for the degree of automation in industrial production processes. More and more robots are being applied to production lines. The vehicles are equipped with automatic guidance devices and can be unmanned forklifts that can run in a cycle according to a predetermined track. Today, we analyze the characteristics of various charging methods for AGV forklifts and roughly discuss the charging methods of AGV according to the following four categories:
(1) According to the charging time, it can be divided into: random charging and full-cycle charging
Random charging means charging at any time without time limit at each parking station of the AGV. If there are more charging points, it can ensure that the power consumed by the AGV during the work process is replenished in time, and the battery is shallowly charged and discharged, which will greatly extend the battery life and reduce the required battery capacity. Full-cycle charging requires the AGV to exit the service and enter the designated charging area and can only be charged when the battery charge drops to the specified range.
(2) According to the charging area, it can be divided into: online charging and offline charging
Online charging means that the AGV does not leave the working route and does not need special time for charging. Instead, it uses the short parking time during the work process to charge. This charging method that fully utilizes fragmented time and does not occupy working time is actually an extension of random charging. It just embeds the charging station into the AGV’s workflow to further improve the AGV’s work efficiency. Offline charging means that the AGV exits the service and drives into the charging area or a dedicated charging station for charging.
(3) According to the operation method, it can be divided into: manual, battery replacement and automatic charging
When the AGV is low on power, it is directed by the ground control center to drive to the designated charging area or station, and a full-time staff manually completes the electrical connection between the AGV and the charger, and then implements charging. After completion, it is also manually disconnected to restore the working state. The characteristics of manual charging AGV are safe and reliable, simple and easy to operate, and low equipment cost. It is often used in occasions where the degree of automation is not very high, there are few vehicles and many people, and the working system is standard. Battery replacement charging means that when the AGV is low on power, a full-time staff manually replaces the battery pack, and the AGV can be put into use. The replaced battery pack is charged and then put into use. Its characteristics are simple and fast, and it can realize 24-hour continuous operation of the AGV. However, it requires twice as many battery packs, which is costly and primitive. It is often used in situations where the timeliness of work response is high and there is a shortage of vehicles. Both of the above methods require special personnel to supervise, which wastes manpower and reduces the degree of automation. Automatic charging means that when the AGV needs to replenish power, it will automatically report and request charging. Under the command of the ground control center, it will drive to the designated charging area or station. The on-board charging connector will automatically connect to the ground charging system and implement charging. After charging is completed, the AGV will automatically detach from the charging system and drive to the work area or standby area for normal operation. Automatic charging AGV is suitable for situations with long working cycles, many vehicles and few people, and high degree of automation.
(4) According to the electrical connection method of the charger, it is divided into: contact charging and wireless charging
Contact charging means that all charging circuits need to use cables and charging contacts to connect the vehicle to the power supply system so that it can be charged directly. Contact charging can provide a large charging current to achieve fast charging. It is currently the preferred method for offline charging. However, it is not suitable for frequent random charging, and there is wear on the charging contacts, which need to be replaced regularly. Sparks may also be generated during the charging process, posing a safety hazard. In addition, because the charging contacts are exposed components, they cannot work properly in low-temperature condensation, humidity, flammable and explosive environments. Wireless charging is a contactless charging device that does not require cables to connect the vehicle to the power supply system. It abandons the charging contacts, and the charger and the power-consuming device can be made without exposed conductive contacts. Wireless charging technology enables electrical isolation between the charging end and the AGV energy storage system, fundamentally eliminating the disadvantages of the plug-in charging method. It is safer and more applicable. At this stage, the charging efficiency of AGV wireless charging products is equivalent to that of contact charging systems. Because it has no contact wear and a high degree of intelligence, it is very suitable for online charging. It has completely achieved charging as soon as you come and stopping as soon as you go. It further improves the degree of automation in the use process of AGV.
