What is Automation Guided Vehicle?
During the operation of the factory, the flow of materials determines the production efficiency of the factory. Recently, automation equipment has gradually become a production line system, but the supply or handling of materials still relies on manual handling operations by personnel, resulting in often unsmooth logistics and production flow. Or there is an interruption, and the production line does not want to occupy a huge space, so Automation Guided Vehicle (AGV) technology responds to it.
Published: Aug 25, 2021
What is Automation Guided Vehicle?
AGVS is a wider application of automated material handling. It is an independent handling system that serves as material storage and transportation during the manufacturing process. It is suitable for handling different materials from different load points to different unloading points. To make the production line flexible and reduce costs, the power is usually supplied by batteries, and the path is usually completed by wires buried under the floor or reflective paint on the floor surface. The sensor on the car guides the car to follow the wire or paint. To achieve unmanned handling.
Automation Guided Vehicle is an unmanned vehicle that can travel according to a predetermined path or program, achieving labor-saving and efficiency improvement. The core of its application lies in logistics planning, production experience, control logic, and mass production implementation. After years of research and development and field verification, AGV technology can stably perform logistics handling work and even connect with the production control system MRP and MES system to achieve the realm of Industry 4.0.
What kinds of AGV control systems are there?
Three main technologies in the AGV control system: Navigation, Layout designing, and Guidance. The AGV control system is divided into the following three points:
- Ground Control System (Stationary System):
That is, the AGV upper control system is the core of the AGV system. The main function is to perform task distribution, vehicle management, traffic management, communication management, etc. for multiple AGV single machines in the AGV system (AGVS). Task management: like the process management of a computer operating system, it provides an explanation and execution environment for the AGV ground control program, scheduling operation according to task priority and start time, and various operations on tasks such as start, stop, cancel, etc. Vehicle management: It is the core module of AGV management. According to the request of material handling tasks, it allocates and dispatches AGV to perform tasks, the principle of shortest AGV walking time, calculates the shortest walking path of AGV, and controls and directs the walking process of AGV to timely issue loading and unloading and Charge command. Traffic management: According to the AGV's physical size, operating status, and path conditions, it provides measures for AGVs to automatically avoid each other, and at the same time avoid deadlock methods for vehicles waiting for each other and deadlock release methods; AGV traffic management mainly includes walking section allocation and deadlock report function. Communication management: Provide the communication function between the AGV ground control system and the AGV stand-alone, ground monitoring system, ground IO equipment, vehicle simulation system, and host computer. The communication with the AGV uses the radio communication mode, and a wireless network needs to be established. The AGV only communicates with the ground system in both directions, and there is no communication between the AGVs. The ground control system uses polling mode and multiple AGV communication; with the ground monitoring system, The communication of the vehicle simulation system and the upper computer uses TCP/IP communication.
- Onboard System:
That is the AGV stand-alone control system. After receiving the instructions from the upper system, it is responsible for the navigation, guidance, route selection, vehicle driving, loading, and unloading operations of the AGV stand-alone.
- Navigation: A single AGV uses its own navigation device to measure and calculate its position and heading in global coordinates.
- Guidance: The single AGV calculates the speed value and steering angle value of the next cycle according to the current position, heading, and preset theoretical trajectory, that is, the command value of the AGV movement.
- Searching: According to the instructions of the upper system, the single AGV pre-selects the path to be run through calculations, and reports the results to the upper control system. Whether it can run or not is uniformly deployed by the upper system according to the location of other AGVs. The path of the AGV single machine is designed according to the actual working conditions, and it is composed of many segments. Each segment indicates the starting point and ending point of the segment, as well as the driving speed and steering information of the AGV in the segment.
- Driving: The single AGV controls the operation of the vehicle through the servo device according to the calculation result of the guidance and route selection information.
- Navigation/Guide Mode and Features:
The reason why AGV can realize unmanned driving, navigation, and guidance has played a vital role in it. With the development of technology, the navigation/guidance technologies that can be used for AGV mainly include the following:
- Cartesian Guidance: Use the positioning block to divide the AGV's driving area into several small coordinate areas. The guidance is realized by counting the small areas. Generally, there are photoelectric and electromagnetic types. The advantage is that the path can be modified, the guidance is reliable, and the environment has no special requirements. The disadvantage is that the ground measurement installation is complex, the workload is large, the guidance accuracy and positioning accuracy are low, and it cannot meet the requirements of complex paths.
- Wire Guidance: It is to embed a metal wire on the driving path of the AGV, and load the guiding frequency into the metal wire, and realize the guidance of the AGV by identifying the guiding frequency. Its main advantage is that the lead is concealed, not easy to be polluted and damaged, the guiding principle is simple and reliable, easy to control and communicate, no interference to sound and light, and has low manufacturing cost. The disadvantage is that the path is difficult to change and extend, and it has great limitations on complex paths.
- Magnetic Tape Guidance: Like electromagnetic guidance, it uses tape on the road instead of burying metal wires under the ground. Guidance is achieved through magnetic induction signals. The flexibility is better, and it is easier to change or expand the path. Tape laying is simple and easy, but this guidance mode is susceptible to interference from metal materials around the loop, and the tape is susceptible to mechanical damage, so the reliability of the guidance is greatly affected by the outside world.
- Optical Guidance: Paint or stick ribbons on the driving path of the AGV, and realize the guidance by simply processing the ribbon image signals taken by the camera. The flexibility is better, and the ground route setting is simple and easy, but the Pollution and mechanical abrasion are very sensitive, the environment requirements are too high, the guidance reliability is poor, and the accuracy is low.
- Laser Navigation: It is to install a precise laser reflector around the driving path of the AGV. The AGV emits a laser beam through a laser scanner and collects the laser beam reflected by the reflector to determine its current position and heading. The trigonometric calculations are used to realize the guidance of the AGV. The biggest advantage of this technology is the precise positioning of the AGV; the ground does not require other positioning facilities; the driving path can be flexible and changeable, and can be suitable for a variety of on-site environments. It is the advanced guidance mode preferred by many foreign AGV manufacturers; the disadvantage is that the manufacturing cost is high. Relatively harsh on the environment, not suitable for outdoor.
- Inertial Navigation: Install a gyroscope on the AGV, and install a positioning block on the ground in the driving area. The AGV can determine its own position and head through the calculation of the gyroscope deviation signal (angular rate) and the collection of the ground positioning block signal, thereby realizing guidance. This technology is widely used in the military field, and its main advantages are advanced technology, compared with wired guidance, less ground processing workload, and strong path flexibility. The disadvantage is that the manufacturing cost is high, and the accuracy and reliability of the guidance are closely related to the manufacturing accuracy of the gyroscope and its subsequent signal processing.
- Visual Navigation: Image recognition of the environment in the AGV driving area to realize intelligent driving is a kind of guidance technology with great potential. At present, there is no practical AGV that adopts this kind of technology in continuous research. But it can be predicted that the combination of image recognition technology and laser guidance technology will make AGV more perfect, such as the accuracy and reliability of guidance, driving safety, and intelligent memory recognition.
- Global Position System (GPS) Navigation: GPS uses satellites to track and guide the controlled objects in the non-fixed road system. This technology is still developing. It is usually used for outdoor long-distance tracking and guidance. Its accuracy depends on the fixed accuracy and number of satellites in the air, as well as the control. Factors such as the surrounding environment of the subject. The result is iGPS and dGPS, which have much higher accuracy than civilian GPS, but the manufacturing cost of ground facilities cannot be afforded by ordinary users.
Published: Aug 25, 2021