Introduction To AGV (Automated Guided Vehicles) | Types Of AGV
Automated Guided Vehicle System (AGVS) Material handling in manufacturing system is becoming easier as the automated machine technology has improved. One of the material handling methods that has been widely used in most industry now a days is the Automated Guided Vehicle System or better known as the AGVS. It has become one of the fastest growing classes of equipment in the material handling industry (Tanchoco and Bilge, 1997). Until today there are many researchers that have shown interests in improving the system in order to achieve more productivity and flexibility in manufacturing environments. According to (Groover, 1987) an Automated Guided Vehicle System (AGVS) is a materials handling system that uses independently operated, self propelled vehicles known as the automated guided vehicle or AGV that moves along defined pathways between delivery points or stations. A typical AGV will consist of the frame, batteries, electrical system, drive unit, steering, on board controller and work platform.
Modern AGV systems differ from the classic ones. Rather than using fixed paths, many modern AGV are ranging, which means the path of the vehicle are so programmed and can be change relatively easy when new stations or even flows are added. Modern technology also allows the vehicle to make decisions on its own compare to the past when control was perform by the central controllers. This leads to adaptive, self-learning system of the AGV (Tuan Le-Anh and De Koster). In this section, AGVS according to the journal by Peters et a1 will be described. According to the journal, the automated guided vehicle system can be divided into three basic levels such as below:
a) Static path
b) Dynamic path
2. Vehicle capacity
a) Single unit load
b) Multiple loads
· 3. Vehicle addressing mechanism
a) Direct address
b) Indirect address
Modern AGV Features
- Modern AGVs are computer-controlled vehicles with onboard microprocessors.
- Position feedback system to correct path
- Communication between vehicles via system controller
- System management computers
- Optimising the AGV utilisation
- Tracking the material in transfer and directing the AGV traffic.
Types of AGVSs
- AGVS towing vehicle
- AGVS unit load carriers
- AGVS pallet trucks
- AGVS forklift trucks
- AGVS light-load transporters
- AGVS assembly-line vehicles
AGVS Guidance system
- The goal of an AGVS guidance system keep the AGV on track/predefined path
- One of the major advantage of AGV is ease in modification given by the guidance system for changing the guide path at low cost compare to conveyors, chains, etc.
- Another benefit is: guide path is flexible which means intersection of path is possible.
- Generally, guide path does not obstruct another systems.
- The guidance systems can be selected based on the type of AGV selected, its application, requirement and environmental limitation.
- Wire-guided -An energized wire is rooted along the guide path. The antenna of the AGV follows the rooted wire.
- Optical-Colorless florescent particles are painted on the concrete/tiled floor.Photosensors are used to track these particles.
- Inertial-The guide path is programmed on a microprocessor which is fixed on the AGV. Sonar system is incorporated for finding obstacles.
- Infrared-Infrared light transmitters are used to detect the position of the vehicle. Reflectors are affixed on the top of vehicle to reflect the light.
- Laser-Laser beam is used to scan wall-mounted bar-coded reflectors. Accurate positioning can be obtained
- Teaching type-AGV learns the guide path by moving the required route. Sends the information to the host computer
- A routing system is used to select the vehicle which is positioned with the optimum path.
- A network controller gives the destination, while the on-board controller navigates the vehicle.
- Commonly used methods:
- Frequency select method
- Path-switch select method