April 2020

44 n CONVEYORS, MATERIALS HANDLING AND AGVs April 2020 www.drivesncontrols.com AGV navigation: what are the options? T here are various technologies available for navigating AGVs (automated guided vehicles) from one point to another. They range from contour navigation to laser radar, optical or inductive guidance, to grid navigation. The choice of technology depends on the application. The price of the AGV itself can also be used as a rough guideline. The navigation technology should not represent more than 5% of the AGV’s cost price. For example, for a €10,000 AGV, contour navigation and laser radar are out of the question because they cost more than €500. Another decisive criterion is whether the AGV is a platform vehicle or a drive-under vehicle. Drive-under vehicles are those that move under the load to be transported and lift it up. Their design makes them unsuitable for guidance systems using laser radar. Platform vehicles are those onto which the load is pushed for transport. Against this background, the individual navigation possibilities are considered in detail below with regard to their possible fields of application. Contour navigation Also referred to as “natural navigation,” these navigation systems are the most technically complex, as well as being the most expensive. They are unmatched in terms of flexibility and accuracy. Should it be necessary to change the transportation path at short notice, contour navigation can do this easily and quickly at the click of a mouse using high- level fleet management software. Because the AGV sensors are usually mounted close to the floor, these systems are suitable for automatic high-lift trucks and tractors, as well as for drive-under or platform vehicles. This type of navigation does not need further tools – such as reflectors, or optical or magnetic traces – nor markings or codes. Laser radar Navigation using laser radar is similar in flexibility to contour navigation. This technology does, however, need additional optical paths between sensors and reflectors. Each sensor must therefore be mounted high enough on the AGV so that it always has a clear view of the reflectors. If the path to the reflectors is interrupted – when entering a shelf aisle, for example – the AGV must switch to another type of navigation. This makes it more difficult to change it to operate in another location, if necessary, limiting its flexibility. Optical and inductive guidance These are usually simple systems that follow a predefined trace. As a result, they are limited in terms of their flexibility. On the other hand, they represent a cost-optimised option. Because the sensor on the AGV is mounted only a short distance from the floor, these forms of navigation are independent of the type of vehicle. Grid navigation In these systems, information is embedded in a grid on or in the area being traversed using, for example, 2D codes or transponders. Using the information gathered while traveling over the grid points – with a 2D code, for example, these are the code information and reading angle – the AGV can navigate between the individual grid points and reach any specified point in the grid. This type of navigation is ideal for clean surfaces that are not subject to heavy loading. The choice of the most suitable navigation system can only be determined in combination with the function of the AGV in an application. However, there is a clear trend towards contour navigation with integrated safety functions. n Various technologies are available for guiding AGVs to their destinations. As Matthias Göhner, industry manager for intralogistics at Leuze electronic, explains, there is no single technology that is suitable for all applications. It depends how and where the AGV is being used. Laser scanners offer a flexible form of navigating AGV paths and ensuring safety Optical guidance systems are a cost-optimised option for following predefined paths