Applications range from moving small packages around sorting operations, to moving heavy machinery in manufacturing operations. Logistics automation removes the need for human operators – improving reliability, reducing operating costs and avoiding accidents. The ability to optimise material flows can be even more significant, reducing inventory, while increasing productivity and warehouse capacity.
“The adoption of robotics has come about through a requirement to cut operating costs and to reduce our reliance on labour. The headcount we needed to attract during peak periods was resulting in us having to adjust our pay structure beyond what we ideally wanted to pay,” said Gordon Knox, director of logistics at apparel brand Superdry.
Also, using AGVs to automate logistics avoids bolting heavy machinery to the floor. Everything can be automated in a flexible way, using standard robots and racking. This greatly increases the flexibility of operations.
“Flexible technology combined with powerful, intelligent software allows for a new way of thinking. A conventional conveyor system is normally installed to an agreed throughput, usually to a projected peak figure. But this results in the asset running below capacity for the majority of the year. On the quietest day, it may only handle a tenth of the volume experienced at peak.
However, a solution using AMRs could be designed for 70% of peak, with additional robots brought in during peak periods. It’s this level of scalability that offers small enterprises a flexible, low-entry point to automation,” says Craig Whitehouse, managing director of Invar Integration.
AGVs and AMRs often function as autonomous forklifts, moving pallets around without the need for a human driver, or as automated tow tractors able to pull several carts at once. Smaller AGVs can be designed to conveniently carry picking containers, while larger versions can move very heavy machinery or assemblies. Forklift/pallet and trailer systems – although established for manual operation – are easily automated. Newer systems may load and unload from conveyors, or use special-purpose materials handling systems.
Very large AGVs might be used to move and precisely position large production machinery such as jigs and machine tools, as well as large assemblies. At the Airbus fuselage assembly plant in Hamburg, a KUKA OmniMove transports and aligns airframe sections weighing up to 90 tonnes.
Safety is a key concern when robots are operating in the same space as humans. In the case of AGVs, safety may actually be improved. Forklifts are the most dangerous form of workplace transport in the UK, injuring more people than heavy goods vehicles. Every year they cause 1,300 debilitating and life-changing injuries, according to the British Safety Council. Although nothing is foolproof, accidents involving AGVs are much less common, due to the greater reliability of the automated safety systems.
NAVIGATION
AGVs follow lines on the floor. These may be simple painted lines or coloured tape, which are tracked using optical sensors. Magnetic tape and conductive wires are also used to mark drive routes, providing greater reliability than optical sensors. Tracking lines may be combined with RFID tags providing waypoints. AGVs can be commanded remotely by a management system, or programmed individually with a console on the AGV.
AGVs always follow the same routes. It is, therefore, important that these routes are always kept clear. AGVs will also operate most efficiently if people don’t walk in their path. Workers must also remember that the scanners that detect obstacles operate close to ground level. Raised objects, such as a pallet on a forklift, may not be detected and so could lead to a collision.
Earlier AGV systems simply follow a programmed drive route, stop when a potential collision is detected, and continue when the route is clear. More sophisticated systems allow robots to communicate with each other to optimise material flows. This allows time-critical deliveries to be prioritised, with AGVs carrying less-urgent deliveries waiting for them to pass. This sort of arrangement,difficult to achieve with human-operated forklifts and carts, highlights the advantages of coordinated automation.
Line-following systems are simple and reliable, but not dynamic. Newer systems use vision cameras and lasers for more flexible autonomous navigation. These autonomous mobile robots (AMRs) do not travel along dedicated paths and can take any route around the factory or warehouse floor. AMRs can be programmed by following a human walking in front of them, or can autonomously find their own route.
Large AGVs often use a type of omni-directional wheel known as a Mecanum wheel. These have several freely-rotating rubber rollers attached at an angle around their circumference. When such a wheel is driven, it produces a force vector which is perpendicular to the rollers. This means that the wheel can cause the vehicle to move in the direction the wheel is rotating, or perpendicular to the direction the wheel is pointing. Typically, such a vehicle has four wheels which can be individually driven, although large mobile platforms may use more wheels. If all the wheels rotate in the same direction, the sideways components of force cancel each other out, and the vehicle travels forward as if it had ordinary wheels. When the wheels are driven at different speeds and in opposite directions, the vehicle can be driven in any direction, or rotate on the spot, about any point between the wheels.
DESIGN FOR AUTOMATION
Zooming out, the big picture is that logistics is currently experiencing a design-for-automation revolution. This has followed the first phase of automation, in which machines are initially used to automate existing operations, which brings limited benefits. Once operations are adapted to make them better suited to automation, more significant benefits are encountered.
In sorting and picking applications, AGVs are designed to move underneath specially-configured racking, forming modular pick-walls. They transport them to picking stations, with a predetermined pick-face presented to the worker.
By eliminating workers’ walking time, and using pick-to-light technology, workers can achieve massive productivity increases, with 99.9% accuracy. Pick-to-light uses the following process:
1. The operator scans an item barcode attached to the holding container he or she is about to load.
2. The display gives the type and quantity of the first item to be loaded, and illuminates a path to its storage location.
3. The operator picks these items, places them in the holding container, and presses a button to confirm the step has been completed.
The system continues in this way, illuminating each sector for picking until all items have been picked and placed in their holding containers.
Put-to-light is a similar system, in which the operator organises incoming goods into different storage containers – essentially the reverse of pick-to-light.
“AMRs offer tremendous flexibility and, importantly, scalability, in traditional labour-intensive tasks such as order picking and put-away. AMR systems combined with pick-to-light technology can boost order picking performance from under 100 units per hour using traditional methods, to up to 600 picks per hour, with an ROI that can be as little as 12 months,” states Whitehouse.
BOX: PARCEL SORTATION BY AGV
LiBiao Robot has supplied parcel sortation solutions based on its ‘Mini Yellow’ autonomous mobile robot technology to four sites operated by Yamato, Japan’s leading parcel delivery company. Cross-belt robots with a capacity of 30kg have been deployed at the facilities. The company recently announced that the model is available in Europe.