What are Factors to Consider when Using AGVs
The make use of automated guided vehicles (AGV) has played a pivotal role in facilitating the process and throughput efficiency in manufacturing and distribution operations. Interfacing with multiple auto-transfer devices, AGVs provide reliable raw materials and merchandise handling, with less prospect of product damage, in comparison to manual ways of transport.
Utilizing a combo of the logic program and wired or wi-fi navigation, AGVs is capable of doing tasks that aren’t possible with other transfer systems-such when the uniform motion and positioning of loads to within just a fraction of a great inch of their specified targets, without hurry and noise, and with a higher amount of safety for personnel and the operational environment.
Transporting these serious loads, however, imparts large forces after these vehicles, leading to significant protection and power requirements to retain AGV fleets operating. Newer models incorporate style, navigation, sensor, and vitality improvements that can drastically streamline their operational effectiveness, cost of protection, and ROI, in addition to prior AGVs.
Various kinds of AGVs exist for use in several industries, including those vehicles suitable for extremely weighty or oversize loads. But also for a big amount of applications in making and distribution, AGVs are used for pallet movement.
AGV Program TYPES FOR PALLET MOVEMENT
For pallet movements, four types of AGVs are generally employed. Basic differentiating elements that require to be regarded for every kind of AGV program are the following:
- Fork AGV System
Outrigger counterbalanced or under-rigger
Pantograph or traversing-mast reach
Single- or double-fork
All-wheel steer, omnidirectional.
- Lift Deck/Device Load AGV System
Electric power lift versus hydraulic lift
Differential steering versus single-steer drive.
- Conveyor Deck AGV System
Single- or dual-conveyor
Off-board power requirements
Payloads up to 60 tons
Dual-steer drive, quad movements.
- Tugger AGV System
Braking-negative g-force to avoid vehicle safely
Grades-much more torque necessary to go upgrades
Automatic coupling and hitching
Floor flatness critical.
You will find a linear relationship between your run time of an AGV and its weight. Presented any battery size, if 10% of the weight is removed from the vehicle, it’ll travel 10% much longer. Commensurately, if 20% of the pounds is reduced, it’ll travel 20% longer.
When contemplating a forked vehicle program, for instance, this weight-to-travel ratio could have considerable implications. A counterbalanced automobile will have to add 40-50% of the vehicle’s pounds for the counterbalance. With an outrigger style, or under-rigger style (for European-design pallets), the expanded wheels support the strain, so that vehicle design is 40-50% lighter.
Other factors enter into play with excess weight as well. The implications of a car of this size which has a 40-50% weight-loss are of enormous effects. Lighter weight cars will need less recurrent battery charging, accordingly, fewer battery chargers will come to be needed to support a fleet. Repair and use requirements for these lighter fat cars are commensurately diminished. The strength draw wanted from AGV batteries is reduced. And repairs necessary for plant floors, due to the AGVs and their load weights, are as well considerably lessened.
Although the outrigger and the under-rigger avoid the counterweight, the counterbalanced vehicle is a far more narrow truck, that will permit movement in extra narrow aisles, enabling denser pallet storage and a smaller floor footprint.
AGVs have got typically been designed so that the fat of the AGV is 40-60% of the expected load. This 40/60 ratio possesses been the traditional AGV style practice for decades. It has nowadays evolved with the launch of lighter, better AGVs, which weigh significantly less than regular AGVs, and so are engineered to lessen wear and energy consumption. They not only meet the payload requirements of modern-day heavier models but meet or exceed those cars’ structural stress thresholds.
Many AGVs in procedure within making plants, and several of those first placed into procedure before 2000, were often built with Ackermann steering links. This set up of linkages, commonly employed for steering automobiles and trucks, remedies the condition of establishing wheel angles in a move, considering that each wheel must trace out circles of several radii. The problem is normally that Ackermann steering geometry simply approximates the mandatory steering angles, permitting inaccuracies that cause wheel scrubbing. With such large loads in transfer, the outcome creates considerable mend and protection requirements. The wheel scrubbing not merely increases amp draw, but may also trigger concrete and tire dress in.
Newer AGVs can also be engineered with electronic independent-wheel steering, which includes considerable implications for AGV operability, vehicle protection, and service requirements, and harm to plant floors.
Electronic independent-wheel steering eliminates Ackermann steering geometry and the problems it creates. The automobile can now get sideways or in virtually any direction, allowing shorter trips, thereby lowering the fleet size. The four-wheel independent steering supplies restricted maneuvering and smoother cornering.
Options for batteries in AGVs are predominantly business lead-acid and Lithium chemistries. The most conventional vitality source found in AGVs possesses been but still is, business lead-acid. But business lead is major. Since the battery run period is immediately proportional to automobile and payload weight, a decrease in vehicle fat on AGVs straight impacts the run period of its batteries. Subsequently, any weight-loss exhibited by AGVs results in a longer run period from the batteries before needing a recharge.
New battery technology also plays a part in fat loss. A Lithium-ion answer, for example, with the ability to put out 140 amp hours of vitality would weigh about 150 pounds. Review this to a business lead-acid battery adding out the same vitality, but weighing 700 pounds. For the same vitality, 550 pounds have already been removed from the automobile.
The recharge time for Lithium-ion solutions is approximately 4X faster than lead-acid. And usual lead-acid recharge cycles happen to be about 1,000, while Lithium-ion phosphate is normally nearer to 4,000 cycles. In a nutshell, the Lithium-ion phosphate battery is certainly charging 4X faster and providing 4X the life in comparison to lead-acid.
AGV systems include navigation systems, predicated on laser and/or perhaps inertial guidance. Each program varies in performance, overall flexibility, and cost.
Laser navigation systems derive from the focus on triangulation to keep carefully the vehicles on training. The vehicle has a rotating laser beam beacon, which scans 360 degrees around the automobile for laser targets attached to columns, walls, and stationary machinery. The reflections from these targets happen to be measured following angles from the automobile and triangulated to permit the automobile to determine its posture. This position is in comparison to a CAD-type map placed in the vehicle’s storage.
The machine uses positive-positioning feedback instantly, computing algorithms a huge selection of times per second. The targets are usually located 20 to 50 feet aside, on both sides of the road to provide satisfactory navigation image resolution. The steering is modified accordingly to keep carefully the AGV on the monitor. It can in that case navigate to a preferred target using the frequently updating position. Laser beam navigation can buy tracking accuracy around +/- .75 inches on vehicles of the size.
Inertial satnav systems use a gyroscope onboard the AGV to find changes in vehicle direction and attitude. Each vehicle includes a CAD-type map of the machine layout in its storage. The automobile steers by comparing info from the gyroscope and odometry sensors (which estimate transformation constantly in place) to the map, and producing necessary course corrections every time it passes over a magnet or transponder.
Commonly, the tracking of inertial satnav systems is +/- one inch of the real path. Magnets or transponders happen to be embedded in the ground every 30 to 60 feet to keep up the tracking accuracy.
Both navigation methods could be seamlessly combined in an idea called multi-navigation, which switches backward and forwards from laser beam to inertial guidance without stopping the automobile. This enables the AGVs to go within a plant and outside, where one program alone might not get access to the physical environment or weather conditions essential to support that system.
AGVs traveling nominally 2 mph, and so are equipped with outboard laser beam bumper sensors for object detection. Within the auto 360 degrees incorporating upwards, the sensors are made to cause the automobiles to change their velocity, or stop if required if an obstacle is certainly detected within their path. After the path is very clear, the AGVs will immediately continue their mission.
Some bumper sensors possess a variety starting at about 1,500 lux (the SI product of illuminance and luminous emittance). These different AGVs utilize the latest safely laser technology, incorporating 15,000 lux devices, with a 10 circumstances bigger tolerance to light.
The smooth functioning of AGVs would depend on the controls system, which includes the duty of coordinating the orders received from the plant’s process system or warehouse management system, or ERP, then directing the task for the automated guided vehicles.
More complex controls systems could be by using a Windows and SQL database architecture that’s in a position to uniquely operate within an individual platform. Communication is supplied by two-approach radio transmissions between your vehicles and the pc. The controls present real-time supervision of the system’s procedure, including management facts, load prioritization, load position, productivity statistics and information, and workload examination. It allows associated features to be automated-such much as receiving, recyclables storage, hotline procedures, roll mill processes, frigid mill processes, finished merchandise storage, and shipping.
The positional status of every AGV is consistently being updated through the controls system, at least one time per second, regarding such factors as whether it’s loaded or unloaded, emergency stopped or soft stopped, operating in manual mode, and battery pack level. A simulation module simulates the AGVs in the machine. An HMI graphical user interface provides the operator a graphical summary of the AGV spots in the machine and monitors each in real-time.
Operational versatility is an integral factor with newer controls systems-not just on its capability to immediate and manage the fleet of AGVs, but also on its expandability. A variety of AGVs can get put into the network, anytime plant development or distribution needs need.
AGVs, with fat loss and electronic independent-wheel steering, can deliver a big decrease in maintenance and fixes. Realistically, up to a 60% decrease in gross annual maintenance, per vehicle, may be accomplished.
Contributing to this can be the accessibility of the AGV to execute maintenance or fixes. With conventional AGVs, usage of wheels, gears, and additional moving parts are generally unexposed, requiring the automobile to come to be hoisted or moved right into a pit to get serviced. That is an inherent problem which includes been resolved in a few recent AGV models.
AGV system simulations provide excellent system development rules for perfect circumstances. But such circumstances seldom exist in making and logistics conveniences. What-if conditions must be factored into the simulation, including the variable of human being interaction on to the floor where AGVs happen to be in motion.
Fleet size is monitored by: a) level of merchandise transported per approach; and b) amount of route. The larger the AGV program, the more important may be the dependence on simulation. In something bigger than five or six cars, the simulation will be a need, as mathematics calculations only cannot adequately account for vehicle-to-throughput ratios.
Likewise influencing the performance of AGV systems is temperature and humidity, wi-fi insurance policy coverage over the region of transportation, electromagnetic interference (EMI), the conductivity of the ground coating, and flooring drain, slopes, and grades. These elements should be considered when deciding the most optimum methodology for an AGV program.
AGVs permit significant efficiencies to development and distribution. They boost development flow by bringing materials to the operators, therefore cutting cycle instances, and eliminating hang on, walk, and search period. They reduce work-in-improvement inventory. They chop labor costs through the elimination of simple jobs linked to material and movements and invite reassignment of those personnel to areas where they can add more benefit to the center. Occasionally, AGVs can practically eradicate product damage with delicate managing of loads, and offer the versatility of process circulation and throughput, as desires change.
Chuck Russell is vice president of revenue with Transbotics Corp., a supplier of automated guided cars, automated guided vehicles, and custom engineered cars for creation and warehouse facilities.