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Free-range mobility for Auto­mated Guided Vehi­cles

Batch sizes are becoming smaller, product life cycles are shorter, rigid conveyor belts and inflex­ible produc­tion lines are giving way to modular concepts. In addi­tion, manu­fac­turing and storage areas are expen­sive and opti­mizing space saves costs. Quick, flex­ible and reli­able mate­rial flow concepts are required to imple­ment this – using freely navi­gable Auto­mated Guided Vehi­cles (AGV). Omni­di­rec­tional mobility is a key feature of trans­port solu­tions.

AGVs have been in use for a long time in many ware­houses, distri­b­u­tion centers and manu­fac­turing facil­i­ties. They are used to trans­port mate­rial in containers or on pallets, without requiring a phys­ical trans­port network. Yet, if you look around many halls, the AGVs move in a rigid and inflex­ible way, running along the line mark­ings made on the floor.

So long as rigid produc­tion lines are being set up, partic­u­larly in manu­fac­turing, there is an elegant mate­rial supply solu­tion using track-guided solu­tions. If the prod­ucts to be manu­fac­tured go through the machines like a pearl chain, from one processing step to the next without vari­ance, the flow of mate­rial does not require any changes.

Track-guided solu­tions have advan­tages, such as a low level of complexity and compa­rably simple safety tech­nology, but their flex­i­bility is very limited. The AGVs can only stop if they reach obsta­cles: they cannot drive around them. However, the far greater disad­van­tage in modern manu­fac­turing scenarios is that selec­tively approaching produc­tion stations and imple­menting auto­matic route changes is not possible. Route changes require new line mark­ings on the floor: it is not possible to simply recon­figure them using soft­ware.

This means that track-guided solu­tions in modern manu­fac­turing and intral­o­gis­tics concepts are no longer keeping pace with the times, because the increasing number of assem­blies with a modular set-up for high product vari­ance require new concepts to keep goods flowing. In addi­tion to a flex­ible flow of mate­rials, mobile machines are also an impor­tant factor. For example, AGVs auto­mat­i­cally trans­port the robot mounted onto them to the next work­sta­tion.

Modern produc­tion concepts require AGVs that can navi­gate completely freely and offer unre­stricted free-range mobility. (Graphic | ebm-papst)

AGVs that can navi­gate completely freely and offer unre­stricted free-range mobility are neces­sary for imple­menting modern manu­fac­turing concepts and opti­mizing intral­o­gis­tics processes. Of course, control­ling and navi­gating vehi­cles with free-range mobility is more complex. There are greater require­ments for sensors and safety tech­nology, but sophis­ti­cated solu­tions already exist. Below, read why exten­sive free-range mobility with omni­di­rec­tional freedom of move­ment in AGVs enables greater effi­ciency in logis­tics and produc­tion.

Reduce space require­ments and the asso­ci­ated costs

On the one hand, space in ware­houses and manu­fac­turing facil­i­ties comes at a high fixed cost. On the other hand, it soon becomes diffi­cult to find space to carry out all of the neces­sary activ­i­ties, partic­u­larly if there is a growing volume of orders. There­fore, making optimum use of space provides an impor­tant contri­bu­tion to the Overall Equip­ment Effec­tive­ness (OEE) in existing build­ings and manu­fac­turing areas as well as in new designs. For track-guided AGVs in partic­ular, a lot of space has to be reserved for the routes.

Limited maneu­ver­ability means that a lot of surface area is required to accom­mo­date the bends and load transfer points. In prin­ciple, these AGVs can be compared with passenger cars, as these too have a limited freedom of move­ment. For example, it is not possible for them to turn when stationary or to move side­ways. In addi­tion, the line-marked routes must always be kept clear, including a safety zone. It is not possible to place tempo­rary struc­tures or to store mate­rials and machines there. Flex­i­bility in the layout of logis­tics and manu­fac­turing areas remains restricted.

Even in very confined envi­ron­ments, the AGVs can carry out exact manoeu­vres with omni­di­rec­tional motion.

However, using freely navi­gable AGVs with drive solu­tions for free-range travel means that a lot less space is required for cornering and maneu­vering at mate­rial transfer points. Omni­di­rec­tional systems with complete free-range mobility enable all travel manoeu­vres. These include moving trans­verse to the direc­tion of travel, turning when stationary and many combi­na­tions of move­ments.

Even in very confined envi­ron­ments, the AGVs can carry out exact manoeu­vres with omni­di­rec­tional motion. In prin­ciple, their maneu­ver­ability is compa­rable with a hover­craft: the orien­ta­tion of the trans­port frame is inde­pen­dent from the direc­tion and posi­tion of travel.

Enabling modular produc­tion

AGVs’ free-range mobility not only saves space. The free navi­ga­tion also reduces the distances that need to be trav­eled and simpli­fies driving around sudden or tempo­rary obsta­cles. This increases the dynamics and speed and, there­fore, the mate­rial throughput. Further­more, the AGVs’ free-range mobility makes it possible to imple­ment future-oriented and modular produc­tions for the first time.

A new drive solu­tion for AGVs with free-range mobility: The Argo­Drive driving/steering system from ebm-papst. (Photo | ebm-papst)

Due to the smaller batch sizes and constantly increasing product vari­ance, rigid conveyor belts and inflex­ible produc­tion lines are increas­ingly becoming a thing of the past. The future of produc­tion means flex­ible manu­fac­turing down to a batch size of one. In this context, both machines and entire produc­tion lines have to be quickly converted using modu­lar­iza­tion. This also requires flex­ible mate­rial trans­port, both to the machine and to the next machine. Mobile robotics is also being increas­ingly imple­mented in modular manu­fac­turing systems.

Appli­ca­tion scenarios for exten­sive free-range mobility

These scenarios can no longer be achieved with track-guided AGVs. The vehicle solu­tions have to be moved freely to the next work­sta­tion via sensors, which is imple­mented using a higher-level local­iza­tion and control system. This control system knows exactly when and where which processing station has to be approached by which AGV with which goods and assigns the appro­priate travel orders.

Since the layout of the space in modern manu­fac­turing scenarios changes often and every angle is utilized, the AGVs must be extremely maneu­ver­able and offer omni­di­rec­tional mobility to reach their desti­na­tion quickly and safely even in very tight envi­ron­ments. The AGV also has to guar­antee quick and safe braking using its drive tech­nology if there are unex­pected obsta­cles. Driving on different floor cover­ings and over­coming gradi­ents are other demands placed on the drive tech­nology to allow greater flex­i­bility in manu­fac­turing and the asso­ci­ated intral­o­gis­tics.

Since the layout of the space in modern manu­fac­turing scenarios changes often, the AGVs must be extremely maneu­ver­able and offer omni­di­rec­tional mobility.

Although the floors at manu­fac­turing sites and logis­tics centers are typi­cally made of smooth, cement-bonded indus­trial screed with an acry­late-based primer, halls often have strong expan­sion joints, rough sections and different cover­ings. In addi­tion, AGVs also have to travel back and forth between halls, for example to get mate­rial from the ware­house.

When doing so, the AGV has to travel over tarred surfaces and often over­come inclines at crossovers. Drive solu­tions with high maneu­ver­ability, such as the Mecanum wheel, quickly run into prob­lems here, because they require smooth ground to move. However, this restric­tion is not neces­sary, as there are driving/steering systems that meet all the require­ments of future-proof AGVs.

Fine posi­tioning for high preci­sion

The omni­di­rec­tional mobility of AGVs, facil­i­tated by modern driving/steering systems, is also required for fine posi­tioning at the machine and at mate­rial transfer stations. Here, precise adjust­ment down to the millimeter is required to enable containers to be moved into the work­sta­tion, for example. Equipped with high-reso­lu­tion sensors and low-back­lash mechanics, an omni­di­rec­tional driving/steering system posi­tions every AGV quickly and effi­ciently with maximum preci­sion.

With the Argo­Drive driving/steering system from ebm-papst, AGVs navi­gate freely and omni­di­rec­tion­ally over the entire area, drive around unex­pected obsta­cles and move easily even in very tight envi­ron­ments. (Graphik | ebm-papst)

However, the majority of current mobile AGVs have a chassis concept with three wheels, in which only one – like a classic fork­lift concept – ensures steering move­ment. Differ­en­tial solu­tions are also wide­spread: in this chassis concept, the AGV can rotate around its own axis but does not perform trans­versal move­ments.

Precise posi­tioning requires time-consuming repeated forward and back­ward move­ments with addi­tional steering or rota­tional move­ments: this also requires addi­tional space. Drive concepts for vehi­cles with omni­di­rec­tional motion, such as pivoted bogies or Mecanum, once again have special require­ments for the floor condi­tion, are slow and have a high level of complexity.

Effi­cient imple­men­ta­tion of free-range mobility

A new drive solu­tion for AGVs with free-range mobility is the Argo­Drive driving/steering system from ebm-papst. It combines propul­sion and steering func­tions in one assembly. This unit consists of motors, special trans­mis­sions, sensors and all the neces­sary connec­tions. Its two motors contribute towards steering, accel­er­a­tion, move­ment and braking, depending on require­ments. The infi­nite steering angle enables space-saving, free-range vehicle move­ment – even from a stationary posi­tion.

The driving/steering system from ebm-papst combines propul­sion and steering func­tions in one assembly.

Two driving/steering systems on the left and right side of the AGV guar­antee full omni­di­rec­tion­ality. Two addi­tional freely moving support wheels on the front and rear ensure stability. Depending on the required size of AGV and the weight of the goods to be moved, three or four driving/steering systems can also be installed. This enables large loads to be achieved even if there are inclines.

ebm-papst offers its Argo­Drive driving/steering system in light, stan­dard and heavy versions for weight classes up to 100, 300 or 500 kg in order to meet every require­ment for moving masses, for braking and for mastering inclines in a scal­able way. For example, four driving/steering systems in the heavy version allow a total vehicle weight of up to two metric tons.

Bene­fits combined in one driving/steering system

There are various chassis concepts for putting AGVs into service. How maneu­ver­able the vehicle is in the end and how much load it can carry depends greatly on the drive and the wheels. Depending on topology, users often have to accept compro­mises and, for example, sacri­fice maneu­ver­ability or compact­ness. New solu­tions such as the driving/steering system from ebm-papst mini­mize any compro­mises for manu­fac­turers of future-oriented AGVs.

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