Smart, compact electromechanical actuators improve AGV productivity and space efficiency
Integration with AGVs on plant floors increases operational intelligence
Automated guided vehicles (AGVs) improve productivity but need room to move about space-constrained factory floors. The more functionality AGV makers pack into a small footprint, the greater value to the end-user.
The right actuation technology is critical to that value, and AGV designers often choose smart electromechanical actuators when seeking high-performance motion control in a small footprint.
In manufacturing, AGVs (see Figure 1) replace much of the human lifting and carrying involved in, for example, delivering blanks to the production line and transferring goods throughout the workshop, warehouse and assembly line. Most AGVs today are guided by laser or magnetic strips, some use cables and fixed tracks, and more and more are communicating wirelessly.
In a typical manufacturing application, a machine operator signals the need for parts using logistics software via workstation call terminal. On receipt of the request, the application forwards it to the AGV management software, which dispatches the nearest vehicle based on priority and optimal pickup and delivery motion. After the operator completes the job, the control system proceeds to the next process step.
The host computer always knows the state, position, speed, direction, fault and power of the AGV, and moves it forward, backward, left and right. When encountering an obstacle, the AGV decelerates and stops to avoid a collision. When the obstacle is removed, AGV operation resumes.
The need for intelligence
As AGV use increases, so does interest in integrating movement with enterprise, automatic storage, modular conveyor and asset management software. The context provided guides creation of optimal workflows for moving materials from one part of a facility to another with the least human effort.
AGV connectivity is accomplished via onboard microprocessors and software to take advantage of digital communications. Smart actuators furnish built-in intelligence as well. This enables integration with AGV automation schemes and communications among actuators themselves. The ability to synchronize actuators with each other, for example, could enable creation of an AGV lift table (see Figure 2).
Electromechanical actuators are best suited for intelligent integration with AGVs intended for plant-floor applications. As illustrated in Figure 3, lower-priced, belt-driven, scissor-type cam gear and hydraulic systems have little or no digital integration capability. Gear screws do have digital integration capability, but also require an additional motor and controller, so can cost as much, if not more, than a smart electromechanical actuator. Hollow-screw actuators have comparable digital integration capability and technologies, but their high cost is difficult to justify except for high-speed, high-volume warehousing and distribution applications, such as e-commerce packaging and shipping.
Benefits of compactness
Optimizing floor space always has benefits, whether it avoids the cost of adding buildings or getting maximum return on existing space. Because AGVs can be configured quickly and easily, they are more space-efficient than conveyor belts, which are typically immobile. But AGVs themselves require operating room in the space. They need to travel around the plant floor and to fit in tighter spaces.
The use of smaller actuators is one way to make operations more space-efficient, but the amount of space required to mount them remains an issue. Typical electromechanical actuators have load adapters in both the front and the rear. Replacing the traditional rear adapter with a mounting flange reduces the overall length and stroke length ratio, returning space to the system designer.
It also makes the AGV easier to deploy in compact spaces, while reducing energy use. The latter is especially important if the AGV design calls for more expensive lithium-ion batteries. Lower energy consumption also means longer work terms and lower charging frequency, which also contribute to overall productivity.
Figure 4: Comparison of actuation options based on operating space requirements. Courtesy: Thomson Industries[/caption]
Wherever goods and parts need to be moved across a level surface, there is a potential role for smart, compact AGVs. Following are examples of industries in which AGVs are commonly used:
Consumer Goods. AGVs are found in consumer goods industries, including electronics, medicine, chemical, cigarette, textiles and home appliances. They trolley everything from parts for fine work and packaging to heavy palletized objects. In air conditioner manufacturing, for example, this might involve transporting mounting plates, rear nets, covers, panels, motors, air outlets, face frames, covers and capacitors to and from appropriate workstations. In addition to the space efficiencies that electromechanical actuators bring to these applications for large, heavy items such as refrigerators, the onboard intelligence provides the ability to synchronize movement across the load.
Fiberglass production. In the production of glass fiber, where silica is drawn into thin filaments that are bonded together, AGVs might integrate with CNC machine tools, intelligent industrial robots and production lines. They would automatically transfer the raw silica cake from drawing to drying to cutting and then onto packaging, stacking and storing. The workflow is tightly orchestrated end to end, and the programmability of electromechanical actuators enables fiberglass producers to optimize efficiency.
Automotive manufacturing. In automotive manufacturing, AGVs replace manual efforts, forklifts and other methods traditionally used to deliver doors, hoods, hinges, bolts and other components to appropriate locations. The high load handling capability of electromechanical actuators is especially valuable in automotive manufacturing.
Electronics manufacturing. Lack of immediate availability of wafers, fixtures or other components is among the most frequent causes of interruption of electronics production line scheduling, and even slight delays can be costly. By helping ensure that the right components are in the right place at the right time, smart, compact AGVs, aided by programmable actuators, enable high process efficiencies for electronics production.
Electronics system testing. Electromagnetics of electronic systems such as control panels must be tested in an environment that would not add electrical discharge. AGVs equipped with actuators can be programmed to push sequences of buttons at consistent rates and be moved from test bays to conduct tests without interfering. This requires actuators that have been thoroughly tested for low electromagnetic radiation during electronic actions such as inductive load switching, positive inductance transience, positive and negative coupling, cranking, load dumping, electromagnetic immunity, conducted emissions, and radiated emissions.
Rising labor costs are a key driver for AGV user growth, but the need to maximize return on all assets is paramount as well. Those assets include the AGVs themselves and the space through which they move. Specifying smart, safe electromechanical actuators that demand minimal space is one significant step that designers can take to optimize today’s AGVs for tomorrow’s applications.
Most analysts are predicting sustained growth in AGV usage as global competitiveness continues to heighten.