SOLUTIONS MATERIAL HANDLING By Chad Carlberg
Smart, compact electromechanical actuators improve AGV productivity and space efficiency Integration with AGVs on plant floors increases operational intelligence
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utomated 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 Figure 1: AGVs increase efficiency in manufacturing applications. Image courtesy: Thomson Industries www.plantengineering.com
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. PLANT ENGINEERING
January/February 2021
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