Relying on PC-based PLC system from Beckhoff, America in Motion’s iBOT Automatic Guided Vehicles break new ground with path planning system.
When one thinks about automated guided vehicles (AGVs), their imagination often stirs up images from science fiction. Tiny robots, scurrying about and completing the menial tasks of their human bosses. Today, we are seeing a technological renaissance where these formerly fantastical concepts have become reality. Take, for example, the autonomous vehicles and drones being developed by Google and Amazon. AGVs in today’s large-scale warehousing operations bear a striking resemblance to the way we may imagine them in this context – autonomous devices conveying products in flurry of a high-tech activity.
America in Motion (AIM), a Charlotte, N.C.-based builder of AGV systems, designs and manufactures just such devices, integrating new technologies to provide tailored application solutions. Rather than building a line of homogenous AGVs and hoping customers can accept them, AIM builds custom solutions, as Tommy Hessler, CEO at AIM explains: “Because the needs of each AGV installation are so varied, our team takes great care to guide customers through the process to discover solutions that are best suited for their automation needs.”
An AGV is a mobile robot that follows markers or wires in the floor, or uses vision, magnets, or lasers for navigation; for industrial applications, they are most often used to move materials around a manufacturing facility or warehouse. Though they all adhere to a basic level of functionality, there is an incredibly wide variety of AGV types, sizes, and price points based on the needs of the application. Whether handling products, delivering mail or performing other automated jobs, these robust, flexible machines can be infinitely configured to complete many tasks.
AGVs provide a lift to upgraded warehouse operations
Approximately three years ago, AIM was approached by a leading home improvement retailer to help expand their distribution facilities with an AGV system tailored for their new storage and shipping centers. The company specified their preferred mechanical platform and asked AIM to apply an automated guidance system to this existing platform. Traditional AGV automation systems lacked the flexibility and robust operation necessary to accomplish this task, leading AIM to ultimately seek out a PC-based control system from Beckhoff.
As a result, the newest iteration of AGVs at AIM is the iBOT series which uses both Kalman filters and odometry for navigation, as well as the Dijkstra algorithm, a mathematical process for finding the shortest path between two points. Instead of using a proprietary, AGV-specific control system, AIM uses standard PC-based control technology to equip these vehicles with modern path-planning functionality, similar to any number of navigation apps used on smartphones. The advanced iBOT series is growing in popularity and, in just one example, has found a home with this large home-improvement retailer, working in the company’s distribution facilities by moving pallets of stock keeping units (SKUs) to locations throughout the facility for storage or outbound shipping. These AGVs use all the typical functions of a forklift, such as forward motion, steering and mast control.
For this application, AIM engineers designed an entire fleet of what are essentially automated robotic forklifts shunting SKUs to various stations within a distribution facility. Each AGV is totally autonomous, carrying out instructions with minimal operator input.
This is deceptively simple, as the nature of the pallets varies from operation to operation. Hessler explains: “As you can imagine, people don’t buy a whole pallet’s worth of products. Each pallet contains a mix of products, so the size and weight of each pallet is constantly changing. The vehicle picks up the packed pallet and drives it to one of several stretch wrappers and drops it off, all while automatically avoiding warehouse shelves, human workers, and the seven other AGVs.”
The scale of the project was daunting, as the 1,200-ft long warehouse necessitated mapping of thousands of positions, and for the system to track order numbers and individual products on the pallets, all while relaying this information back to the central computer for collection and monitoring. Complicating matters further, the fleet of AGVs receives around 80 orders at a time, so it is important to optimize the operation of the AGVs by minimizing distances and travel times, which also ensures error-free operation.
The future of AGV controls, guided by PC-based PLC system
For much of AGV history, a dedicated, hard-coded system running some sort of path-planning algorithm provided the motion control of the robotic system. Hard-wired controls and general system complexity made programming and commissioning these vehicles a time and labor-intensive process.
“You can view an AGV just like any piece of equipment, as each consists of 3 different component categories: mechanics, electrical wiring, and electronic controls with software,” said Hessler. “Most end users have the experience to address any mechanical or electrical issues on an AGV, but when it comes to the controls and the software, they are often boxed in and have no choice but to rely on a single source vendor for support.” This makes an AGV system a less attractive option for many users, as their operation will be dependent on a single vendor. Hessler continues: “With the iBOT series, we now have an AGV based on a PLC system from Beckhoff that makes breaks down that barrier. Suddenly, an AGV can be supported just like a traditional PLC system with standard parts, enabling easy replacement of components.”
Again, AIM chose a different path and implemented a PC-based control system in their iBOT series, in this case CP6606-0001-0020 Panel PCs running TwinCAT software. These systems enable AIM to program PLC functionality in software creating a PLC in software while being able to integrate numerous other features into the Windows system. A step up from the previous version using a separate control panel and Embedded PC, the new system features an integrated Panel PC which provides all the necessary processing power in the iBOT systems. The device features a 1 GHz ARM Cortex-A8 CPU, Windows Embedded Compact 7 operating system, 1 GB of RAM, fanless operation and no rotating components. The Panel PC is integrated directly on the AGV, handling the iBOT system HMI display and reducing control component count.
In addition, four stationary display panels, in this case 19-in. Stainless Steel, IP 65-rated CP7703 Panel PCs, are mounted at various locations around the home improvement retailer’s distribution facility. Each device displays the positions and traffic statistics of the eight AGVs and tracks performance, loads per hour, and any errors or performance inadequacies.
Traditional onboard navigational systems use laser sensors and an algorithm to determine X, Y and T (angle) of the vehicle in relation to obstacles in a warehouse. Through the TwinCAT automation platform running on the Embedded PC, this functionality can be accomplished in software and carried out in real-time via the EtherCAT industrial Ethernet system. TwinCAT 2 currently provides the programming environment and runtime for the automation system, enabling PLC functions in software and adding a measure of accessibility to the system. TwinCAT TCP/IP server provides a layer of communication between the AGVs and the end users’ corporate networks and facilitates communication between the controller and the onboard third party navigational system components. The processes handled by the controller are time critical, as the navigation system needs to know where the vehicle is at all times to avoid potential crashes and damaged product. A selection of EtherCAT I/O terminals provides fast onboard communication for the AGVs.
The I/O system also provides flexibility in communication to non-EtherCAT devices via EL6751 CANopen terminals and EL6021 RS422 terminals, which serve as interfaces for routing back to the navigation controller. In addition, an EL6224 IO-Link terminal provides communication for height sensors on the AGV forklift mast. “Precision is key for the height sensors, given the nature of the application,” said Hessler. “For example, say the tines of a fork need to travel over a height of 30-ft to reach a pallet located on a shelf. Misalignment of only one or two percent is enough to miss the pallet entirely, which is completely unacceptable in a time-critical application such as this. We tried several alternative options, but IO-Link components from Beckhoff remain the easiest way to remove any noise or faulty information from the operation.”
The iBOT series AGVs also monitor the onboard battery, offering an automatic “quick charge” system that can replenish the battery in just 6 minutes after an hour of running.
AGVs with “shortest-path optimization” ̶ the strongest link in the supply chain
Click To Tweet Said Hessler, “This is a huge step toward to position the AGV as a mainstream material handling and logistics solution. By removing a significant portion of the cost and by making the programming much more accessible, more customers accept highly automated systems, thereby growing our business.”
By using this new PC-based control architecture, AIM was able to slash around 40% off the cost of a traditional PLC-based AGV control system. According to Hessler, this is primarily a function of the economies of scale. “Traditionally, AGV control system volumes are relatively low, often around 100 or so orders for any series, making each unit much more expensive. We reduced our costs dramatically by moving to a standard system with PC-based hardware and an economical automation software platform like TwinCAT ̶ savings we pass along to our customers,” said Hessler.
Hessler continued, noting that AIM is fully onboard with the PC-based control philosophy, as it is the standard platform for every AGV and AGC (automatic guided cart) the company manufactures. AIM also intends to further implement advance the PC- and EtherCAT-based platforms in future AGV and AGC offerings. “There is still incredible potential with the PC Control platform and with the ability to program path-planning and PLC functionality in software. We have several new projects in the works with large customers that will also feature the iBOT system, and look forward to continuing our progress with the PC-based platform in these applications.”
As consumer product orders from large retailers, both online and brick and mortar, continue to grow unabated, automation will play a significant role to meet demand, satisfy customers and boost profitability. The increased adoption of AGVs and other automated warehousing systems is a primary example here. The fantasy that once typified robotics in science fiction has become a tangible reality today, and companies like America in Motion and Beckhoff maintain a solid foothold in this growth market, ideally positioned to provide the next generation of automation solutions.