Drives & Controls March 2023

26 n MOBILE ROBOTS March 2023 www.drivesncontrols.com Choosing comms to keep mobile robots moving M obile robots are everywhere, fromwarehouses to hospitals and even on the street. Their popularity is easy to understand: they’re often cheaper, safer, easier to find, and more productive than human workers. They’re easy to scale or combine with other machines. And because mobile robots collect a lot of real-time data, companies can use them to begin their IIoT journeys. Let's first define what we mean by mobile robots. Mobile robots transport materials from one location to another and come in two main types: AGVs (automated guided vehicles) and AMRs (autonomous mobile robots). AGVs use guiding infrastructure such as wires, reflectors or magnetic strips, to follow predetermined routes. If an object blocks an AGV’s path, it stops and waits until the object is removed. AMRs are more dynamic. They navigate via maps and use data from cameras, built-in sensors, or laser scanners to detect their surroundings and choose the most efficient route. If an object blocks an AMR’s planned route, it chooses an alternative. Because AMRs are not reliant on guiding infrastructure, they're quicker to install and can adapt to logistical changes. Implementing mobile robotic systems poses several communications and safety challenges. We outline the main ones below. Establishing a wireless connection The first challenge is to select the most suitable wireless communications technology. The usual advice is to establish the requirements, evaluate the standards, and choose the best match. Unfortunately, this isn't always possible because mobile robot manufacturers often they don’t know where their machines will be used or the details of the target application. Sometimes a Bluetooth connection will be fine because it offers a stable non-congested connection. Other applications will require high-speed, secure cellular connections. The second challenge is to ensure that the installation works as planned. Before installing a wireless system, a predictive site survey based on facility drawings needs to be performed to ensure that the mobile robots will have sufficient signal coverage throughout the site. This survey should identify the optimal location for access points (APs), the type of antenna to use, and how to mitigate interference. After installation, you can use wireless sniffer tools can check and adjust APs or antennae as required. Connecting mobile robots to industrial networks Mobile robots need to communicate with controllers, even though they often will use different protocols. For example, an AGV might use CANopen while the controller uses Profinet. You might also want to deploy the same AGV model at a different site where the controller uses an different industrial network, such as EtherCat. Mobile robots need sufficient communications capacity to process the required amount of data. This will vary depending on the size and type of installation. Large installations may use more data because the routing algorithms need to cover a larger area, more vehicles and more potential routes. Vision-based navigation systems need more processing power than those based on other technologies such as reflectors. As a result, installations face following challenges: n the need for a networking technology that supports all major fieldbus and industrial Ethernet networks; n the ability to change the networking technology easily to enable the mobile robots to communicate on the same industrial network as the controller without changing the hardware; and n the need to ensure that the networking technology has sufficient capacity and functionality to process the required data. Creating a safe system The need for mobile robots to transport material safely is a critical, but challenging, task. Installations need to take into account different types of mobile robot, structures and people in the environment. The robots need to be able to react to external actions, such as someone opening a safety door or pushing an emergency stop button, and the networks need to be able to process different safety To work efficiently, mobile robots need safe, reliable communications. Mark Crossley, Daniel Heinzler, Fredrik Brynolf and Thomas Carlsson from HMS Industrial Networks outline the main communication and safety challenges, and suggest ways to overcome them to keep mobile robots moving. The advantages and disadvantages of various wireless communications technologies