Page 18

Industrial Ethernet Book 105

Improving the reliability of motion control networks Network reliability can be the difference in producing a damaged part or a production part. Network topologies and protocols with built-in capabilities can ensure that electrical noise doesn’t damage parts are all part of optimizing system performance. THE MOST POPULAR MOTION control networks today are Ethernet based. Ethernet has won the battle for the hardware layer in these types of networks. The ubiquity of Ethernet in computer networks has led to speed and cost advantages that are difficult to compete against. But the hardware layer is just the first decision when designing a reliable network. Other choices include the right protocol and the network topology. While speed is important, it should not be the only criteria that you use to select an Ethernet protocol for your motion control network. Reliability of the network can be the difference in producing a damaged part or a production part. Certain protocols have features built in to ensure that electrical noise does not ruin your part. As an example, Yaskawa’s Mechatrolink III protocol has a retry feature built into the ASIC chip of the products that will resend a packet during the same communication cycle if the original packet failed to reach its destination. This feature has proven its reliability in applications like machine tools and semiconductor Master controller Setup tool HMI Servo Drive IO Temperature Inverter controller manufacturing where a minor flaw in the part can cause significant financial losses. Another often overlooked contributor to a network’s reliability is its topology. Network topology refers to how the network is connected or structured. It can refer to the physical layout and to the logical layout. The Ethernet etc Star connection logical structure is how the controller sees the network which may or may not be the same as the physical layout. However, in motion control networks they are usually the same. The easiest and by far the most common topology is the cascading bus. In this network you have a cable that plugs into your controller and into the first drive. That drive has two identical connectors and you use the second connector to cable from the first drive to the second. This continues until all of the nodes of the network have been connected. The nodes don’t have to be the same product type and usually consist of a variety of servos, inverters and remote I/O blocks. The popularity of this topology come s f rom its simplicity and cost. However, it does have some disadvantages. The dependency on the serial nature of this topology Technology Slave#1 Slave#2 Transmission Cycle Slave#3 Slave#1 Slave#3 Slave#1 18 industrial ethernet book 4.2018 SOURCE: YASKAWA SYNC CMD RSP CMD RSP CMD RSP CMD RSP Retry CMD RSP SYNC Cyclic Communication CMD RSP C1 master ASIC tries to send the command as a retry to the slave again if the retry time remains. Stepping motor Ethernet Gateway Slave controller Cascade MECHATROLINK-III connection MECHATROLINK-III Master controller MECHATROLINK Hub The easiest and by far the most common topology is the cascading sus, but a star topology offers significant benefits. Mechatrolink III has a retry feature that resends a packet during the same cycle if the original packet failed to reach its destination. SOURCE: YASKAWA


Industrial Ethernet Book 105
To see the actual publication please follow the link above