Introduction To The SERCOS interfaceâ¢ - Sercos N.A.

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The format used for an IDN plus a sample IDN are shown in the following illustration. IDN Name (abbreviation) Function/description Length in bytes Minimum input value Maximum input value Scaling/resolution Units S-00047 Position command value During the position control drive operation mode, the position command values are transferred from the control unit to the drive according to the time pattern of the control unit cycle. 4 Min. ≥ -2 31 Max. ≤ +2 31 -1 Scaling type: IDN00076 Scaling factor: IDN 00077 Scaling exponent: IDN 00078 Rotational position resolution: IDN 00079 G. Cycle Times The SERCOS interface cycle time is specified in a flexible format of 62.5 microseconds, 125, 250, 500, and then multiples of 1 millisecond. SERCOS III cycle times begin at 31.25 microseconds. The amount & type of data contained in a cycle is also variable. This flexibility permits a designer to vary cycle time, content and number of drives to achieve a particular project’s requirements. More data can be sent faster to a smaller number of drives. Slowing the rate down permits a higher density of drives per ring. For example, with generations I and II, 4 to 8 axes are common on a ring in machine tool applications where intense communication is required to control a high-speed tool path. Up to 40 axes may be controlled on a ring in packaging applications, and up to 100 axes may be found in web-fed printing applications, where electronic line shafting is utilized to synchronize a number of print cylinders and auxiliary axes. When necessary, multiple rings can be employed in an application. H. Error Correction/Diagnostics The SERCOS interface offers extensive diagnostic reporting and produces detailed reports on fault conditions. This allows vendors to incorporate detailed context-sensitive troubleshooting procedures in their motion controls. An operator can go to his control panel and acquire instant diagnosis of every axis motor and drive at every section of the machine. Failures can be immediately pinpointed by the control system and quickly and easily be repaired as opposed to hit and miss troubleshooting. I. Service and IP Channels Generations I and II SERCOS interface include a service channel, which can be used for the transfer of communication data as well as parameter or diagnostic data in non-realtime. To maintain downward compatibility, SERCOS III also has the service channel. SERCOS III also offers an optional IP channel for transfer of real-time and non-real-time data via standard Ethernet frames. The service channel and IP channel are configurable. Introduction to the SERCOS interface -- Sept. 2006 -- Page 8
VIII. Differences and Similarities with other Communication Busses Fieldbus protocols (DeviceNet, Profibus and others) were designed for I/O and are intended for low-level devices -- such as sensors, motor starters and inverters -- which are mainly turned on and off, or which require an asynchronous analog command value. A number of these busses can be used for control of loosely coupled drives – but motion control is not their primary function. On the other hand, the SERCOS interface was designed for high-speed control of tightly coupled motion axes, where deterministic control is of high importance. In a high-speed packaging line or multi-axis machine tool, sub-microsecond synchronization accuracy of multiple axes in the system is required. Although the SERCOS interface was not designed primarily to be a fieldbus, it has the ability to decentralize I/O via multiple I/O nodes that connect to the field devices. The I/O requirements may be satisfied via the SERCOS interface, negating the need for a separate fieldbus. However, in high-power applications, such as flexible machine systems, both a fieldbus and SERCOS interface often exist in the same control system. The decision of whether to use a fieldbus, SERCOS interface, or both, depends on the application. If only loose coupling between axes is required, a series of single-axis position drives connected via a fieldbus may be adequate. However, in a synchronized motion application, the SERCOS interface is required; and I/O can be handled over the SERCOS interface, depending on the requirements and complexity of the system. A number of manufacturers offer SERCOS interface I/O systems. Introduction to the SERCOS interface -- Sept. 2006 -- Page 9
Page 1 and 2: I. General Description Introduction
Page 3 and 4: III. Three Generations of the SERCO
Page 5 and 6: the motion bus, and use Ethernet ha
Page 7: B. Communications Structure In orde
Page 11 and 12: X. Ideal for Distributed Multi-axis
Page 13 and 14: Typical applications for such a pro

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