Patent Abstract:
A data transmission system with distributed control functionality for machine tools, production machines, and robots, having a plurality of control functional units, has a respectively networked movement control system which controls the operation of the control functional units in complex processes. Information relating to movement control can be interchanged by means of real-time cross-communication between the control functional units. An Ethernet link can be used for real-time cross-communication. The use of the data transmission system for printing machines also represents an advantageous application of the invention.

Full Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims priority to German application number 101 213 22.0 filed May 2, 2001. 
   FIELD OF THE INVENTION 
   The invention relates to a data transmission system having distributed control functionality for machine tools and production machines, and robots, hereinafter referred to generally as machines, and further having a networked movement control system which controls complex processes. 
   BACKGROUND OF THE INVENTION 
   A data transmission system which can be used for machine tools, production machines, and robots, is disclosed in the document “Standardisierter Feldbus für die elektrische Antriebstechnik” [Standardized fieldbus for electrical drive technology], VDI Reports 844, “SERCOS Interface” report, page 69 et seq. The SERCOS interface allows time-controlled bus access to drives. The data messages which are intended for the individual drives are in this case sent in a fixed time frame. An open-loop or closed-loop control system carries out the master function (control functionality) and sends a synchronization signal in time with the cycle time, in response to which the individual drives, i.e., the slaves (secondary functionality), transmit their information to the master. 
   A drive concept for a printing machine without a shaft is disclosed in WO 97/11848. There, information which ensures that the angles of the drives are synchronized during printing rotation is transmitted exclusively via a synchronization bus. 
   Today, it is becoming increasingly important to provide machines, such as machine tools, production machines, and robots, with a network data communications structure, in order to allow production data to be gathered, evaluated and distributed. It is also frequently necessary to match machine units or subunits, and robots, to one another in a production process. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to provide information for movement control systems, which simultaneously control complex processes in networked machine tools, production machines, and robots, in addition to existing data links. This object is achieved through the discovery that information relating to movement control can be interchanged by means of real-time, cross-communication between the control functional units. All movement control systems which control complex processes can thus react simultaneously to relevant events in a matched manner. 
   In a preferred embodiment of the present invention, real-time cross-communication is carried out using Ethernet links. Using Ethernet makes it is possible to use known bus protocols. Particularly when using fast Ethernet, the very short bus cycles used can result in a wider dynamic range due to the movement control system controlling the complex processes. The wider dynamic range advantageously makes it possible to stabilize process discrepancies more quickly. 
   In a further preferred embodiment of the present invention, the control functional units are synchronized by means of Ethernet real-time cross-communication. This enables the stringent requirements for synchronized running to be satisfied, since the master drives can be matched in real time. 
   In yet a further preferred embodiment of the present invention, data and synchronization signals from drive regulators are interchanged with an associated control functional unit using Ethernet real-time communication. Matching of all the drive regulators in a drive group using real-time Ethernet advantageously makes use of all the conventions defined in an Ethernet, and allows real-time matching of all the drives in a group. Thus, for example, high-precision and low-error position control actions can be carried out. 
   One preferred use of the present invention is in printing machines. In modern printing machines there are a range of individually driven rotating machine elements which are dependent on one another and are matched to one another. A disturbance in a driven machine element in a printing machine can thus also be reported immediately, that is to say in real time, to other machine elements. All movement control systems controlling complex processes can react simultaneously to the disturbance in a matched manner and, for example, can avoid paper jams and torn paper webs. Printing machine downtimes can thus be minimized. 

   
     DRAWINGS 
     The invention is described in greater detail below and in the context of the drawing, in which: 
     The single FIGURE is a schematic layout of a printing machine incorporating the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the printing machine illustrated in the drawing, paper webs PB 1  to PB 3  run from paper rolls P 1  to P 3  through printing units D 1  to D 3 , and to a folding apparatus F. After passing through the printing unit D 1 , the paper web PB 1  also passes through further processing units; however, they are not shown in the drawing. Thus, in the drawing, the paper web PB 1  ends in a dashed line. 
   Each printing unit D 1  to D 3  is represented in the illustration by an approximately H-shaped outer contour. The printing units D 1  to D 3  each contain ten cylinders, which are arranged in two groups of five cylinders each. The cylinders represent all the cylindrical or wheel-like machine elements in respective printing units D 1  to D 3 . The paper webs PB 1  to PB 3  run via these cylinder groups, which constitute printing points in the printing units D 1  to D 3 . 
   A printing point essentially comprises a rubber cylinder, a plate cylinder and an inking and moistening mechanism. Each printing point can print ink on one side. All the printing points whose printed paper webs PB 1  to PB 3  are passed to folding apparatus F, are included in a rotation process. In this case, the printing units D 1  to D 3  are normally accommodated in printing towers. Each individually driven cylinder has an associated drive with a respective drive regulator A 1  to A 35 . Each group of drive regulators, A 1  to A 10 , A 11  to A 20  and A 26  to A 35  of respective printing units D 1  to D 3  and A 21  to A 25  for the rotating machine elements of the folding apparatus F has one drive regulator, A 1 , A 20 , A 21  and A 26  with a control functionality LF 1  to LF 4 , for each group. Each group of drive regulators are networked intrinsically in the form of a ring. However, an important feature is that an individual drive regulator A 1 , A 20 , A 21  and A 26  with control functionality LF 1  to LF 4 , is available for each group. Any other data networking which can be carried out within a group is thus also possible. This also includes, for example, serial or star linking. The drive regulators A 1 , A 20 , A 21  and A 26  which have the control functionality LF 1  to LF 4 , are represented by a rectangle drawn with a thicker line than the other regulators. 
   Each of the control functional units LF 1  to LF 4  is coupled to a respective one of associated control computers L 1  to L 4 . The control computers L 1  to L 4  are networked in a control computer communication system by links LK 1  to LK 3  and illustrated in the drawing by dashed lines. Other embodiments of the data networking are also possible. 
   A control computer L 1  to L 4  carries out higher-level process organization and, in the process, normally defines data or parameters that are not time-critical. Thus, for example, the control computers L 1  to L 4  can be used to define the printing units D 1  to D 3  via which a paper webs PB 1  to PB 3  will run, and which drives are intended to run synchronously to one another. 
   In the event of a fault, an operator of a printing machine thus has flexibility to decide which of the printing units D 1  to D 3  will be used. However, this also requires the capability to pass information relating to movement control flexibly to individual printing units D 1  to D 3 . According to the present invention, this is achieved by cross-communication Q 1 , Q 2  and Q 3 . Cross-communication Q 1  to Q 3  is a data link with real-time capability and thus ensures that essential information is available at all movement control points simultaneously. This includes, for example, synchronization and error signals, and signals which necessitate immediate action. 
   In what follows, it is assumed that a specific fault in the folding apparatus F can be rectified by reducing the speed of the paper through the system. Once this fault has been detected, the drive A 21  with the control functionality LF 3  of the folding apparatus F transmits a speed reduction signal to other control functional units LF 1 , LF 2  and LF 4 . The control functional units LF 1 , LF 2  and LF 4  know, via the control computers L 1  to L 4 , which of drive regulators A 1  to A 35  are controlling the movement of the paper webs PB 1  to PB 3  to the folding apparatus F. The respective control functional units LF 1 , LF 2  and LF 4  signal the above-mentioned speed reduction to the appropriate drive regulators. 
   The cross-communication Q 1  to Q 3  in real-time means that all the control functional units LF 1  to LF 4  have this information at the same time. Once a fault has been identified and a counter measure has been initiated, this leads to an immediate reaction at the same time in the drive groups. This advantageously allows an improved printed product quality to be achieved. 
   Since all the control functional units LF 1  to LF 4  are connected by means of real-time cross-communication Q 1  to Q 3 , this ensures that all the information relating to movement control is available all the time throughout the system. Even if the system operator has to reconfigure the system, in terms of the profile of the paper webs PB 1  to PB 3 , as a result of a fault, there is nevertheless no need for him to carry out any rewiring for information distribution. In particular, complex, freely configurable production lines which use machine tools, production machines, and robots in the end profit from the real-time capability of the cross-communication Q 1  to Q 3 . It is even conceivable for such flexibility to be made possible for the first time by the use of cross-communication Q 1  to Q 3  with a real-time capability.

Technology Classification (CPC): 6