Abstract:
A data transmission system is described that connects a controller with drives in machine tools and production machines. The controller can be connected via an internal data bus with at least one internal drive, wherein the same data bus profiles are used for the internal data bus as for an external data bus. A user then sees the same data interface both for a central control topology and a drive-based control topology. This allows the user to readily interchange the two topologies and port existing applications to the various control topologies.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]    This application claims the priority of German Patent Application, Serial No. 103 08 654.4, filed Feb. 27, 2003, pursuant to 35 U.S.C.  119 ( a )-( d ), the disclosure of which is incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a data transmission system for connecting a controller with drives in machine tools or production machines via a data bus, and more particularly for connecting a controller with differently configured drives or for connecting differently configured drives with each other using different bus systems. In the application, the term “production machine” is used here in a generic sense and includes also robots which generally follow the concepts outlined here.  
           [0003]    Currently two different commercially available control topologies are used for controlling motors and/or axles of machine tools or production machines, including robots. One control topology is referred to as a central control topology, whereas the other control topology is referred to as a drive-based control topology.  
           [0004]    [0004]FIG. 1 shows in the form of a block diagram an exemplary conventional central control topology. This control topology includes a controller  1  which forms a self-contained building block and is connected for data exchange via an external data bus  2  to external drives  3   a ,  3   b  and  3   c , and optionally to additional drives (not shown for sake of clarity). Each drive  3   a ,  3   b  and  3   c  includes control modules implemented as hardware and/or software modules, as well as a converter module for controlling and powering a motor  5   a ,  5   b  or  5   c  which drives, for example, an axle of the machine tool or production machine. The converter module need not be integrated in the drive, but can also be an external module connected to the drive. The control modules and the converter modules are not shown for sake of clarity.  
           [0005]    For determining the actual controlled variables, the individual drives are connected with transducers, whereby only one corresponding transducer  6   a ,  6   b  and  6   c  is shown in FIG. 1 for sake of clarity. In addition, as depicted in FIG. 1, the drives  3   a ,  3   b  and  3   c  are frequently connected with I/O units (input output units)  4   a ,  4   b  and  4   c  to enable exchange of data and/or signals between the drives and the I/O units. The I/O units  4   a ,  4   b  and  4   c  can also be an integral component of the corresponding drive. For controlling a motor of an axle of the machine, the controller  1  transmits via the external data bus  2  a desired axle value (e.g., desired position value or desired rotation speed value) to the external drive  3   a  which controls the motor  5   a  according to a preset desired axle position value. With the central control topology, the controller  1  and the external drives form separate units that are connected with each other for data exchange via the external data bus  2  which can be implemented, for example, as a Profibus.  
           [0006]    [0006]FIG. 2 shows in form of a block diagram a different conventional control topology referred to as drive-based control topology. Unlike the central control topology depicted in FIG. 1, the controller  1  of the drive-based control topology together with an internal drive  8  forms a single unit which is referred to as drive-based controller  7 . The controller  1  and the internal drive  8  is connected for data exchange via an internal data bus  12  which can be implemented for example as PCI (Peripheral Component Interconnect) data bus. The internal drive  8  is also connected with an I/O unit  9 , a motor  10  and a transducer  11 . The drive  8  includes control modules implemented as hardware and/or software modules, as well as converter modules for controlling and powering a motor  10  which drives, for example, an axle of the machine tool or production machine. The converter module need not be integrated in the drive  8 , but can also be an external module connected to the drive. A single drive can also include several converter modules. The control modules and the converter modules are not shown in FIG. 2 for sake of clarity. The motor  10  is controlled in the same manner as described above with reference to the central control topology, by transmitting desired values from the controller  1  via the internal data bus  12  to the internal drive  8   a  as desired controlled variables. Optionally, the drive-based controller  7  can also have several internal drives, as illustrated in FIG. 8.  
           [0007]    In the two control topologies described above, the actual values determined by the transducers and I/O units are returned to the controller via the data bus, for example for display to an operator. It should be mentioned that the internal drive  8  can also be connected to several motors, transducers or additional I/O units, so that several axles can be controlled simultaneously using a single internal drive  8 .  
           [0008]    The drive-based control topologies of FIG. 2 are increasingly used due to their favorable cost and performance. However, disadvantageously, the drive-based control topology can control only a limited number of motors and/or drives when using a single drive-based controller  7 . To this date, it has not been possible to expand drive-based control topologies by, for example, connecting external drives to a drive-based controller.  
           [0009]    It would therefore be desirable and advantageous to provide an improved system for controlling drives of machine tools and/or production machines that are capable of operating with different drive topologies, which obviates prior art shortcomings and more specifically facilitates porting existing user applications between the different drive topologies.  
         SUMMARY OF THE INVENTION  
         [0010]    According to one aspect of the present invention, a data transmission system for machine tools or production machines includes a controller, at least one internal drive and at least one external drive. An internal parallel data bus with an internal data bus profile connects the controller with the internal drive. An external data bus with an external data bus profile that is identical to the internal data bus profile connects the controller with the external drive. The external bus can be a Profibus, a real-time Ethernet bus, a USB bus, a FireWire bus, a Sercos bus and/or a Profinet bus or a combination thereof.  
           [0011]    According to another aspect of the invention, a data transmission system for machine tools or production machines includes a controller, at least one internal drive and at least one external drive. An internal parallel data bus with an internal data bus profile connects the controller with the internal drive. An external data bus with an external data bus profile that is identical to the internal data bus profile connects an internal drive with an external drive. The external bus can be a Profibus, a real-time Ethernet bus, a USB bus, a FireWire bus, a Sercos bus and/or a Profinet bus or a combination thereof.  
           [0012]    The afore-described embodiments advantageously retain the user interfaces that relate to the bus participant, such as the functions of activating/deactivating bus participants when using Profibus. The data transmission system of the invention, due to the uniform logical appearance of the internal and external drives, can be easily scaled, i.e., the number of drives and I/O units that can be connected to the controller can be readily increased, and the drives and the I/O units integrated in the drives or externally connected to the drives can be more efficiently utilized.  
           [0013]    With the uniform approach for configuring and programming the internal and external drives, including the corresponding I/O units, applications and/or programs for the controller can be generated that operate identically for both internal and external drives and can therefore be easily interchanged between the different control topologies. The user interface, from the controller to the internal and external drives, is identical and uses identical data bus profiles. In addition, the internal drive is modeled in the same way as an external bus participant and can be configured as a so-called slave. This means that the user interfaces related to the bus participant, for example the functions of activating/deactivating bus participants with Profibus, remain identical. The interface between controller and internal drives, which are modeled as bus participants, has the same system properties as the interface between controller and external drives. This applies in particular to the timing and the exchange of desired and actual data. The scalability is enhanced by enabling additional drives and I/O units to be homogeneously connected to a drive-based controller via an external fieldbus.  
           [0014]    Moreover, with the data transmission system of the invention, drives from other manufacturers can be readily connected to drive-based controllers via an external fieldbus.  
           [0015]    According to another feature of the invention, if the external data bus supports a secure data communication (e.g. PROFIsafe), this secure data communication is also available on the internal data bus without additional measures, since the internal and external data bus profiles are identical. Internal and external drive can also be closely coupled, since the same timing characteristic and performance can be set for these drives. When using central control topologies, the I/O units typically used with internal drives and integrated in the external drive can be homogeneously integrated into the configuration and programming concepts in the same way as the I/O units of external drives. I/O units can therefore be transparently expanded outside the external data bus.  
           [0016]    According to another feature of the present invention, the internal data can be a parallel bus, in particular a PCI bus. A PCI bus is a widespread bus system.  
           [0017]    According to another feature of the present invention, the external data bus can be a Profibus, a real-time Ethernet bus, a USB bus, a FireWire bus, a Sercos bus and/or a Profinet bus. Profibus, real-time Ethernet bus, FireWire bus, Sercos bus and Profinet bus are well-known bus systems.  
           [0018]    According to another feature of the present invention, the I/O units integrated in the internal drives or connected externally can be integrated with external drives having the same data bus profile. The I/O units of internal and external drives can then be treated equally by the user.  
           [0019]    Advantageously, the internal data bus, the controller and the internal drive can be logically configured in the same manner as the external data bus.  
           [0020]    According to another feature of the present invention, the at least one internal drive and the at least one external drive are closely coupled, in particular with respect to clock pulse synchronization and/or identical timing and/or synchronized acquisition of actual values. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0021]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:  
         [0022]    [0022]FIG. 1 shows a schematic block diagram of a conventional central control topology;  
         [0023]    [0023]FIG. 2 shows a schematic block diagram of a conventional drive-based control topology;  
         [0024]    [0024]FIG. 3 shows a schematic block diagram of a drive-based control topology with additional decentralized drives according to the present invention;  
         [0025]    [0025]FIG. 4 shows schematic block diagram of an alternative drive-based control topology with additional decentralized drives according to the invention;  
         [0026]    [0026]FIG. 5 shows a logical design and programming diagram of the integration of the drives to the controller;  
         [0027]    [0027]FIG. 6 shows schematic block diagram of a design of a drive axle;  
         [0028]    [0028]FIG. 7 shows an illustration of a data bus profile: and  
         [0029]    [0029]FIG. 8 shows a schematic block diagram of a drive-based control topology with several internal drives.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0030]    Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.  
         [0031]    Turning now to the drawing, and in particular to FIG. 3, there is shown in form of block diagram a physical view of the data transmission system according to the present invention. A drive-based controller  7  is connected for data exchange with the internal drive  8  via an internal bus  12  which in the illustrated embodiment is implemented as a PCI bus. The drive  8  is connected with an external I/O unit  9 , a motor  10  and a transducer  11 . The internal drive  8  includes control and converter modules for controlling and powering the motor  10 . The control and converter modules are not shown for the sake of clarity.  
         [0032]    The controller  1 , the internal data bus  12  and the internal drive  8  are implemented in a common unit. The internal drive  8  is capable of simultaneously controlling several motors or axles of the machine, whereby only one motor  10 , one I/O unit  9  and one transducer  11  are shown for sake of clarity. The I/O unit which is depicted as an external I/O unit, can also be an integral component of the internal drive  8 .  
         [0033]    The motor  10  is controlled by presetting in the control module of the drive  8 , for example with the help of a position controller implemented inside the controller  1 , via the internal bus  12  a desired axle rotation value as a desired value. The drive  8  then controls the motor according to the desired axle value and moves, for example, an axle of the machine to the corresponding desired axle position value.  
         [0034]    So far, FIG. 3 is identical with FIG. 2. However, unlike FIG. 2, the drive-based controller  7  or the controller  1  in FIG. 3 is connected with the external drives  3   a ,  3   b  and  3   c  for data exchange via an external data bus  2 , which in the illustrated embodiment is implemented as a Profibus. Each of the drives  3   a ,  3   b  and  3   c  is connected with a corresponding external I/O unit  4   a ,  4   b  and  4   c  as well as with a corresponding motor  5   a ,  5   b  and  5   c  and a corresponding transducer  6   a ,  6   b  and  6   c . The motor  5   a  is again controlled by computing in the controller  1  a desired axle position value which is transmitted to a control module located, for example, inside the external drive  3   a . The external drive  3   a  controls with an actual value signal generated by the transducer  6   a  the motor  5   a  according to the desired value set by the controller  1 . Conversely, signals from the drives  3   a ,  3   b  and  3   c  can be transmitted, for example for display purposes, from the I/O units to the controller  1 . The external data bus  2  can, of course, also be a real-time Ethernet bus, a FireWire bus, a Sercos bus, a Profinet bus, and/or a USB (Universal Serial Bus) bus.  
         [0035]    For configuring and programming the system, the internal drive  8  and the external drives  3   a ,  3   b  and  3   c  should be logically equivalent, since a designer, programmer or user would then no longer have to be concerned with the differences between an internal drive  8  and an external drive  3   a ,  3   b  and  3   c . Applications and/or programs, which were originally written, for example, for the central control topology of FIG. 1 or the entirely drive-based control topology according to FIG. 2, or for a drive-based control topology depicted FIG. 3, can then be interchangeably used also for one of the other topologies.  
         [0036]    Each the data bus has a so-called data bus profile. FIG. 7 shows an embodiment of a data bus profile. In a physical sense, a message is transmitted on the data bus as a sequence of data bytes. The data bus profile describes the content, i.e., the meaning of a message, e.g., the employed data type (bytes, word), and the significance (e.g., actual value, desired value, control word or status word). The sender and recipient of different manufacturers can then interpret the message in the same way. In one example, the two first bytes in a data bus profile may represent a control word, e.g. a command for a drive, with the bytes  3  to  6  representing, for example, a desired rotation speed value. In a response message from a drive, the first to bytes can describe, for example, the state of the drive and the bytes  3  to  6  can describe an actual rotation speed value. Optionally, a data bus can also include several different data bus profiles. A data bus profile can also include at the beginning and the end of a message additional data used to coordinate the message traffic on the data bus. These additional data are not shown in FIG. 7 for sake of clarity.  
         [0037]    According to the invention, the same data bus profiles are used for communicating on the internal data bus  12  as on the external data bus  2 . In the embodiment depicted in FIG. 3, the internal data bus  12  which is implemented as a PCI bus operates in principle like a Profibus due to its data bus profile which is identical to the data bus profile of the external data bus  2  implemented as a Profibus. The data interface between the controller  1  and the internal drive  8  is hence defined like the data interface between the controller  1  and the drives  3   a ,  3   b  and  3   c.    
         [0038]    [0038]FIG. 5 shows in form of a block diagram the resulting logical programming and configuration view of the data interface between the controller  1  and the internal drive  8 , as well as between the controller  1  and the external drives  3   a ,  3   b  and  3   c . When looking at the logical connection, all internal drives are connected to a so-called internal virtual Profibus  9   a  which is also depicted in FIG. 5. All external drives are connected, again looking at their logical connection, to an external Profibus  9   a , also depicted in FIG. 5. In the depicted embodiment, external and internal drives are connected to separate Profibuses  9   a  and  9   b . Alternatively, the external and internal drives can also be connected to a common Profibus, or individual drives or groups of drives can be connected to a dedicated Profibus, looking at their logical connection. The controller  1  operates as a so-called master  18 , whereas the drives operate as slaves. Accordingly, a slave  22  is associated with the internal drive  8 , a slave  19  is associated with the external drive  3   a , a slave  20  is associated with the external drive  3   b , and a slave  21  is associated with the external drive  3   c . The internal drive  8  therefore appears, with respect to the logical and bus-topological connection, like an additional slave  22  that is connected to the virtual internal Profibus  9   a . The slaves  19 ,  20  and  21  are connected to the external Profibus  9   b.    
         [0039]    The virtual internal Profibus  9   a  is configured in the same manner at the external Profibus  9   b . The settings defined by the integration boundary conditions can shorten the design phase, because optionally fixed settings can be used. The configuration of the internal virtual Profibus  9   a  is only marginally different from the configuration of the external Profibus  9   b , due to physical differences (e.g., transmission duration with a PCI bus as compared to a 12 MBaud Profibus solution).  
         [0040]    [0040]FIG. 5 uses the same identifiers for the I/O units, the motors and the transducers as FIG. 3. It should be mentioned that an I/O unit connected to the external drive  8  or an I/O unit integrated in the internal drive  8  is homogeneously integrated by the data transmission system of the invention in the same manner as the I/O units of the decentralized drives  3   a ,  3   b  and  3   c . This approach enables scaling of the number of I/O units close to the drives.  
         [0041]    [0041]FIG. 6 shows in form of a block diagram an advantageous exemplary configuration of the data transmission system of the invention. The machine axles and drives are represented by a rectangular functional blocks. For example, an operator assigns a machine axle  15  to the internal drive  8 , which can be accomplished graphically by connecting the machine axle  15  with the internal drive  8  by a connecting line  16 . If the operator inputs a position and a desired displacement of the machine axle  15 , for example 20 mm, then the drive axle  15  associated with the external drive  8  will be moved by 20 mm. If in the depicted embodiment an axle associated with the external drive  3   a  is to be moved instead of the axle  15  associated with the internal drive  8 , then the operator has to delete the connection  15  and establish a connection  17  indicated by a dotted line. Configuring an internal or external axle appears therefore identical to a user.  
         [0042]    [0042]FIG. 4 shows a block diagram of another alternative embodiment of the data transmission system of the invention. This block diagram corresponds essentially to that of FIG. 3, with the exception that the external data bus is not connected with the controller  1 , but with the internal drive  8 . The data from the internal controller  1  are then physically transmitted first to the internal drive  8  and from there via the external bus  2  to the external drives  3   a ,  3   b  and  3   c  and vice versa. Such bus structure or network structure can be employed to externally extend the internal data bus so as to scale the number of drives via a kind of “back wall bus.” For example, the drive-internal communication system can then be used for connecting drive components (such as power components, motors, transducers) for a “back wall bus extension.” 
         [0043]    The external extension can be implemented by a different medium, such as a real-time Ethernet bus, FireWire bus or Profibus.  
         [0044]    By configuring the data bus profile of the internal data bus  12  identical to the data bus profile of the external data bus  2 , the logical configuration and programming environment is again identical to that depicted in FIG. 5, depending on the employed external bus system. The external data bus  2  can, of course, also be implemented as a USB (Universal Serial Bus) bus. The identifiers used in FIG. 4 for the I/O units, motors and transducers are identical to those of FIG. 3.  
         [0045]    The block diagram of FIG. 8 shows another embodiment of the data transmission system of the invention. A drive-based controller  7  is connected with the internal drives  8   a ,  8   b  and  8   c  for data exchange via an internal bus  12 , which in this embodiment is implemented as a PCI bus. Each of the drives  8   a ,  8   b  and  8   c  is connected with a corresponding internal I/O unit  9   a ,  9   b  and  9   c  that is integrated in the corresponding drive, with a motor  10   a ,  10   b  and  10   c  and with a transducer  11   a ,  11   b  and  11   c . The internal drives  8   a ,  8   b  and  8   c  each include control modules which can be implemented as hardware or software modules, as well as a converter for controlling and powering the motor  10 . The control modules and the converter are not shown for sake of clarity. The controller  1 , the internal data bus  12  and the internal drives  8   a ,  8   b  and  8   c  are located in a common unit. The individual drives  8   a ,  8   b  and  8   c  can be addressed in an identical manner due to the fact that the same data bus profiles are used on the internal data bus  12  as on the external data bus, so that they appear logically to be connected to an external data bus. The external data bus, which is not physically implemented in the embodiment of FIG. 8, can be defined, for example, as a Profibus. Accordingly, the user can address the individual drives  8   a ,  8   b  and  8   c  as Profibus participants, for example as slaves. The application and/or the program on the controller  1  remain fully functional even if the system is expanded at a later date by connecting to an external data bus. The additional drives, for example external drives, are then logically connected to the bus system simply as additional slaves.  
         [0046]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.  
         [0047]    What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: