Abstract:
The disclosure comprises methods for controlling a production machine having a converter controlled drive wherein the applicable converter receives data from its associated drive as well as additional data from the machine and wherein the converter provides actuation commands to the drive and to the machine. Related systems are also disclosed.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a control method for a machine, in particular a production machine, for example a plastics injection-molding machine, with at least one converter-controlled drive, a converter outputting activation commands with a drive clock to the drive and acquiring actual data of the drive. 
   Every machine with a converter-controlled drive is operated in this way. 
   BACKGROUND OF THE INVENTION 
   In particular in the case of production machines, the movement of drives must often be captured by data acquisition and undergo automatic control dependent on process data. For example, the advancement of a screw of a plastics injection-molding machine must be automatically controlled exactly in dependence on the back pressure. Accurate process data acquisition is the basis for the exact reproducibility of the production process carried out by the production machine. 
   Accurate process data acquisition necessitates high acquisition frequencies and—in the case of analog signals—a high resolution of the analog-digital converters. Furthermore, as many of the process data as possible, preferably all of them, should be acquired time-synchronously, since a time difference between the acquisition of different process data leads to inaccuracies in the subsequent automatic control. 
   In the prior art, the acquisition of the process data takes place by means of high-speed input modules, by means of which the analog signals to be acquired are digitized. The digitized signals are then transmitted to a higher-level controller, which also supplies the converter with setpoint values. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to design a control method of the type stated at the beginning in such a way that the acquisition of the process data is possible in a more simple and less costly way. 
   The object is achieved by the converter outputting in addition to the output of the activation commands further activation commands to the machine and/or acquiring in addition to the acquisition of the actual data of the drive further actual data of the machine. 
   This results in many advantages. 
   On the one hand, it is possible in a simple way to ensure that the output of the further activation commands takes place synchronously with the output of the activation commands and/or the acquisition of the further actual data takes place synchronously with the acquisition of the actual data of the drive. 
   The further activation commands and/or the further data may in this case be optionally analog or digital signals. 
   The drive clock should have a frequency of at least 200 Hz, in particular of 1000 Hz or more. It may be generated internally in the converter. Preferably, however, it is fed to the converter from the outside. This is so because it allows in particular a number of converter-controlled drives, each with their own assigned converter, to be synchronized with one another in a simple way. 
   The actual data of the drive generally comprise the position, rotational speed and/or torque or current of the drive. In particular in the case of plastics injection-molding machines, the further actual data of the machine generally comprise a temperature and/or a pressure or force. They may also comprise status messages and manual inputs. 
   In the case of a conventional construction, the control data for the drive are transmitted from a higher-level controller to the converter via a bus. In this case, the converter also transmits the further actual data of the machine to the higher-level controller. It is possible, however, for the further actual data of the machine to be preprocessed, for example smoothed, summated or interpolated by the converter before the transmission to the higher-level controller. The further activation commands—in the same way as the control data for the drive—are likewise transmitted from the controller to the converter via the bus. 
   On account of the acquisition of the further machine data by the converter, it is possible to implement the higher-level controller in a PC or a microprocessor device. In particular in these cases, it is also possible to form the converter as a decentralized peripheral module and to form the bus as a field bus. 
   However, as an alternative to the provision of a higher-level controller, it is also possible by the present invention for the converter to control the machine completely. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages and details emerge from the description which follows of an exemplary embodiment in conjunction with the drawings, in which, in a basic representation: 
       FIG. 1  shows a machine with an associated control system, 
       FIG. 2  shows a converter and 
       FIG. 3  shows the machine from  FIG. 1  with a converter. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   According to  FIG. 1 , a production machine  1 , here a plastics injection-molding machine  1 , has at least one converter-controlled drive  2 . By means of the drive  2 , an advancing screw  3  is made to move for example, in order to press plasticized granules into an injection mold  4  (mold  4 ). As this happens, it is possible to make the speed, the position or the pressure undergo automatic control—even dependent on the state of the process. A purely time-controlled method is also conceivable. 
   The plastics injection-molding machine  1  is controlled by a control system. The control system has a higher-level controller  5 . The higher-level controller  5  is implemented, for example, as a so-called soft programmable controller in a PC or a microprocessor device. 
   The higher-level controller  5  transmits to a converter  6  control data s*, n* and/or m* for the drive  2 . The control data s*, n* and/or m* comprise in particular a setpoint value s* for a position s, a setpoint value n* for a rotational speed n and also a setpoint value m* for a torque m (or a current) of the drive  2 . The rotational speed n of the drive  2  corresponds to the advancing speed of the advancing screw  3 , the position s of the drive corresponds to the position of the advancing screw  3 , the torque m corresponds to the force of the advancing screw  3 . 
   The higher-level controller  5  also transmits further activation commands p*, T* and/or x* to the converter  6 . The further activation commands p*, T* and/or x* comprise in particular setpoint values p*, T* for a pressure p and a temperature T in a space  7  in front of the screw and also further setpoint values x*. The further setpoint values x* may comprise, for example, a setpoint value for an internal or external metering system, an actuator (for example a piezoelectric actuator), control signals for an operator control and observation panel or a release command for the injection mold  4  for removal of the injection molding. 
   The control data s*, n* and/or m* and the further activation commands p*, T* and/or x* are transmitted to the converter  6  via a converter-external bus  8 . According to  FIG. 1 , the bus  8  is formed as a field bus  8 . Corresponding to this, the converter  6  is formed as a decentralized peripheral module. 
   According to  FIG. 1 , a drive clock is also fed to the converter  6  from the outside. The drive clock could, however, also be generated internally in the converter. In the present case, the drive clock has a frequency between 1000 and 2500 Hz. If appropriate, the frequency may also be less than 1000 Hz. However, it should not go below 200 Hz. With this drive clock, the converter  6  outputs the activation commands s*, n*, m* to the drive  2 . At the same time, it acquires the actual data s, n, m of the drive  2 . The actual data s, n, m comprise in particular the position s, the rotational speed n and the torque m (or the current) of the drive  2 . 
   Synchronously with the output of the activation commands s*, n*, m*, that is in particular also with the drive clock, the converter  6  additionally also outputs the further activation commands p*, T*, x* to the plastics injection-molding machine  1  or a device  10  assigned to the plastics injection-molding machine  1 . 
   In addition to and synchonously with the acquisition of the actual data s, n, m of the drive  2 , the converter  6  also acquires further actual data p, T, x of the plastics injection-molding machine  1  or of the assigned device  10 . The further actual data p, T and/or x of the plastics injection-molding machine  1  or of the assigned device  10  comprise, for example, the temperature T and the pressure p in the space  7  in front of the screw and, for example, a (binary) status message of a sensor. The signals p, T are analog signals. The further actual data p, T, x also comprise, however, for example the acquired position of the injection mold  4 , that is whether it is open or closed. This signal is a digital or binary signal. 
   The acquired actual data n, s and/or m of the drive  2  and also the acquired further actual data p, T and/or x of the plastics injection-molding machine  1  or of the assigned device  10  are transmitted from the converter  6  to the higher-level controller  5 . It is possible in this case to transmit the actual data s, n, m, p, T, x directly to the higher-level controller  5 . 
   Preferably, however, the actual data s, n, m, p, T, x are preprocessed, for example smoothed or averaged, by the converter  6  before the transmission to the higher-level controller  5 . This is indicated in  FIG. 1  by the data that are transmitted to the higher-level controller  5  respectively having an apostrophe. 
   The higher-level controller  5  determines on the basis of the actual values s′, n′, m′, p′, T′, x′ obtained whether a step-enabling condition for the plastics injection-molding machine  1  has been achieved. If appropriate, it then outputs new control data s*, n*, m* and/or new activation commands p*, T*, x* to the converter  6 . 
   According to  FIG. 2 , the converter  6  internally has a processing unit  11 , usually a microprocessor  11 , and also a memory  12 . The processing unit  11  is in this case connected to the bus  8 . 
   The converter  6  also has input devices  13 ,  14  and output devices  15 ,  16 . The input and output devices  13  to  16  are likewise connected to the processing unit  11 . Furthermore, the drive clock is fed to them. 
   With each clock, the input units  13 ,  14  read the actual data n, s, m, p, T, x from the plastics injection-molding machine  1  or the assigned device  10  into internal memories. These memories can then be read out by the processing unit  11 . The signal present at the input unit  14  is in this case digitized before storage in the internal memory by means of an analog/digital converter  17 . 
   Similarly, with every clock, an output signal, for example x, is output by the output units  15  to the plastics injection-molding machine  1  or the assigned device  10 . The signal output by the input unit  16  is in this case analogized in a digital-analog converter  18 . After outputting, a new signal to be output can then be written by the processing unit  11  into internal memories of the output units  15 ,  16 . 
   The output of an analog signal, the output of a digital signal, the input of an analog signal and the input of a digital signal are described above. It is evident that all the signals are synchronously output to the plastics injection-molding machine  1  or the assigned device  10  or the drive  2  or read in by them. 
   The processing unit  11  of the converter  6  is generally considerably more powerful than a possible processing unit of a customary high-speed input-output module. It is therefore possible, as schematically indicated in  FIG. 3 , for the converter  6  to control the injection-molding machine  1  completely. In this case it is possible to dispense with the higher-level controlller  5 . The converter-external bus  8  is also not required. The converter  6  in this case represents as it were a stand-alone controller for the plastics injection-molding machine  1 . 
   It is consequently possible by the present invention to execute the acquisition of the further actual data p, T, x of the machine  1  and/or the output of the further activation commands p*, T*, x* to the machine  1  via the converter  6  directly. As a result, not only is an input and output of the process signals achieved time-synchronously with the acquisition of the rotational speed and/or displacement of the drive  2 , but also short signal propagation times are achieved. The accuracy of the automatic control can consequently be increased significantly. In an individual case, the entire control can even be realized in the converter  6 .