Virtualize and optimize new machines before they are built: Sounds like science fiction? Yes. But this is at the heart of the concept of what is called a digital twin. KEB Automation has implemented this using a dSPACE SCALEXIO real-time system, significantly shortening development times for new machines.

Simulations play an important role in the development of industrial machines. Virtual commissioning (described in the VD/VDE Guideline 3693), which is carried out with the aid of a virtual copy of the machine – the digital twin – has become established in this field. In a virtual implementation, machines are virtually commissioned together with their sensors and actuators by means of real-time-capable HIL simulations before the real machine is built (Figure 1), including emulated fieldbus or real-time Ethernet interfaces and the real programmable logic controller (PLC). This way, programming errors in the PLC control code can be detected and corrected before the real machine is commissioned. The result of the virtual commissioning depends, to a large extent, on the level of detail of the plant models.

The Classic Way: Behavior Model

Today, behavior models are often still used for drive controllers that partly result from re-engineering or from the use of isolated firmware code from the real component. However, these behavior models usually only take partial aspects of the real drive controller into account, which can ultimately lead to an error that might only become apparent when the real machine is commissioned. This means: The better the behavior model, the lower the number of iteration loops in machine development.

 

Figure 1: The principle of virtual commissioning.

Step 1: A machine operator has an idea for a new machine and passes this idea on to a mechanical engineer.

Step 2: The mechanical engineer derives the requirements and specifications for the new machine. In addition, component suppliers define the components required for the machine. This way, a digital twin of the machine is created.

Step 3: With the help of the machine’s digital twin, the PLC code developer can start developing the PLC code before the real machine exists. The PLC code can be evaluated on the digital twin of the machine at a very early stage by means of virtual commissioning. This way, errors can be detected and corrected at an early stage.

 

The Better Way: Firmware Simulation Models

Using comprehensive firmware code of the drive controller instead of a behavior model in simulation models has two major advantages: Firstly, the behavior of the firmware simulation models is much more detailed and realistic, for example, in aspects such as diagnostics, detecting configuration errors, and testing parameters. Secondly, their range of functions expands automatically with each firmware update.

Engine Simulation Models Require Powerful Tools

Common simulation tools for virtual commissioning are mainly designed for the simulation of mechanical and material flow elements, including the connection of real PLCs via an emulated fieldbus and real-time Ethernet connection. This is sufficient for the simulation of the mechanical and material flow elements, but not for engine simulation models. Therefore, drive controllers are only abstracted and motors are simulated only in an idealized way, if at all.

 

Figure 2: Virtual commissioning with the help of a dSPACE SCALEXIO real-time system. For the PLC, there is no discernible difference between the digital twin and a real machine.

Profile: EtherCAT Network Simulation

The dSPACE EtherCAT Network Simulation is used to simulate an EtherCAT network in such a way that the controller does not notice any difference in the communication.

Function

The EtherCAT Network Simulation receives EtherCAT frames from the controller and modifies them in such a way that the responses to them look as if they had passed through an EtherCAT participant. Viewed from the outside, only two participants communicate: the controller and the dSPACE system.

Scalable Level of Detail

A dSPACE SCALEXIO system including FPGA can be used to simulate the network participants and the controlled systems connected to them, to varying degrees of quality. A selection of FPGA boards is available for the simulation of very fast processes.

 

Virtual Commissioning in Real Time

This gives the digital twin a platform and a communication interface with which the timing behavior corresponds to that of the real machine, allowing realistic testing of the PLC code. The variable level of detail also lets you simulate energy flows to check the utilization of feed-ins, for example. Another plus: The parameterization of the network participants or even software updates can also be tested before they are applied to a real device and before the real devices are even available.

 

Firmware Simulation with dSPACE SCALEXIO

In contrast, an entire power drive system (PDS) consisting of drive controller and motor models can be executed on the dSPACE SCALEXIO real-time system with switching frequencies up to 16 kHz because of the high-performance processor and FPGA units (Figure 2). This generally enables real-time simulation up to the power output stage. The addition of an emulated fieldbus and a real-time Ethernet interface also allows virtual commissioning that takes into account the power flows. Optimizations for the plant design can also be derived from this simulation. For this purpose, the dSPACE Fieldbus Solution has been extended to include EtherCAT network simulation (info box). With these extensions, the firmware simulation models with all details can also be operated on the SCALEXIO system via a fieldbus and real-time Ethernet with a real PLC. Conclusion and Outlook With the performance of SCALEXIO systems in combination with the expansion of the Fieldbus Solution (info box) regarding virtual EtherCAT slaves, new fields of application are opening up for KEB Automation: The testing of KEB drive controllers via HIL simulations can now be extended to include SIL simulations of the KEB firmware. This makes it possible to find and correct programming errors in the firmware code, even before the HIL simulations begin. Therefore, KEB plans to expand the portfolio of firmware simulation models for further KEB drive converters; in addition, the firmware simulation models will also be provided as Functional Mock-up Units (FMUs) in the future.

 

Conclusion and Outlook

With the performance of SCALEXIO systems in combination with the expansion of the Fieldbus Solution (info box) regarding virtual EtherCAT slaves, new fields of application are opening up for KEB Automation: The testing of KEB drive controllers via HIL simulations can now be extended to include SIL simulations of the KEB firmware. This makes it possible to find and correct programming errors in the firmware code, even before the HIL simulations begin. Therefore, KEB plans to expand the portfolio of firmware simulation models for further KEB drive converters; in addition, the firmware simulation models will also be provided as Functional Mock-up Units (FMUs) in the future.

Manuel Brose, KEB Automation​​​​​​​

 
Company Profile KEB Automation

Company Profile KEB Automation

As a well-known supplier of drive technology, KEB Automation offers the full range of solutions for automation. Plastics machinery, wood processing, process technology, and intralogistics, or even wind energy and e-mobility: KEB is the source of a complete solution from HMIs to controls and drives to motors, gears, and brakes. Family-run since 1972, the KEB Automation Group, headquartered in Barntrup (NRW), is active worldwide with almost 1,500 employees in twelve subsidiaries and more than 50 partners.

dSPACE MAGAZINE, PUBLISHED JUNE 2022

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