Interview with mrm²
Martin Rieg, Managing Director of mrm², talks to Aaron Windmüller, Product Marketing employee at the CODESYS Group, about the space project.
Aaron:
Hello Martin, mrm² has been a Premium System Partner of the CODESYS Group for years. Now you have realized a special project in the aerospace sector. Can you briefly describe it?
Martin:
Yes, it's a semi-automated production line for payload fairings for Ariane 6 rockets - more precisely for Ariane 6 Short and Long, as well as Vega platforms and Vulcan systems.
Aaron:
You describe yourselves as a special machine manufacturer with a special focus on software. Is space travel your specialty?
Martin:
Of course we also do other highly complex things that require very good software in special machine construction. As this requirement is particularly true for space travel, we are already very familiar with this sector and know it well. In short, aerospace is our specialty, but not the only one. For example, we also work intensively in food technology or in the sensory sector.
Aaron:
Can you please describe your project with Beyond Gravity briefly?
Martin:
The majority of Beyond Gravity's production facilities in Switzerland and also most of their facilities in Decatur in the USA are equipped with electrical technology from mrm². At the Swiss production site in Emmen, there is a laying table for carbon fiber mats, two systems for loading fairing half-shells and a highly complex, fully automated system for processing the fairing half-shells, which is a horizontal integration station. In production, we have to deal with a large number of synchronously running axes, with repeat accuracies of 0.02 mm over a length of 26 m, tool changing systems including program management, other synchronously running and externally monitored drive systems, multi-user operable visualizations - all in all highly networked systems. We developed and programmed them all on the CODESYS software platform - partly with native CODESYS, partly with TwinCAT from Beckhoff. In any case, everything complies with IEC 61131.
Aaron:
Aerospace products have to meet extreme requirements in terms of precision and accuracy, as errors in the process can have massive consequences. How do you ensure that your products meet these requirements?
Martin:
As with all our projects, the outstanding technical expertise of our employees, seamless project management and our 15 years of experience with challenging projects all play a role. Everyone involved in the project works closely together and all work steps are perfectly interlinked.
In software development, understanding the task at hand is crucial. After the detailed creation of a specification sheet, the implementation and programming of the software begins step by step. It goes without saying that our development engineers always work at the cutting edge of technology through regular training and use the latest methods.
Aaron:
Can you explain the production process to us in more detail? And of course: What role does CODESYS play in the project?
Martin:
There are 4 process steps in total. In the first process step, Prepreg, a carbon fiber composite material, is laid out in different lanes on the layup table. These sheets are then placed on the negative of the half-shells via a traverse and then baked.
The carbon fiber foils are unrolled via 7 axes. These axes are controlled synchronously via CANopen. Where the webs have to be applied diagonally, we control them via CODESYS SoftMotion. The visualization is also programmed with CODESYS.
In the second process step, the hardened half-shell is inspected for defects and specified tolerances in an automated non-destructive inspection using an ultrasonic testing method.
In this process, two robot arms equipped with air-ultrasonic probes scan the surfaces in a highly synchronized manner and perform the inspection at a defined distance. This means that defective areas are detected at this stage of the process,. Repairs can be carried out at this stage. Absolutely high-precision dual-loop control of the robot arms is necessary so that the ultrasonic process can be carried out with the required precision. Incidentally, the system is a cooperation project with Robo-Technology GmbH.
The path curves of the external robot are calculated in real time using axis transformations. This enables exact positioning. The external robot is an in-house designed 5-axis robot with a reach of 5.5 m. The standard industrial internal robot is then synchronized with the external robot in real-time, so that an absolutely precise tool center point of the two ultrasonic heads on the robot systems is always achieved. Positioning on the linear axes is carried out via external magnetic tape encoders. We use decentralized Beckhoff SoftMotion including EtherCAT fieldbus and IO-Link to control and read out all sensors.
Aaron:
The tolerance in length certainly makes controlling the robot arms challenging. When laying the CFRP strips, you use CANopen for communication in the first process step and EtherCAT in the second one. Is this due to the drive and dependence on the manufacturer? Or were there other reasons for your decision?
Martin:
As the systems were built at different times, the decision simply has a historical component. The system on which the carbon fiber webs are laid and which is controlled via CANopen is much older. The functionalities of EtherCAT were not yet so well developed. In addition, at that time there was a special function in CANopen that was required to implement the diagonal or crossing process. EtherCAT is more flexible and therefore later became the communication protocol of choice.
Aaron:
Ok, that makes sense. Then back to the manufacturing process!
Martin: In the 3rd process step, excess material is trimmed off over a length of 26 m on the horizontal integration station. Over 20 synchronized axes position the cladding for further processing. The axes are controlled via SoftMotion from Beckhoff. Over 450 holes are drilled into the cladding and its associated profiles on each half-side. So-called snap rings are integrated, which blast off the payload fairing in a coordinated manner or expose the satellite or the payload.
Assembly work is carried out in the 4th and final process step in which our systems are involved, the machining station drive assembly, .
Both half shells are picked up with the help of driven rings and assembled into one of two final fairing elements. The rings can rotate the cladding element by up to 180° in order to drill holes and carry out further assembly steps. Torsional loads must be completely eliminated over the entire component length of up to 26 meters. The two rings must therefore work absolutely synchronously in order to avoid stresses.
CODESYS SoftMotion controls the synchronized drive of the rings and can easily meet the high requirements of the component and the aerospace industry thanks to real-time control.
Aaron:
The visualization of the control system is a standard feature of the CODESYS Suite. Controlling the drives with the help of SoftMotion is much more demanding. In some cases, you control more than 20 drives synchronously in one application. How did you manage that?
Martin:
Quite simply through a very good, sophisticated software architecture and an equally carefully planned electrotechnical hardware topology.
Aaron:
With EtherCAT, FSoE, IO-Link and CANopen, you have various protocols in use. What criteria do you apply when deciding which communication path to use? Were there any problems during implementation?
Martin:
For a long time, CANopen was the best protocol for drive technology. From our point of view, however, it is no longer state of the art, hence the switch to EtherCAT, which is now the leader in drive technology. EtherCAT and then FSoE (Fail Safe over EtherCAT) can cope very well with long distances between components. FSoE is also well suited for safety functions in drive technology. IO-Link, on the other hand, has its advantages with a decentralized structure, decentralized sensors and short distances in the moving units. IO-Link is also very easy to maintain, components can be easily replaced and expanded.
Aaron:
Thanks for the insights into your projects, Martin. We think it's really great that CODESYS helps conquering space. Your project with Beyond Gravity is a prime example of applications that communicate in real-time via different protocols such as CANopen, EtherCAT, IO-Link or FSoE and at the same time meet the highest level of accuracy. This is certainly a challenge that we at CODESYS are happy to take on in order to constantly learn and improve. We wish you all the best for your future work - we are proud to be a part of it.