Fraunhofer Institute for Industrial Mathematics ITWM
Fraunhofer Institute for Industrial Mathematics ITWM
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Woubrugge, Netherlands - March 19, 2013: a crane stands on a pile of sand in a green, flat, misty polder landscape, ready to start loading a truck (not visible); a row of bare trees along a road disappears in the mist.

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Hardware-in-the-Loop Validation of Electronic Controls

Due to highly complex controls and dynamism, mobile cranes are ideal for rapid prototyping with HiL simulation (icon).
© iStockphoto
Due to highly complex controls and dynamism, mobile cranes are ideal for rapid prototyping with HiL simulation (icon).

The growing technical importance of distributed systems is accompanied by a strong change in the structure of control systems. A single control unit is no longer used for the control of the complete process. Instead, a plurality of controllers together with sensors and actuators as well as the control loop itself form a digitally networked dynamic system.

The concept of hardware-in-the-loop (HiL) is increasingly used to validate the control concepts. In this case, the electronic control units to be tested are not integrated directly into the real system, but into a test bench with a mathematical system simulation. The control unit is connected to the HiL platform by means of a corresponding electronic interface so that there is no difference between the test bench and the later controlled system from its viewpoint. While HiL tests are well-established in automotive engineering, there are no prefabricated simulation components for special machines such as tractors, cranes and excavators.

 

Control Design and HiL Tests

A high degree of networking between the mechanical functions – coupled with the hydraulics and electronics as well as numerous actuators and sensors – rapidly leads to a complex dynamic model. Furthermore, many components pose technical constraints (e. g. hoses) that depend on the overall system status. We have many years of experience in the development of appropriate mathematical system representations for heavy construction equipment and other commercial vehicles. These systems are capable of real time use and are very robust against noise, for example, as present in analog control signals. In addition, a monitoring environment is always implemented, which facilitates the detection of faulty adjusting signals and the control of the functional efficiency of the controller being tested.

The digital twin in the animated graphical representation – here a concrete pump – responds to each signal it receives from the control unit.
© Fraunhofer ITWM
The digital twin in the animated graphical representation – here a concrete pump – responds to each signal it receives from the control unit.

In 2015, we acquired an HiL simulator with a sophisticated I/O interface, which enables the connection of the electronic controllers to simulations of the implemented systems for testing. This facilitates the generation of turnkey system models, for example, for customers that do not have access to an HiL simulator, and the testing and validation can be performed directly at our institute. Besides the special machinery, issues in Industry 4.0 and intelligent energy grids are also being addressed.

In addition to the development of real-time simulation models, the control units and the design of the control algorithms and logic dependencies are a key area of interest to the department. For HiL testing, the department develops efficient controls for the modeled systems based on experience in system modeling and status monitoring. If necessary, these can be implemented on in-house programmable control units and tested on the HiL simulator.

 

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