German university researchers and electromobility company leverage fast and flexible Beckhoff technologies, along with a digital twin, to simulate realistic driving conditions
For auto manufacturers of any size, being able to count on comprehensive test bench technology that is fast, flexible and cost-effective is hugely important. Kempten University of Applied Sciences (HS Kempten) implemented a test bench just like this for ABT e-Line GmbH. In cooperation with Volkswagen (VW) Commercial Vehicles, ABT develops and produces electric vehicle (EV) variants of common light commercial models, such as the Transporter. As such, the test bench solution evaluates the capabilities of these vehicles after the EV conversion process. PC-based control from Beckhoff is central to the system’s standard industrial technologies.
The test bench at HS Kempten is primarily used for testing vehicle functions. It was developed in the university’s Laboratory for Control Engineering and Vehicle Systems, which examines applied research and development topics from the automotive and automation sectors. The lab was originally founded in 2016 for the purpose of testing components, although its range of activities has since expanded to include complex complete system test benches and even teaching in addition to research.
“In the case of an electric vehicle, the aim is to test whether the HVAC systems, which both draw their necessary power from the high-voltage battery, have an influence on the vehicle’s most important functions, such as switching on, switching off and driving. This involves specifying a test cycle that repeatedly starts, stops and accelerates the vehicle. The state of the vehicle changes as a result, i.e. the HVAC system is switched on or off and the battery charge level is varied,” explains Florian Zerbes, a research assistant at the Allgäu Research Center at HS Kempten.
“With the test bench at HS Kempten, this test can run completely independently over several hours or even days,” he adds. “The process involves continuously recording the data from the test bench and the vehicle so that it can be analyzed and transferred into the final test result.”
Automation tech and a digital twin simulate road conditions
The output motors flanged to the vehicle wheels provide resistance to the propulsion of the wheels, which is intended to simulate driving on a road. A robot inside the vehicle turns the ignition key, moves the gearshift and operates various buttons, such as those for interior climate control. Linear motors on the pedals press the accelerator and brake pedals, while a steering motor turns the steering wheel. A second robot outside the vehicle plugs and unplugs the various charging cables into and out of the charging socket.
Measurement technology acquires the currents and voltages in the vehicle’s wiring harnesses for subsequent analysis. The Beckhoff control platform – a C6030 ultra-compact Industrial PC (IPC) with TwinCAT 3 automation software – communicates with the individual components and the vehicle via the CAN bus. This central control unit coordinates the individual components and controls them accordingly.
A range of different tests can be implemented, all with different procedures. The seamless integration of the CAN devices in the EtherCAT industrial Ethernet system is simple; nine EL6751 EtherCAT Terminals, single-channel communication interfaces, make it easy for the test bench to integrate any CAN and CANopen devices.
During the test procedure, the vehicle experiences real-world driving conditions. For this purpose, a drive test bench moves the wheels according to the simulated torques and can even accommodate steering movements. Even the driver’s actions are simulated by corresponding actuators. Industrial robots perform most of the actions to facilitate as many different actions as possible. The surroundings are also simulated along with how the vehicle communicates with the environment – for example, via GPS. In addition to developing the real test bench, HS Kempten has also created a digital twin of the system. Not only does this facilitate pre-commissioning of the test bench, but it also offers comprehensive visualization and monitoring of the system.
Industrial technology reduces costs and increases flexibility
A major consideration when developing the new test bench was how to make the system as cost-effective as possible. The use of standard industrial components such as converters, motors and controls was key to achieving this goal. Another consideration was to ensure that the system could be installed and removed from the vehicle quickly, and essentially regardless of the vehicle model in question. The test bench therefore had to be easy to adapt, according to Dr. Andreas Stiegelmeyr, Professor of Mechanical Engineering at HS Kempten.
“We developed a test bench that is capable of testing most vehicle functions using standard vehicle interfaces. This makes it possible to test functions with a high degree of connectivity with minimal effort, regardless of the vehicle type,” Stiegelmeyr says. “We have created a great alternative for vehicle manufacturers with a wide range of vehicle variants and for manufacturers of small series in particular.”
To achieve the cost and flexibility requirements, PC-based automation from Beckhoff was critical, Zerbes adds: “We chose a system from Beckhoff as the central control because it already offers many different interfaces to industrial components. What’s more, the control technology can be easily expanded by adding EtherCAT I/O terminals, and even optimally distributed throughout a space due to the exceptional freedom of the EtherCAT topology. The sheer volume of hardware and software products available means many measurement and control tasks can be completed with minimal effort. And to top it all off, PC-based control from Beckhoff offers a clear cost advantage over systems from the automotive sector.”
Toolchain to determine test sequences
The test sequences are written in Structured Text (ST) using a specially developed toolchain and generated with MATLAB®/Simulink®. This makes it possible to use TwinCAT and Simulink® together effectively. “Blocks that already contain the information for the hardware links can be generated automatically in Simulink®. When compiling the respective model, the corresponding hardware links are automatically set by the TwinCAT Automation Interface and a link layer is created between the model and the hardware,” Zerbes says.
The new toolchain offers the following capabilities:
The required Simulink® model can be created with virtually no effort.
Different databases can be used without problems.
The connection to the hardware can be automated and configured directly in the Simulink® model.
Users benefit from an incredibly straightforward interface.
The current focus of the toolchain is on the CAN bus, which in concrete terms means that CAN message blocks can be created very quickly via a DBC file, for example. Blocks like this can then be directly connected to the rest of the model and the connection to the hardware can be configured in Simulink®.
Users can configure the individual messages via a GUI and configure other connections to the hardware directly in Simulink®. Once the Simulink® model has been created, it can be easily connected to TwinCAT via the toolchain with minimal effort. All users have to do is decide which Simulink® model to link to which TwinCAT project.
Otherwise, everything runs completely automatically. At the same time, it is also possible to make adjustments to the TwinCAT project in terms of the hardware or the implementation of PLC projects, for example.
Regarding the test bench, ABT offered this comment: “The test bench at Kempten University of Applied Sciences allows us to respond quickly to changing requirements. Within a very short time, this enables us to implement new and comprehensive test scenarios and test our vehicle on a fully automated basis. The test bench therefore provides us with innovative support throughout our agile development process.”
How can expandable measurement technology help you boost the quality of your DAQ and test-bench applications? Contact your local Beckhoff sales engineer today.
Philip Ehlers is the Automotive Industry Manager for Beckhoff Automation LLC.
A version of this article previously appeared in Machine Design.