Using simulation to enable faster and better transmission design choices

Seeking faster optimization

Hyundai Mobis develops and supplies a variety of systems for automotive manufacturers, including steering and electric drive transmissions. Previously, the company needed to build many prototypes of these systems, but with customers demanding increasingly shorter lead times, it was necessary to adopt a more streamlined approach. Without the masking noise of the internal combustion engine (ICE), every minor sound or vibration is much more noticeable in an electric vehicle (EV). Using simulation enables much faster iteration and optimization with a digital twin that ensures engineers can make well informed design choices.

To meet the need for accelerated development, Hyundai Mobis adopted Simcenter™ 3D software, part of the Siemens Xcelerator business platform of software, services and hardware. The simulation capabilities of this software make it possible for engineers to accurately predict the performance of systems and expedite design optimization without creating prototypes.

Simcenter 3D Motion

Ho-Gil Yoo, noise, vibration and harshness (NVH) research engineer at Hyundai Mobis, says the company has already had great results with Simcenter 3D and wanted to extend this further. “We chose Simcenter 3D due to its powerful acoustic simulation capabilities,” he explains. “We had used it successfully with other systems, but we needed new tools to simulate the electric drivetrain. Transmission errors are a leading cause of poor NVH performance but most gear systems engineering tools are quasi-static, making this hard to identify. We added Simcenter 3D Motion to our toolset as its time-domain simulation capabilities allow us to accurately capture the dynamic characteristics of the system and optimize designs.”

Yoo says that while it takes time to create the complex models, the software effectively streamlined the process. “Simcenter 3D makes it straightforward to synchronize structural acoustic analysis with motion models in one procedure,” he explains. “Once we had the simple model, we increased the fidelity by adding compliance to the system. We used the Simcenter Nastran structural solver to calculate the flexible bodies then input these to the Simcenter 3D Motion model.”

Validation with test data

To make sure the simulation data and any resulting design changes accurately predicted performance, it was crucial for Yoo and his team to validate the results against physical NVH testing. After comparing the initial data, he found there were significant differences between the mode frequencies of test and simulation, so he used a combination of Simcenter Testlab™ software and Simcenter 3D Correlation to improve the structural finite element (FE) models and achieve modal correlation. This helped give Yoo confidence in the simulation
results.

“When we imported the test results into Simcenter 3D Correlation, we could see if we needed more iterations for higher fidelity,” says Yoo. “If so, we connected the model to HEEDS to automatically run simulations to find an optimized result in a statistically efficient way, which increased our speed and accuracy of correlation.

“We have found that Simcenter 3D Motion is very powerful for investigating systems at a deeper level. It accurately mirrors physical test results to give us confidence in using simulation to improve our designs.”

Faster and better

As Yoo has expanded the use of Simcenter 3D, he is happy with the support he has received from Siemens Digital Industries Software. “All the Siemens engineers know the software incredibly well,” he says. “They take the time to understand the problems we are working on and always offer excellent insights on the best way for us to proceed.”

The simulations led to design changes in the microgeometry that reduced transmission errors and improved NVH performance. “We’ve found that HEEDS inspires design ideas we wouldn’t think of ourselves, so not only does it help us optimize faster, but it also leads to better and more efficient design choices.

“As humans, it’s easy to not even consider certain options because they don’t seem realistic. But the automated algorithm isn’t limited by these thoughts. It simply looks for the best optimization so it explores every possible configuration, including those that would be too time-consuming to investigate manually.”

Now that the new process is in place, Yoo expects design time to be significantly reduced in the future: “A detailed flexible body model containing every single component is precise, but the simulation takes a long time. However, Simcenter 3D allows us to reduce the detail of the model when we create the motion model while retaining enough accuracy for NVH analysis.”

Beyond transmissions

Having experienced this success with transmission design, Yoo is keen to use similar methodology with other systems. “We’re looking at using Simcenter 3D Motion to analyze steering, braking and other electric drive systems,” he says. “This will deliver better optimization and help us to further improve the overall NVH performance of vehicles.

“We’ve also recently added the Simcenter 3D Motion Gear Design Optimization (GDO) tool, which combined with HEEDS should speed up iterations even more. This process has taken up to two weeks in the past, but it is reducing it to just three or four days at the most.”