Use virtual testing to accelerate product development time


The use of simulation for product development in a virtual test environment is becoming increasingly common.

Punch Powertrain applies a range of simulation tools that can complement traditional physical testing methods. This is evident in testing new transmissions.

The company points out that testing transmissions can be a complicated undertaking. Transmissions must align with all other components in a car, while some parts are still in development and not available for testing. This is where hybrid test beds come in.

Punch Powertrain tests its transmissions in a part-physical, part-virtual setup, where software simulates certain components. It boasts state-of-the-art technology that allows for quick rotation and flexibility.

One area where this proves useful is in acoustic testing. Engineers test the shift noise of a transmission. It’s something they can start doing even if they don’t have key components, like the engine, yet. Virtual engine simulation also offers the advantage that there is less noise from a combustion engine, which allows a better evaluation of transmission noise.

Punch Powertrain can simulate a range of conditions using its software. “For example, we can give the car more slope or load, and we can play with the speed and the forces,” explains Ilyas Barrou, developer of the test bench software. “It’s like having a real car on the test bench.”

The simulation is not just limited to the engine. “Before you can test a drivetrain, you also need to simulate components like ABS,” says test bench engineer Pepijn Peeters. “We also simulate the load on the wheels, so the transmission experiences similar conditions to a real vehicle. We even go so far that if you suddenly accelerate, the dyno will simulate the car’s thrust, which has a small effect on the drivetrain.

Punch Powertrain argues that its testing capability is quite unique. “For example, there are only 12 NDTS acoustic test rigs like ours in the world, and most of them are in China,” says Peeters.

Security and speed

Why is this combination of virtual and physical testing so useful? Punch says it’s much faster because engineers don’t have to wait for components that are still in development. But hybrid testing isn’t just about speed. “You also don’t have fuel lines hanging around, which makes it safer,” says Peeters. “Virtual testing is more accurate than using older, non-representative models of certain components. And we can switch easily, allowing us for example to test a transmission with different engine types.

“To validate a transmission, we have to do many tests,” adds Barrou. “Now we can do it partly using software. We can see how the transmission behaves on the highway or around town. Anything you can do in a real car, we can simulate on our test bench.

Testing hybrids brings new challenges

One of Punch Powertrain’s next technical challenges is to simulate a hybrid car, which is more difficult compared to a car with just an internal combustion engine. “A hybrid drivetrain adds another layer of complexity,” says Peeters. “It’s not just the engine with the ICU and the transmission with a TCU, you also have the electric machine with an MCU and a battery, with an associated management system. On top of that there’s a unit powertrain control unit, or PCU, so there are a lot more components that need to be simulated.

Designing a hybrid testbed that could handle this was complicated. It is described by Punch as an important step on the way to preparing the company for the future. “Testing hybrid drivetrains is the most complicated test you can do,” says Peeters. “An electric vehicle, on the other hand, is simpler. So if you know how to simulate a hybrid, you’re ready for electric vehicles. »

The purpose of all these tests is to better serve Punch Powertrain customers. “This gives a development project the maximum degree of flexibility,” adds Peeters. “We are ready for the future with our new test benches. If you compare our business to five years ago, we are making tremendous progress.

Punch Powertrain applies a wide range of simulation tools and methods, which can support engineers in the design phase and help validate the performance of their design, at different levels of complexity and integration, including at the vehicle.

Performing simulations and virtual tests on complete components and products allows Punch Powertrain to verify the performance of its products early in the process without any physical production. For this, the company uses commercial software, supplemented by tools, scripts and processes developed in-house. These make it possible to model the complete transmission, all the mechanical and electronic parts, as well as the control side as close as possible to reality. “The programs allow us to look at a wide range of very detailed aspects of a product,” says Hervé Bratec, Simulation Plant Manager at Punch Powertrain. “On all possible parameters: performance, handling, durability, etc. We can predict fuel consumption, acoustic performance, vibration, resistance and wear, etc., both at the component and transmission level. ”

Reduced test cycle cost by 50%

Compared to physical testing, the digital test environment offers various advantages. Bratec summarizes the difference in approach: “Physical testing typically provides a pass or fail result. To understand why the pass or fail occurred or how successful a fail was, a thorough analysis and time is required. With a virtual test, using simulations, this information is available much more easily, depending on the predefined level of accuracy.”

A second major benefit is cost, as it eliminates the cost of physical preparations, as well as the production of physical parts and systems in-house or by external parties. Therefore, virtual simulations lead to a reduction in the cost of the estimated test cycle by more than 50%. “In addition, the accelerated validation process further benefits our ecosystem partners, such as component suppliers, allowing them to participate in the development process and begin their tooling build preparations at an earlier stage.” , says Bratec. “All taken together, digital testing enables us to shorten time to market and accelerate product launches.”

Tests before engine availability

Punch maintains that the customer benefits are clear as it can quickly test the interaction between an engine and a gearbox before physical engines and vehicles are available.

Bratec points out that the complete engine block can be simulated using its main characteristics, given by the OEM customer. “The car itself is factored into the equation by entering its parameters, such as its weight and tire dimensions. This makes it possible to calculate, for example, the share of the transmission in the fuel consumption. By changing the specs, we can check how our transmission performs on different types of cars, like an SUV, sedan, or sports car,” he says.

“As part of virtual transmission assembly, it can be pre-calibrated virtually: which involves fine-tuning the transmission control for a specific vehicle. This will allow us to understand how the transmission reacts with the same engine in different vehicles.

AI to facilitate calibration

In the future, artificial intelligence will greatly support pre-calibration, says Bratec. “AI can help by taking already known data into account and using it for new car models.

“Pre-calibration with AI could reduce the traditional calibration period from months to just a few weeks, speeding up the whole process.”

Physical and digital and “the best of both worlds”

While offering many benefits, virtual testing is not a complete replacement for physical testing, Bratec points out. “The two are complementary. Virtual physical support to select the most appropriate physical tests and this reduces unnecessary time and effort spent. The physical supports the virtual making it more efficient and delivering better results. Their combination gives us the best of both worlds.


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