Automotive supplier uses Simcenter 3D Motion to digitalize windshield wiper design and reduce physical prototyping

Not as simple as it seems

Windshield wipers contribute to driver safety by striving for visibility at all speeds and in all circumstances. They effectively remove water, snow and dust by moving back and forth across the front and rear windshield. Although design variations exist, most systems combine an electrical motor with a worm gear to power the mechanism with a linkage that converts the rotational motor output to the wiper motion. It seems simple, but the reality is very complex.

The blades need to perfectly fit the windshield shape and have to repeat the same action countless times in various operational conditions. Heavy rains may require strong accelerations, which takes a lot of force from the motor. Sensors are used to detect the amount of water to be removed (so that the driver does not have to pay too much attention to it) and ensure that when the wiping action is finished, the blades return to the park position.

“Number one tool for system dimensioning”

“Two load cases are crucial when dimensioning our systems: snow load and the blade being frozen to the windshield,” says Christophe Joly, Valeo Wiper Systems Simulation Manager. “Testing those conditions requires a cumbersome setup and really takes a lot of our time, especially if we have to repeat it for several prototype rounds. So, it is very important to optimize these performance aspects upfront through simulation. That can drastically reduce the work in the lab.”

Valeo engineers decided to evaluate dynamic multi-body simulation using Simcenter™ 3D Motion software, which is part of the Siemens Xcelerator business platform of software, hardware and services.

Simcenter 3D Motion enables realistic force predictions for problematic load cases with wiper blades stalled in different angles. As the simulation results correlated well with measured data during the evaluation, they adopted this software as a part of the daily product development activities.

Simcenter 3D Motion is now the number one tool for system dimensioning,” confirms Joly. “For this reason, it is used throughout the wiper department for every project. It is also used to verify if the motor is powerful enough to work in extreme circumstances.”

During the evaluation, Valeo engineers created two different virtual wiper systems, combining kinematic models for the mechanism with finite elements (FE) for the flexible parts. The results were compared with measurements by several force and torque sensors on the actual systems.

”The difference between both remained under 20 percent for both the peaks in the snow load case and the equilibrium loads of the frozen lock case, in which the wipers are clamped,” says Joly. “And the gap becomes even smaller when the laboratory dispersion is taken into account. Moreover, we could do research on the stalling angle, which was new for us.”

The software allowed Valeo engineers to finally deploy a standard methodology for realistic mechanical simulation.

“Before, the forces were often defined by experience and we used static methods. This was not necessarily correct,” says Joly. “With Simcenter 3D Motion, we can really simulate what we do in the lab, taking into account the real motor, system stiffness values, temperature and more.”

Reducing the need for physical prototypes

Valeo’s engineers were also impressed by how easily they could implement this new process. The new software seamlessly integrated with their standard design environment, making realistic model creation straightforward. On top of that, the Simcenter 3D Motion solvers ran very fast, especially considering their precision.

“In a few days, we could do all the calculations and have a complete detailed report on an entire wiper system,” confirms Joly.

This combination of efficiency and accuracy significantly reduces the required number of physical prototypes.

“We still spend the same proportion of our time in simulation as before,” says Joly. “But within this time, we achieve much higher quality results. We can now have confidence in our simulations and use them for predictions. This has reduced our need for physical prototyping. That is exactly what our customers want. With Simcenter 3D Motion, we make a much better impression by being able to show that we can bring a lot of value.”

Building a complete mechatronic simulation solution

In addition to the mechanical system’s dimensioning, the same simulation technologies can also handle motor design and overall refinement. Valeo engineers are currently investigating the capabilities for this purpose. In a first phase, Simcenter 3D Motion could be used to create a complete rigid-body motor model and determine the loads and torques in the joints, check contacts between gear parts and extract the loads to size the gearbox. Afterwards the gearbox can be replaced by a flexible component in FE for dynamic multi-body simulation.

As a result, it will be possible to investigate the gearbox stresses and deformations. On top of that, this model could be extended with a flexible arm and blades. This would allow numerous extra simulations that support a large set of applications, including studying how to reduce material usage, checking the influence of part stiffness on an angle, defining the target eigenfrequencies before the real windshield is available and modifying electro-magnetic input. Valeo engineers would like to deploy these simulation-based activities to promote the collaboration between their mechanical and electrical motor teams.

In the same context, current research at Valeo also focuses on co-simulation between Simcenter 3D Motion and MathWorks’ MATLAB® environment and Simulink® environment. This combination includes controls and enables the simulation process to address the challenges of full mechatronic simulation.

"If we want to reach the highest possible precision, we need to include the exact behavior of the motor,” says Joly. “If we have to wait until the electrical motor team can provide all parameters, we lose time.”

Co-simulation will enable making realistic calculations before the motor prototype is available, leading to increased accuracy earlier in development and more bilateral information exchanges between teams.

“The combined simulation between Simcenter 3D Motion and the MATLAB and Simulink environments is the type of technology we are looking for,” concludes Joly. “It will allow the mechanical team to make much better simulations, and the electrical motor team to get more input on the overall functioning earlier in their project. This will help us better understand the behavior of our products and save us a lot of development time in future.”