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LMS helps transmission manufacturer AISIN AW to predict and eliminate clutch judder

5/10/2012

LMS, the leading partner in test and mechatronic simulation, helped AISIN AW to evaluate transmissions in a whole vehicle context at an early stage in the development process to reduce the chances of self-excited judder occurring. LMS completed a project using a hybrid approach of combining simulation and test to correlate and validate a repeatable methodology for future use. This methodology allows AISIN AW to evaluate new vehicle applications for their transmission more quickly, saving time and money.

In the Automotive Industry, the quest for greater efficiency, lower emissions and a greener brand image has put pressure on sub-system and component design; in particular transmission design has had some particular challenges to overcome. AISIN AW requested LMS to explore the possibilities of using simulation to improve the prediction of judder phenomenon. This was achieved using a 1-D model to simulate the transmission and vehicle influences combined with testing to correlate and validate the method for future use in their development processes.

To understand and diagnose problems using 1-D simulation a three step project was devised and executed to transfer the technology and knowledge.

- Step 1 - Model the transmission units accurately using a 1-D model in LMS Imagine.Lab, including gearbox internals, torque converter, lock up clutch and lock up clutch controls.

- Step 2 - Model whole vehicle driveline, bench testing carried out to understand correct parameters for driveline components (impedance & damping).

- Step 3 - Carry out a sensitivity analysis to predict mode shapes and influencing components allowing design improvement activities to be targeted at specific components.

Steps 1 and 2 developed a 1-D transmission model using bench testing for validation and then added the whole vehicle parameters that affected judder (engine, driveline and tires). This whole vehicle model was correlated against a measured system to ensure its accuracy.

Step 3 used the validated model in the development process to analyze the judder phenomena and the component contributions to each judder mode found for a specific vehicle application. By ranking each components contribution recommendations and target damping values were worked out and simulated to test their effectiveness. These targets were then interpreted by AISIN AW into component design changes to improve their product.

The 1-D model developed allows AISIN to simulate several drive cycle scenarios and a wide range of vehicle parameters. Since calculation times are small, it is possible to evaluate many scenarios allowing it to also be used for troubleshooting. The project proved that 1-D simulation and analysis could bring benefits to the transmission engineering team, helping them to understand the NVH contribution of each component and allowing them to focus their efforts on areas that will give the best results. Importantly the process and knowledge on how to repeat this work was retained by AISIN AW for future transmission projects as part of LMS commitment to technology transfer.

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