Development of a Cable Model for Virtual Shift Feeling Evaluation 2015-01-2332
Shift quality of a gearbox is one of the most important items contributing to the overall subjective impression of driving comfort for a vehicle with a manual transmission. Often the transmission is the only point of attention for shift quality issues with a focus on the synchronizer being the main area of optimization. This is however not always sufficient. What the driver feels at the gear lever is a result of the interaction between the gear lever, the selector system, the transmission internals and the driveline.
For most of these subsystems, well established models are available which can be used in early development to get a first idea of the shift quality. However, accurately representing the physical feel of the transmission cable, connecting the gearbox and the shifter, remains a challenge.
This paper describes the joint efforts of LMS Engineering and Nissan to create a cable model, capable of predicting the effect of cable geometry on gear shift quality, represented by the friction forces.
By experience it is known that the 3D positioning and curvature of the cable affects the friction force and therefore the shift feeling. Also the position of the cable brackets and their mounting stiffness have been identified as important parameters. The creation of a virtual model that can predict these effects is understood to be a complex problem.
Detailed measurements on a test-rig supported the creation of the model and gave insights into the required complexity. Validation measurements in vehicle condition finally proved the value of the model in a development process.