Analyzing the functionality of flexible components early on to save on real parts
Whether you want to release the front hood or door locks, operate the window lift inside the door or actuate the shift cable to the gearbox – Bowden cables are all around in today’s vehicles, but usually go unnoticed by the customer. Due to their physical behavior, Bowden cables pose a particular challenge to simulation techniques. In the context of today’s product development at BMW, numerous technical questions are discussed on the basis of virtual vehicles. Flexible parts like hoses, cables and Bowden cables are usually represented as rigid parts. Their shapes, however, often deviate from the physically correct ones. A joint project between BMW and ITI tried to find ways of simulating Bowden cables that would reflect a realistic physical behavior.
A Bowden cable is a type of flexible cable used to transmit mechanical force or energy by the movement of an inner cable (most commonly of steel or stainless steel) relative to a hollow outer cable housing. The housing is generally of composite construction, consisting of a helical steel wire, often lined with plastic, and with a plastic outer sheath.
Regardless of a particular application, the behavior of Bowden cables is mostly a matter of the effective direction. Despite fundamental similarities between various applications, there is, however, a multitude of varying parameters concerning the Bowden cable itself as well as its structural and functional boundary conditions.
In order to be able to deal with certain issues at a very early stage without the need to have real parts available, BMW has chosen to go with virtual product development. However, BMW’s experience was shaped by finite elements simulation and other time-consuming methods which often required advanced hardware resources. The field of virtual system simulation was new, and the expectations for the simulation software were high.