Abstract
Keywords: Variable force bumper, magneto-strictive, controlled interference, cost-benefit, child safety.
The paper addresses an anticipated requirement for bumpers with controllable energy absorption to minimise injury to all classes of pedestrians to allow either pre-crash setting or real-time modulation of the collision force according to obstacle identification systems.
The paper reports a review of the limitations of existing approaches and presents novel forcevarying actuation devices. The solutions are presented as two categories:
- passive devices with inherent force-regulation selectable in discrete steps
- continuously variable devices with open or closed loop force control
In both cases, selection is possible according to the type of anticipated collision to minimize peak forces by utilization of the entire deformation region available behind the front-end module.
Outline concepts are presented which apply the following approaches:
- multiple selectable deformation columns
- multiple selectable hydraulic pistons
- profiled hydraulic piston with multiple selectable discharge elements
- hydraulic modulation with a fast acting pilot valve
- magneto-rheological and electro-rheological fluid circuits
- controllable interference fit on a moving rod using a magneto-strictive device
Selection criteria are weighted and then applied to identify the costbenefit for each concept. The approach provides preferred solutions for devices with discrete fixed load and fully variable characteristics and includes considerations of long-term dormancy and technology maturity. Calculations and design details are presented for the most effective variant using magneto-strictive principles to control the interference fit of a moving rod.