Recent innovations in vehicle suspension employs active suspension system which imparts best in class ride and handling of vehicle. Active suspension is a type of automotive suspension that controls the vertical movement of the wheels relative to the chassis or vehicle body with an onboard system, rather than in passive suspension where the movement is being determined entirely by the road surface. These technologies allow car manufacturers to achieve a greater degree of ride quality and car handling by keeping the tires perpendicular to the road in corners, allowing better traction (engineering) and control.
The drawbacks of these active suspensions are high cost, added complication and mass of the apparatus, and the need for frequent maintenance on some implementations. Maintenance can require specialized tools, and some problems can be difficult to diagnose.
An attempt is made to convert simple automotive leaf spring in to a variable stiffness active spring.
Principle of Working:
This works on very basic principle --
Higher the reaction support span, lower will be the spring rate.
Lower the reaction support span, higher spring rate will be achieved.
In general, by varying reaction the supports location variable stiffness (or spring rate) can be achieved.
In conventional leaf spring of vehicle are fixed. The basic idea is that the additional reaction supports are provided and distance between them keeps varying with respect to road profile input displacement there by achieving variable stiffness.
When the compressive Displacement input is experienced by spring following events will take place. (Refer Fig)
1. Link 1 (with hinge fixed) will move up and will push Link2
2. Link 2 acts as bell crank lever (hinged at one end to fixed bracket 5) will push link 3.
3. Link 3 pushes link 4at mid hinge point
4. Link 4 (one end hinged to chassis and other end with roller support slides on leaf spring) rollers will act as reaction to spring and these reaction point move apart.
5. As rollers move apart reaction points experienced by spring changes and spring stiffness changes
6. When displacement input released, rollers will come back (Link 1 will pull back) to its original position.
The above mechanism provides option of variable stiffness by aligning its roller reactions on spring leaf based on road input displacement in turn enhancing ride and comfort quality