Skyhook damping with linearised magnetorheological dampers

In recent years, much research has focused on the development of effective control strategies for smart fluid dampers. In particular, skyhook control principles are frequently shown to demonstrate significant performance improvements over conventional passive systems. However these investigations are often either model-based and assume that the controlled damper can accurately track a prescribed force, or they are based on on/off type control strategies where such accurate tracking is not required. In this paper, the authors present an investigation of a magnetorheological (MR) skyhook controlled SDOF mass isolator subject to broadband input excitations. The semi-active element is an MR smart fluid damper. The study utilises feedback linearisation, which is demonstrated experimentally, to convert the non-linear damper into a linear controllable device. This approach can be effectively harnessed to implement skyhook control since it permits the accurate tracking of a desired force within the controllable limits of the MR damper. Using a validated model of an MR damper, it is demonstrated that feedback linearisation can yield significant performance improvements over more simplistic on/off control strategies. The same strategy could be integrated within larger scale vibrating structures (such as vehicle suspensions or aircraft landing gear) to implement more complex control strategies, e.g. optimal control.