Magneto-rheological damper modeling using LPV systems

Abstract

The present research is focused in the dynamical modeling of a Magneto-Rheological Damper as a semi-active actuator. This device shows a complex behavior including non-linearities and hysteresis, features that are to be emulated by a dynamical system, in order to express mathematically the conduct of this device under mechanical vibrations. The M R damper is part of a semi-active suspension system, and by the use of the information of the model designed in this thesis it might be possible to produce a control design for the quarter of car system, in order to regulate the vibrations received by the suspension, incrementing the comfort and safety of the passengers in the vehicle. In order to obtain experimental data from this semi-active device, a set of tests were performed, introducing displacement and current excitation patterns into the shock absorber and measuring the dynamical response of it. Using the experimental results, a set of state of the art models (Semi-Phenomenologial, Phenomenological, Black-Box) were learned to reproduce this data. This work proposes an LP V (Linear Parameter-Varying) system, as a model for the M R damper, which is capable of reproduce both the non-linear and hysteretic behavior of the damper.The LP V model proposed has the capacity to create a relationship between the main excitation variables, and the damper force, in a single structure. Due to this feature, it might later be added to a bigger strategy, such as for control or observation. The model was designed using an LP V polynomial system and an switching variable, which depends on the input velocity and current. Output results shows a higher accuracy from the LP V proposed model, in comparison with the state of the art models reviewed: it has ESR index average values below 0.04 while most of the studied models only achieve values below 0.1. The proposed model of this thesis provides a dynamical description of the Magneto-Rheological damper that generates a link between the main input variables implicated on the damper, and the output force. This feature might become an advantage to later provide an extended model of the quarter of car, and design a controller to regulate the vibrations applied to the suspension.