Development of a simple ER damper model for fault-tolerant control design

This work presents a concise control-oriented model for electro-rheological ( ER ) dampers. This model can serve for fault-tolerant control purposes, considering automotive suspension performance enhancement. ER dampers present, basically, a resistance against shearing that varies according to a controlled electric field. The main purpose of this work is to describe the force dynamics delivered by these ER dampers with a simple/reduced-order model that catches its overall behaviour with accuracy. One of the key points in the proposed approach is to describe the dynamics of the controlled portion of the damper force as a first-order system. Synthetically, this study is twofold: (1) the first part is an analytical approach towards the dynamic modelling of the ER damper force, wherein a reduced-order model is obtained, parameters are identified, and validation results are presented; (2) the second analyses the possible faults on these dampers and incorporates their affect to the developed model, which is of paramount importance for diagnosis and reliability of suspension systems. Hence, the proposed model is adequate for the design and synthesis of fault detection and diagnosis/fault-tolerant control ( FDD / FTC ) schemes, being able to run fast in real time in embedded electronic control units, that usually operate within 1–10 ms. Throughout this study, simulation and experimental validation tests are performed on a real 1/5-scaled vehicle testbed. Model parameters are identified via relatively simple procedures performed in this testbed. Results are shown to illustrate how the model can be used for FDD and FTC of semi-active suspension systems. The overall results assess the ability and the accuracy of the proposed model to characterize the force delivered by ER dampers in both healthy and faulty conditions.