Robust Full-Order Observer Design for Damper Force in Vehicle Suspensions

Vehicle suspensions are complex systems when they can modify the damping forces according to a control approach. This complexity is even more higher when all system variables are not available and the operating conditions are time-varying. A very common practice to estimate the force in vehicle suspension is using Quarter of Vehicle based model, which decouples the effects among the four vehicle corners. To address this problematic and to analyze the effects without decoupling them for each corner, this paper proposes a robust full-order observer design for the damper forces in a full-vehicle suspension system considering the nonlinear dynamics of four Magneto-Rheological (MR) dampers as semi-active actuators. The proposed robust observer design is based on the direct Lyapunov method through LMI-based conditions to guarantee robustness mainly to road disturbances, dynamic actuation signals, and measurement noise. The above robustness capabilities were evaluated using three different simulation scenarios in a MATLAB/Simulink environment. Simulation results showed that the observation error trends to zero in a fast and stable way for the three tests, demonstrating the robustness performance of the proposed observer in face to different road roughness, dynamic changes in the actuation signals of the MR dampers and measurement noise at different levels.