H∞ Control of Input delay systems with Derivative Feedback
This thesis presents H∞ controller design for input delay systems with derivative feedback in presence of both constant and time-varying delay. By this control law, the resulting closed-loop system turns into a specific time-delay system of neutral type with both delayed-term coefficients depending on the control law parameters. proportional-derivative state feedback and output derivative feedback are two examples of this control law. In this thesis, these two examples are fully investigated. In some practical problems such as active vibration suppression systems the state-derivative signals are easier to access than the state variables. To this aim, an H ∞ -based state-derivative feedback control problem for input-delayed systems has been considered in this thesis, as an special case of proportional-derivative state feedback. Moreover, we have addressed an H ∞ PD controller for input-delayed systems, which leads to the aforementioned special closed-loop system of neutral type. It can be easily shown that designing a PD controller for an augmented plant model with an integrator, is equivalent to the design of a PI controller for the original plant model. Considering this fact and widespread application of PI controller in industrial plants, the significance of the developed theory will be better appreciated. Lyapunov-Krasovskii functional has been used for the design of both H ∞ proportional-derivative state feedback and H ∞ PD/PI controller for input delay systems. Consequently, new delay-dependent sufficient conditions for the existence of both H ∞ proportional-derivative state feedback and H ∞ state-derivative feedback in presence of uncertain delay are derived in terms of some matrix inequalities. Furthermore, descriptor model transformation is used to derive delay-dependent sufficient conditions for the existence of H ∞ PD/PI controller in terms of some matrix inequalities as well. The resulting H ∞ controllers stabilize the closed-loop neutral system and assure that the H ∞ -norm to be less than a prescribed level. Some application examples are presented to illustrate the effectiveness of the proposed methods.
|2012||Ph.D.||Dynamical Systems Analysis and Control|
Robust H∞ Control Of Active Suspension
In this research first an H∞, controller is designed for hydraulically actuated active suspension system of a quarter-modelled vehicle in a cascade feedback structure. Using the proposed structure, the nonlinear behavior of the actuator is reduced significantly. Therefore, in the controller synthesis, a proportional controller is used in the inner loop, and a robust H∞, controller forms the outer loop. By this means, the vehicle oscillations in the human sensitivity frequency range is reduced to a minimum. Optimal observer estimates the output of the quarter-car model of vehicle. The above strategy is also used for a half-car and full-car model of vehicle in decentralized control form. Statistical analysis of the simulation results using random input as road roughness, illustrates the effectiveness of the proposed control algorithm.
|2003||M.Sc.||Dynamical Systems Analysis and Control|