H2/H∞ controller design for input-delay and preview systems based on state decomposition approach

This thesis concentrates on the efficient solution methods of H2/H∞ optimal control problems for input-delay and preview systems. Although the problems can be reformulated to the ones for delay-free systems by augmenting the state space of the controlled systems, the numerical solution of the Riccati/KYP (Kalman-Yakubovich-Popov) equations for the augmented systems requires special efforts, and complicates controller tuning. On the other hand, it is known that the optimal control laws for certain classes of time-delay systems can be constructed without solving the augmented Riccati/KYP equations. Such design problems are called reduced-order construction problems in this thesis. The solutions of the reducedorder construction problems are still limited in theoretical and practical perspectives. The main purpose of the thesis is to propose a new approach for the reduced-order construction problems, which enables to derive the optimal output feedback controllers for input-delayed and preview systems in a unified manner. We focus on the internal dynamics of the overall systems, and decompose it toward the H^2 and H^∞ performance objectives. The fundamental idea of our approach is first introduced for the discrete-time inputdelayed H^2/H^∞ control problems. The state decomposition enables to solve the output feedback problem through the simpler ones, namely, the full information and output estimation problems. The discrete-time optimal controllers are obtained in the Smith predictor form. They are constructed from the Riccati/KYP equations for the delay-free systems. The solution procedure is further extended to the continuous-time preview H^2/H^∞ control problems in an output feedback setting. The optimal utilization of the preview information is exploited at the full information and output estimation problems. The clear structures of the optimal controllers are revealed as the combination of the finite-dimensional observers and preview-feedforward compensation. In the H^∞ control problems for the input-delayed and preview systems, the J-spectral factorization techniques in the literature are employed. Their interconnection to the augmented Riccati/KYP equations is clarified by reviewing the techniques from a view point of the internal state dynamics.首都大学東京, 2014-03-25, 博士(工学), 甲第440号首都大学東

Semi-active control for independently rotating wheelset in railway vehicles with MR dampers

This thesis presents details of an investigation of a controller for MR damper in the implementation of semi-active control, for primary suspensions of the independently rotating railway vehicles. This research focuses on using MR damper and it addresses on three main aspects when designing semi-active control systems for this application.One aspect is magnetorheological dampers categorised as a controllable fluid damper which can reversibly change from a flowing viscose fluid to semi-solid viscose fluid. The second aspect is the controllable yield strength can change in a millisecond by inducing an electric or magnetic field. Third aspect is MR damper is cheaper than actuators which are usually use in full active controllerThis research is a combination of a lookup table based on the inverse MR damper model to control the current input (to the MR damper) from required force and relative velocity of the device. The MR damper produces the desired force as precisely as possible. However, it is not possible to have precise knowledge of MR parameters and it is also difficult to account for the hysteresis present in MR dampers in the lookup table. Therefore, an additional local PI feedback controller is also used to improve the robustness for the MR control.As the main result, this study provides a comparison between semi-active controller with the use of MR damper and a full active controller system. The results show semi-active controller with the use of MR damper performed as good as full active controller. However semi-active control systems with MR dampers offer an overall efficiency and robustness when compared to the full active control system. Also, this system delivers comparable performance with the benefit of increased reliability and lower cost.In order to assess the developed system comprehensively, a two–axle vehicle model and a full bogie vehicle model are both evaluated individually in the study.The performance and robustness assessments of the developed semi-active controller with the full active control system are evaluated with the use of both two–axle vehicle model and the full bogie vehicle model with different operational track features such as curved track and straight track with lateral irregularities with various travel speeds.This study designed and developed a semi-active control systems with use of MR damper in primary suspension for independent rotation wheelsets in railway vehicles. Computer simulation results verified the suggested semi-active control is able to provide required stability and guidance control for independently- rotating wheelsets. Also, the result performed as well as full active control with the advantage of utilizing a lower cost device for semi-active control rather than an expensive actuator for full active control

Analysis on actuator dynamics in active wheelsetcontrol

This thesis presents details of an investigation conducted to evaluate the applicability and requirements of actuators in the implementation of active solid–axle wheelset control systems, for primary suspensions of the railway vehicles, and the effects of actuator dynamics on the overall active control system. The research is focused on the use of electric–mechanical (EM) actuators and it addresses on two main aspects when designing active control systems for this application. One aspect is the detailed study on actuator dynamics and parameter optimisation to improve the effectiveness/efficiency of actuator performances while the second aspect is the development of a state observer to estimate key feedback signals, for the control of actuators, which are difficult to measure using readily available sensing techniques. The study of the actuator dynamics and its optimisation is conducted by varying key factors of the electro–mechanical (EM) actuator used in this application such as gear ratio, inertial values of the motor rotor/gear–wheel and stiffness/damping at the actuator–wheelset (load) connection, while assessing key actuator performance indicators such as output torque and power consumption. This analysis provides insight in to the task of finding optimal actuator parameter values for this particular application of active wheelset control such that the effectiveness, efficiency and robustness of the overall active wheelset control system can be improved. In order to assess the developed system comprehensively, both a two–axle vehicle model and a full bogie vehicle model are being evaluated individually in the study In addition, a state observer is developed in this study to estimate the output torque of the electro–mechanical (EM) actuator since feedback measurements are essential for the actuator control system developed in this case in order to ensure that actuator responds appropriately by delivering accurate and fast control efforts to maintain the stability of wheelsets. The formulation and design of the observer is done based only on the use of the actuator model such that it substantially reduces the complexity and difficult uncertainties related to the full model of a rail vehicle. Furthermore, a robustness assessment of the state observer is undertaken by conducting an assessment of its performance when key parameters of the model used to develop the state observer is varied within reasonable margins. The performance and robustness assessments of the state estimator integrated with the full active wheelset control system and with optimised actuator parameters are carried out with the use of both two–axle vehicle model and the full bogie vehicle model with different operational track features such as curved track and straight track with lateral irregularities with various travel speeds