István Szászi

Design of robust controllers for active vehicle suspension using the mixed μ synthesis

Summary The mixed µ synthesis for active suspension problems is proposed. Applying this method the real parametric uncertainties can be taken into consideration, which is more realistic than the traditional approaches, and the design process yields a less conservative compensator than other robust control design methods. The concept of the active suspension design using full-car models to handle the uncertain components is presented. The result of the mixed µ method is compared with the complex µ synthesis, and the passive system.

Linear parameter-varying detection filter design for a boeing 747-100/200 aircraft

We present a fault detection and isolation (FDI) filter design using a linear parameter-varying (LPV) model of the longitudinal dynamics of a Boeing 747 series 100/200. The LPV FDI filter design is based on an extension of the fundamental problem of residual generation concepts elaborated for linear, time-invariant systems. Typically, the FDI filters are designed for open-loop models, and applied in closed loop. An application is shown of an LPV FDI filter for actuator failure detection and isolation in the closed-loop longitudinal LPV system to the full nonlinear Boeing 747 aircraft simulation, which represents the “true” system.

Active suspension design using linear parameter varying control

In this paper, the linear parameter-varying (LPV) method is applied to the modelling and control of the active suspension system of vehicles. Besides the nonlinear characteristics of the suspensions, in the construction of the LPV model both the performance requirements and the model uncertainties are taken into consideration. The trade-off between the performance demands is guaranteed by using parameter dependent gains. The synthesis and the analysis of the LPV based robust control design is performed. Finally, the method is demonstrated in a quarter-car model.

The Design of a Combined Control Structure to Prevent the Rollover of Heavy Vehicles

In this paper a combined control structure to decrease the rollover risk of heavy vehicles is developed. In this structure active anti-roll bars are combined with an active brake control. Selecting the forward velocity and the lateral load transfer at the rear as scheduling parameters, a linear parameter varying model is constructed. In the control design the changes in the forward velocity, the performance specifications and the model uncertainties are taken into consideration. The control mechanism is demonstrated in various maneuver situations.

Active Suspension Design using LPV Control

Abstract In the paper the linear parameter varying (LPV) method is applied to the modelling and control of active suspension systems. The suspension structure contains nonlinear components, i.e. actuator dynamics and the dynamics of the dampings and the springs. The model is augmented with weighting functions specified by the performance demands and the uncertainty assumption. By selecting scheduling parameters an LPV model is generated in which the model structure is nonlinear in the parameters but linear in the states. The design of the active suspension is illustrated in the demonstration example.

Design of FDI filter for an aircraft control system

This paper presents a fault detection and isolation (FDI) filter design to linearize longitudinal dynamics of a Boeing 747 series 100/200. The FDI filter design is based on a geometric approach which relies on the use of (C,A) invariant subspaces and provides conditions on separability and mutual detectability of the failures. In our case the fault detection filter is sensitive to elevator faults and pitch rate sensor faults. Typically, the FDI filter design approach is elaborated for an open loop model and applied in the closed loop. The robustness aspect of FDI is considered and the effect of closing the loop is shown in the nominal case as well as in the uncertain case. The FDI filter designed for aircraft control systems is analyzed for a nominal closed loop system in the presence of sensor noise.

Fault-tolerant control structure to prevent the rollover of heavy vehicles

Abstract In this paper a combined control structure with an active antiroll bar control and an active braking control is developed to decrease the rollover risk of heavy vehicles. This control structure also results in a fault-tolerant system since in case of a failure an adequate tuning of the control mechanism guarantees the roll stability. The control design is based on LPV model of the vehicle in which the forward velocity and the lateral load transfer at the rear are selected as scheduling parameters. In the actual controlled system, the compensator also uses the output of a fault detection filter. The operation of the control mechanism is demonstrated in a double lane change maneuver

DESIGN OF ROBUST CONTROLLERS FOR ACTIVE VEHICLE SUSPENSIONS

Abstract This paper is concerned with the design of robust controllers for active suspensions using μ methods, which take the structure of the model uncertainty into consideration. The complex μ method is conservative in the case of the real parametric uncertainty, while in the mixed μ method, both the real parametric and the complex uncertainties are handled together. Two half-car model structures are constructed, a rigid half-car model, and a high-order flexible one, which is more realistic and closer to the real situation. In the example, the result of the mixed μ method will be compared with the complex μ method and the traditional methods.

Rollover Stability Control for Heavy Vehicles by Using LPV Model

Abstract The paper is concerned with the use of active roll control systems employing active anti roll bars in order to improve the roll stability of heavy vehicles. Since the forward velocity of the vehicle changes in time, the combined yaw-roll dynamic model has a nonlinear structure. Selecting the velocity as a scheduling parameter, a Linear Parameter Varying (LPV) model is constructed. In the control design based on an LPV method, the changes in the forward velocity and both the performance requirements and the model uncertainties are taken into consideration. The control design is demonstrated in different situations.

Robust Servo Control Design Using Identified Models

Abstract In this paper, a servo control synthesis based on the H ∞ /µ method is applied. In this method, a robust controller which achieves nominal performance and meets robust stability specifications can be designed. Moreover, it provides the track of the predefined reference signal, reduces the effects of the disturbances and takes the structured uncertainty into consideration. The control design is based on an identified model. In this paper, the design strategy is illustrated for an inverted pendulum device.