Tudor Sireteanu

Semi-active suspension control : improved vehicle ride and road friendliness

Dampers and Vehicle Modelling.- Human Body Analysis.- Semi-active Control Algorithms.- Friction Dampers.- Magnetorheological Dampers.- Case Studies.

Model parameter identification for vehicle vibration control with magnetorheological dampers using computational intelligence methods

Abstract The parameter identification of magnetorheological dampers by an inverse method is proposed. A modified Bouc-Wen modified dynamic model is considered and its parameters are obtained by using genetic algorithms. The experimental data consist of time histories of current, displacement, velocity, and force measured for both constant and variable current. The model parameters are determined using a set of experimental measurements corresponding to different constant current values and the resulting model is validated on the data measured for variable current. Based on this model a semi-active control of vehicle suspension is studied and a fuzzy controller is developed to reduce the chattering effect.

From robust control to antiwindup compensation of electrohydraulic servo actuators

A method of designing the controller to solve the robust servomechanism problem is applied in the case of an electrohydraulic servo actuating primary flight control. This method is based on the well‐known solution consisting of two separate devices: a servocompensator, in fact an internal model of the exogenous dynamics, including the reference commands and disturbance signals; and a stabilizing compensator. The proof is made involving the servocompensator structure which is close to the one designed for step signals. The stabilizing compensator is assured by way of a linear quadratic optimal procedure. An antiwindup compensation is added to deal with the adverse effects caused by actuator saturation.

Subharmonic generation in piezoelectrics with Cantor-like structure

The purpose of this paper is to explain the subharmonic generation of waves (SWG) in piezoelectric plates with Cantor-like structure. We show that SWG is due to a nonlinear superposition of cnoidal waves in both phonon and fracton vibration regimes. We propose an original inverse method based on a genetic algorithm for an optimal identification of system parameters by inversion of the vibrational data.

Hybrid variable structure-fuzzy control of a magnetorheological damper for a seat suspension

The paper concerns an investigation of the use of a controlled magnetorheological damper for a semi-active seat suspension in vehicles not equipped with primary suspensions (e.g. some types of agricultural, forestry and roadwork vehicles). A magnetorheological damper can produce a variable damping action without requiring moving parts, such as valves, as opposed to a more conventional controlled damper. This paper presents a control strategy targeted to improve driver comfort based on a hybrid variable structure-fuzzy logic controller. Variable structure control is inherently a switching logic, hence more prone to cause chattering. Fuzzy logic helps reduce chatter without penalising damper dynamic response. An experimentally validated model of a magnetorheological damper which also includes hysteresis, and a vibration model of the human body have been developed and the system performance investigated via numerical simulation.

Damp-by-wire: Magnetorheological vs Friction Dampers

Abstract A comparison is made of a magnetorheological damper (MRD) and a friction damper (FD) in semi-active suspension design; both devices are closed-loop controlled. Experimentally validated models of both dampers have been developed and a hybrid variable structure-fuzzy control algorithm designed. It is shown that the two devices, albeit based on very different physical principles, can be described by a general common mathematical model, with the FD model being regarded as a particular case of the model for a MRD. The control strategy is targeted to improve occupant comfort. Performance has been investigated numerical simulation in a quarter car vehicle model and compared to that obtained with a classical passive damper.

On intrinsic time measure in the modeling of cyclic behavior of a Nitinol cubic block

In this paper, the cyclic behavior of a superelastic-plastic nitinol cubic block is described by using the Bouc?Wen model coupled to an intrinsic time measure other than clock time, which governs the behavior of the materials. As a consequence, the thermodynamic admissibility of the Bouc?Wen model is provided by the endochronic theory of plasticity. The role of the intrinsic time measure is described by capturing the stiffness and strength degradation and the opposite phenomena. Such behavior is due to the permanent-strain addition of residual martensite and alterations in the properties of the texture during phase transformation.

A Genetic Algorithms Method for Fitting the Generalized Bouc-Wen Model to Experimental Asymmetric Hysteretic Loops

The Bouc-Wen class models are widely used to portray different types of hysteretic behavior. This paper presents an effective genetic algorithms-based method for fitting a generalized Bouc-Wen model, proposed by Song and Der Kiureghian [2006, “Generalized Bouc-Wen Model for Highly Asymmetric Hysteresis,” ASCE J. Eng. Mech., 132 (6), p. 610618], to highly asymmetric experimental hysteretic loops. The performance function is based on integral relationships derived from the generalized Bouc-Wen differential equation for each of the six different phases of asymmetric hysteretic loops. The conditions, which must be satisfied by the model parameters to obtain closed and smooth hysteretic loops, are specified. The method is applied to fit the generalized Bouc-Wen model to hysteretic loops, which are obtained in laboratory experiments for a new type of mounts used for base isolation of forging hammers. By using a single degree of freedom (SDOF) system with the predicted hysteretic characteristics, a remarkably close agreement between the measured and simulated vibrations of hammer was obtained.

Transverse vibrations analysis of a beam with degrading hysteretic behavior by using Euler-Bernoulli beam model

Abstract The paper is based on the analytical and experimental results from [14], [15] and reveals, by mathematical methods, the degradation of ma- terial stifiness due to the decrease of the first natural frequency, when the driving frequency is slightly lower than the first natural frequency of the undegradated structure. By considering the vibration of the uni- form slender cantilever beam as an oscillating system with degrading hysteretic behavior the following equation is considered subjected to the boundary conditions To approximate the solution of the this problem, we use the method of Newton interpolating series (see [6]) and the Taylor series method (see [8]).

A novel vibration absorber with variable stiffness controlled by electromagnetic force

In this paper, a novel method to control the stiffness characteristic of an oscillating system is analytically studied and experimentally assessed. The method principle consists in a controlled modification of tension or compression forces applied along the elastic column beams which support the system sprung mass. The control is achieved without contact by electromagnetic forces applied to the sprung mass, modulated through the supplied voltage. The stiffness variation versus the supplied voltage is obtained by measuring the frequency of the system free vibrations. The model parameters are determined by using inverse methods based on experimental data. The effectiveness of the proposed stiffness control method is illustrated for a smart vibration absorber placed on an oscillating system excited by a chirp input.