Laboratory investigations of an active vehicle suspension of an in-series structure of the slow-active type are presented in this paper. The multidimensional model is reduced to a case representing quarter car suspension. Control laws for active vibration reduction systems are usually determined based upon linear models of objects. Active suspensions are characterised by nonlinearity, connected most often with actuating systems and their energetic restrictions. This causes divergences between theoretical quality factors and those determined experimentally. The second essential problem is finding a compromise between opposed quality factors (for example, minimum power requirement and high efficiency of vibration reduction).Thanks to the use of the proper control law in the active vibration reduction system of vehicle suspension, the goal of ensuring a high level of ride comfort, good vehicle handling and incessant contact of the wheels with the road surface with a minimum power requirement may be attained. The authors, in seeking a compromise, determined classical LQR controllers for the proposed quality indicators realising the aims mentioned above. These controllers are determined for a linearised suspension model obtained from identification. Experimental characteristics are determined for all of the suspension control systems.

Studies of systems with energy regeneration have been carried out for years, because they primarily cover the assemblies with electrodynamic actuators. This paper addresses the issue of active reduction of mechanical vibration using an electrohydraulic actuator. The testing procedure aims to assess the potential use of those assemblies in a different frequency band and force range than in electrodynamic actuators. The paper explains the operating principle of the system, and the findings of laboratory tests are presented. The tested vibration reducing system is the physical model of a 2 degree-of-freedom (DOF) suspension. An initial analysis has been conducted to explore the potential use of the energy produced by the vibration of unsprung mass in the first degree of the suspension system, for power supply to the active component incorporated in the second suspension degree. The energy recuperated from the first suspension DOF is transferred by a dedicated hydraulic system and stored in an accumulator. Results of the experiments revealed that the mechanical parameters of the system can be selected in such a way that for specific interfering signals the accumulated energy should be at least equal to the energy used up by the system.

This paper is focused on the problem of active suspensions of wheeled vehicles with electro-hydraulic actuators. Two dynamic structures first with actuator connected with spring in series and second in parallel -called slow active and full active respectively -were considered. The considerations described in the paper concern physical quarter-vehicle models of suspensions. These models were constructed and installed on a rig for dynamic tests of structures. A laboratory rig enables the simulation of real conditions by disturbing investigated suspension by kinematic excitation. Research was carried out for various algorithms controlling the actuator of the active unit. For evaluation of laboratory research results, comparisons were proposed of frequency response functions and of time curves of instantaneous power taken by the active system from supply, obtained at the same excitation signals. Quantitative aggregated indicators in the form of an averaged coefficient of vibration transmissibility and power required for the active unit to achieve vibration transmissibility function were also proposed. s, Φ(·,·)-nonlinear part of equation governing the actuator dynamic, Φ (t) -function Φ on trajectories of the system, Y(f) -Fourier transform of output signal y(t) , X(f) -Fourier transform of input signal x(t), f start -low frequency limit of considered bandwidth, f stop -high frequency limit of considered bandwidth. INTRODUCTION Mechanical structure of the active suspension -overviewSuspensions of vehicles historically have been divided into passive, semi-active and active. The essence of controlled suspensions classification [1,2] is the division into five kinds of suspensions ordered according to external energy demand: adaptive suspension, semi-active suspension, load levelling suspension, slow active suspension and full active suspension. The first two kinds are suspensions in which the efficiency of vibration reduction is obtained by controlling changes in parameters such as viscous damping or spring ratio [3]. In these systems energy supplied to the controlled suspension is used entirely for changes in parameters such as stiffness and/or damping [4,5]. The difference between these suspensions consists of the frequency range of operation. Adaptive systems are limited to slow changes (below 5 Hz [2]) to which they adapt, for example, changes in road irregularities -from gravel to asphalt surface. In turn semi-active suspensions reduce vibration of frequencies up to as much as 40 Hz [6]. Load levelling, slow active and full active suspensions are characterised by the direct use of energy for generating force and/or displacement, causing a decrease in vibration intensity. The efficiency of vibration reduction in the case of these three suspensions is better than for adaptive and semi-active systems. The first system in which energy is supplied to the suspension through generating forces or displacement, in the opposite direction as disturbances from road irregularities is the load levelling system. In thi...

Use of springs made of an alloy with shape memory (SMA) to shape the dynamic characteristics of a resonance vibration screen is proposed in this paper. These springs change spring constant as a result of temperature changes. Thus it is possible to change their resonance frequency in real time. In the paper a mathematical model of a controlled SMA spring was formulated and its parameters were identified. In the model both the effect of spring coefficient changes and damping changes depending upon alloy temperature and spring vibration frequency were taken into consideration. Experimental investigations of the examined spring and screen physical model were carried out and selected characteristics were also included. The investigations were carried out at the Dynamics and Control of Structures Laboratory of AGH University of Science and Technology. The control law was formulated. Simulation investigations of the mathematical vibration screen model in both open and closed loop systems were made. It was shown that the elaborated control system is robust of vibration mass changes by as much as ±30%.

No abstract