A. Milecki

Investigation and control of magneto–rheological fluid dampers

Abstract A semi-active controllable fluid damper is described and studied in this paper. The damper employs magneto–rheological fluid that changes its properties in the presence of a magnetic field. This results in a damper whose characteristics may by adapted in real time to the users requirements. Such dampers can be used to eliminate oscillations in different servo drive machine tools systems. In this paper a simulation model of those dampers is proposed and some control analyses are made. Construction of such a damper is described and finally experimental results of its performance are presented.

MR haptic joystick in control of virtual servo drive

In the paper the one-axis haptic joystick is proposed and described. This joystick utilizes a magnethoreological (MR) brake in order to obtain operator movement opposite force which creates feedback force. The MR brake investigations results are shown. The designed and built joystick was then connected to the computer, and used to control of prepared in Matlab/Simulink software, virtual model of electrohydraulic drive. The main equations describing this drive were shortly described. Finally the investigations stand and some results are presented.

Investigation of Dynamic Properties and Control Method Influences on MR Fluid Dampers’ Performance

Semi-active, controllable fluid dampers and their control devices are described and studied in this paper. Such dampers can be used to eliminate oscillations in different servo drive robots and machine tools systems, where their good dynamic parameters are required. In this paper, different control circuits and its influence on MR damper properties are investigated. The experimental results of coil current transients response during switching on and off with different circuits and elements are shown. Construction of the above mentioned damper is described and finally, experimental results of control circuits influence on dampers’ dynamic performance are presented.

Applications of magnetorheological brakes in manual control of lifting devices and manipulators

The article is aimed to design and testing of joystick with force feedback used in direct, human control of lifting device. The paper starts with the basic description of designed and tested by us MR rotary brake. Some initial laboratory investigations results of such brakes are presented. The usage of MR brakes in 2 axis joystick is proposed. Such, built by as joystick, is described. It was used as Human-Machine Interface in active control of lifting device. The designed and built 2 axis manipulator with electrohydraulic drive is described. In the paper, the based on PC with input/output card, control system of mentioned above joystick with MR brake and manipulator is described. Finally the control algorithm is proposed.

Controllability of MR shock absorber for vehicles

In the paper, shock absorbers with magnetorheological (MR) fluids were described. These elements can be used in many applications related to vehicle machines such as bumpers, dampers, shock absorbers, vibration eliminators, etc. Basic theoretical relationships which allow design and modelling of MR fluid shock absorbers are shown. Experimental designs of MR absorber and some example results of research were presented and discussed. The application of PI force controller used to improve the dissipation characteristic of built MR shock absorber has been shown.

Modelling of electrohydraulic servo drive used in very low velocity applications

In the paper, the discussion is focused on modelling of the electrohydraulic servo drive with stepping motor and electric feedback linkage, which is capable of obtaining very low velocity. The main features of drive operation are described and some specific problem areas, due to the nature of very low velocity movement, are considered. Some important features of the servo drive flow control valve construction are outlined, with reference to modelling possibilities. For all drive elements i.e., the stepping motor unit, hydraulic valve and cylinder theoretical equations, characteristics and a simulation model were proposed. In particular, the shapes and characteristics of hydraulic flow valve window are given in detail. A prototype electrohydraulic servo drive with stepping motor has been designed, constructed and investigated. The investigation results (curves) of valve dead zone and clogging process are included into the model. Finally, the whole servo drive investigations results are compared with results obtained by simulation. Both results are very similar, which means that the proposed simulation model in the paper corresponds quite well to the real servo drive.

The Use of Magnetorheological Fluid Dampers to Reduce Servo Drive Velocity Jumps due to Load Changes

A problem of velocity control of servo drives in the presence of high load changes is described and studied in this article. The rapid fall of load causes an unexpected jump of the movable elements of the machine. The increase of velocity is harmful and may be reduced by usage of electrically controllable dampers. Such dampers employ a magnetorheological fluid that changes its properties in the presence of a magnetic field. This results in a damper whose characteristics may by adapted in real time to the user’s requirements. In this article the construction of such a damper is described and a machine tool servo drive with an MRF damper is presented. Its simulation model is proposed and some simulation and control analyses are made. Finally experimental results of servo drive velocity control in the presence of load changes are presented. The article is focused on velocity jump reduction which is caused by load decrease.

THE USAGE OF ACCELERATION SIGNAL TO CONTROL MAGNETO-RHEOLOGICAL FLUID DAMPER.

A semi-active controllable linear magneto-rheological (MR) fluid damper is described and studied in this paper. The damping characteristics of the damper may be adapted in real time to the users requirements. Such dampers can then be used to eliminate vibrations in applications like vehicles and different machines. In this paper, a simple control method, which uses an acceleration signal to switch the damper on and off, is proposed. The construction of such a control system is described and finally experimental results of oscillation damping are presented.