This work presents a new concept of fine position control of vehicle lift systems used for maintenance services, to facilitate specialized tasks such as height balancing of tilted vehicles. The research goal is accomplished by utilizing a controllable hydraulic circuit associated with magnetorheological valves. After establishing the required dynamic forces and position control range of the vehicle’s lift system, a two-coil type of magnetorheological valve is designed with consideration of the field-dependent properties of the magnetorheological fluid and the magnetic flux intensity, which is analyzed using the finite element method. Magnetorheological valves are then manufactured and the pressure drops are evaluated as a function of the input current (magnetic field). A hydraulic circuit with magnetorheological valves is formulated to control the height of the lift with an accuracy of ±1 mm with a load of 2000 kg on the each lifts. It is experimentally demonstrated that ramp and sinusoidal positions (or height) are well tracked within the targeted accuracy by controlling the magnetorheological valves. In addition, it is shown that the tilted position of the loaded vehicle with an eccentric mass placed on the lift is well controlled showing the balanced height.

Abstract:In this study, a semi-active magneto-rheological (MR) mount is designed and manufactured to minimize unwanted vibrations for the cabin of heavy vehicles. Normally, working conditions in heavy vehicles are extremely rugged. Usually, the heavy vehicles use passive rubber mounts for the reduction of vibrations from road. However, the passive mount has definite performance limitations because the passive mount has a fixed resonance frequency when the design is finished. An MR application is one of the solutions because the viscosity of MR fluid can be controlled. As a first step, an experimental apparatus was established for performance evaluation of the mounts. The apparatus has hydraulic excitatory, force, and displacement sensors. Performance of two different passive mounts used in industrial fields were evaluated. The passive mount data of force-displacement, force-velocity, and displacement transmissibility were collected and tested. After that, an MR mount was designed and manufactured that provides better performance using the passive mount data. The MR mount uses two different flow paths, annular duct and radial channels, for generating the required damping force. The field-dependent damping forces were then evaluated with respect to the moving stroke and input current. In this work, in order to control the damping force, an on-off controller associated with the fast Fourier transform (FFT) was used. The control results of the MR mount were compared with the results of passive rubber mounts. It was shown that the semi-active MR mount can attenuate vibrations more effectively at all frequency ranges compared with the passive rubber mount.

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