In this paper, a type of magneto-rheological (MR) damper with an inner bypass
and magnetic bias is proposed to fulfill the requirements of both large scalability
and low base-damping, which are critical for vibration suppression. With the
magnetic bias feature, low base-damping and large scalability can be obtained by the
bi-directional excitation of the applied current. The inner bypass feature can eliminate or
alleviate the flow block that occurs in the damping gap, however keeping the
advantage of suitability for vehicle suspension installation. In contrast to the original
mixed mode, the new MR damper adds a concentric damping gap in the piston,
which is controlled by the magnetic field, while the original gap will be free of any
magnetic field because of the shielding by non-magnetic material. The magnetic
bias in the added gap is obtained by the inclusion of a permanent magnet in the
piston. A magnetic analysis is carried out to verify the magnetic distribution under
permanent and electro-magnetic excitation. Based on the fabricated prototype, both
quasi-steady and dynamic tests are carried out, and it is shown that the MR
damper achieves bi-directional operation of the damping force with scalability
up to 8, and that the flow block is partly alleviated in a high applied current.
Magneto-rheological (MR) suspension systems display non-linearity and parameter uncertainty and thus it is difficult to derive an accurate model for designing a model-based controller. In this study, a novel fuzzy sliding mode control (FSMC) approach based on the hybrid Taguchi genetic algorithm (HTGA) is proposed to suppress the vibration of the MR suspension system. As the first step, the MR absorber is designed and manufactured based on the damping force level and mechanical dimensions required for the test car. After experimentally measuring the current-dependent damping force characteristic, a precise inverse model of the MR absorber is formulated. Subsequently, FSMC based on the HTGA is formulated on the basis of a quarter car model incorporated with an MR absorber. The linguistic variables and control rules of the fuzzy logic controller are optimized using the HTGA. For comparison purposes, two representative controllers including a conventional sliding mode controller and a fuzzy logic controller are also proposed. Finally, simulations and a road test are performed to validate the effectiveness and robustness of the proposed FSMC.
Reducing the vibration of an automotive magnetorheological (MR) suspension system can contribute greatly to enhancing vehicle performance. However, it is difficult to design a control system that depends on a complicated whole-vehicle vibration model. This paper proposes a hierarchical controller that consists of a control level and a coordination level for heave, roll, and pitch vibration control of a vehicle with an MR suspension system. On the control level, a local fuzzy controller is designed for each quarter-vehicle MR suspension system, based on a hybrid control strategy of skyhook control and groundhook control. On the coordination level, a coordination controller is designed to tune four local independent fuzzy controllers by adjusting their output parameters on the basis of system feedback. A test and control system for MR suspensions is set up and implemented on a minibus equipped with four controllable MR dampers. The results on random rough roads confirm that the hierarchical controller can reduce automotive vertical vibration, roll motion, and pitch motion more effectively than a passive suspension or an MR suspension using a hybrid control strategy. It achieves better ride comfort and automobile handling stability, although data for bump input indicate that the hierarchical controller does not decrease automotive vertical vibration more effectively than hybrid control or a passive system. However, it yields better results in decreasing pitch and roll motions.
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