Magnetorheological semi-active mount system for engines: Prototyping and testing

In order to maximize the controllability of magnetorheological (MR) mount for engines, a novel (MR) mount with an internal bypass (MRM-IB), which provides particular advantages of large dynamic stiffness range, small field-off dynamic stiffness and long available stroke under full vibration frequency range, is proposed and investigated in this paper. The proposed MRM-IB consists of a main rubber spring unit for supporting static load and a MR damping unit for mechanical energy dissipation. The MR damping unit is composed of a piston assembly, a MR fluid chamber and an annular MR fluid channel sandwiched by two concentric cylinders, that is, the inner and outer cylinders. Electromagnetic coil winding is wound on the outside of the inner cylinder and continuous damping/dynamic stiffness of the MRM-IB is tuned by the applied current in the coils. Structural principle of the magnetic circuit of the proposed MRM-IB is validated and analyzed, and the mathematical model of the controllable damping force is then established. In addition, a frequency-based piecewise controller and a fuzzy controller for a specific MR semi-active automotive mount system are designed, and the theoretical simulation and the experimental tests of the system are conducted, compared and analyzed.

Validating the Model of a No-Till Coulter Assembly Equipped with a Magnetorheological Damping System

Variability in soil conditions has a significant influence on the performance of a no-till seeder in terms of an inconsistency in the depth of seeding. This occurs due to the inappropriate dynamic responses of the coulter to the variable soil conditions. In this work, the dynamics of a coulter assembly, designed with a magnetorheological (MR) damping system, were simulated, in terms of vertical movement and ground impact. The developed model used measured inputs from previously performed experiments, i.e., surface profiles and vertical forces. Subsequently, the actual coulter was reassembled with an MR damping system. Multiple sensors were attached to the developed coulter in order to capture its motion behavior together with the profiles, which were followed by the packer wheel. With the aim to validate the correctness of the simulation model, the simulation outputs, i.e., pitch angles and damper forces, were compared to the measured ones. The comparison was based on the root-mean-squared error (RMSE) in percentage, the root-mean-squared deviation (RMSD), and the correlation coefficient. The average value of the RMSE for the pitch angle, for all currents applied on the MR damper, was below 10% and 8% for the speeds of 10 km h−1 and 12 km h−1, respectively. For the damper force, these figures were 15% and 13%. The RMSD was below 0.5 deg and 1.3 N for the pitch angle and the damper force, respectively. The correlation coefficient for all datasets was above 0.95 and 0.7 for the pitch angle and the damper force, respectively. Since the damper force indicated a comparatively lower correlation in the time domain, its frequency domain and coherence were investigated. The coherence value was above 0.9 for all datasets.

Adaptive Semiactive Cable Vibration Control: A Frequency Domain Perspective

An adaptive solution to semiactive control of cable vibration is formulated by extending the linear quadratic Gaussian (LQG) control from time domain to frequency domain. Frequency shaping is introduced via the frequency dependent weights in the cost function to address the control effectiveness and robustness. The Hilbert-Huang transform (HHT) technique is further synthesized for online tuning of the controller gain adaptively to track the cable vibration evolution, which also obviates the iterative optimal gain selection for the trade-off between control performance and energy in the conventional time domain LQG (T-LQG) control. The developed adaptive frequency-shaped LQG (AF-LQG) control is realized by collocated self-sensing magnetorheological (MR) dampers considering the nonlinear damper dynamics for force tracking control. Performance of the AF-LQG control is numerically validated on a bridge cable transversely attached with a self-sensing MR damper. The results demonstrate the adaptivity in gain tuning of the AF-LQG control to target for the dominant cable mode for vibration energy dissipation, as well as its enhanced control efficacy over the optimal passive MR damping control and the T-LQG control for different excitation modes and damper locations.

Magnetic Circuit Analyses and Turning Chatter Suppression Based on a Squeeze-Mode Magnetorheological Damping Turning Tool

As a smart material, magnetorheological fluid (MRF) has been utilized in fields including civil engineering and automotive engineering, and so on. In this study, the MR damping turning tool based on the squeeze-mode was developed to improve the vibration resistance of the tool system on the lathe. The 3D magnetic circuit simulations of the damper were performed. The influences of damper structural parameters, such as coil positions, plate thicknesses, and others, on the magnetic induction strength were investigated. Orthogonal experiments were carried out and the optimal combination of damper parameters was determined. The chatter suppressive experiments were carried out to evaluate the performance of the MR damping turning tool.

Experimental Validation and Adjustment of the Semi-Active Suspension Numerical Model Incorporating a MR Damping

The purpose of this paper is to experimentally validate the performance of a semi-active suspension incorporating a magneto-rheological damper (MR), where the parameters of the numerical models are often poorly adapted to real responses measured experimentally. To ensure a better representation of a real semi-active suspension, we must consider the internal dynamics of the MR damper in its numerical modeling. By adopting models which demonstrate that dynamic, such as the Bingham and Bouc-Wen models, we can approach the measured responses by adjusting their internal parameters. The law control introduction for feedback control of the semi-active suspension incorporating the internal dynamics of the MR damper allows, through the analysis of its robustness and response time, to better assess its performance. To validate the performance of these models, a comparative analysis was made between the experimentally measured responses by the dSPACE system used as an acquisition and control chain and the calculated or predicted responses. A rapprochement between measured responses and those calculated for the same dynamic characteristics of the test bed is possible by adjusting the most influential parameters of Bouc-Wen model.