As an intelligent device, the magnetorheological (MR) damper has received extensive attention in many fields. However, in the real-time control system, it is still extremely necessary to develop a simple, accurate and invertible dynamic model of the MR damper. In this work, a new invertible MR dynamic model based on sigmoid function is proposed. According to the experimental data of a common MR damper, it is assumed that the damping force at zero velocity under constant current is only related to current and independent of the excitation frequency. The preliminary sigmoid model based on this hypothesis can better adapt to different frequency excitations while reducing the complexity of the model. In addition, according to the parameter analysis of the proposed preliminary model, the relationship between the parameters and the input current is reasonably simplified, so that the final model can meet reversibility requirements in the control system while ensuring accuracy. In order to evaluate the performance of the proposed model, it is compared with the existing sigmoid models from the literature. The results show that the proposed model has certain advantages in the number of parameters, accuracy and reversibility, which is suitable for the real-time control system.

The realization of the desired damping characteristics based on magnetorheological (MR) dampers is important for semi-active control and useful for the matching process of suspension damper. To reduce the cost of the control system and improve the output accuracy of the desired damping force, this study proposes an open-loop control method featuring an accurate inverse model of the MR damper and a tripolar current driver. The reversible sigmoid model is used to accurately and quickly calculate the desired current. Furthermore, the change characteristic of the desired current is analyzed qualitatively and quantitatively, which shows that the desired current needs to change suddenly to make the actual damping force velocity curve quickly approach the desired one. To meet the demand of the desired current, a tripolar current driver controlled by an improved PI control algorithm is proposed, which is with fast response and low noise. Finally, the bench test verifies that the control system can achieve different desired damping characteristics well, and the inherent error in this process is explained through the gap between the available damping force area and the desired damping characteristic curve and the crossover phenomenon of the dynamic characteristic curves of the MR damper.

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