基于增量本构关系的磁流变减振器动力学模型研究

Magnetorheological damper(MRD) is an excellent performance intelligent damping device, and can be widely used in semi-active suspension system of heavy-duty and high-speed vehicle. The damping force of MRD is difficult to predict because of the nonlinear hysteretic characteristics. In order to solve these problems, the dynamics model based on incremental constitutive is being studied using magnetic-flow- variable effect, taking MRD hysteresis model as target. Firstly, researching the basic principles and methods to characterize the mechanical behavior of MRF, and finding the release rules of them by analysing constitutive model and numerical solution, after that a stress-strain "incremental" equation is proposed to characterize the viscoplastic constitutive relation of MRF. Then, hysteresis curve features are analyzed to reveal the relationship between the excitation current, state of motion and lags. Combined with the magnetorheological fluid constitutive model, a nonlinear hysteretic model will be built combined with the magnetorheological fluid constitutive model. Finally, the nonlinear characteristics of MRD such as hysteresis, yield and magnetic saturation is studied by testing. The results can correct the model lags and reveal the parameters. It is expected that the research results can provide a new way for the design and modeling of MRD, and propose a new approach to study semi-active suspension control system of heavy-duty and high-speed vehicle.

磁流变减振器是性能优良的智能减振装置，可广泛用于重载提速车辆的半主动悬架系统。针对磁流变减振器非线性滞回特性导致阻尼力难以预测和控制的关键科学问题，以构建磁流变减振器滞回模型为目标，利用磁流变液的磁-流-变效应，开展基于增量本构关系的磁流变减振器动力学模型研究。首先，研究表征磁流变液力学行为的基本原理和方法，通过分析屈服前的粘弹性和屈服后的粘塑性流变特性，探索磁流变液本构模型和数值解法，提出用应力-应变“增量”方程表征磁流变液的粘塑性本构关系；其次，分析滞回曲线的特征，揭示磁流变减振器励磁电流、运动状态与滞回环节之间的联系，结合磁流变液本构模型，研究磁流变减振器建模方法，建立其非线性滞回模型；最后，试验研究磁流变减振器的滞回、屈服和磁饱和等非线性特性，修正模型滞回环节，并进行参数辨识。研究结果有望为磁流变减振器的设计与建模提供新思路，为重载提速车辆半主动悬架控制系统的研究提供新方法。

首先，针对磁流变液剪切稀化与稠化现象，通过零磁场强度下的旋转变剪切测试，得到不同温度下磁流变液粘度和剪切应力随剪切速率的变化规律，计算出屈服应力点，得到磁流变液屈服前和屈服后的粘弹性本构模型。其次，构建磁流变液高温高频状态下的稳定性实验模型，通过振荡振幅扫描、频率扫描和旋转变剪切温度扫描测试，分析了磁流变液的温度稳定性和结构稳定性，得到了不同温度下的磁流变液的粘弹性区间。研究结果表明，当频率不变时，磁流变液弹性模量和黏性模量随着温度上升而逐渐减小；在1-100HZ频率范围内磁流变液的弹性模量始终大于黏性模量，表现为胶体状态，结构较为稳定；磁流变液在低剪切速率且室温范围内温度稳定性较好，在经过温度循环后磁流变液的流变性能未发生显著变化。最后，基于流体动力学理论对流经阻尼通道的磁流变液进行了动力学分析，研究了阻尼通道内磁流变液的流动特性，建立阻尼力数学模型，对自行研制的磁流变阻尼器进行了外特性试验，研究磁流变阻尼器活塞速度和励磁电流对其力学特性的影响，建立了阻尼力简化模型并对其进行了精度验证。