悬棒运动中的拍频以及张力突变现象——兼谈来自课本的研究性

拓展一道基础训练题的内容,对其非线性效应中的"非典型"拍频现象和"突变张力"点进行了研究.就其出现的成因和导致的结果作了初步分析,通过模拟计算阐明原力学模型不够完善的地方.

A practical robust nonlinear controller for maglev levitation system

In order to explore the precise dynamic response of the maglev train and verify the validity of proposed controller,a maglev guideway-electromagnet-air spring-cabin coupled model is developed in the first step.Based on the coupled model,the stresses of the modules are analyzed,and it is pointed out that the inherent nonlinearity,the inner coupling,misalignments between the sensors and actuators,and external disturbances are the main issues that should be considered for the maglev engineering.Furthermore,a feedback linearization controller based on the mathematical model of a maglev module is derived,in which the nonlinearity,coupling and misalignments are taken into account.Then,to attenuate the effect of external disturbances,a disturbance observer is proposed and the dynamics of the estimation error is analyzed using the input-to-state stability theory.It shows that the error is negligible under a low-frequency disturbance.However,at the high-frequency range,the error is unacceptable and the disturbances can not be compensated in time,which lead to over designed fluctuations of levitation gap,even a clash between the upper surface of electromagnet and lower surface of guideway.To solve this problem,a novel nonlinear acceleration feedback is put forward to enhancing the attenuation ability of fast varying disturbances.Finally,numerical comparisons show that the proposed controller outperforms the traditional feedback linearization controller and maintains good robustness under disturbances.

A new semi-active suspension control strategy through mixed H_2/H_∞ robust technique

A new semi-active suspension control strategy through mixed H2/H∞ robust technique was developed due to its flexibility and robustness to model uncertainties.A full car model with seven degrees of freedom was established to demonstrate the effectiveness of the new control approach.Magneto-rheological(MR) dampers were designed,manufactured and characterized as available semi-active actuators in the developed semi-active suspension system.The four independent mixed H2/H∞ controllers were devised in order to perform a distributed semi-active control system in the vehicle by which the response velocity and reliability can be improved significantly.The performance of the proposed new approach was investigated in time and frequency domains.A good balance between vehicle's comfort and road holding was achieved.An effective and practical control strategy for semi-active suspension system was thus obtained.This new approach exhibits some advantages in implementation,performance flexibility and robustness compared to existing methods.

Robust control for active suspension system under steering condition

To minimize the auto body's posture change caused by steering and uneven road, and improve the vehicle's riding comfort and handling stability, this paper presents an H∞ robust controller of the active suspension system, which considers the effects of different steering conditions on its dynamic performance. The vehicle's vibration in the yaw, roll, pitch and vertical direction and the suspension's dynamic deflection in the steering process are taken into account for the designed H∞ robust controller, and it introduces the frequency weight function to improve the riding comfort in the specific sensitive frequency bands to human body. The proposed robust controller is testified through simulation and steering wheel angle step test. The results show that the active suspension with the designed robust controller can enhance the anti-roll capability of the vehicle, inhibit the changes of the body, and improve the riding comfort of the vehicle under steering condition. The results of this study can provide certain theoretical basis for the research and application of active suspension system.