The vibration isolation system with cubic stiffness and Bouc-Wen type hysteresis shows complex nonlinear dynamic characteristics. An undamped response model is established based on an anhysteretic restoring force. An approximate analytical solution is derived by the harmonic balance method (HBM) and the Taylor expansion. An analytical/numerical method is proposed to calculate the damped response of the vibration isolation system, based on the HBM and Levenberg-Marquardt algorithm. For the multi-value non-smooth function terms, the harmonic term coefficients are obtained by applying the fast Fourier Transform for the calculated time-domain response. The proposed methods are applied to a nonlinear vibration isolation system with horizontal wire ropes. It is verified that the vibration isolation system has a softening-hardening stiffness with cubic stiffness and Bouc-Wen type hysteresis. Both hysteretic damping and linear damping can effectively suppress the resonance, while with the hysteretic damping, better vibration isolation performance is shown at high frequencies.
In view of the fact that the Extend Kalman Filter (EKF) is prone to be divergent in the autonomous navigation by X-ray pulsars, this paper proposes an algorithm utilizing the fading memory filter. Based on the study of the error pattern of the EKF with the increase of iterations, some possible reasons for the divergency are analyzed. The fading memory filter can be used to reduce the peak of error, while delaying the divergence
When driving on a bend, due to the high gravity center and the heavy load, large trucks or lorries are easy to roll-over if their speed is high. This paper proposes a simplified theoretical model of the roll-over process of a truck during its turning, based on the dynamics analysis. Two critical velocities are defined to evaluate the state of the truck: the tilting critical velocity and the roll-over critical velocity. For a truck of given parameters, the main factors that affect the roll-over process are analyzed, including the weight of the truck, the height of the gravity center, and the turning radius of the road. Finally, some qualitative driving suggestions are given about how to avoid roll-over of large trucks.