In this paper, a novel nonlinear model and high-precision lifting motion control method of a hydraulic manipulator driven by a proportional valve are presented, with consideration of severe system nonlinearities, various uncertainties as well as valve backlash/deadzone input nonlinearities. To accomplish this mission, based on the independent valve orifice throttling process, a new comprehensive pressure-flow model is proposed to uniformly indicate both the backlash and deadzone effects on the flow characteristics. Furthermore, in the manipulator lifting dynamics, considering mechanism nonlinearity and utilizing a smooth LuGre friction model to describe the friction dynamics, a nonlinear state-space mathematical model of hydraulic manipulation system is then established. To suppress the adverse effects of severe nonlinearities and uncertainties in the system, a high precision adaptive robust control method is proposed via backstepping, in which a projection-type adaptive law in combination with a robust feedback term is conducted to attenuate various uncertainties and disturbances. Lyapunov stability analysis demonstrates that the proposed control scheme can acquire transient and steady-state close-loop stability, and the excellent tracking performance of the designed control law is verified by comparative simulation results.

The objective of this article is to investigate the rollover threshold of a heavy-duty vehicle during cornering. Based on the multi-body dynamics theory, a high-fidelity model is established, which takes account of the chassis flexibility, the suspension nonlinear characteristics, the tire handling model, and Ackermann steering strategy. Furthermore, by the inverse fast Fourier transform method, a three-dimensional stochastic road in space domain is employed in the model to improve the accuracy. A full-size heavy-duty vehicle test was carried out to validate the model. Based on the validated model, the rollover stability and rollover threshold of the heavy-duty vehicle during cornering are investigated. Lateral acceleration, yaw rate, roll angle, and vehicle torsional deflection in different cornering conditions are analyzed. The rollover threshold is summarized by the response surface methodology for the safe cornering purpose. The result shows the practical meaning of improving transportation safety of heavy-duty vehicles and also provides useful insights for developing the rollover warning system.

During the sea launch of a launch vehicle in low sea state, a rolling phenomenon of the launch vehicle has been observed. In rough sea conditions, launch may failure. This study utilizes dimensionality reduction-driven spatial system projection methods and virtual prototype modeling technology to reveal that the launch vehicle’s rolling is caused by differences in the motion paths of the center of mass. Additionally, during the prelaunch stage, the variation in the trajectory of the launch vehicle’s center of mass caused by the rolling and pitching motions of the transportation vessel has a significant impact on the roll motion of the launch vehicle. The motion in other degrees of freedom has minimal influence on the launch vehicle’s rolling. The minimum rocket rolling occurs when the dynamic coefficient of friction of the launchpad–launch vehicle contact is 0.05, and the dynamic coefficient of friction of the adapters and guideways is 0.4. The conclusions provide a theoretical foundation for optimizing the sea launch system and enhancing the reliability of sea launch in rough sea conditions.

When designing flight control allocator for an over-actuated flight system, actuator dynamics, generally, are assumed to be ideal since the bandwidths of actuators are much larger than the frequency of aircraft. However, under incremental nonlinear dynamic inversion controller, the interaction between the constrained control allocation frame and actuator dynamics can cause serious consequence. In this work, a method is developed to compensate for actuator dynamics in s-domain analysis. Here, first-order and second-order actuator dynamics are taken into consideration as more complicated actuator dynamics can be combined by these two simplified models. This method solves for gains, which post-processe the output of control allocation frame. The gains are terse in form and are easy to be calculated, which means that it can be implemented into typical flight computer. Simulation results show proposed method can significantly compensate the flaw caused by actuator dynamics.