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Sliding mode control of semi-active suspensions possesses excellent performance as well as high robustness. However, it is difficult to obtain sufficient data concerning the various states of the suspension. A model reference sliding mode controller that is easy to implement has been designed. The proposed controller needs only two acceleration sensors and eliminates the necessity of measuring road signals in real-time. The controller uses an approximate ideal skyhook system as a reference model, and the control law is determined so that an asymptotically stable sliding mode will occur in the error dynamics between the plant and the reference model states. The effectiveness of this controller has been verified via experimental studies. A real-time control system has been constructed with a virtual instrument system. Experimental rapid control prototyping for the proposed controller has been conducted on a quarter-car suspension system. The experimental results indicate that, compared with a practical skyhook controller and a passive suspension, the sliding mode controller can effectively improve ride comfort and safety performance. The designed controller should be directly transferable to commercial implementations of semi-active vehicle suspensions.

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The morphological changes of leaves under the airflow have a significant effect on the deposition of pesticide droplets on the leaves, but the wind-induced vibration of the leaves is complicated to measure. In this study, an aerodynamic test of the pear leaf was conducted in the wind tunnel, and binocular high-speed photography was used to record the deformation and vibration of the leaves under various airflow velocities. Experiments showed that air velocity (v) had a significant effect on the morphological response of the leaf. As v increased, the leaf was in three states, including static deformation, low-frequency vibration, and reconfiguration of airfoil steady state. The mutation from one state to another occurred at the critical velocity of vcr1and vcr2. By tracking the leaf marker point, various morphological parameters were calculated, including the bending angle of the petiole, the wind deflection angle, and the twist angle of leaves under different air velocities. When vcr1 ≤v ≤vcr2, the parameters changed periodically. When v< vcr1, the petiole and the leaf bent statically, and the bending angle of the petiole and the wind deflection angle of the leaf gradually increased. When v >vcr2, the morphology of the leaf and the petiole was stable. Besides, this study tracked and measured the wind deflection area of leaf, which was consistent with the theoretical calculation results. The measurement of the leaf morphological parameters can reflect the morphological changes of leaves under airflow, thus providing a basis for the decision-making of air-assisted spray airflow.

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