This study explores the steady-state performance of a dual-stage vibration isolator, which is configured by a bistable oscillator and a linear oscillator. The potential force of the bistable stage comprises negative linear and positive cubic nonlinear stiffnesses such that the two restoring force contributions may counterbalance to minimize dynamic force transmission. By applying a first-order harmonic balance, it is predicted that the bistable dual-stage isolator may significantly outperform an equivalent pure linear dual-stage isolator. This conclusion is verified through a series of numerical investigations. Following a parametric study, design guidelines are detailed to achieve performance improvements. Then, the 'valley' response, which is the special phenomenon of the bistable dual-stage isolator due to the counterbalance of the negative linear and positive nonlinear potential forces, is revealed and quantitatively explained. Numerical studies demonstrate the role of initial conditions, and it is shown that the likelihood of beneficial single periodic valley and intra-well responses for isolation purposes can be increased by greater bistable stage damping. Finally, a bistable dual-stage isolator prototype is developed and tested, and the numerical and experimental results verify the theoretical predictions.

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Wet clutch transmits its power by the friction torque between friction and separate disks. Conical groove friction disk is a new attempt in Wet clutch. Its configurations allow significant enhancement of torque delivery performances, compared with the traditional plane friction disk. In order to study the frictional performances of the conical groove friction configuration, the friction coefficient calculation model of conical groove friction disk was established, and experimental investigation was used to measure the friction coefficient under sliding velocity conditions. The influence of configuration parameters: cone heights and angles on friction coefficients were evaluated in a typical variable speed test. The results indicated that configuration parameters can affect friction performance in a constant speed period. The equivalent radius can directly describe the friction region of a conical groove friction disk. The constant speed test can be a useful method.

This article presents a robust control method of an active-passive hybrid vibration absorber for vibration suppression in a wide frequency band based on skyhook damping strategy. The technology of linear extended state observer is applied to automatically change pole locations of the system for stabilising the skyhook damping control, so that a high control gain can be used for effective control performance. Simulations on the vibration control of a single-degree-of-freedom primary structure via a hybrid vibration absorber are conducted to analyse the stability and performance of the present method. The results reveal that the present method is effective for vibration suppression and robust against marked parameter variations in both the primary structure and the absorber, when the controller is stabilised. Finally, this article demonstrates the effectiveness of the present approach for active control of multiple hybrid vibration absorbers to suppress multimode vibration. Simulation results show that the robustness against structural parameter variations is significantly improved compared to the previous approach, and all the vibration modes of the primary structure are suppressed effectively. In addition, by means of commercial dynamics software, simulations on vibration control of a cantilever panel via two hybrid absorbers are performed to further demonstrate the control effectiveness for a complex structure, where an analytical model is not available. Results indicate that the present method is effective and stable despite the large changes of the parameters.