Bi-objective optimization of simultaneous vibration suppression and energy harvesting in suspension systems based on mixed H2/H∞ control.

Simultaneous vibration suppression and energy harvesting (SVSEH) of suspension systems has attracted significant attention over the past few decades. Nevertheless, vibration suppression and energy harvesting often compete with each other due to using single-objective control methods and the tradeoff has limited the effectiveness of current systems. To reduce the tradeoff, the innovation of this paper is to propose a bi-objective control strategy in which vibration suppression and energy harvesting are optimized by two independent objective functions. Firstly, the state equation of the quarter-suspension SVSEH system is derived and nonlinear restoring force is linearized. Then the reduced-tradeoff control of the quarter-suspension SVSEH system is first equivalent to a bi-objective H2-norm optimization subject to an H∞-norm constraint. Next, the mixed H2/H∞ state feedback-based control method is presented in detail and a low-pass filter is adopted to ensure the "strictly proper" condition of H2 control. In the end, a Simulink model is built and the results indicate that it achieves a 6.2% improvement in vibration reduction and a 17.9% increase in energy harvesting compared to existing method. It confirms the proposed method can greatly reduce the tradeoff between vibration suppression and energy harvesting. Consequently, this research can contribute to developing next-generation energy-regenerative suspensions.