Hierarchical control for car attitude with double-skyhook semi-active ISD suspension

As a novel control model, the inertance and damping double-skyhook configuration offers a straightforward algorithm and demonstrates flexibility in adapting to different road conditions and loads. However, current research on the double-skyhook configuration focuses primarily on minimizing the vertical vibration to enhance ride comfort, and there is a lack of research on the full-car multiple degrees of freedom (multi-DOF) comprehensive control concerning ride comfort and handling safety. This paper builds on the full-car model, revealing the deficiency that the double-skyhook control strategy overly optimizes car body acceleration, leading to drastic changes in car attitude and significantly compromising handling safety. To address the issue, a hierarchical control strategy is proposed to suppress full-car motion with multi-DOF. The control strategy incorporates a fuzzy control approach based on the double-skyhook configuration. The lower-level controller employs a double-skyhook control strategy to restrain vertical vibrations. The upper-level controller employs a variable universe fuzzy control to coordinate the optimal double-skyhook control forces, suppressing pitch and roll vibrations, thereby achieving a coordinating control of full-car. The 7-DOF full-car suspension model with hierarchical control is set up, followed by simulation analysis and semi-physical experiments. The results indicate that, compared to the double-skyhook suspension, the handling safety of the suspension has been significantly improved while maintaining ride comfort, effectively demonstrating the necessity and benefits of introducing hierarchical control in car suspension systems.