Initial Pitch Control for Semi-active Suspension System

The aim of this study is to develop an Add-On Feature that could support the semi-active suspension system controller during longitudinal dynamics maneuvers. The Add-On Feature called Initial Pitch Control (IPC) is activated during launching, shifting, and braking to enhance the pitch motion characteristics and road-holding capability. A sixteen degrees-of-freedom (DoF) vehicle mathematical model represents the vertical and longitudinal dynamics developed and validated via laboratory and road tests. A hydraulic four-poster test rig is used to carry out the laboratory tests for the vertical dynamics verification, while the longitudinal dynamic verification is achieved through the performed tests on a highway track. In order to design the IPC algorithm, the Rule-Optimized (RO) semi-active suspension controller, an Anti-lock Braking System (ABS) controller, and seven gears Dual-Clutch Transmission (DCT) controller are implemented in the vehicle model. An optimization routine has been applied to find the optimum force gains for the IPC algorithm. The IPC algorithm is evaluated in terms of the body pitching motion and the road holding during launching and braking. Comparisons between the passive suspension and semi-active suspension systems with and without the proposed IPC algorithm have been performed. The obtained results illustrated that the IPC algorithm with the semi-active controller improved both the pitching motion and road-holding characteristics of the vehicle compared with the passive suspension system and semi-active suspension without IPC.