Design optimization of active trailer differential braking systems for car-trailer combinations
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The thesis studies active trailer differential braking (ATDB) systems to improve the lateral stability of car-trailer (CT) combinations. CT combinations exhibit unique unstable motion modes, including jack-knifing, trailer sway, and roll-over. To address this CT stability problem, two ATDB controllers are proposed, which are designed using the Linear Quadratic Regulator (LQR) and 𝐻∞ robust control techniques. In order to design the ATDB controllers, a linear 3 degrees of freedom (DOF) and a linear 5-DOF model are generated and validated with a nonlinear CT model derived using CarSim software. Eigenvalue analysis is conducted to examine the effects of typical trailer parameters on the lateral stability of CT combinations. The contribution of the LQR-based ATDB controller to the enhancement of CT stability is assessed. The thesis also investigates the insensitivity of the 𝐻∞ controller to parameter uncertainties. A genetic algorithm (GA) is applied to find optimal control variables of the active safety systems. Numerical simulations demonstrate that the parametric study may provide a guideline for trailer design variable selections, and the proposed ATDB systems can effectively increase the safety of CT combinations.