Dynamics of vehicle stability control subjected to feedback delay

Mechanical systems with feedback control commonly contain time delays which usually tend to destabilise the system. With increasing accuracy requirements of data acquisition and calculation, investigation of the effect of the feedback delay including the computational time, actuating time, and signalling time is crucial for developing advanced chassis control. A 2-dimensional vehicle handling model with feedback control torque is introduced to analyse the dynamics of vehicle stability control system. A revised version of the PAC-2002 tyre model is used to create two qualitatively different steering characteristics by tuning the contact friction coefficients at the front and rear wheels. The stability charts in the space of the control gains are constructed. In understeer and oversteer cases, the control gains are optimised to achieve the fastest settling signals against small perturbations. While the optimised gains provide global stability of the cornering manoeuvres in the oversteer case, the gains should be further tuned in the understeer case to ensure fast settling signals and also global stability. The optimisation procedure is presented for various realistic time delays.