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As active chassis controllers are becoming increasingly complex and sophisticated, the performance of these controllers is very sensitive to a vehicle's inertial parameters such as the vehicle mass and mass centre height. Also, these parameters vary with the number of passengers and with different load situations. In this paper, in order to determine the vehicle mass during arbitrary vehicle manoeuvring, an online estimation system is proposed considering available driving conditions, which includes two estimation algorithms. One is designed on the basis of the vehicle's longitudinal motion using the recursive least-squares method with the disturbance observer technique. The other is designed on the basis of the vehicle's lateral motion by estimating the lateral velocity. Then, two estimation algorithms are combined to extract the vehicle mass information using the recursive least-squares method. The performance of the proposed estimation system is demonstrated through experimental tests.

The effect of entrained air in the hydraulic brake system of a platoon vehicle in a controlled braking manoeuvre was theoretically investigated. The actuator dynamics with the load inertia was considered, and non-linear and linearized system equations were derived in dimensionless form. It was found that the principal resonant critical frequency decreases as a result of the entrained air, and that the resonant peak amplitude increases as the air content increases. The decreased resonant frequency leads to a reduction in the bandwidth of the brake actuator. A stability criterion for the system reveals that the entrained air reduces the allowable open-loop gain, diminishing the stability in a closed-loop system. Numerical simulations for frequency response show that even small amounts of entrained air could drastically affect the braking performance.

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