Hide/Show Apps


Okyay, Ahmet
Ciğeroğlu, Ender
In this paper, a sliding mode control methodology is implemented for the ABS control problem. Tire-road adhesion coefficient is taken as an uncertain parameter within known limits. This allows designing a robust sliding mode controller which does not require utilization of road coefficient of adhesion information, which is difficult to measure. As an improvement over previous studies, the sliding plane is formed to include both integral and derivative terms of the slip ratio error rather than only one of them. A design routine was identified in which the integral term, the derivative term and the relay action replaced by saturation compensate for each other's drawbacks. Simulations were carried out using a quarter car model, where hydraulic components were assumed to introduce an additional first order dynamics due to hydraulic delay. Results show that, reference tracking performance and stability benefits of the integral term, which allowed for a more flexible relay term, could be used without causing oscillations. Conversely, possible instability at low speeds caused by the derivative term could be prevented by the relaxation of the relay term by means of saturation. As a result, stable controller operation with reduced chattering at both low and high velocities is realized. Finally, the enriched set of parameters involved in the sliding plane is observed to enable the designer to shape different stages of response while maintaining stability and, partly, performance characteristics.