The importance of energy efficiency, as one of the most crucial issues in automotive industry, has grown more rapidly considering the global energy crisis and climate change in recent years. This paper aims to introduce a method to increase the powertrain efficiency based on the minimization of tire power loss. Slip resistance is taken into account as well as rolling resistance to yield the modified tire resistance considered in this study. It is shown that the general optimal control problem can be reduced to an instantaneous minimization problem in which the equivalent force of tire power loss is to be minimized at each instant of time. Moreover, tire inflation pressure is selected as the control input bearing its major influence on tire resistance and its potential of being controllable in the mind. In addition, a polynomial inverse tire model is developed in order to find the solution of the minimization problem with lower computational cost. The coefficients used in inverse tire model are characterized as a function of friction coefficient, normal load, and inflation pressure so that the reliability and accuracy of the model are guaranteed under different conditions. The effectiveness of the proposed online control system, called Tire Inflation Pressure Regulation System, is simulated in some driving cycles, i.e. NEDC, FTP, HWFET, and ARTEMIS-Urban, and it is shown that up to 2% improvement is achievable.
Investigation of vehicle resistant forces and power losses is of crucial importance owing to current state of energy consumption in transport sector. Meanwhile, considerable portion of resistant forces in a ground vehicle is traced back to tires. Pneumatic tires are known to be a source of energy dissipation as a consequence of their viscoelastic nature. The current study aims to provide a modification to tire resistance by considering the power loss in a tire due to longitudinal slip. The modified tire resistance is comprised of rolling resistance and a newly introduced resistance caused by tire slip, called slip resistance. The physical model is chosen for parameters sensitivity study since the tractive force is described in this model via tangible physical parameters, e.g. tire tangential stiffness, coefficient of friction, and contact patch length. Hence, the tire physical model is capable to investigate the influence of different parameters such as coefficient of friction, normal load, and inflation pressure on dependency of tractive force upon longitudinal slip. The results show that tractive force is a determining factor in the modified tire resistance. In addition, it is seen that behavior of the modified tire resistance undergoes qualitative changes so that for a specified tractive force, it might be a strictly decreasing function of the mentioned parameters. But as the tractive force gradually increases, it might be changed to a non-monotonic function and after that to a strictly increasing function of the above parameters. Furthermore, the results are validated by measuring the vehicle constant-speed fuel consumption experimentally. History
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