Prospective Powering Strategy Development for Intelligent-Tire Sensor Power Charger Application

Tire sensors embedded in a vehicle tire are stand-alone autonomous devices. A tire sensor reserve power strategy is crucial due to sensor energy sources limitations for long operational periods. This paper presents an innovative tire sensor powering strategy for the intelligent-tire system. The powering strategy offers a green concept, maintenance-free, and low-cost method in order to extend the tire sensor lifetime for long operating periods. The proposed strategy adopts wireless power transfer (WPT) technology to transfer power to an electrical load mounted on the rotational system without an interconnection cable. It is composed of a power transmitter designed to be mounted on the vehicle’s inner fender liner, and a power receiver that provides power to recharge the tire sensor battery/energy storage. The transmitter transfers power from the vehicle battery/accumulator to a power receiver coupled with the tire sensor which is mounted on the vehicle tire inner wall. WPT devices were designed based on induction electromagnetic coupling and can provide an output current up to 1A at 5 V. The proposed powering strategy was verified using a vehicle tire simulator model to emulate rotational motion. A voltage and current sensor module as well microcontroller and data logger modules were utilized as the load for the developed WPT system. The verification experimental and preliminary test results reveal that the proposed strategy can provide constant power to the load (in this case, the voltage is around 4.3 V and the current is around 21.1 mA) although the vehicle tire model was rotated at different speeds from 0 rpm to 800 rpm. The proposed system has the potential and feasibility for implementation in tire sensor power applications in the intelligent-tire system.

IN SITU MEASUREMENT OF TIRE PLY STEER BASED ON AN INTELLIGENT TIRE SYSTEM

ABSTRACT Ply steer is an inherent property of a belted tire, manifesting as the nonzero side force at a slip angle of zero, and it is thus an important design factor relevant to a vehicle's straight running, safety, and comfort. Although ply steer is a rolling contact phenomenon, there is a lack of approaches for direct measurement and modeling of tire ply steer force in motion. Thus, we developed an in situ measurement method for tire ply steer based on a recently proposed accelerometer-based intelligent tire system. This new measurement method is significant for three main reasons: it facilitates understanding of the inherent mechanism of ply steer for radial tires, it improves the intelligent tire's accuracy based on the accelerometer, and it provides an in situ measurement approach for tire ply steer. An accelerometer-based intelligent tire was developed to obtain acceleration measurements at different conditions in which the lateral behavior is of particular interest. Two unusual phenomena that have never been reported are observed: (1) lateral accelerations demonstrate asymmetrical behavior with respect to positive/negative slip angles and (2) lateral accelerations at zero slip angle still exist. It is hypothesized that the underlying reason for these two unusual phenomena is the ply steer–dependent kinematics, which can conversely be used to measure tire ply steer in situ. To this end, the mixed Lagrange–Euler approach for rolling contact kinematics is used to formulate tire lateral acceleration, which links both rigid motion and elastic displacement. It is clearly found that the lateral acceleration is proportional to the square of the rotating velocity and the second-order gradient of displacement. Based on this kinematic model, the features of lateral acceleration can be easily explained by tire ply steer, which manifests as the sinusoidal lateral deformation modes due to the coupling of the bending-twist deformation of the cord–rubber composites of the tire belt. The proposed hypothesis has been verified by finite element method simulations, and the experimental results prove that tire ply steer leads to the observed unusual lateral acceleration pattern. Thus, the quantitative value of ply steer could be measured in situ by integrating the obtained lateral acceleration and thus the apparent elastic slip angle, even under zero external wheel slip angle. In this manner, the intelligent tire system provides a direct measurement approach for tire ply in motion. In addition, the accuracy of the intelligent tire's algorithm might be improved by suitable modeling of the asymmetrical acceleration with respect to left/right slip based on the proposed hypothesis of ply steer–dependent kinematics.