Real-Time Individual Tire Force Estimation for an All-Wheel Drive Vehicle

Due to demands for active control systems that can enhance driving performance, active-type all-wheel drive (AWD) systems have drawn interest recently. Equipped with an electronically actuated motor to control a wet clutch in a transfer case, the active-type AWD facilitates the variable distribution of torque from the main driveshaft to the subdriveshaft. The conventional approaches to the estimation of tire force, developed to implement chassis control, have only focused on the two-wheel drive vehicle dynamics model. In this paper, an individual tire force estimation algorithm that is particularly designed for AWD vehicles is proposed. Using the interacting multiple model filter method, the suggested algorithm can help avoid the chattering response caused by immediately switching between vehicle dynamic models. Data obtained from the controller area network of production vehicles were used for the real-time application of the proposed estimator to chassis control. Then, the proposed estimator was validated using an AWD vehicle in various driving scenarios.

I. Introduction

In contradistinction to two-wheel drive (2WD) vehicles, all-wheel drive (AWD) vehicles allow the distribution of the driving torque generated by the engine to both the front and rear wheels by attaching a transfer case at the transmission output shaft. Recently, the number of vehicles with AWD systems installed has increased, even for on-road vehicles, because 2WD can allow excessive slip during the generation of tire-road traction force due to increases in engine power and drivetrain efficiency. The electronically actuated AWD system discussed in this paper differs from a passive-type AWD, because it controls the amount of driving torque distributed to the sub-driveshaft by changing the engagement force of the wet clutch in the transfer case.