Longitudinal Tire Force Estimation Using Youla Controller Output Observer

Advanced powertrain and vehicle dynamics controls often require estimates of longitudinal tire force to maximize the vehicle's performance. One of the key advantages of hybrid electric vehicles and electric vehicles (EVs) is that measurements of the traction motor torque are readily available with good accuracy. This letter introduces a unique longitudinal tire force estimation strategy using the Youla controller output observer framework which only relies on motor torque and wheel speed measurements. The estimation strategy is applied to a rear-wheel-drive EV in order to obtain estimates of the rear axle longitudinal tire forces. A simple drivetrain model of the system is developed using bond graphs and is used in co-simulation with a high fidelity vehicle model from CarSim. It is shown in the simulation environment that the proposed estimation strategy is able to obtain accurate estimates of longitudinal tire force on high, low, and split-μ road surfaces. The proposed estimation strategy only requires information on the tire's effective rolling radius and does not require a tire model.