A study on the influences of tyre lags and suspension damping on the instantaneous response of a vehicle

Abstract

The paper aims to quantify the influence of non-steady-state tyre behaviour and suspension damping on the instantaneous response of a vehicle to handling manoeuvres. The influence of such parameters cannot be determined using steady-state tests. In the present work, a recently developed methodology is employed, which has been applied in the past to simple transient handling studies. Here, the approach is applied to more demanding situations and the effects of tyre lags and suspension damping are directly related to the under-, over, or neutral-steer character of the vehicle under test. To distinguish the effect of tyre force lags, tyre non-linearities and combined tyre-vehicle non-linearities, an increasingly complex approach is adopted, which involves the implementation of a linear bicycle-model, a nonlinear bicycle-model and a 10-DOF non-linear vehicle model. In all cases tyre force lags are simulated using the relaxation length concept. The 10-DOF vehicle model is validated against experimental measurements and forms the basis for fully non-linear studies. It is shown that even inherently under-steering vehicles may initially over-steer as a result of the delayed response of tyres. Finally, it is demonstrated that the proposed approach captures the effect of suspension damping and some problems are discussed regarding its application.

Identification of Tire Transient Parameters from Vehicle Onboard Sensors Data

“…A model capable of faithfully reproduce the axle characteristics at varying the steering frequency will also coincide with the real on all the other transfer functions, because all the single track model dynamics is obtained from axle characteristics and some further macro-parameters assigned in this work: vehicle mass, rotational inertia, wheelbase, center of gravity longitudinal position and steering ratio [15]. The gain values of C a1 s ð Þ and C a2 s ð Þ are determined by the known parameters: tire cornering stiffness, while the delay values are determined by relaxation length, that is depending from the unknown parameters: the tire carcass lateral stiffnesses C Fy1 and C Fy2 , as shown in (1).…”

“…Correctly simulating the behavior of the vehicle is now becoming fundamental for manufacturers in its prototyping phase, when, even in the early stages of design, there is the need to correctly predict and reproduce all aspects of vehicle motion, including the driver's feedback, which is heavily affected by delays between inputs and the system dynamics [1].…”

A new efficient free-rolling tyre-testing procedure for the parameterisation of vehicle dynamics tyre models

“…Of these, the modelling of the pneumatic tyre to support the simulations of vehicle dynamics studies into the ride and the handling 1, 2 remains one of the most challenging and is the subject of advanced and specialist research. Studies for example into areas such as braking 3 or anti-lock braking systems 4 require an understanding of the longitudinal force on the tyre as it varies with the slip ratio while, for vehicle-handling studies, estimation of the cornering stiffness of the tyres 5 and the relaxation length 6 is also important.…”

“…Of these, the modelling of the pneumatic tyre to support the simulation of vehicle dynamics studies into ride and handling [1, 2] remains one of the most challenging and is the subject of advanced and specialist research. Studies for example into areas such as braking [3] or anti-lock braking systems [4] will require an understanding of the longitudinal force in the tyre as it varies with slip ratio while for vehicle handling studies estimating tyre cornering stiffness [5] and relaxation length [6] are also important.The appropriate method of modelling a tyre depends on the intended application and can range from large physical models using a finite element approach to represent the tyre structure and materials, to empirical models that represent the forces and moments measured in the tyre contact patch using a tyre test rig. The finite element approach requires detailed and confidential information regarding the tyres material properties and construction; it is therefore best used internally by tyre manufacturers or for specialist research applications [7,8].…”