Vladimir Ivanović

Modeling and Analysis of Active Differential Dynamics

Active differentials are used to improve the overall performance of traction control and vehicle dynamics control systems. This paper presents the development of a unified mathematical model of active differential dynamics using the bond graph modeling technique. The study includes active limited slip differential and various common types of torque vectoring differentials. Different levels of model complexity are considered, starting from, a second-order model with lumped input and output inertia toward higher-order models including the gear inertia and half-shaft compliance. The model is used for a theoretical analysis of drivability and time response characteristics of the active differential dynamics. The analysts is illustrated by simulation results.

Dry clutch control based on electromechanical actuator position feedback loop

The paper presents identification and control of an experimental dry clutch actuated by a geared dc motor and ball-ramp mechanism. The identification results are used to describe the multi-dimensional clutch friction coefficient characteristic. The proposed clutch torque control system is based on closed-loop actuator position control and the identified friction coefficient curves. In order to compensate for a clutch pack thermal expansion effect, which affects the torque control accuracy, the control strategy is extended with feedforward or feedback path that outputs a position reference additive signal. The torque control strategy is verified experimentally within a clutch slip speed control system.

Extensions of the LuGre tyre friction model related to variable slip speed along the contact patch length

The recently developed LuGre model describes the three-dimensional tyre friction dynamics given in the brush representation. The model has a three-state lumped-parameter form and an analytical solution for tyre static curves. It is simplified using the assumption of a constant slip speed along the contact patch length. This assumption is abandoned in this paper in order to extend the model with several secondary but potentially important effects such as camber, carcass compliance, conicity, ply steer and rolling resistance. Two approaches to the introduction of a variable-slip-speed effect are considered. The first is based on stepwise approximation of the slip speed along the contact patch length, and the second includes a specific, spatially distributed additive deflection term. Both approaches preserve the three-state lumped-parameter model form and an analytical steady-state solution. Qualitative and quantitative validation results point to consistency and benefits of the proposed model extensions.

Experimental identification of dynamic tire friction potential on ice surfaces

Recently, it has been shown that the tire–ice friction is characterized by a significant dynamic potential for abrupt increases of wheel torque. With the aim to gain insight into the dynamic tire friction potential features and to provide a comprehensive set of experimental data for model validation, a detailed experimental investigation of the dynamic potential has been presented in this article. The experimental data have been collected by using an experimental electrical vehicle with an in-wheel motor. Influence of the following operating parameters has been analyzed: rate of change of applied wheel torque, time for which the tire stands still on ice before applying the abrupt transient, initial vehicle speed, and initial tire force. In order to check a possible correlation between the dynamic potential and the rubber–ice friction dynamics, an experimental analysis based on a pin-on-disc tribometer has also been presented.

Experimental analysis and modelling of longitudinal tyre friction dynamics for abrupt transients

A test vehicle has been used to collect experimental data related to abrupt engine throttle tip-in transients. The data point to a significant dynamic potential of the longitudinal tyre frictional force on an ice surface. Such a behaviour cannot be predicted by using the available brush-type dynamic tyre friction models. Based on the results of experimental and simulation analyses, the LuGre tyre friction model is extended to predict the dynamic friction potential. The extended model is validated against the experimental data.

Vehicle Sideslip Angle EKF Estimator based on Nonlinear Vehicle Dynamics Model and Stochastic Tire Forces Modeling

This paper presents the extended Kalman filter-based sideslip angle estimator design using nonlinear 5DoF single-track vehicle dynamics model with stochastic modeling of tire forces. Lumped front and rear tire forces have been modeled as first order random walk state variables. The proposed estimator is primarily designed for vehicle sideslip angle estimation ; however it can also be used for estimation of tire forces and cornering stiffness. This estimator design does not rely on linearization of the tire force characteristics and it is robust against the variations of tire parameters and does not require the information on coefficient of friction. The estimator performance has been first analyzed by means of computer simulations using the 10DOF two-track vehicle dynamics model and underlying magic formula tire model, and then validated by running the estimator algorithm off-line on the experimental data sets recorded on the test vehicle.

Bond Graph Modeling of Automotive Transmissions and Drivelines

Abstract The paper presents an overview of the bond graph models of advanced automotive transmission and driveline systems. This includes one-mode and two-mode series-parallel hybrid electric vehicle transmissions, a continuous variable transmission, active-limited slip and torque vectoring differentials in 2WD and 4WD configurations, and electromechanical actuator-based wet and dry clutch actuation systems. It is illustrated that the bond graph method can be effectively used to gain valuable insights about the system dynamics structure and behavior.

An in-wheel motor-based tyre test vehicle

An experimental three-wheel electrical vehicle has been developed in order to provide a platform for experimental verifications of advanced tyre friction models, estimators and controllers. The vehicle comprises a high-torque permanent-magnet synchronous motor built in the front wheel and precise incremental encoders for the front- and rear-wheel speed measurements. The paper presents a description of the vehicle and gives characteristic experimental procedures and results related to motor static and dynamic behaviour. Experimental results on tyre friction identification are also presented.

SI Engine Load Torque Estimator Based on Adaptive Kalman Filter and Its Application to Idle Speed Control

The paper presents a detailed design procedure of an Sl engine load torque estimator based on an adaptive Kalman filter. The adaptation mechanism is based on a simple and robust load torque change detection algorithm. The presented simulation and experimental results point out that the estimator is characterized by a fast response and good noise suppression. The proposed estimator is used to establish a fast load torque compensation path in an idle speed control system. The presented simulation and experimental results show that this yields a significant improvement of idle speed control performance.

Modelling of electromechanically actuated active differential wet-clutch dynamics

The paper presents a lumped-parameter dynamic model of an electromechanically actuated wet clutch found in an active limited slip differential. The bond graph modelling technique is used to describe the multi-physical clutch system including the clutch actuator dynamics, the axial dynamics with the fluid film squeeze effect, the thermal dynamics, and the torque development dynamics with a multi-functional clutch friction coefficient static characteristic. Different variants of the individual subsystem models are considered, ranging from first-principle models to simplified and numerically more efficient models. The proposed models are parameterized and thoroughly validated on the basis of the experimental data collected by using an active differential and clutch test rig. The modelling results are used for the purpose of analysis of the clutch steady state and transient behaviour under various operating modes.