Abstract: This paper studies hysteresis of vehicle brakes and its influence on the vehicle dynamics. The experimental investigation clearly shows the non-linear and asymmetric characteristics of hysteresis of the disk brakes in passenger cars. A computational model of the brake mechanism with hysteretic elements, based on the BoucâWen method, is developed and verified with experimental data. Using the developed model, the influence of hysteresis on the vehicle dynamics during straight-line braking with an anti-lock braking system is analysed. It is also observed that the variations in the hysteresis parameters have important influences on the main vehicle brake characteristics such as the stopping (brake) distance, the time of braking and the average deceleration. A comparative analysis of the simulation results is also given for braking with zero hysteresis or with hysteresis represented as a signal delay and linear function.
Abstract: This work proposes an optimal control allocation method for the brake system and the wheel motors of an electric vehicle. The realization of the method is proposed for vehicle dynamics control and energy recuperation. The control allocation takes into account temperature of electric motors, SOC and voltage of battery, vehicle velocity, fault situations, wheel slip, and vehicle subsystem prioritization depending on parameters of vehicle dynamics. To illustrate the functional properties of the control allocation method, the corresponding simulation study is performed for the straight-line braking and âsine with dwellâ cornering. The simulations use a number of mathematical models including the 14 DoF model of vehicle motion and the models of electric vehicle systems. The simulation results confirmed effectiveness of the proposed approach both for regenerative braking and vehicle stability.
Abstract: During vehicle operation, the control objectives of stability, handling, energy consumption and comfort have different priorities, which are determined by road conditions and driver behavior. To achieve better operation characteristics of vehicle, coordinated control of vehicle subsystems is actively used. The fact of more active vehicle subsystems in a modern passenger car provides more flexibility for vehicle control and control algorithm development. Since the modern vehicle can be considered as over-actuated system, control allocation is an effective control technique to solve such kind of problem.
This paper describes coordination of frictional brake system, individual-wheel drive electric motors, active front and rear steering, active camber mechanisms and tyre pressure control system. To coordinate vehicle subsystems, optimization-based control allocation with dynamic weights is applied. The influence of different weights (subsystem restriction) on criteria of vehicle dynamics (RMSE of yaw rate, sideslip angle, dynamic tyre load factor) and energy consumption and losses (consumed/recuperated energy during maneuver, longitudinal velocity decline, tyre energy dissipation) were analyzed. Based on this analysis, the optimal solution was selected. The proposed control strategy is based on the switching between optimal criteria related to vehicle safety and energy efficiency during vehicle motion. Dynamic weights were utilized to achieve this switching.
The simulation-based analysis and evaluation of both variants was carried out using a nonlinear vehicle model with detailed models of actuators. The test maneuver is âSine with Dwellâ. Both variants of control allocation guarantees vehicle stability of motion and good handling. Meanwhile, proposed variant demonstrates slightly higher longitudinal velocity at the end of maneuver and higher amount of recuperated energy up to 15%; however, tyre dissipation energy increased to 5% compared to optimal solution from simulation-based analysis.
Abstract: Coordination between friction brake system, individual-wheel drive electric motors and tire inflation pressure system is considered. To coordinate vehicle subsystems, optimization-based control allocation is used. The influence of subsystem coordination on criteria of vehicle dynamics (braking distance, RMSE of longitudinal acceleration, RMSE of yaw rate, sideslip angle) and energy consumption and losses (recuperated energy during maneuver and tire energy dissipation) were analyzed for straight-line braking and brake-in-turn maneuvers by simulation investigation. The proposed control system was investigated using HIL test rig with hardware components of friction brake system and tire inflation pressure system.
Abstract: The paper introduces the architecture and technical realization of the hardware-in-the-loop (HIL) platform designed specifically for development and testing of integrated vehicle control systems. Starting with the formulation of functional and configuration requirements, the work explains a concept of new HIL test rig and describes its main components. The proposed HIL platform allows integrated testing of different configurations of brake systems, steering, and dynamic tyre pressure control. The case study illustrates operation of the test rig.
Abstract: There are various strategies of control demand distribution between frictional brake system and electric motors of an electric vehicle. However, influence of subsystem coordination on electric vehicle (EV) characteristics, such as stability of motion, braking performance, energy recuperation and energy losses, is still weak-investigated. Moreover, subsystem coordination depends strongly on dynamic performance of actuators and on the vehicle manoeuvre. The main research objective of the presented study is a simulation-based analysis of EV subsystem coordination under various driving manoeuvres. The engineering objective is a development and testing of the blending control strategy providing optimal EV characteristics.
The work introduces the control system, which provides the coordination between a friction brake system and electric motors, and includes three levels: PI controller of vehicle dynamics control and demand correction, optimization-based control allocation with actuator and tyre friction constraints, low-level PI/PID actuator control. The simulation analysis of the proposed control system has been carried out using the full vehicle simulator in IPG/Carmaker. Based on simulation analysis, the coordination weights for the control allocation were defined to reach optimal characteristics of vehicle motion and energy consumption / losses. The experimental investigation of proposed control system has been performed on the hardware-in-the-loop (HIL) test rig with the real friction brake system, emulators of electric motors and IPG/Carmaker vehicle simulator.
The modelling covers three typical types of vehicle motion: straight-line braking, braking-in-turn and lateral motion based on âSine with Dwellâ test. Evaluation criteria for vehicle dynamics and stability of motion are (i) the braking distance, (ii) the root mean square error (RMSE) of yaw rate and (iii) the RMSE of sideslip angle. The measures for energy consumption and power losses are (i) the total amount of recuperated energy and (ii) the tyre energy dissipation. These criteria are investigated in respect to the blended operation of the friction brake system and electric motors. Thereby, obtained results demonstrate an influence of each subsystem on stability of motion, braking performance, energy recuperation and energy losses. Two variants of subsystem coordination are investigated using HIL test rig and compared.
The first part of the article, having more theoretical significance, relates to coordination analysis and has been investigated by computational simulation. The second part of the paper covers the emulation of electric motors and vehicle dynamics and refers to an application of online optimization-based control allocation, which requires heavier computation time as compared with other techniques.
The results proposed in this study leads to a novel EV brake blending strategy based on optimal control allocation with different subsystem coordination.
Abstract: Integrated vehicle dynamics control with the coordination of several vehicle subsystems is considered. The proposed algorithms of subsystem coordination based on restriction weights into the optimal control allocation allow to achieve lower energy consumption without significant impairment of stability of motion and vehicle handling compared with standard control allocation. The proposed control system was investigated using HIL test rig with hardware components of friction brake system and dynamic tire pressure system.
Abstract: The hysteresis in mechanical subsystems is a well-known effect. It causes a delay of system reaction and reduces the control accuracy. For brake system, the static hysteresis is usually considered in loading-unloading cycle. Usually for simulation studies, hysteresis is expressed as a time delay or as linear functions. The paper introduces investigations of hysteresis-characterized processes in the brake system and relevant dynamic model of this effect for further application to ABS and ESC control algorithms. The paper is organized as follows: the first part analyzes the literature sources and previous research works on the experimental data of hysteresis-characterized processes under different operational conditions. The hysteresis process is analyzed for the cases: (i) "input pressure vs. brake piston displacement", and (ii) "input pressure vs. realized brake moment in the friction pair". The experimental results demonstrated that the hysteresis taking place in the brake mechanism has a nonlinear asymmetric form. The second part of the article introduces a mathematical model based on the Bouc-Wen method and its computer realization in Matlab to describe an asymmetrical hysteresis. The method is verified through the experimental results. The analysis of hysteresis influence on vehicle dynamics has been provided for the case of the ABS straight-line braking by considering two variants of the ABS controller: PID control and sliding mode control. The nonlinear behaviour of hysteresis requires a more complex control law to achieve precise tracking of reference signals. This issue is marked out as future work.
Abstract: This paper describes a multi-layer structure based on control allocation with dynamic weight scheduling. The computational investigation of the proposed control structure is carried out using 14 DoF vehicle model in the wide range of vehicle curvilinear motion for âSine with Dwellâ test. The proposed control allocation with dynamic weight scheduling demonstrates lower energy loss without significant impairment of stability of motion and vehicle handling compared to control allocation with fixed weight distribution.
