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Technical Paper

Kinematic Discrepancy Minimization for AWD Terrain Vehicle Dynamics Control

Stability of motion, turnability, mobility and fuel consumption of all-wheel drive terrain vehicles strongly depends on engine power distribution among the front and rear driving axles and then between the left and right wheels of each axle. This paper considers kinematic discrepancy, which characterizes the difference of the theoretical velocities of the front and rear wheels, as the main factor that influences power distribution among the driving axles/wheels of vehicles with positively locked front and rear axles. The paper presents a new algorithm which enables minimization of the kinematic discrepancy factor for the improvement of AWD terrain vehicle dynamics while keeping up with minimal power losses for tire slip. Three control modes associated with gear ratio control of the front and rear driving axles are derived to provide the required change in kinematic discrepancy. Computer simulation results are presented for different scenarios of terrain and road conditions.
Journal Article

Advancement of Vehicle Dynamics Control with Monitoring the Tire Rolling Environment

One of the most important challenges for electronic stability control (ESC) systems is the identification and monitoring of tire rolling environment, especially actual tire-road friction parameters. The presented research considers an advanced variant of the ESC system deducing the mentioned factors based on intelligent methods as fuzzy sets. The paper includes: Overview of key issues in prototyping the algorithms of Electronic Stability Control. Case study for vehicle model. Procedures for monitoring of tire rolling environment: theoretical backgrounds, computing methods, fuzzy input and output variables, fuzzy inference systems, interface with ESC algorithm. Case study for ESC control algorithm. Examples of simulation using Hardware-in-the-Loop procedures. The proposed approach can be widely used for the next-generation of ESC devices having the close integration with Intelligent Transport Systems.
Technical Paper

Comparison of Different Methods for the Determination of the Friction Temperature of Disc Brakes

In the paper the dynamometer investigations on evaluating of friction temperature in disc brakes have been described. The goal of these investigations was to compare different methods (thermocouples, pyrometers and thermoscanner) regarding to their accuracy and suitability for specified test procedures. The problems of the evaluation and the changing of the disc surface emissivity and a way of its correction have also been discussed. Furthermore the possibilities of non-contact measuring methods for the evaluation of non-homogeneous temperature distribution over the disc surface under various braking conditions have been shown.
Technical Paper

Combined Testing Technique: Development of Friction Brake System for Electric Vehicle

The presented research discusses the experimental procedure developed for testing of friction brake systems installed on the modern electric vehicles. Approach of combined experimental technique utilizing hardware-in-the-loop platform and brake dynamometer is introduced. As the case study, an influence of brake lining coefficient of friction fluctuations on the anti-lock brake system (ABS) performance is investigated. The ABS algorithm is represented by the direct slip control aimed to the precise tracking of reference slip ratio by means of electric and friction brake system. Vehicle prototype is represented by RWD electric vehicle with in-wheel motors. Results, representing the investigated phenomenon, are derived using the developed combined test bench. The achieved results give a basis for further extension of standard brake testing procedures.
Technical Paper

Mojacar Brake Wear and NVH: Dyno Simulation Concept

Efficient development and testing of brake systems requires further substitution of expensive and time consuming vehicle testing by appropriate dynamometer testing. Some of the current simulation methods do not reflect the needs of engineering and the progress made in the development of test equipment. The lack of suitable procedures may cause unexpected delays in the realization of projects. Road load simulations for lifetime prediction on brake dynamometers have a long history, however never got a real break-through in Europe - possibly because the prediction quality and efficiency did not satisfy. This paper concentrates first on the analysis of the vehicle data recorded in Mojacar (Spain) which is a sign-off test for wear and noise for brands of Ford Motor Company for European market. Specific attention is given to different types of driving resistances and road profiles and to consideration of different methods for numerical description and comparison of road load data.
Technical Paper

Comparison Between Different Investigation Methods of Quasi-Static and Dynamic Brake Pad Behaviour

The paper offers an investigation of whether the knowledge of the laws materials will follow and of the parameters for the materials can be obtained from integral testing, i.e. the testing of complete brake pads. Dynamic tests were designed for the purpose, with attention to both the axial and the radial / tangential directions of stress as mechanical properties of brake pads. The tests were run and evaluated on brake pads with a variety of patterns and constructions. The term used throughout this paper to describe these features is the matrix. It was shown that brake pads clearly demonstrate visco-elastic behaviour which is most definitely non-linear, and whose characteristic values for stiffness, damping and internal friction will alter in ratio to the load.
Technical Paper

Investigation of Brake Control Using Test Rig-in-the-Loop Technique

Research and development tools for investigations of various facets of braking processes cover three major groups of devices: Dynamometer test rigs: assessment of performance, durability, life cycle and others; Tribometer test rigs: definition of parameters of friction and wear; Hardware-in-the-loop: estimation of functional properties of controlled braking. A combination of the listed devices allows to research complex phenomena related to braking systems. The presented work discusses a novel approach of test rig fusion, namely the combination of a brake dynamometer and hardware in the loop test rig. First investigations have been done during the operation of the anti-lock braking system (ABS) system to demonstrate the functionality of the approach.
Journal Article

Influence of the Tire Inflation Pressure Variation on Braking Efficiency and Driving Comfort of Full Electric Vehicle with Continuous Anti-Lock Braking System

The presented study demonstrates results of experimental investigations of the anti-lock braking system (ABS) performance under variation of tire inflation pressure. This research is motivated by the fact that the changes in tire inflation pressure during the vehicle operation can distinctly affect peak value of friction coefficient, stiffness and other tire characteristics, which are influencing on the ABS performance. In particular, alteration of tire parameters can cause distortion of the ABS functions resulting in increase of the braking distance. The study is based on experimental tests performed for continuous ABS control algorithm, which was implemented to the full electric vehicle with four individual on-board electric motors. All straight-line braking tests are performed on the low-friction surface where wheels are more tended to lock.
Journal Article

Estimation of Brake Friction Coefficient for Blending Function of Base Braking Control

The brake architecture of hybrid and full electric vehicle includes the distinctive function of brake blending. Known approaches draw upon the maximum energy recuperation strategy and neglect the operation mode of friction brakes. Within this framework, an efficient control of the blending functions is demanded to compensate external disturbances induced by unpredictable variations of the pad disc friction coefficient. In addition, the control demand distribution between the conventional frictional brake system and the electric motors can incur failures that compromise the frictional braking performance and safety. However, deviation of friction coefficient value given in controller from actual one can induce undesirable deterioration of brake control functions.