Milan Kostelac

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.

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.

Modeling of electromagnetic circuit of a magnetorheological fluid clutch

The steady-state and transient accuracy of magnetorheological fluid (MRF) clutch torque control is affected by the magnetic hysteresis and eddy current lag. The paper presents a nonlinear analytical model of the MRF clutch electromagnetic circuit dynamics. The model includes two state variables describing the combined solenoid and eddy current dynamics, and the dynamics induced by the magnetic hysteresis effect. The overall nonlinear model is experimentally validated under the clutch current-control conditions. It is demonstrated that the use of second state variable for magnetic hysteresis significantly improves the modeling accuracy when compared to the more traditional first-order linear model.

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.

Tyre friction behaviour under abrupt wheel torque transients on slippery road surfaces: experimental analysis and modelling

The paper shows that, during abrupt wheel torque transients for ice surface and low vehicle speeds, the tyre can develop significantly larger longitudinal force than the peak value of the tyre static curve. This so-called dynamic tyre friction potential (DTFP) effect has many influencing factors such as the rate of change of the wheel torque, the vehicle speed, and the tyre dwell time. The paper presents a detailed analysis of the DTFP behaviour based on the experimental data collected by using an in-wheel motor-based tyre test vehicle. The analysis results and an insight into the brush structure of a tyre model lead to the hypothesis that the different influencing factors may be predominantly explained by the bristle dwell time (BDT) effect. Following this hypothesis, the LuGre model of the tyre friction dynamics is extended with a physical BDT sub-model. The experimental validation results show that the proposed model can accurately capture the low-speed tyre–ice friction behaviour during abrupt wheel torque transients.

Mathematical identification of influential parameters on the elastic buckling of variable geometry plate

The problem of elastic stability of plates with square, rectangular, and circular holes as well as slotted holes was discussed. The existence of the hole reduces the deformation energy of the plate and it affects the redistribution of stress flow in comparison to a uniform plate which causes a change of the external operation of compressive forces. The distribution of compressive force is defined as the approximate model of plane state of stress. The significant parameters of elastic stability compared to the uniform plate, including the dominant role of the shape, size, and orientation of the hole were identified. Comparative analysis of the shape of the hole was carried out on the data from the literature, which are based on different approaches and methods. Qualitative and quantitative accordance of the results has been found out and it verifies exposed methodology as applicable in the study of the phenomenon of elastic stability. Sensitivity factor is defined that is proportional to the reciprocal value of the buckling coefficient and it is a measure of sensitivity of plate to the existence of the hole. Mechanism of loss of stability is interpreted through the absorption of the external operation, induced by the shape of the hole.

Design of Normal Force Control System for a Pin-on-Disk Tribometer including Active and Passive Suppression of Vertical Vibrations

This paper presents the design of a computer-controlled pin-on-disk tribometer for friction characterization of various friction sliding pairs. The tribometer setup comprises two high-bandwidth servomotors for the control of the rotating disk and the normal load-related spindle drive, as well as a high-precision tri-axial piezoelectric force sensor for normal and tangential forces measurement. Since the spindle drive system is characterized by notable compliance effects, the normal force cascade control system is designed with the aim of vertical vibrations active damping. In order to compensate for the unevenness of the rotating disk surface and associated high-level perturbations in the specimen normal force, the normal force control system is extended with a feedforward compensator of the disk unevenness disturbance, and a dedicated leaf spring suspension system is designed. The effectiveness of the proposed system of vertical vibrations damping is verified experimentally.

Modeling Elastic Stability of a Pressed Box Girder Flange

The paper examines the elastic stability of pressed sheet metal flange of a box girder. Mathematical interpretation of elastic stability is performed on the model plate with two freely supported and two elastically restrained edges subjected to combined loads. The research is based on the energy analysis approach, using the principle of minimum deformation energy and the method of cross-sectional girder element decomposition. The plate elastic stability mechanism is investigated in an interactive environment that simulates local loads and compressive longitudinal forces produced by global stress. The significant geometric parameters, as well as support and load conditions affecting the loss of stability, are identified. The research results can be applied as a constraint on the local flange stability in the optimization of box girders.

Golden ratio (sectiona aurea) in markovian ants AI hybrid

The exponential pheromone signal of the AI hybrid of Markovian Ant Queuing System - MAQS, is divided into the spatial and deposit pheromone fractions which have the identical values. A new hybrid is formed. The convolution of two new exponential signals has the Erlang distribution. Introducing the interstate in the process of markovization the Erlang Queuing Ant System - EQAS, is solved. Comparison of the average distance between artificial ants in MAQS and EAQS gave particular numerical specificity. The average distances are in ? equilibrium. Constant ? is a famous constant of the Golden ratio.

Normal force control for a pin-on-disk tribometer including active or passive suppression of vertical vibrations

This paper presents the design of a computer-controlled pin-on-disk tribometer for friction characterization of various sliding pairs. The pin-on-disk setup comprises two high-bandwidth servomotors for the control of the rotating disk and the normal load-related spindle drive, as well as a high-precision tri-axial piezoelectric force sensor for normal and tangential forces measurement. Since the spindle drive system is characterized by notable compliance effects, the normal force cascade control system is designed with the aim of vertical vibrations active damping. In order to account for notable unevenness of the rotating disk surface and related high-level perturbations in the specimen normal force, the normal force control system is extended with a feedforward compensator of the disk unevenness disturbance, and, in particular, a dedicated leaf spring suspension system is designed. The effectiveness of the proposed system of vertical vibrations damping is verified experimentally.