Modeliranje i regulacija elemenata pogona vozila s izraženim učincima trenja

Ivanović, Vladimir (2010) Modeliranje i regulacija elemenata pogona vozila s izraženim učincima trenja. = Modeling and Control of Vehicle Powertrain Components with Emphasized Friction Effects. Doctoral thesis , Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, UNSPECIFIED. Mentor: Deur, Joško.

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Abstract (Croatian)

kvalitete regulacije dvaju karakterističnih elemenata pogona vozila s izraženim učincima trenja: autoguma na ledenoj podlozi i uljna lamelna spojka aktivnog diferencijala s elektromehaničkim aktuatorskim sustavom. Dinamika autogume razmatra se s ciljem utvrđivanja fizikalne podloge za uočeni učinak povećanja potencijala trenja u uvjetima nagle promjene pogonskog momenta (dinamički potencijal trenja) i istraživanja mogućnosti primjene navedenog učinka u svrhu poboljšanja sustava regulacije vuče vozila. Uljna lamelna spojka aktivnog diferencijala razmatra se s ciljem stjecanja uvida u dinamičko ponašanje cjelokupnog sustava, objašnjenja fizikalne podloge učinka sporog odziva momenta spojke pri malim relativnim brzinama i istraživanja naprednijeg koncepta upravljanja momentom spojke. Metodologija i rezultati prikazani u ovom istraživanju primjenjivi su na druge elemente vozila poput suhih spojki, kočnica, sustava skretanja, kotača pružnih vozila, te općenito na razne mehatroničke sustave. Dinamički potencijal trenja autogume detaljno se analizira temeljem eksperimentalnih rezultata dobivenih korištenjem eksperimentalnog električnog vozila na skliskim podlogama. Pokazuje se kako je utjecaj raznih radnih parametara, poput vremena porasta primijenjenog momenta i brzine vozila zapravo posljedica karakteristične rotacijske kinematike gume i utjecaja vremena kontakta elemenata nagazne površine gume (tzv. vlakana) i podloge na potencijal trenja. Temeljem ovog saznanja, LuGre vlaknasti model trenja gume proširen je prostorno raspodijeljenim fizikalnim modelom vremena mirovanja vlakana i eksperimentalno određenom ovisnosnošću potencijala trenja i vremena mirovanja vlakna. Rezultati eksperimentalne provjere pokazuju kako razvijeni model točno opisuje dinamiku trenja gume u širokom opsegu radnih uvjeta. Konačno, predlaže se i eksperimentalno provjerava koncept regulacije vuče koji koristi dinamički potencijal trenja za svladavanje sila otpora vožnje na uzbrdici prekrivenoj ledom, koje su veće od statičkog potencijala trenja gume. U drugom dijelu rada, postavlja se višefizikalni model spojke koji uključuje dinamiku aktuatora (razvijanje normalne sile spojke), dinamiku razvijanja momenta spojke, toplinsku dinamiku i višefunkcionalnu karakteristiku trenja. Analiziraju se razni načini modeliranja elemenata s trenjem i predlažu pragmatična pojednostavljenja modela s ciljem povećanja računalne učinkovitosti. Parametri modela određuju se eksperimentalnim putem primjenom razvijenih postava. Rezultati eksperimentalne provjere modela ukazuju na visok stupanj točnosti modela. Analiza rezultata pokazuje kako učinci trenja aktuatorskog mehanizma i trenja spojke imaju značajan utjecaj na dinamiku sustava i kako uobičajeni koncept upravljanja momentom spojke putem regulacije struje aktuatora ima značajne nedostatke. Temeljem eksperimentalno utvrđene jednoznačne eksperimentalne ovisnosti normalne sile spojke i pozicije motora aktuatora predložen je i eksperimentalno provjeren koncept upravljanja momentom spojke u krugu regulacije pozicije aktuatora, koji pokazuje visoku statičku i dinamičku točnost upravljanja.

Abstract

The thesis deals with modeling, experimental identification, and control system improvement of two characteristic vehicle powertrain components with emphasized friction effects: the tire on ice surface and the active differential wet clutch with electromechanical actuation system. The tire dynamics are considered in order to provide a physical explanation of observed effect of tire friction potential increase during an abrupt change of driving motor torque (dynamic tire friction potential, DTFP) and to investigate a possibility of the DTFP exploitation for the purpose of traction control system improvement. The active differential wet clutch research is aimed to gain insights into dynamic behavior of the overall clutch system, provide physical explanation of slow clutch torque response at low clutch relative speeds, and provide a basis for investigation of an advanced clutch control system. The presented methodology and results can also be applied to other vehicle elements such as brake or steering systems, dry clutches, railway vehicle wheels, and generally various mechatronic systems. A detailed analysis of the DTFP effect is given based on a comprehensive set of experimental results recorded by using an experimental electrical vehicle on slippery roads. It is shown that the influence of various operating parameters, such as the applied torque rise time or the vehicle speed, are actually a consequence of the characteristic tire rotation kinematics and the tire friction potential dependence on the dwell time of tire tread elements (so-called bristles). Based on these findings, the dynamic brush-type LuGre tire friction model has been extended with a distributed-parameter dynamic bristle dwell time model and an experimentally obtained dependence between the static friction potential and the bristle dwell time. The experimental validation results point out that the proposed model accurately describes the tire friction dynamics for a wide range of operating parameters. Finally, a concept of the traction control system is proposed and experimentally verified, which exploits the DTFP effect for the purpose of providing vehicle driving on an icy hill in the case when the static tire friction potential is lower than the up-hill driving resistive force. In the second part of the thesis, a multi-physical mathematical model of the active differential wet clutch is developed, which includes actuator dynamics (clutch normal force development dynamics), clutch torque development dynamics, thermal dynamics, and a multi-functional clutch friction coefficient model. Various approaches of friction elements modeling are analyzed and pragmatic model simplifications are proposed in order to increase the computational efficiency. The model parameters are obtained experimentally by using developed experimental setups. The model validation results point to a high level of modeling accuracy. The analysis of system responses shows that the actuator and the clutch friction effects have significant influence on the overall system dynamic response and that the traditional concept of clutch torque control based on actuator current control can be characterized by significant disadvantages. Using an experimentally obtained hysteresis-free dependence between the clutch normal force and the actuator motor position, a concept of clutch torque control based on actuator motor position closed-loop control is proposed, which shows a high static and dynamic control accuracy.

Item Type: Thesis (Doctoral thesis)
Uncontrolled Keywords: trenje; autoguma na ledenoj podlozi; električno vozilo; uljna spojka; elektromehanički aktuator; matematičko modeliranje; eksperimentalna identifikacija; regulacija
Keywords (Croatian): friction; tire on ice surface; electrical vehicle; wet clutch; electromechanical actuator; mathematical modeling; experimental identification; control
Divisions: 900 Department of Robotics and Production System Automation > 910 Chair of Engineering Automation
Date Deposited: 22 Sep 2014 18:00
Last Modified: 16 Oct 2015 13:08
URI: http://repozitorij.fsb.hr/id/eprint/1083

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