VIRTUAL PROTOTYPING OF AN ARTICULATED DUMP TRUCK In fulfillment of the degree MScEng (MECH) Date ofsubmission : 01 st September 2003 Candidate : Mr. Deena Govender Supervisor : Dr. S. Kaczmarczyk 11 DECLARATION I state unequivocally that the work presented herein is my own unaided effort and that all external sources have been explicitly stated and referenced. This work has not been submitted in whole or part, for any degree to any institution previously. I hereby submit this dissertation in whole fulfilment ofthe requirements for the degree ofMSc Eng (MECH) to the University of Natal, Durban on this the 1st Day ofSeptember 2003. Mr. Deena Govender TIDNo.7612275054083 111 ACKNOWLEDGEMENTS The author would like to place on record his thanks to the following individuals and organisations:- Dr. S. Kaczmarczyk for his sincere support and understanding throughout this project. BELL Equipment (pTY) Ltd. for their financial support and providing the impetus for this research effort. Danie du Plessis and Rick Chianese (BELL Equipment) for being the link to the BELL ADT and for their time and advice. Shaun Savy and Desmond Rooplal (School of Mechanical Engineering, UND) for their assistance with computing matters at odd hours and without whom this project would have been immeasurably more difficult. Clinton Stone (MSC Africa) for assisting with ADAMS and for always being a valuable source ofadvice. The various members ofthe ADAMS ASK online mailing list for their often eleventh-hour advice. The students ofthe undergraduate teams who assisted with this project in 2000 and 2001. BMW S.A. for allowing me time offwork to complete important stages ofthe project. Mr. Ewald Fischer and Arne Margold (EF-31, BMW AG) for their assistance with the use ofADAMS during October to December 2002. Mr. Hans Heltmann (EG-32, BMW AG) for his advice on analysing test data from automotive compliant suspension components. My parents and family for their encouragement throughout. My friends who provided me with support in times of need and for being prepared to discuss the merits ofthis work with me. Dinesh BaUiah who was my pillar of strength through times when the task ahead of me seemed insurmountable and who always believed I could complete this work. IV ABSTRACT In the modem automotive industry product times to market are being increasingly compressed. In the earthmoving and construction machine industry this is also true with the manufacturer having to respond to new customer requirements quickly and decisively. Virtual prototyping is a vital tool in the vehicle engineer's armoury, allowing a large portion of developmental investigation to be done on the virtual model with the attendant savings in time and cost and allowing often dangerous manoeuvres to be predicted and investigated prior to actual physical prototype testing. The University of NatallBELL Equipment collaborative effort involves the vehicle dynamics modelling and model validation of a BELL Equipment manufactured B40C Articulated Dump Truck (ADT). The modelling was completed using the multibody system (MBS) simulation software package, ADAMS. Initial modelling and simulation results are presented with specific attention paid to the introduction ofvalid data for compliant joints in the MBS as well as modelling ofthe tire. The physical testing ofthe ADT is also presented as well as a discussion ofthe data acquisition system. Key results from the physical testing ofthe ADT are also presented and discussed. KEYWORDS: Vehicle dynamics, Virtual Prototyping, Articulated Dump Trucks, Vehicle testing, Multibody Systems Simulation v CONTENTS Declaration ii Acknowledgements iii Abstract iv Contents v 1. Introduction 1 2. Fundamentals of Vehicle Dynamics 7 2.1. The Pneumatic Tire 7 2.1.1. Tire Fundamentals and Construction 8 2.1.2. Axes, Notation and Principle Forces and Moments 10 2.1.3. Mechanics ofForce Generation at the Contact patch 12 2.1.4. Rolling Resistance 15 2.1.5. The Generation ofPrinciple Forces and Moments 21 2.1.5.1. Stationary In-Plane Dynamics 21 2.1.5.2. Stationary Out-of-P1ane Dynamics 25 2.1.5.3. Combined Slip and Non-stationary Behaviour 34 2.1.6. Tire Modelling for Vehicle Dynamics Simulation 40 2.2. Approaches to Modelling ofCompliant suspension components in MBS codes 46 2.3. General Vehicle Dynamics Fundamentals 49 3. Vehicle Testing and Data Analysis 56 3.1. Vehicle Tests 57 3.1.1. Steady State Track Lapping 58 3.1.2. Single Lane Change Tests 59 3.1.3. Straight-line Acceleration and Brake Tests 60 3.1.4. Bump Test 60 3.2. Measurement Equipment and Sensors 61 3.3. Test Setup 64 3.4. Test Results 68 3.4.1. Steady-State Handling Tests 68 VI 3.4.2. Transient Handling Tests 73 3.4.3. Vertical Response tests 77 4. ADAMS Modelling 82 4.1. ADAMS Modelling Principles 82 4.2. Constructing the rigid body model in the ADAMS environment 86 4.3. Compliant suspension components 94 4.3.1. Determining the Stiffness and Damping Values 95 4.3.2. Spherelastic Bearing 100 4.3.3. A-Frame Bearing 102 4.3.4. Sandwich Box 106 4.3.5. Asymmetric Bearing 109 4.3.6. Suspension Strut 111 4.3.7. Discussion ofTest Results for Compliant Suspension Components 119 4.3.8. Implementation ofthe Compliance Force Effects in ADAMS 121 4.4. Modelling the Tire and Road 125 4.4.1. The Fiala Tire Model in ADAMS 127 4.4.2. The Road Model in ADAMS 146 4.4.3. Discussion ofthe Various Methods ofConstructing ADAMS Road Data Files 150 4.5. Dynamic Controllers 155 4.5.1. Modelling Controllers in ADAMS 156 4.5.2. The Speed Controller 159 4.5.3. The Path-following Controller 162 5. Simulation ofthe ADAMS ADT Model 170 5.1. Simulating the ADAMS ADT model 172 5.2. Simulation Results 179 6. Conclusion 200 A. Appendix A 203 B. Appendix B 206 C. Appendix C 211 D. Appendix D 214 E. Appendix E 220 References 229 1 1. INTRODUCTION This work has as its focus the vehicle dynamics modelling of the BELL Equipment B40C articulated dump truck (ADT) via the construction and validation of a virtual prototype. More specifically the study is a first attempt at virtual prototyping of the construction, mining and agricultural machinery manufactured at BELL Equipment. Virtual prototyping for vehicle dynamics applications has fast become a valuable conceptua1isation and design tool of the modem automotive engineer. This chapter begins by introducing the concept of virtual prototyping and examines the reasons for its increasing value in automotive design along with discussing the enabling technologies that have brought it to the fore. The section concludes by outlining the structure ofthis project and presents an overview ofthis dissertation. In a conventional design process many physical prototypes have to be built. This is because the physical system is the ultimate model of reality. It is reality. As analytical techniques are developed engineers are able to predict to a greater extent beforehand how a desired system will behave. But it is still a requirement, given our current technological capabilities that physical prototypes have to be built. For a complex system like a vehicle, whose physical behaviour is impossible to understand in its entirety prior to its complete construction, many physical prototypes have to be built. Thus there is a gradual development of the vehicle using a combination of analytical techniques to predict behaviour and testing of physical prototypes to validate that prediction. Generally many subsystems of the desired system are tested in isolation and typically the process is iterative, requiring a significant number of prototypes, which have to be manufactured at significant cost. Due to the large number oftests that need to be conducted for a manufacturer to be able to manufacture and market a product within the parameters ofthe stringent safety and environmental requirements in place today, this process of gradual development is costly in terms oftime as well. In addition sometimes the system being designed is required to operate in dangerous environments and situations. Without absolute knowledge ofhow a system under test will behave, the safety oftest personnel is compromised when testing prototypes under these dangerous conditions. With the traditional methodology of a product's or system's development, testing of a prototype suggests improvements, which in turn needs to be verified, necessitating the modification, or building, of further prototypes. It is obvious that the more a priori knowledge a designer has of the physical behaviour of a desired system, the more efficient the development of the system can proceed in terms of three key parameters, cost, time and safety oftest personnel. 2 This is where virtual prototyping comes to the fore. Virtual prototyping as the name suggests is the construction of a prototype in the virtual environment of a computer. By simulating the boundary conditions and physics ofa system's behaviour on a computer, a system prototype can be constructed to be tested virtually. A virtual prototype immediately attacks the three key impediments to a traditional design cycle mentioned above. By having a virtual prototype, the requirement of having to build many prototypes saves a design project money, with the initial capital outlay for virtual prototyping software and computing hardware being rapidly recovered as the project proceeds. Changes to a prototype suggested by virtual tests can be implemented rapidly on the virtual prototype negating the need to modify or manufacture a new prototype, again saving costs but also time. Dangerous system behaviour can be tested safely with the virtual model. Simulations such as this can predict or highlight dangerous situations, and suggest precautions to be taken when the system is finally tested with a physical prototype. With specific regard to virtual prototyping of automotive vehicle behaviour, the technology is used during many different and sometimes all the stages ofa design process.