Evaluation of a snowmobile track motion resistances with multibody dynamics simulation

Abstract. In this work, target is to build and validate a simulation model of a snowmobile track entity with multibody dynamics simulation software Adams. A full vehicle snowmobile simulation model is also explored. Before there has been a problem with the track model being inaccurate. The focus on this thesis is on implementing a track model, but a full vehicle model is also discussed and presented as the work with the model will continue. Existing tracked vehicle theory is studied and presented how Adams tracked vehicle plugin utilizes these theories. Research consists of simulations with the track model were driven with a real snowmobile and measured for torque and velocity data. Model validation proves that the track model acts quite accurately up to 25 km/h drive speed but with 50 km/h speed the model becomes unstable. With 10 km/h speed simulation result error is 19,87 % and with 25 km/h simulation result error is 1,17 %. In the future the model will be further improved with building a proper chassis and validating the full vehicle model. Knowledge gained from this thesis may be used with simulating a snowmobile before production phase accurately and the model can be used for studying the motion resistances of a snowmobile track. This type of track model may be built to any tracked vehicle and validated in the way done in this thesis.Moottorikelkan telaston ajovastuksien määrittäminen monikappaledynamiikka simuloinnilla. Tiivistelmä. Tässä työssä tavoitteena on rakentaa ja validoida moottorikelkan telaston simulointimalli Adams ohjelmistolla. Telastomallin lisäksi tarkastellaan myös kokonaisen moottorikelkan simulointimallia. Aiemmin on ollut ongelmana telamattomallin epätarkkuus. Työssä keskitytään etenkin kumitelamattomallin implementointiin, mutta kokonaista ajoneuvokokoonpanoa arvioidaan lisäksi, sillä työ mallin kanssa jatkuu. Olemassa olevaa tela-ajoneuvoteoriaa tutkitaan ja esitetään, kuinka Adamsin telaajoneuvo lisäosassa hyödynnetään kyseisiä teorioita. Tutkimus koostuu simulaatioista telamattomallilla sellaisilla nopeuksilla, joita tutkimuksen aikana on mitattu todellisesta moottorikelkasta vääntötiedon kanssa. Validoinnissa todistetaan, että telamalli käyttäytyy suhteellisen tarkasti 25 km/h nopeuteen asti, mutta 50 km/h nopeudessa malli muuttuu epävakaaksi. 10 km/h nopeudella simulaatiotuloksien virhe on 19,87 % verrattuna mitattuihin tuloksiin ja 25 km/h nopeudella simulaatiotuloksien virhe on 1,17 % verrattuna mitattuihin tuloksiin. Tulevaisuudessa mallia tullaan kehittämään lisäämällä siihen runkomalli ja validoimalla täydellinen ajoneuvokokoonpano. Työstä saatavaa tietoa voidaan hyödyntää tulevaisuuden moottorikelkkasimulaatioissa tarkan tiedon saavuttamiseksi ja nykyisellään mallia voidaan hyödyntää telastosta johtuvien ajovastusten tutkimiseen. Työssä esitellyn mallin rakennustavan pohjalta voitaisiin rakentaa telasto mihin tahansa tela–ajoneuvoon ja validoida se työtä vastaavalla tavalla

Tracked Vehicle Performance Evaluation using Multi Body Dynamics

The objective of the study was to shorten the design cycle and evaluate the performance of infantry fighting vehicle using advanced multi body dynamics (MBD) environment before physical prototypes built. The MBD model is built with tracked vehicle module consisting of tracks (Links), sprocket, Support rollers, and hydro pneumatic suspension with suitable connections. Hull, turret are characterised by mass and inertial properties. The dynamic analysis was carried out for different field conditions i.e. trench crossing, step and ramp climbing, etc., to extract the hull forces at joints, power required to manuever, track tension forces to determine overall vehicle stability and look for possible design modifications. Recommendations were then suggested for power train, number of track segments, tensioner force, etc to ensure proper behavior during different manuevers. The MBD results are used in FEA to determine structural response in terms of stress, deformation, fatigue etc., and reflects in design modification before physical prototype made and are validated with base level analytical results

Holistic simulation for integrated vehicle design

A holistic vehicle simulation capability is necessary for front-loading component, subsystem, and controller design, for the early detection of component and subsystem design flaws, as well as for the model-based calibration of powertrain control modules. The current document explores the concept of holistic vehicle simulation by means of reviewing the current trends automotive system design and available solutions in terms of model interfaces and neutral modelling environments. The review is followed by the presentation of a Simulink-based Multi- disciplinary Modelling Environment (MME) developed by the authors to accommodate simulation work across the vehicle development cycle

Models for the dynamic simulation of tank track components

This project has been sponsored by QinetiQ Limited (QinetiQ); whose aim it is to model the dynamics of a prototype high-speed military tracked vehicle. Specifically their objective is to describe the mechanism by which force inputs are transmitted from the ground to the vehicle’s hull. Many track running gear components are steel and can be modelled as simple lumped masses or as linear springs without internal damping. These present no difficulty to the modeller. However tracked vehicle running gear also has nonlinear components that require more detailed descriptions. Models for two rubber components, the road wheel tyre and track link bush, and a model for the suspensions rotary damper, are developed here. These three components all have highly nonlinear dynamic responses. Rubber component nonlinearities are caused by the materials nonlinear elastic and viscoelastic characteristics. Stiffness is amplitude dependent and the material exhibits a significant amount of internal damping, which is predominantly Coulombic in nature but also relaxes overtime. In this work, a novel method for measuring the elastic and viscoelastic response of Carbon Black Filled Natural Rubber components has been devised and a ‘general purpose’ mathematical model developed that describes the materials response and is suited to use in multibody dynamic analysis software. The vehicle’s suspension rotary damper model describes three viscous flow regimes (laminar, turbulent and pressure relief), as a continuous curved response that relates angular velocity to damping torque. Hysteresis due to the compression of entrapped gas, compliance of the dampers structure and compression of damper oil is described by a single non-parametric equation. Friction is considered negligible and is omitted from the model. All components are modelled using MSC.ADAMS TM multibody dynamic analysis software. The models are shown to be easily implemented and computationally robust. QinetiQ’s requirement for ‘practical’ track running gear component models has been met.EThOS - Electronic Theses Online ServiceQinetiQ LimitedGBUnited Kingdo

Advances in Mechanical Systems Dynamics 2020

The fundamentals of mechanical system dynamics were established before the beginning of the industrial era. The 18th century was a very important time for science and was characterized by the development of classical mechanics. This development progressed in the 19th century, and new, important applications related to industrialization were found and studied. The development of computers in the 20th century revolutionized mechanical system dynamics owing to the development of numerical simulation. We are now in the presence of the fourth industrial revolution. Mechanical systems are increasingly integrated with electrical, fluidic, and electronic systems, and the industrial environment has become characterized by the cyber-physical systems of industry 4.0. Within this framework, the status-of-the-art has become represented by integrated mechanical systems and supported by accurate dynamic models able to predict their dynamic behavior. Therefore, mechanical systems dynamics will play a central role in forthcoming years. This Special Issue aims to disseminate the latest research findings and ideas in the field of mechanical systems dynamics, with particular emphasis on novel trends and applications

Virtual Prototyping Platform for Designing Mechanical and Mechatronic Systems

The chapter deals with the description of a virtual prototyping platform that facilitates the design process of the mechanical and mechatronic systems. The virtual prototyping stages are defined and then integrated in a block diagram, highlighting how the data are transferred between these stages in order to finally obtain a valid and optimal virtual model, close (as structure and functionality) to the real one. The whole process is guided by the basic principle for successful virtual prototyping: as complicated as necessary and as simple as possible. The real modeling case, the specific simplifying assumptions, and the validity (viability) fields of the simplifying assumptions are discussed with reference to the main components of a mechanical or mechatronic system (bodies, connections between bodies, actuating elements). The purpose is to manipulate the simplifying assumptions in a way that reduces the complexity of the virtual model, but without altering the accuracy of the results. The basic types of analysis/simulation are depicted by considering their particularities, highlighting their role in the process of designing mechanical/mechatronic systems, and then the optimization is conducted by the use of parametric design tools. Finally, a case study is developed following those mentioned above

Planetary Rover Simulation for Lunar Exploration Missions

When planning planetary rover missions it is useful to develop intuition and skills driving in, quite literally, alien environments before incurring the cost of reaching said locales. Simulators make it possible to operate in environments that have the physical characteristics of target locations without the expense and overhead of extensive physical tests. To that end, NASA Ames and Open Robotics collaborated on a Lunar rover driving simulator based on the open source Gazebo simulation platform and leveraging ROS (Robotic Operating System) components. The simulator was integrated with research and mission software for rover driving, system monitoring, and science instrument simulation to constitute an end-to-end Lunar mission simulation capability. Although we expect our simulator to be applicable to arbitrary Lunar regions, we designed to a reference mission of prospecting in polar regions. The harsh lighting and low illumination angles at the Lunar poles combine with the unique reflectance properties of Lunar regolith to present a challenging visual environment for both human and computer perception. Our simulator placed an emphasis on high fidelity visual simulation in order to produce synthetic imagery suitable for evaluating human rover drivers with navigation tasks, as well as providing test data for computer vision software development.In this paper, we describe the software used to construct the simulated Lunar environment and the components of the driving simulation. Our synthetic terrain generation software artificially increases the resolution of Lunar digital elevation maps by fractal synthesis and inserts craters and rocks based on Lunar size-frequency distribution models. We describe the necessary enhancements to import large scale, high resolution terrains into Gazebo, as well as our approach to modeling the visual environment of the Lunar surface. An overview of the mission software system is provided, along with how ROS was used to emulate flight software components that had not been developed yet. Finally, we discuss the effect of using the high-fidelity synthetic Lunar images for visual odometry. We also characterize the wheel slip model, and find some inconsistencies in the produced wheel slip behaviour

Robotic Visual Tracking of Relevant Cues in Underwater Environments with Poor Visibility Conditions

Using visual sensors for detecting regions of interest in underwater environments is fundamental for many robotic applications. Particularly, for an autonomous exploration task, an underwater vehicle must be guided towards features that are of interest. If the relevant features can be seen from the distance, then smooth control movements of the vehicle are feasible in order to position itself close enough with the final goal of gathering visual quality images. However, it is a challenging task for a robotic system to achieve stable tracking of the same regions since marine environments are unstructured and highly dynamic and usually have poor visibility. In this paper, a framework that robustly detects and tracks regions of interest in real time is presented. We use the chromatic channels of a perceptual uniform color space to detect relevant regions and adapt a visual attention scheme to underwater scenes. For the tracking, we associate with each relevant point superpixel descriptors which are invariant to changes in illumination and shape. The field experiment results have demonstrated that our approach is robust when tested on different visibility conditions and depths in underwater explorations