<p>In this thesis, an explicit time integration code which integrates multibody dynamics (MBD) and the discrete element method (DEM) is validated using three previously published steady-state physical experiments for non-cohesive sand-type material, namely: shear-cell for measuring shear stress versus normal stress; penetroplate pressure-sinkage test; and wheel drawbar pull-torque-slip test. The test results are used to calibrate the material properties of the DEM soft soil model and validate the coupled MBD-DEM code. All three tests are important because each test measures specific mechanical characteristics of the soil under various loading conditions. Shear strength of the soil as a function of normal load help to understand shearing of the soil under a vehicle wheel contact patch causing loss of traction. Penetroplate pressure-sinkage test is used to calibrate and validate friction and shear strength characteristics of the soil. Finally the rigid wheel-soil interaction test is used to predict drawbar pull force and wheel torque vs. slip percentage and normal stress for a rigid wheel. Wheel-Soil interaction test is important because it plays the role of ultimate validation of the soil model tuned in the previous two experiments and also shows how the soil model behaves in vehicle mobility applications.</p> <p><br></p> <p>All the aforementioned tests were modeled in the multibody dynamics software using rigid bodies and various joints and actuators. The sand-type material is modeled using discrete cubical particles. A penalty technique is used to impose normal contact constraints (including particle-particle and particle-wall contact). An asperity-based friction model is used to model friction. A Cartesian Eulerian grid contact search algorithm is used to allow fast contact detection between particles. A recursive bounding box contact search algorithm enabled fast contact detection between the particles and polygonal body surfaces (such as walls, penetrometer, and wheel). The governing equations of motion are solved along with contact constraint equations using a time-accurate explicit solution procedure. The results show very good agreement between the simulation and the experimental measurements. The model is then demonstrated in a full-scale application of high-speed off-road vehicle mobility on the sand-type soil.</p>

O objetivo do trabalho é melhorar o controle do comportamento dinâmico sob excitação vertical de um modelo veicular completo levando em consideração os três movimentos principais, de elevação (heave), balanço (pitch) e de rolagem (roll), em termos de aceleração. Com essa finalidade desenvolve-se a programação necessária para implementação de um modelo de veículo completo de 7 GDL no programa MATLAB® que interage com o sistema de controle ativo desenvolvido em diagrama de blocos no programa Simulink®. Em seguida, o desempenho do modelo é avaliado através de programas desenvolvidos de excitações de estrada com perfil senoidal e randômico. Os resultados obtidos mostram que o movimento da massa suspensa, em termos de aceleração, acima e abaixo do valor da frequência natural da roda pode ser diminuído pela filtragem dos coeficientes de mola e amortecimento através de um laço de controle interno, mais a utilização de amortecimento skyhook das velocidades de elevação, balanço e rolagem com um laço de controle externo. A atenuação das constantes de mola abaixo da frequência do corpo do veículo reduz as perturbações da estrada, mas podem bater nos limitadores do percurso da suspensão. / The aim of this work is to improve the control of the dynamic behavior under vertical excitation of a full vehicular model whilst taking into consideration the three main movements of heave, pitch and roll in terms of acceleration. With this goal in mind, the necessary programming was carried out for the implementation of a full vehicular model of 7 DOF using the software MATLAB® which interacts with the active control system developed via blocks diagram using the software Simulink®. Following on from that, the performance of the model is evaluated by means of programmes developed from road excitations with a sinusoidal and random profile. The results show that the motion of the sprung mass, in terms of acceleration, above and below the natural frequency of the wheel can be reduced by filtering the spring and damping coefficients through an internal control loop, plus the usage of skyhook damping of heave, pitch and roll velocities with an external control loop. The mitigation of the spring constants below the frequency of the body of the vehicle reduces the excitations of the road, but may strike against the path limiters of the suspension.

O objetivo do trabalho é melhorar o controle do comportamento dinâmico sob excitação vertical de um modelo veicular completo levando em consideração os três movimentos principais, de elevação (heave), balanço (pitch) e de rolagem (roll), em termos de aceleração. Com essa finalidade desenvolve-se a programação necessária para implementação de um modelo de veículo completo de 7 GDL no programa MATLAB® que interage com o sistema de controle ativo desenvolvido em diagrama de blocos no programa Simulink®. Em seguida, o desempenho do modelo é avaliado através de programas desenvolvidos de excitações de estrada com perfil senoidal e randômico. Os resultados obtidos mostram que o movimento da massa suspensa, em termos de aceleração, acima e abaixo do valor da frequência natural da roda pode ser diminuído pela filtragem dos coeficientes de mola e amortecimento através de um laço de controle interno, mais a utilização de amortecimento skyhook das velocidades de elevação, balanço e rolagem com um laço de controle externo. A atenuação das constantes de mola abaixo da frequência do corpo do veículo reduz as perturbações da estrada, mas podem bater nos limitadores do percurso da suspensão. / The aim of this work is to improve the control of the dynamic behavior under vertical excitation of a full vehicular model whilst taking into consideration the three main movements of heave, pitch and roll in terms of acceleration. With this goal in mind, the necessary programming was carried out for the implementation of a full vehicular model of 7 DOF using the software MATLAB® which interacts with the active control system developed via blocks diagram using the software Simulink®. Following on from that, the performance of the model is evaluated by means of programmes developed from road excitations with a sinusoidal and random profile. The results show that the motion of the sprung mass, in terms of acceleration, above and below the natural frequency of the wheel can be reduced by filtering the spring and damping coefficients through an internal control loop, plus the usage of skyhook damping of heave, pitch and roll velocities with an external control loop. The mitigation of the spring constants below the frequency of the body of the vehicle reduces the excitations of the road, but may strike against the path limiters of the suspension.

O objetivo do trabalho é melhorar o controle do comportamento dinâmico sob excitação vertical de um modelo veicular completo levando em consideração os três movimentos principais, de elevação (heave), balanço (pitch) e de rolagem (roll), em termos de aceleração. Com essa finalidade desenvolve-se a programação necessária para implementação de um modelo de veículo completo de 7 GDL no programa MATLAB® que interage com o sistema de controle ativo desenvolvido em diagrama de blocos no programa Simulink®. Em seguida, o desempenho do modelo é avaliado através de programas desenvolvidos de excitações de estrada com perfil senoidal e randômico. Os resultados obtidos mostram que o movimento da massa suspensa, em termos de aceleração, acima e abaixo do valor da frequência natural da roda pode ser diminuído pela filtragem dos coeficientes de mola e amortecimento através de um laço de controle interno, mais a utilização de amortecimento skyhook das velocidades de elevação, balanço e rolagem com um laço de controle externo. A atenuação das constantes de mola abaixo da frequência do corpo do veículo reduz as perturbações da estrada, mas podem bater nos limitadores do percurso da suspensão. / The aim of this work is to improve the control of the dynamic behavior under vertical excitation of a full vehicular model whilst taking into consideration the three main movements of heave, pitch and roll in terms of acceleration. With this goal in mind, the necessary programming was carried out for the implementation of a full vehicular model of 7 DOF using the software MATLAB® which interacts with the active control system developed via blocks diagram using the software Simulink®. Following on from that, the performance of the model is evaluated by means of programmes developed from road excitations with a sinusoidal and random profile. The results show that the motion of the sprung mass, in terms of acceleration, above and below the natural frequency of the wheel can be reduced by filtering the spring and damping coefficients through an internal control loop, plus the usage of skyhook damping of heave, pitch and roll velocities with an external control loop. The mitigation of the spring constants below the frequency of the body of the vehicle reduces the excitations of the road, but may strike against the path limiters of the suspension.

The ability to stand still in one place is important in a variety of activities of daily living. For persons with motion disorders, orthopaedic treatment, which changes geometric or biomechanical properties, can improve the individual'sposture and walking ability. Decisions on such treatment require insight in how posture and walking ability are aected, however, despite expectations based on experience, it is never a-priori known how a patient will react to a treatment. As this is very challenging to observe by the naked eye, engineering tools are increasingly employed to support clinical diagnostics and treatment planning. The development of predictive simulations allows for the evaluation of the eect of changed biomechanical parameters on the human biological system behavior and could become a valuable tool in future clinical decision making. In the first paper, we evaluated the use of the Zero Moment Point as a computationally inexpensive tool to obtain the ground reaction forces (GRFs) for normal human gait. The method was applied on ten healthy subjects walking in a motion analysis laboratory and predicted GRFs are evaluated against the simultaneously measured force plate data. Apart from the antero-posterior forces, GRFs are well-predicted and errors fall within the error ranges from other published methods. The computationally inexpensive method evaluated in this study can reasonably well predict the GRFs for normal human gait without using prior knowledge of common gait kinetics. The second manuscript addresses the complications in the creation and analysis of a posture prediction framework. The fmincon optimization function in MATLAB was used in conjunction with a musculoskeletal model in OpenSim. One clear local minimum was found in the form of a symmetric standing posture but perturbation analyses revealed the presence of many other postural congurations, each representing its own unique local minimum in the feasible parameter space. For human postural stance, this can translate to there being many different ways of standing without actually noticing a difference in the efforts required for these poses. / <p>This work was financially supported by the Swedish Scientic Council(Vetenskapsrådet) grant no. 2010-9401-79187-68, the ProMobilia handicapfoundation (ref. 13093), Sunnerdahls Handicap foundation (ansökan nr 11/14),and Norrbacka-Eugenia foundation (ansökan nr 218/15).</p><p></p><p></p>

Redundantly actuated manipulators have only recently aroused significant scientific interest. Their advantages in terms of enlarged workspace, higher payload ratio and better manipulability with respect to non-redundantly actuated systems explain the appearance of numerous applications in various fields: high-precision machining, fault-tolerant manipulators, transport and outer-space applications, surgical operation assistance, etc. The present Ph.D. research proposes a unified approach for modeling and actuation of redundantly actuated parallel manipulators. The approach takes advantage of the actuator redundancy principles and thus allows for following trajectories that contain parallel (force) singularities, and for eliminating the negative effect of the latter. As a first step of the approach, parallel manipulator kinematic and dynamic models are generated and treated in such a way that they do not suffer from kinematic loop closure numeric problems. Using symbolic models based on the multibody formalism and a Newton-Euler recursive computation scheme, faster-than-real-time computer simulations can thus be achieved. Further, an original piecewise actuation strategy is applied to the manipulators in order to eliminate singularity effects during their motion. Depending on the manipulator and the trajectories to be followed, this strategy results in non-redundant or redundant actuation solutions that satisfy actuator performance limits and additional optimality criteria. Finally, a validation of the theoretical results and the redundant actuation benefits is performed on the basis of well-known control algorithms applied on two parallel manipulators of different complexity. This is done both by means of computer simulations and experimental runs on a prototype designed at the Center for Research in Mechatronics of the UCL. The advantages of the actuator redundancy of parallel manipulators with respect to the elimination of singularity effects during motion and the actuator load optimization are thus confirmed (virtually and experimentally) and highlighted thanks to the proposed approach for modeling, simulation and control.

<p>Constrained optimization is used to derive human postures and movements. In the first study a static 3D model with 30 muscle groups is used to analyse postures. The activation levels of these muscles are minimized in order to represent the individual's choice of posture. Subject specific data in terms of anthropometry, strength and orthopedic aids serve as input. The aim is to study effects from orthopedic treatment and altered abilities of the subject. Initial validation shows qualitative agreement of posture strategies but further details about passive stiffness and anthropometry are needed, especially to predict pelvis orientation. In the second application, the athletic long jump, a problem formulation is developed to find optimal movements of a multibody system when subjected to contact. The model was based on rigid links, joint actuators and a wobbling mass. The contact to the ground was modelled as a spring-damper system with tuned properties. The movement in the degrees of freedom representing physical joints was described over contact time through two fifth-order polynomials, with a variable transition time, while the motion in the degrees of freedom of contact and wobbling mass was integrated forwards in time, as a consequence. Muscle activation variables were then optimized in order to maximize ballistic flight distance. The optimization determined contact time, end configuration, activation and interaction with the ground from an initial configuration. The results from optimization show a reasonable agreement with experimentally recorded jumps, but individual recordings and measurements are needed for more precise conclusions.</p><p> </p>

Optimization has been used to simulate human neural control and resulting movement patterns. The short term aim was to develop the methodology required for solving the movement optimization problem often arising when modelling human movements. A long term aim is the contribution to increased knowledge about various human movements, wherein postures is one specific case. Simulation tools can give valuable information to improve orthopeadic treatments and technique for training and performance in sports. In one study a static 3D model with 30 muscle groups was used to analyse postures. The activation levels of these muscles are minimized in order to represent the individual’s choice of posture. Subject specific data in terms of anthropometry, strength and orthopedic aids serve as input. The specific aim of this part was to study effects from orthopedic treatment and altered abilities of the subject. Initial validation shows qualitative agreement of posture strategies but further details about passive stiffness and anthropometry are needed, especially to predict pelvis orientation. Four studies dealt with movement optimization. The main methodological advance was to introduce contact constraints to the movement optimization. A freetime multiple phase formulation was derived to be able to analyse movements where different constraints and degrees of freedom are present in subsequent phases of the movements. The athletic long jump, a two foot high jump, a backward somersault and rowing were used as applications with their different need of formulation. Maximum performance as well as least effort cost functions have been explored. Even though it has been a secondary aim in this work the results show reasonable agreement to expected movements in reality. Case specific subject properties and inclusion of muscle dynamics are required to draw conclusions about improvements in the sport activity, respectively. / <p>QC 20120910</p>

The design process includes many different activities inwhich various computational mechanics tools are used forbehaviour modelling of mechanical systems and their buildingblocks, e.g. machine elements. These tools usually supportlarge and complex models and they produce large quantities ofdata with a high degree of complexity. In these situations,efficient data management and the ability to search and sharedata are important issues to achieve an efficient designprocess. Today, this ability is usually not supported by theindividual applications even though this probably would improveand facilitate the ability to search for data on a higher levelin the engineering information system. This work investigates the ability of searching andcomparing analysis data within behaviour models of technicalsystems as well as over the analysis results. This is done byinvestigating the potential benefits of integrating moderndatabase technology with a multibody system (MBS) analysissoftware in the same manner that has been successfully done forbusiness and administrative applications. This has resulted inan implemented pilot system, named MECHAMOS, that integratesthe main-memory resident object-relational database managementsystem (DBMS) AMOSwith the symbolic multibody system (MBS)software SOPHIA operating in MapleV. This provides MECHAMOSwith both symbolic and numeric mathematical capabilities forMBS analysis and data management capabilities to search andcompare engineering data in the database. The approach, making data managing tools available in acomputer aided engineering software, considerably improves theanalysis of technical systems. The analysis is brought to ahigher level through the available query language and thedesired data is specified, fairly intuitively, in a query. Whenthe query is processed, the DBMS knows how to retrieve andautomatically derive the required data. As shown in someexamples, the ability to search over stored and derived data inthe database is not restricted to a single MBS-model inMECHAMOS. Because of the implemented materialisation handling,it is also possible to search, combine, and compare data fromseveral simulation results which are based on several differentmodels in the database. This extends the ability to performoptimisation from a traditional parameter study to thepossibility to analyse and compare different technical conceptsthrough the query language and hereby retrieve those conceptsthat fulfil certain requirements. If submodel techniques aresupported, queries over a set of components in the databasewould automatically create, analyse and compare the possibleconcepts. This would assist the designer in choosing the bestcomponents for a design.

Saab Aerostructures has developed the Crew Entrance Door (CED) for Airbus A400M. Airbus has decided some different load cases for which the Crew Entrance Door must be built to withstand without something breaking down. The door is maneuvered by a mechanical system and the load cases are essential for the sizing of the components in the mechanical system. Saab has previously used MS Excel to analytically calculate resulting forces in the mechanical system due to external and/or internal loads in the different load cases. This report describes how the mechanical system for A400M Crew Entrance Door instead can be modeled and solved numerically with the computer program MSC Adams/View. Creating a model of a mechanical system in MSC Adams/View proved to be easy and fairly quick. The benefit of working with MSC Adams instead of MS Excel is that it is quicker and more user friendly. The major differences when comparing results were believed to be an effect of comparing results from a kinematic model with results from a dynamic model. Therefore it is in the Authors opinion that the analytical method to calculate resulting forces with MS Excel can be replaced by numerical calculations with MSC Adams/View. However, apart from calculating reaction forces there are additional post-simulation calculations for which it is perhaps more beneficial to use MS Excel. To do these post-simulation calculations in MS Excel it is easy to use exported results from MSC Adams. If Saab Aerostructures decide to start working with MSC Adams/View and if Saab wants geometry to be imported to the model, then an advise from the Author is to have a software installed which can convert step-files (*.stp or *.step) to the MSC Adams preferred file format Parasolid (*.xmt_txt or *.x_t). The software should also be able to repair geometry which will greatly increase mass accuracy.