Co-Simulation in Virtual Verification of Vehicles with Mechatronic Systems

In virtual verification of vehicle and mechatronic systems, a mixture of subsystems are integrated numerically in an offline simulation or integrated physically in a hardware-in-loop (HIL) simulation. This heterogeneous engineering approach is crucial for system-level development and widely spreads with\ua0the industrial standard, e.g. Functional Mock-Up Interface (FMI) standard.For the engineers, not only the local subsystem and solver should be known,\ua0but also the global coupled dynamic system and its coupling effect need to be\ua0understood. Both the local and global factors influence the stability, accuracy, numerical efficiency and further on the real-time simulation capability.In this thesis, the explicit parallel co-simulation, which is the most common and closest to the integration with a physical system, is investigated.In the vehicle development, the vehicle and the mechatronic system, e.g. an\ua0Electrcial Power Assisted Steering (EPAS) system can be simulated moreefficiently by a tailored solver and communicative step. The accuracy and\ua0numerical stability problem, which highly depends on the interface dynamics, can be investigated similarly in the linear robust control framework. The\ua0vehicle-mechatronic system should be coupled to give a smaller loop gain for robustness and stability. Physically, it indicates that the splitting part\ua0should be less stiff and the force or torque variable should be applied towardsthe part with a higher impedance in the force-displacement coupling. Furthermore, to compensate the troublesome low-passed and delay effect fromthe coupling, a new coupling method based on H∞ synthesis is developed,\ua0which can improve the accuracy of co-simulation. The method shows robustness to the system dynamics, which makes it more applicable for a complex\ua0vehicle-mechatronic system

Virtual prototyping of vehicular electric steering assistance system using co-simulations

Virtual prototyping is a practical necessity in vehicle system development. From desktop simulation to track testing, several simulation approaches, such as co-simulation and hardware-in-loop (HIL) simulation, are used. However, due to interfacing problems, the consistency of testing results may not be ensured. Correspondingly, inherent inaccuracies result from numerical coupling error and non-transparent HIL interface, which involves control tracking error, delay error, and attached hardware and noise effects. This work aims to resolve these problems and provide seamless virtual prototypes for vehicle and electric power-assisted steering (EPAS) system development.The accuracy and stability of explicit parallel co-simulation and HIL simulation are investigated. The imperfect factors propagate in the simulation tools like perturbations, yield inaccuracy, and even instability according to system dynamics. Hence, reducing perturbations (coupling problem) and improving system robustness (architecture problem) are considered.In the coupling problem, a delay compensation method relying on adaptive filters is developed for real-time simulation. A novel co-simulation coupling method on H-infinity synthesis is developed to improve accuracy for a wide frequency range and achieve low computational cost. In the architecture problem, a force(torque)-velocity coupling approach is employed. The application of a force (torque) variable to a component with considerable impedance, e.g., the steering rack (EPAS motor), yields a small loop gain as well as robust co-simulation and HIL simulation. On a given EPAS HIL system, an interface algorithm is developed for virtually shifting the impedance, thus enhancing system robustness.The theoretical findings and formulated methods are tested on generic benchmarks and implemented on a vehicle-EPAS engineering case. In addition to the acceleration of simulation speed, accuracy and robustness are also improved. Consequently, consistent testing results and extended validated ranges of virtual prototypes are obtained

Explicit parallel co-simulation approach: analysis and improved coupling method based on H-infinity synthesis

Co-simulation is widely used in the industry for the simulation of multidomain systems. Because the coupling variables cannot be communicated continuously, the co-simulation results can be unstable and inaccurate, especially when an explicit parallel approach is applied. To address this issue, new coupling methods to improve the stability and accuracy have been developed in recent years. However, the assessment of their performance is sometimes not straightforward or is even impossible owing to the case-dependent effect. The selection of the coupling method and its tuning cannot be performed before running the co-simulation, especially with a time-varying system. In this work, the co-simulation system is analyzed in the frequency domain as a sampled-data interconnection. Then a new coupling method based on the H-infinity synthesis is developed. The method intends to reconstruct the coupling variable by adding a compensator and smoother at the interface and to minimize the error from the sample-hold process. A convergence analysis in the frequency domain shows that the coupling error can be reduced in a wide frequency range, which implies good robustness. The new method is verified using two co-simulation cases. The first case is a dual mass–spring–damper system with random parameters and the second case is a co-simulation of a multibody dynamic (MBD) vehicle model and an electric power-assisted steering (EPAS) system model. Experimental results show that the method can improve the stability and accuracy, which enables a larger communication step to speed up the explicit parallel co-simulation

Needs for Physical Models and Related Methods for Development of Automated Road Vehicles

Road vehicle automation is a trendy topic in research and media. Some automation such as adaptive cruise control and lane keeping is already on market, while totally driverless vehicles in real everyday transportation tasks is still only a vision. How far the products will reach and when can be debated, but any step forward will benefit of, or need, support of modelling formats and related methods.The presentation will explain typical functional/control architecture for vehicles and then focus on development of the partitions Traffic Situation Management and Vehicle Motion Management, assuming that the partition Environment Observation (image processing etc.) comes in place to a certain known maturity. Models will be used with methods for on-line optimization, on-line predictive simulation, virtual off-line verification for right and faulty function, system safety, simulations for legal assessment of long combination vehicles, etc. A goal for novel methods is that, with physical non-causal models, one can avoid some of the enormous amount of verification simulations needed if only input/output (fixed causality) models are used.Examples from heavy vehicles and passenger cars will be given; what is achieved and what are the challenges for next steps

Integration and Analysis of EPAS and Chassis System in FMI-based co-simulation

The vehicle steering characteristics and active functions can be virtually developed with a high-fidelity electric power assisted steering (EPAS) model and a multibody chassis model. The simulation of the EPAS model requires small integration step due to high stiffness and interfacing with the controller. The multibody chassis model is computationally heavy for each integration step due to calculation of large matrices. A mono-simulation based on a single solver is not efficient for this case. Instead a co-simulation (solver coupling) approach has been used to overcome the drawbacks.In this paper the EPAS system and chassis system are modeled in Dymola and further exported as separate functional mockup units (FMUs) and integrated with the control algorithms in Matlab. A co-simulation based on the explicit parallel calculation scheme (Jacobi scheme) has been used. A huge simulation speed-up has shown the potential and effectiveness of the approach. To understand its accuracy and tolerance, analysis on the numerical error and dynamics of the coupled-system are given

Formulação axiomática de uma política florestal: preservação das espécies arbóreas tropicais e desenvolvimento econômico

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção.Este trabalho nasceu do duplo desafio de elaborar uma tecnologia de manejo da floresta tropical sem prejuízo de sua diversidade biológica original e, ao mesmo tempo, verificar sob que condições de política econômica e florestal esta tecnologia se poderia tornar economicamente viável. A tecnologia, denominada de manejo natural, foi gradativamente se cristalizando ao longo de mais de duas décadas de manejo comercial em propriedade situada na Mata Atlântica de Santa Catarina, com sua riqueza de mais de cem espécies arbóreas. Tendo sido estabelecidas determinadas normas de seleção de árvores para corte, se colocou a questão de como, formalmente, a elas se chegara. Verificou-se que as relações causais que caracterizam os conhecimentos técnico-científicos de engenharia florestal e de produção, como os organizados em modelo da dinâmica da floresta, eram somente um dos componentes de um processo decisório que culminava com o estabelecimento das regras de seleção. Com isto, o enfoque foi centrado na descrição do processo decisório em si. A formalização da sua estrutura conduziu à agregação de um componente adicional às relações causais e às normas, qual seja, o universo dos desejos individuais e dos valores sociais. O cerne formal do trabalho se constitui na formulação de uma axiomática do que se denominou uma práxis, integradora dos três componentes da estrutura de um processo decisório. Elementos da filosofia da linguagem e da lógica modal foram utilizados para se estabelecer uma forma única de expressão dos valores, das relações causais e das normas. Esta forma é a sentença intencional da filosofia continental da Europa, também denominada de propositional attitude pela filosofia inglesa. Uma vez descrito o processo decisório do manejo natural tout court, procedeu-se à sua integração ao processo decisório global de uma empresa florestal competitiva. O limitado conceito de função de produção da microeconomia neoclássica foi, inicialmente, revisto para abrigar os detalhes da engenharia da produção e, posteriormente, inserido em contexto mais amplo para coadunar o esforço de desenvolvimento da empresa e o estabelecimento de uma política florestal promotora do desenvolvimento macroeconômico. Conclui-se como Indispensável para a viabilização econômica do manejo natural o acesso ao mercado internacional de créditos de carbono, cuja institucionalização veio na esteira do Protocolo de Quioto