A demonstration of motion base design alternatives for the National Advanced Driving Simulator

A demonstration of the capability of NASA's Vertical Motion Simulator to simulate two alternative motion base designs for the National Advanced Driving simulator (NADS) is reported. The VMS is located at ARC. The motion base conditions used in this demonstration were as follows: (1) a large translational motion base; and (2) a motion base design with limited translational capability. The latter had translational capability representative of a typical synergistic motion platform. These alternatives were selected to test the prediction that large amplitude translational motion would result in a lower incidence or severity of simulator induced sickness (SIS) than would a limited translational motion base. A total of 10 drivers performed two tasks, slaloms and quick-stops, using each of the motion bases. Physiological, objective, and subjective measures were collected. No reliable differences in SIS between the motion base conditions was found in this demonstration. However, in light of the cost considerations and engineering challenges associated with implementing a large translation motion base, performance of a formal study is recommended

Driving Simulator Motion Cueing Assessment: A Platform Design Perspective

The overall aim of this thesis was to study the effects of a simulator’s motion system on vestibular motion cueing fidelity in different contexts, evaluated in terms of drivers’ perception and behaviour, in low and high road friction conditions. The effects of manipulating the motion cueing algorithm (MCA), was found to be a function of the vehicle motion in a manoeuvre, and significant effects were observed. The applicability of simulators for the assessment of vehicle driven attribute qualities such as ride, steering and handling were studied by manipulating vehicle ride height (RH). The differences between the RHs were subjectively distinguishable by the drivers in the simulator. Incongruities between the subjective preferences and objective performances were observed in both of the independent comparisons of the MCAs and RHs. The effects of motion platform (MP) workspace size were found to be dependent on the manoeuvres and road friction level. In the low-friction condition, with the increase of MP size, two opposite effects were observed on drivers’ preferences and their performances, depending on the manoeuvre. In high-friction, in most of the handling and steering qualities, a direct relation was found between the MP size and appropriate vehicle RH. Furthermore, the optimal tuning of the MCAs and optimisation of the MP workspace size was introduced. A conservative motion cueing fidelity criteria was defined. A multi-layered optimisation method was developed that uses the optimal setting of the MCA, to address the MP translational workspace size, and to meet the fidelity criteria; applicable for different manoeuvres. This method was tested on the drivers’ performance data collected from the experiments in the simulator

Model-Based Control Techniques for Automotive Applications

Two different topics are covered in the thesis. Model Predictive Control applied to the Motion Cueing Problem In the last years the interest about dynamic driving simulators is increasing and new commercial solutions are arising. Driving simulators play an important role in the development of new vehicles and advanced driver assistance devices: in fact, on the one hand, having a human driver on a driving simulator allows automotive manufacturers to bridge the gap between virtual prototyping and on-road testing during the vehicle development phase; on the other hand, novel driver assistance systems (such as advanced accident avoidance systems) can be safely tested by having the driver operating the vehicle in a virtual, highly realistic environment, while being exposed to hazardous situations. In both applications, it is crucial to faithfully reproduce in the simulator the driver's perception of forces acting on the vehicle and its acceleration. This has to be achieved while keeping the platform within its limited operation space. Such strategies go under the name of Motion Cueing Algorithms. In this work, a particular implementation of a Motion Cueing algorithm is described, that is based on Model Predictive Control technique. A distinctive feature of such approach is that it exploits a detailed model of the human vestibular system, and consequently differs from standard Motion Cueing strategies based on Washout Filters: such feature allows for better implementation of tilt coordination and more efficient handling of the platform limits. The algorithm has been evaluated in practice on a small-size, innovative platform, by performing tests with professional drivers. Results show that the MPC-based motion cueing algorithm allows to effectively handle the platform working area, to limit the presence of those platform movements that are typically associated with driver motion sickness, and to devise simple and intuitive tuning procedures. Moreover, the availability of an effective virtual driver allows the development of effective predictive strategies, and first simulation results are reported in the thesis. Control Techniques for a Hybrid Sport Motorcycle Reduction of the environmental impact of transportation systems is a world wide priority. Hybrid propulsion vehicles have proved to have a strong potential to this regard, and different four-wheels solutions have spread out in the market. Differently from cars, and even if they are considered the ideal solution for urban mobility, motorbikes and mopeds have not seen a wide application of hybrid propulsion yet, mostly due to the more strict constraints on available space and driving feeling. In the thesis, the problem of providing a commercial 125cc motorbike with a hybrid propulsion system is considered, by adding an electric engine to its standard internal combustion engine. The aim for the prototype is to use the electrical machine (directly keyed on the drive shaft) to obtain a torque boost during accelerations, improving and regularizing the supplied power while reducing the emissions. Two different control algorithms are proposed 1) the first is based on a standard heuristic with adaptive features, simpler to implement on the ECU for the prototype; 2) the second is a torque-split optimal-control strategy, managing the different contributions from the two engines. A crucial point is the implementation of a Simulink virtual environment, realized starting from a commercial tool, VI-BikeRealTime, to test the algorithms. The hybrid engine model has been implemented in the tool from scratch, as well as a simple battery model, derived directly from data-sheet characteristics by using polynomial interpolation. The simulation system is completed by a virtual rider and a tool for build test circuits. Results of the simulations on a realistic track are included, to evaluate the different performance of the two strategies in a closed loop environment (thanks to the virtual rider). The results from on-track tests of the real prototype, using the first control strategy, are reported too

Subjective perception and prediction model of vehicle stability under aerodynamic excitations

The current automotive era is moving towards electrified vehicle propulsion. As a result, an\ua0energy efficient vehicle design becomes one of the top priorities. From an aerodynamics point\ua0of view, the vehicle should be more streamlined for minimal aerodynamic drag. Such designs\ua0have the potential to enhance vehicle sensitivity when exposed to external disturbances such\ua0as unsteady aerodynamic forces and moments created by the flow of air around the vehicle.Before signing off for production, several on-road test scenarios are conducted by professional\ua0drivers to evaluate the new vehicle’s performance. Finding vehicle instabilities and proposing\ua0solutions to problem’s during such late phases of development is challenging in many aspects.The objective of this paper is to correlate and predict the driver’s subjective perception on\ua0high-speed straight-line driving stability with measurable quantities in the early phase of\ua0development.In this work, different aerodynamic devices were used for generating higher lift and asymmetric\ua0aerodynamic forces resulting in substandard straight-line drivability on-road. An inverted wing,\ua0an inverted wing with an asymmetric flat plate, and an asymmetric air curtain attached under\ua0the bumper were the selected aerodynamic devices paired with and without bumper side-kicks.\ua0The side-kicks help define the flow separation, thus improving the drivability of the tested\ua0vehicle. Plots of mean and standard deviation and ride diagrams of lateral acceleration, yaw\ua0velocity, steering angle, and steering torque are used to understand vehicle behaviour for the\ua0paired configurations and relate to the difference of subjective judgment of drivability within\ua0each pair. The ride diagram was used to separate the presence of transient behaviour and\ua0study its impact on subjective judgement. The qualitative assessment of the resulting trends\ua0agrees well with the subjective judgement of the driver.Clinical tests were conducted using driving simulators, in order to have an in-depth understanding\ua0of the subjective perception and responses of drivers towards external disturbances.\ua0Both common and experienced test drivers were involved in this test. The results provided an\ua0insight towards the disturbance frequencies and amplitudes of interest. From the test data,\ua0a model is generated that can predict the drivers’ subjective perception after experiencing\ua0induced external disturbances. The outcome also shows the impact of drivers’ steering action\ua0on their subjective perceptions towards these disturbances

Predictive model of perceived driving stability at high speeds under aerodynamic excitations

The automotive industry is continuously advancing towards more energy-efficient vehicle designs.\ua0Streamlined vehicles have low aerodynamic drag but have the potential to be unstable when\ua0exposed to external excitations such as unsteady aerodynamic forces created by the flow of air\ua0around them.\ua0Before signing off a new vehicle for production, several on-road test scenarios are\ua0conducted by professional drivers to evaluate the performance. Finding vehicle instabilities and\ua0proposing solutions to problems during late phases of development is challenging and costly. The objective of this thesis is to correlate and predict the driver\u27s subjective evaluation of high\ua0speed straight-line driving stability with measurable quantities in early design phases.\ua0In this work, substandard straight-line drivability was investigated on-road using different\ua0aerodynamic devices for generating high rear lift and asymmetric aerodynamic forces. These\ua0aerodynamic devices were then paired with stabilizers, called side-kicks, which helped to define\ua0the flow separation and improved the drivability of the tested vehicle. Vector plots of the\ua0mean and standard deviation of lateral acceleration, yaw velocity, steering angle, and steering\ua0torque were used to understand vehicle behavior for the paired configurations and relate\ua0to the difference of subjective evaluation of drivability within each pair. The ride diagram\ua0was used to separate the presence of transient behavior and study its impact on subjective\ua0evaluation. The qualitative assessment of the resulting trends agrees well with the subjective\ua0evaluation of the driver. Following this, experimental trials were conducted in driving simulators and on-road, in order to\ua0have an in-depth understanding of drivers\u27 subjective evaluation and responses to external\ua0excitations. Both common and professional test drivers were involved in the study. The results\ua0provided insight into the excitation frequencies and amplitudes of interest. From the test\ua0data, mathematical models were generated that can predict the drivers\u27 subjective evaluation\ua0after experiencing induced external excitations. The outcome showed the impact of drivers\u27\ua0steering on their subjective evaluations towards these excitations. The on-road study revealed\ua0that higher roll and longitudinal noises reduce the drivers\u27 sensitivity to external excitations.\ua0Headwind magnitude and lateral motion in a certain frequency range experienced by the\ua0human upper body contribute to drivers\u27 identification of excitations. The resulting predictive\ua0model can be used to pinpoint the time of occurrence of observable aerodynamic excitations\ua0and provides their characteristics in early development phases. Since the models represent\ua0measurements from the cabin, they should be valid for different vehicles

Virtual Techniques for Prototype HMI Evaluation

The aim of this project was to investigate the behavioural validity of virtual methods, namely driving simulators and computational models, as prototype HMI evaluation tools. A driving study was designed where participants had to perform secondary tasks while driving in a real world and a driving simulator setting. Statistical analysis of the data, along with an in-depth review of related findings was used to identify the levels of behavioural validity that could be achieved by different simulator settings across different metrics. A further analysis was performed to identify behavioural strategies that drivers employ regarding their visual attention sharing while executing HMI tasks concurrently to driving. Finally, two existing computational models were validated and a novel model was proposed that can account for drivers’ behavioural phenomena, not previously accounted for

Experimental evidence supporting simpler Action Point paradigms for car-following

The Action Point theory is one of the paradigms that can be applied to understand and reproduce car-following behaviour. Several different approaches to this theory have been proposed, some more simple and others more complex. In particular, the reference point in this field is still the paradigm from Wiedemann, which requires the identification of four action-point thresholds. In this paper we review Action Point theories in order to highlight similarities and differences and to ascertain whether all the thresholds proposed by Wiedemann actually bind the driving behaviour. Based on a large-scale experiment in which car-following data were collected, we identified all candidate action points assuming that the more complex (four-threshold) theory holds. Then we tested these points with respect to the large data set of available observations, in order to check whether actual actions are performed at the points. The results show that very often simpler approaches better match the observed data and that in order to explain car-following behaviour it is sufficient in most cases to refer to two thresholds. The results obtained by real-world observation were also tested in virtual environments (two different kinds of driving simulators) and were confirmed

Development and application of smart actuation methods for vehicle simulators

Driving simulators are complex virtual reality systems that integrate visual displays, sound rendering systems, motion platforms, and human-machine-interface devices. They are used in different research areas and consequently, different studies are conducted using these systems, in conditions that would not be safe to be carried out in the real world. However, driving simulators are very expensive research tools. When building such a system, a compromise usually has to be made. Although a driving simulator cannot reproduce 1:1 real life situations or sensations because of its limitations, researchers still need to use such a device for training and research purposes, due to the realistic driving experience it has to offer to its driver. This work focuses on developing a three-degrees of freedom Essential Function Driving Simulator that integrates cost and design constraints, the human perception of motion and real vehicle motion achieved through simulated vehicle models, and the classical motion cueing strategy. The goal is, on the first hand, to immerse the driver to a certain extend into the simulation environment by using this virtual reality device and, on the second hand, to investigate the degree of realism of such a solution. Different actuation solutions are modelled and discussed in this research, with respect to the available workspace, singularity configurations, the system’s behaviour and the maximum forces needed in the frame of the overall cost constraints. A solution was chosen following kinematical and dynamical analyses, as a trade off solution among the above mentioned constraints. The human body finds itself in continuous movement and interaction with the environment. Motion is sensed by the human being through the vestibular system and the skin. The human motion perception mechanisms are mathematically modelled and studied, in order to apply their characteristics in the three-degrees of freedom driving simulator. Due to the limited workspace and degrees of freedom of the discussed simulator, the motion of the simulated vehicle cannot be identically reproduced by the motion system. Thus, special algorithms are designed to transform the motion of the vehicle model in achievable positions for the three actuators, and additionally, to render correct motion cues. The influence of the three variable parameters on the overall subjective degree of freedom is investigated using an optimisation method. The studied parameters are: motion, optical flow and haptic response, introduced by using a lane departure warning assistance system. It is shown in this research that the influence of motion cues on the subjective degree of realism rated by the drivers is of 84%. The vibrations in the steering wheel improve the realism of the simulation and have a 15% impact. The participants of these experiments could easily adapt to the provided assistance system and their immersion in the simulated environment was significantly influenced by the activation of the lane departure warning option. It has also been shown that drivers rated the motion and the accelerations felt in the simulator with 70.41%, compared to the experience of driving a real vehicle. These results are interpreted in this research by putting the emphasis on the fact that irrespective of the DOF of the actuation mechanism, a motion driving simulator should provide correct motion cues. The development of the vehicle models and of the motion cueing algorithms should be approached, so that the system provides motion as similar as possible to the real vehicle, as it is further discussed here.Entwicklung und Anwendung von intelligenten Ansteuerungsmethoden für Fahrzeugsimulatoren Fahrsimulatoren sind Virtual-Reality Systeme, die aus geeigneten Mensch-Maschinen-Schnittstellen, optische und akustische Wiedergabe und, wenn das Bedarf besteht, aus einen Bewegungsapparat bestehen. Sie werden in unterschiedlichen Forschungsfeldern verwendet um verschiedene Studien durchzuführen. Unter anderem können dadurch Manöverstudien durchgeführt werden, die in realen Fahrsituationen zu gefährlich für den Fahrer wären. Der Bau komplexer und hochauflösender Fahrsimulationen ist jedoch sehr Kostenintensiv. Obwohl ein Fahrsimulator die in realen Fahrsituationen empfundenen Fahrgefühle nicht originalgetreu wiedergegeben kann, durch den begrenzten Arbeitsraum, eignet sich ein solches Gerät zu Lehr- und Forschungszwecken. Diese Arbeit befasst sich mit der Entwickelung eines kostengünstigen Fahrsimulators mit drei Freiheitsgraden, der durch eine geeignete Motion-Cueing Strategie dem Fahrer ein ausreichendes Fahrgefühl widergibt. Es werden verschiedene Aktuierungslösungen in Bezug auf den begrenzten Arbeitsraum, singulären Stellungen, des maximalen Kraftbedarfs modelliert, verglichen und diskutiert. Es wurde eine Kompromisslösung gefunden basierend auf der kinematischen und dynamischen Analyse, die diese Begrenzungen berücksichtigt. Der menschliche Körper befindet sich in einer kontinuierlichen Bewegung und interagiert dabei mit der Umgebung. Die Bewegung wird durch das Vestibularorgan und durch die Haut wahrgenommen. Die menschliche Wahrnehmung wird durch ein geeignetes mathematisches Modell widergegeben. Der Bewegungsablauf des Fahrsimulators wurde unter Berücksichtigung der menschlichen Wahrnehmung ausgelegt und untersucht. Wegen dem begrenztem Arbeitsraum und der geringen Anzahl von Systemfreiheitsgraden kann der Simulator die reelle Fahrdynamik nicht im vollen Umfang an die Testperson weitergeben. Deshalb werden angepasste Algorithmen entwickelt um den Bewegungsablauf beschränkt durch drei Aktuatoren in einem akzeptablem umfang widerzugeben. Der Einfluss der drei Aktuatorparameter auf den Bewegungsablauf wird durch geeignete Optimierungsmethoden untersucht. Die Größen die anschließend durch das Fahrsimulator Setup untersucht werden sind unter anderem der Bewegungsablauf, die optische Darstellung und die haptische Wiedergabe. Die Wichtigkeit der empfundenen Fahrbewegung wurde durch die Probanden, im Vergleich zu einem statischen Fahrsimulator, mit 84% bewertet. Die Vibrationen im Lenkrad erhöhen das Realitätsempfinden um 15%. Die Testpersonen konnten sich schnell an die aktuierten Fahrsimulation anpassen und auch Assistenzsysteme wie Spurhalteassistent benutzen. Es wurde gezeigt, dass die im Fahrsimulator gefühlten Beschleunigungen zu ca. 70% an die im realen Fahrbetrieb empfundenen Beschleunigungen herankommen. Es hat sich gezeigt, dass der Immersionsgrad vor allem vom verwendeten Fahrzeugmodellen und den Motion-Cueing Algorithmus abhängig ist

Modelling, Controlling And Real Time System Implementation Of A Hexapod Platform

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2010Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2010Bu çalışmada, hareket benzetim platformu olarak tasarlanan altı bacaklı bir paralel manipülatörün modellenmesi, kontrolü ve gerçek zamanlı sistem uygulaması ele alınmıştır. Tasarlanan sistem hareketli üst platform, sabit alt platform ve bu iki platformu birbirine bağlayan, dönel hareket kabiliyeti ile uzunluğu değişebilen, altı bacaktan oluşur. Altı serbestlik derecesinde, ASELSAN A.Ş. MGEO bünyesinde, tasarlanan hareket benzetim platformuna hareket profili olarak tank hareket profili uygulanmış ve tanklarda yaygın olarak kullanılan stabilize alın aynasının test kriterleri oluşturulmuştur. Hareket profili, APG parkuru üzerindeki tankın hareket verisinden elde edilmiştir. Tank kulesi iki serbestlik derecesine sahiptir. Bu nedenle, hareket benzetim platformunun yan-sapma ve yükseliş-yunuslama eksenlerindeki hareketi, tank hareketinin benzetiminde yeterli olacaktır. Tasarlanan hareket benzetim platformu, hızlı prototipleme (rapid prototyping) ve çevrimsel donanım benzetimi (hardware-in-the-loop) test uygulamaları için örnek teşkil eder. Alın aynasının stabilizasyon performansını ölçebilmek için otokolimatör ve sayısal kontrolöre sahip bir test sistemi tasarlanmıştır. Hareket benzetim platformu kontrol ve stabilize alın aynası test yazılımı kullanıcı arayüzleri tasarım gerekliliklerine göre geliştirilmiştir. Üst platform hareket eksenleri üzerindeki ivmeölçerlerden toplanan veriler incelenerek, tasarlanan sistem ASELSAN MGEO Tasarım Kalite Bölümü tarafından doğrulanmıştır.In this study, modelling, controlling and real-time system implementation of a hexapod parallel manipulator designed as a motion simulator are explained. The designed hexapod platform has a mobile top platform, a fixed base platform and six rotationally extensible legs connecting the base platform to the top platform. A tank’s motion profile is performed as the motion profile of the motion simulator with six degrees of freedom, designed in ASELSAN Inc. MGEO organization, and the test criteria of the two-axis gyro stabilized head mirror commonly used on tanks are formed. The motion profile is obtained from the motion data of a tank on APG track. The tank turret has two degrees of freedom. Therefore, the motions in yaw and pitch axes of the motion simulator are sufficient for the simulation of the tank motion. The designed motion simulator is an example for rapid prototyping and hardware-in-the-loop test applications. A test system includes autocollimator and digital controller is designed to evaluate the stabilization performance of the head mirror. The user interfaces of the Hexapod platform control and the stabilized head mirror test software are developed in compliance with the design specifications. The designed system is approved by Design Quality Department of ASELSAN after analyzing gathered data from accelerometers on the top platform’s motion axes.Yüksek LisansM.Sc