Extension of the Application Potential of Wheeled Mobile Driving Simulators to Uneven Grounds

Driving simulators are an important element of vehicle development, since the design of driver assistance systems in particular requires the investigation of the driver-vehicle interaction. In the future, an even greater application potential is to be expected with regard to automated driving, since, for example, handover strategies can be investigated in a secure environment. However, today's driving simulator concepts have reached a limit with regard to the achievable quality of motion simulation. Especially urban driving scenarios require a range of motion that is not economically viable with the sled systems applied in current high-end systems. One way out of this limitation is provided by wheeled mobile driving simulators, which generate the demanded accelerations through tire forces. This enables an application on different driving surfaces, which allows flexible adaptation of the movement area to the requirements of the scenario. However, due to the contact between tire and driving surface, unevenness induces vibrations into the system which disturb the immersion of the subject. The known previous research on wheeled mobile driving simulators gathered in literature neglected this aspect and postulated a sufficient driving surface quality. However, it is unclear what sufficient means in this context. In addition, the flexibility advantage of the concept may be significantly limited by the requirement of a high quality surface. Thus, this work aims at quantifying the required driving surface quality and the development and evaluation of approaches for the reduction of disturbances induced by unevenness. First, an analysis of the current development state of the driving simulator at FZD, which includes a purely tire-sprung system with solid rubber tires, is conducted. This analysis shows that driving surface qualities with a maximum height deviation of 0.01 mm over a length of 4 m (so-called depth gauge) are required to use a driving simulator of this configuration without deteriorating the immersion of the subject. This quality is not achievable with asphalt surfaces, which offer the highest application potential for WMDS. The minimum achievable depth gauge amounts to 2 mm. Thereupon, an active compensation of the driving surface-induced vibrations with the Hexapod, which is already available in simulators, is investigated. The active approach increases the tolerable depth gauge by a factor of 4 compared to the passive tire-sprung system. Nevertheless, it is still only 3 % of the target value. Especially the high dead time of the hexapod as well as the low damping and the parameter fluctuations of the tire limit the potential of the concept. Therefore, the potential of implementing an additional suspension in combination with the active approach is investigated. In order to achieve a low natural frequency, which is advantageous in terms of vibration isolation, a kinematics is developed that reduces the suspension movements of the omnidirectional motion platform by support forces. In addition, the motion control of the driving simulator is adapted in order to adjust the wheel force distribution to the demands of the suspension. These measures reduce the disturbances caused by suspension movements to values below the perception threshold up to a horizontal acceleration of 4.5 m/s². The simulation of an urban driving scenario with a multibody model shows that this covers the majority of the occurring accelerations and that within more than 99% of the simulation time the disturbance motions remain below the perception threshold. With pneumatic tires, the acceleration range with ideal support can be increased to 5.4 m/s². With regard to the required driving surface quality, this allows an increase of the acceptable depth gauge to 0.8 mm, which corresponds to an improvement of almost two orders of magnitude compared to the initial situation. Nevertheless, the value is slightly below the minimum of 2 mm achievable with asphalt surfaces. However, the determined value is only required to remain below the perception threshold with the disturbance vibrations. As vibration in vehicles is not uncommon, the negative effects on the immersion could possibly be lower, allowing a slight exceeding of the threshold. Future subject studies must examine this aspect in more detail

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Extension of the Application Potential of Wheeled Mobile Driving Simulators to Uneven Grounds

Driving simulators are an important element of vehicle development, since the design of driver assistance systems in particular requires the investigation of the driver-vehicle interaction. In the future, an even greater application potential is to be expected with regard to automated driving, since, for example, handover strategies can be investigated in a secure environment. However, today's driving simulator concepts have reached a limit with regard to the achievable quality of motion simulation. Especially urban driving scenarios require a range of motion that is not economically viable with the sled systems applied in current high-end systems. One way out of this limitation is provided by wheeled mobile driving simulators, which generate the demanded accelerations through tire forces. This enables an application on different driving surfaces, which allows flexible adaptation of the movement area to the requirements of the scenario. However, due to the contact between tire and driving surface, unevenness induces vibrations into the system which disturb the immersion of the subject. The known previous research on wheeled mobile driving simulators gathered in literature neglected this aspect and postulated a sufficient driving surface quality. However, it is unclear what sufficient means in this context. In addition, the flexibility advantage of the concept may be significantly limited by the requirement of a high quality surface. Thus, this work aims at quantifying the required driving surface quality and the development and evaluation of approaches for the reduction of disturbances induced by unevenness. First, an analysis of the current development state of the driving simulator at FZD, which includes a purely tire-sprung system with solid rubber tires, is conducted. This analysis shows that driving surface qualities with a maximum height deviation of 0.01 mm over a length of 4 m (so-called depth gauge) are required to use a driving simulator of this configuration without deteriorating the immersion of the subject. This quality is not achievable with asphalt surfaces, which offer the highest application potential for WMDS. The minimum achievable depth gauge amounts to 2 mm. Thereupon, an active compensation of the driving surface-induced vibrations with the Hexapod, which is already available in simulators, is investigated. The active approach increases the tolerable depth gauge by a factor of 4 compared to the passive tire-sprung system. Nevertheless, it is still only 3 % of the target value. Especially the high dead time of the hexapod as well as the low damping and the parameter fluctuations of the tire limit the potential of the concept. Therefore, the potential of implementing an additional suspension in combination with the active approach is investigated. In order to achieve a low natural frequency, which is advantageous in terms of vibration isolation, a kinematics is developed that reduces the suspension movements of the omnidirectional motion platform by support forces. In addition, the motion control of the driving simulator is adapted in order to adjust the wheel force distribution to the demands of the suspension. These measures reduce the disturbances caused by suspension movements to values below the perception threshold up to a horizontal acceleration of 4.5 m/s². The simulation of an urban driving scenario with a multibody model shows that this covers the majority of the occurring accelerations and that within more than 99% of the simulation time the disturbance motions remain below the perception threshold. With pneumatic tires, the acceleration range with ideal support can be increased to 5.4 m/s². With regard to the required driving surface quality, this allows an increase of the acceptable depth gauge to 0.8 mm, which corresponds to an improvement of almost two orders of magnitude compared to the initial situation. Nevertheless, the value is slightly below the minimum of 2 mm achievable with asphalt surfaces. However, the determined value is only required to remain below the perception threshold with the disturbance vibrations. As vibration in vehicles is not uncommon, the negative effects on the immersion could possibly be lower, allowing a slight exceeding of the threshold. Future subject studies must examine this aspect in more detail

Tires and vertical dynamics of wheeled mobile driving simulators

Wheeled Mobile Driving Simulators (WMDS) promise a high potential for urban traffic simulation. The tires generate the accelerations of WMDS and therefore are a key compo- nent of this simulator type. Hence, the choice of a proper tire concept is of high importance. Solid tires with compact dimensions and a high vertical stiffness are a possible alternative approach to conventional pneumatic tires. To assess the application potential of solid tires their characteristics are identified. The results show that high slip values and slip angles are necessary to reach the maximum friction coefficient of about 0.8 while their correlation is highly nonlinear. With the identified tire properties, the impact of the tires on energy con- sumption and motion control performance of WMDS is investigated. The solid tires show an increased energy consumption of about 4% compared to pneumatic tires in representa- tive urban driving cycle simulations. Solid tires with their nonlinear characteristics lead to five times higher lateral acceleration errors in relation to pneumatic tires at accelerations of 5 m/s 2 during a horizontal eight maneuver. The vertical properties of both tires were identified to be not sufficient for the application of a WMDS solely sprung by tires on uneven grounds of common quality

Rolling out a new Driving Simulator Concept - Design and Challenges of Wheeled Mobile Driving Simulators

Wheeled mobile driving simulators (WMDS) intend to cue the motion of road vehicles by moving a tire-bound, electrically driven, omnidirectional platform. The motion space of a WMDS is a planar surface, which can theoretically be increased infinitely without having to modify the system itself. The concept therefore has high potential to represent scenarios with long-lasting, longitudinal and lateral accelerations with high immersion. For this reason, the Technical University of Darmstadt and the Technische Universität Dresden are both independently developing full-scale prototypes of a WMDS. Both are currently working on common research questions and challenges, which arise from the tire characteristics and the unboundness of the system. This paper aims to give an overview of the two simulator designs and an insight into the main research topics and solution approaches for the development of wheeled mobile driving simulators