Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version

Instrumentation and Control of Unmanned Air Vehicles

This thesis treats a number of instrumentation and control problems related to autonomous Unmanned Aerial Vehicles (UAV’s). Autonomous Micro Air Vehicles (MAV’s) are of special interest to the Author. These are characterised by their small size, typically below 10kg takeoff weight. Due to their small size, normal avionics are not suited for MAV’s. Instead it is more appropriate to use standard model airplane components and actuators. This has the added benefit of reducing the vehicle cost. However this also means that the vehicle designer has to characterise and design many of the instruments and actuators used for MAV’s.The first part of this thesis concentrates on obtaining an aerodynamic model for a canard configuration fixed wing UAV. Particular emphasis is placed on treatment of uncertainties in the model and the resulting influence on the UAV dynamics. A model of an electric propulsion system is also proposed, based partly on propeller characteristics obtained by comparing the geometry of the propeller with that of a propeller with known characteristics.Model airplane actuators are a logical choice for MAV’s because of there availability, price and performance. It is however difficult to obtain published data concerning the dynamics of these actuators. For these reasons a part of this thesis treats the procedure used in experimentally identifying a dynamic model of model airplane actuators. It is shown that a particular make of actuators employ a proportional-derivative bang-bang controller scheme. As a result of this observation, a feedback linearization scheme is proposed and simulated for this type of actuator.Different lateral guidance strategies are discussed based on the assumption that the desired flight path of the UAV is defined by a number of “waypoints”. It is shown that a “moving point” guidance strategy has certain advantages with respect to autopilot implementation and smooth transition from one heading to another in the vicinity of a waypoint.The most critical flight phase with respect to guidance and navigation accuracy is the approach and landing. In order to accomplish an autonomous landing it is important to be able to determine the position of the UAV with great accuracy and reliability. The only practical system for accurate navigation at the present, which does not require expensive ground based equipment, is the satellite based Global Positioning System, commonly known as GPS. However this alone does not have sufficient accuracy for the task. By using a differential positioning approach involving a ground based GPS receiver at a known location, it is possible to construct a Differential GPS (DGPS). Such a system has been implemented and studied in detail using a pair of commercially available receivers. It is shown through analysis of experimental data that the most significant error source in DGPS systems is multipath, caused by reflections of the signal from objects in the vicinity of the receiver antennas. Furthermore it is shown that these errors can be correlated with the receiver Signal to Noise Ratio (SNR). Using this information a kinematic Kalman filter is proposed for filtering the raw measurement data. “Simulation” of this filter using actual measurement data shows that a significant improvement in positioning accuracy is obtained.Finally some issues relating to the design of an Inertial Navigation System (INS) and realtime synchronized instruments are discussed

Quaternion-based attitude synchronisation for multiple rigid bodies in the presence of actuator saturation

This paper concentrates on the quaternion-based attitude synchronisation problems of networked rigid bodies under fixed and undirected communication topology without relative angular measurements in the presence of actuator saturation. We first consider the leaderless attitude synchronisation problem with zero final angular velocity. In this case, we not only discuss the performance under the acyclic communication topology with the proposed bounded control algorithm, but also analyse that if there exist cycles in the topology, the proposed bounded algorithm guarantees that all equilibrium points are unstable except that the attitudes of networked rigid bodies achieve synchronisation. We also expand the result to the case of attitude tracking synchronisation with a static leader in the presence of actuator saturation. Next, the tracking synchronisation problem with the desired time-varying attitude is addressed in the presence of actuator saturation. Numerical examples are provided to validate the effectiveness of the proposed bounded schemes and illustrate the performances of multiple rigid bodies.This work was partially supported by National Natural Science Foundation of China[grant number 61375072] and Nature Science Foundation of Zhejiang Province [grant number LQ16F030005]