G. Sequenzia

Error control in UAV image acquisitions for 3D reconstruction of extensive architectures

This work describes a simple, fast, and robust method for identifying, checking and managing the overlapping image keypoints for 3D reconstruction of large objects with numerous geometric singularities and multiple features at different lighting levels. In particular a precision 3D reconstruction of an extensive architecture captured by aerial digital photogrammetry using Unmanned Aerial Vehicles (UAV) is developed. The method was experimentally applied to survey and reconstruct the ‘Saraceni’ Bridge’ at Adrano (Sicily), a valuable example of Roman architecture in brick of historical/cultural interest. The variety of features and different lighting levels required robust self-correlation techniques which would recognise features sometimes even smaller than a pixel in the digital images so as to automatically identify the keypoints necessary for image overlapping and 3D reconstruction. Feature Based Matching (FBM) was used for the low lighting areas like the intrados and the inner arch surfaces, and Area Based Matching (ABM) was used in conjunction to capture the sides and upper surfaces of the bridge. Applying SIFT (Scale Invariant Feature Transform) algorithm during capture helped find distinct features invariant to position, scale and rotation as well as robust for the affinity transformations (changes in scale, rotation, size and position) and lighting variations which are particularly effective in image overlapping. Errors were compared with surveys by total station theodolites, GPS and laser systems. The method can facilitate reconstruction of the most difficult to access parts like the arch intrados and the bridge cavities with high correlation indices.

Dynamics of a high-performance motorcycle by an advanced multibody/control co-simulation

The present work aims at the development of an advanced control system implemented through Adams/View-Matlab/Simulink co-simulation for a high-performance motorcycle dynamics study. In particular, the purpose of this study is to create a model able to consider several aspects of the rider–motorbike dynamic simulation and its control system, generally treated separately in the literature, making also use of an original and accurate modelling of the rider. From a previous multi-body model of motorcycle/virtual rider, developed by the authors, a flexible tool is created to simulate system dynamics to follow any trajectory at a prescribed velocity profile. Considering high-performance motorcycle dynamics are greatly influenced by the rider’s weight, his movements have been accurately replicated to obtain the most realistic results. To simulate the passive impedance of rider’s arms, a torque was applied to the steering as per the literature. The aerodynamic force was modelled as a function of kinematics variables and rider’s posture. The control system is very flexible and adaptable to different manoeuvres realistically reproducing engine and braking performance, steering torque and rider movements. Numerical results show that the control system can accurately direct the motorcycle/rider system along an entire lap of the Monza circuit, following a desired path at a given velocity profile. The model developed allows a complete view of the motorbike-rider dynamic behaviour thus being useful during both design phase and set-up, with a considerable saving in terms of both cost and time; it can also evaluate the influence on the system dynamics of riders with different anatomical characteristics and driving styles.

An advanced multibody model for evaluating rider’s influence on motorcycle dynamics

The dynamics of a high-performance motorcycle are greatly influenced by the rider’s weight and movements especially when the power-to-weight ratio is very high. Generally in motor vehicles, the driver’s/rider’s weight is a significant fraction of the entire system. This work is about ADAMS/View multibody modelling of a motorcycle and virtual rider who simulates handlebar interaction and saddle sliding. In the literature, the rider’s influence is unrealistic being limited to considering him as a concentrated mass or in other cases as a fixed passive system. Even vehicle modelling is often inaccurate, referring at best to simplified models of rigid bodies. In this work, the vehicle and rider have been accurately modelled to most realistically reproduce the dynamic behaviour of the system. The motorcycle was modelled with 12 bodies incorporating concentrated flexibility for the two suspension units and considering the chassis as a flexible body using modal synthesis. The virtual rider is made up of 15 rigid bodies and has 28 degrees of freedom. To study the effects on the motorcycle of the rider’s movements as well as the motorcycle’s dynamics and performance, a monitoring system similar to that in the literature was used to read handlebar torque and engine and braking torque. Furthermore, in the literature there are simulations of standard manoeuvres whereas in this work an entire lap of Monza was simulated. There were simulations of a fixed and mobile rider validating the model in advance and thereafter monitoring the most significant dynamic parameters. The multibody model provides useful results at the design phase and insights into the whole vehicle/rider dynamic to setup all the reference parameters for immediately evaluating system effects.

An effective model for the sliding contact forces in a multibody environment

This work describes an integrated method of 3D modelling algorithms with a modal approach in a multibody environment which provides a slimmer and more efficient simulation of flexible component contacts realistically reproducing system impacts and vibrations. A non-linear numerical model of the impulse contact forces based on the continuity approach of Lankarani and Nikravesh is developed. The model developed can evaluate deformation energy taking into account the material’s characteristics, surface geometries and the velocity variations of the bodies in contact. ADAMS®-type modelling is applied to the sliding contacts of the links of a chain and its mechanical tensioner (“blade”) in the timing of an internal combustion engine. The blade was discretized by subdividing it into smaller components inter-connected with corresponding centres of gravity through 3D General Forces. Static and dynamic tests were performed to evaluate the stiffness, damping and friction parameters for the multibody model and to validate the methodology.

Flexible Multibody Model of Desmodromic Timing System

Abstract In the present study, the authors performed a dynamic analysis of the desmodromic timing system, where the valve lifter is realized by conjugate cams, using a methodology of modal synthesis to examine the effects of the deformability of the principal parts, and evaluating the deformations and vibrations of the components under various operating conditions. With this aim, a virtual 3D model and a multibody calculation program were used in a concentrated parameter model, requiring the choice of numerous parameters that greatly affect the results of the analysis. It was therefore important that, within the variability range of these parameters, the values adopted rendered the behavior of the analytical model as close as possible to that of the real system. Finally, the need to evaluate some of the more important aspects of the dynamic system (such as values of clearances, stiffnesses and damping at contacts, and stiffnesses and damping of shafts and belt) made it necessary to validate the model through comparison with experimental trials conducted to determine the valve motion and to measure the strain on the distribution belt.

An integrated approach to customize the packaging of heritage artefacts

The shipment of heritage artefacts for restoration or temporary/travelling exhibition has been virtually lacking in customised packaging. Hitherto, packaging has been empirical and intuitive which has unnecessarily put the artefacts at risk. So, this research arises from the need to identify a way of designing and creating packaging for artefacts which takes into account structural criticalities to deal with deteriorating weather, special morphology, constituent materials and manufacturing techniques. The proposed methodology for semi-automatically designing packaging for heritage artefacts includes the integrated and interactive use of Reverse Engineering (RE), Finite Element Analysis (FEA) and Rapid Prototyping (RP). The methodology presented has been applied to create a customised packaging for a small C3rd BC bronze statue of Heracles (Museo Civico “F.L. Belgiorno” di Modica -Italy). This methodology has highlighted how the risk of damage to heritage artefacts can be reduced during shipping. Furthermore, this approach can identify each safety factor and the corresponding risk parameter to stipulate in the insurance policy.

An integrated approach to design an innovative motorcycle rear suspension with eccentric mechanism

In the present work, by means of an integrated approach, a new rear suspension for motorcycles, able to achieve the required progressiveness in terms of rigidity by using a constant-stiffness spring and a compact mechanism, has been studied. The key component is an eccentric system inserted in the shock absorber head. As reference, we analyzed the rear suspension of the Ducati Multistrada MY 2010, characterized by the use of a variable-stiffness spring. The aim of the paper is to prove that the new proposed solution can obtain a response, in terms of load to the wheel, similar to that of the actual system. At first, a mathematical model to simulate the kinematics of the new suspension is presented. This model is able to evaluate the influence of geometric dimensions of the components, checking successfully the ability to reproduce the behavior of the original suspension. After the preliminary design, the kinematic and static models are included within an optimization algorithm ad-hoc created to calculate the exact dimensions of each component. Two Matlab/Simulink® lumped mass models, respectively referred to the novel and reference suspension, are used to compare the dynamic responses during the travelling of a particular road profile used in Ducati’s experimental tests. Finally, an accurate modeling of the components, considering also the production processes to be used for their creation, is provided.