Design methods for mobility

Titanium and its alloys are nowadays widely used in many sectors: in the medical field (orthopedic and dental ones), in the architectural field, in the chemical plants field and in aeronautic. In this last field it is more and more used both for its contribution to make lightweight and time durable structures and for its compatibility with new materials, first of all Carbon Fiber Reinforced Plastics (CFRP). To this aim, lots of researches are now focusing on new and emerging technologies capable to make titanium objects and, at the same time, reducing the scrap, since titanium alloys for aeronautic application are very expensive. This paper examines Grade 5 Titanium Alloy (Ti6Al4V) welded by Laser Beam (LBW) in butt-joint configuration. The source was Nd:YAG laser, moreover two inert gases were used, in order to provide a shield both on the top and on the bottom of the weld bead. The joints were studied by varying two process parameters: welding speed and power of the laser beam. It was not possible to realize a full experimental plan, due to technological limits in making titanium laser beam welds. The joints were tested to measure their mechanical properties and the corrosion resistance. The process parameters do not significantly affect the maximum static strength of the joints. Microscopic analysis showed that welds made with high power and low welding speed have a uniform weld bead, and no macroscopic defect occurs. Fatigue test results, instead, show a marked influence of the morphology of the weld bead: the occurrence of some defects, such as the undercut, both on the top and on the bottom of the weld bead, dramatically reduced fatigue resistance of the joints. Corrosion resistance was studied using the electrochemical micro cell technique, which allows to distinguish electrochemical properties of each zone of the weld bead, even when, as in this case, they are very narrow. By a general point of view, it has been demonstrated that the joints showing the best mechanical performances also possess better electrochemical properties. What's more, in these cases, the weld bead shows a cathodic behavior with respect to the parent material. © 2011 American Institute of Physics.

Keywords: electrochemical micro cell , fatigue tests , Laser , Titanium , Welding

Polymer-based composite materials are ideal for applications where high stiffness-to-weight and strength-to-weight ratios are required. From aerospace and aeronautical field to biomedical applications, fiber-reinforced polymers have replaced metals, thus emerging as an interesting alternative. As widely reported, the mechanical behavior of the composite materials involves investigation on micro- and macro-scale, taking into consideration micromechanics, macromechanics and lamination theory. Clinical situations often require repairing connective tissues and the use of composite materials may be suitable for these applications because of the possibility to design tissue substitutes or implants with the required mechanical properties. Accordingly, this review aims at stressing the importance of fiber-reinforced composite materials to make advanced and biomimetic prostheses with tailored mechanical properties, starting from the basic principle design, technologies, and a brief overview of composites applications in several fields. Fiber-reinforced composite materials for artificial tendons, ligaments, and intervertebral discs, as well as for hip stems and mandible models will be reviewed, highlighting the possibility to mimic the mechanical properties of the soft and hard tissues that they replace. © 2011 Società Italiana Biomateriali.

Keywords: Applications , Basic principles , Fiber-reinforced composite materials , Prosthetic implants and models , Tailored properties , Technologies

This paper presents a multi-physic modeling of an electromechanical energy scavenging device able to supply energy inside car tires for wireless sensors. A permanent magnet, connected to the inner liner of a tire, is accelerated along a guide by the tire deformation during car motion; by interacting with coils it generates a power which is conditioned by a proper electronic interfaced to an external load. The original approach implemented in this kind of device is the nonlinear dynamic properties designed and controlled: adaptive resonance in function of car velocity is optimized for increasing its global efficiency. The energy conversion process takes into account the simulation of different phenomena such as: non linear dynamic and adaptive resonant behavior of the seismic mass, electromagnetic and magneto-static coupling between moving mass and coils, transfer of the generated power to an external load by means of a nonlinear circuit interface. An integrated model of the cascaded energy steps is developed inside the Simulink/Stateflow environment. A good agreement is found in the comparison between theoretical model and experiments conducted on prototypes produced by means of drawings directly obtained from 3D CAD models. To compare these results to other energy harvesting devices found in Literature, the same device adapted with symmetric configuration is derived. Empirical formulas to measure efficiency are evaluated for this device and compared with Literature results. The accurate modeling of the energy conversion device is a breakthrough in the modeling of these kinds of devices and allows to reach interesting power/volume ratios: small dimensions (about one cubic centimeter) and relatively high power output (more than one milliwatt). © 2011 SAE International.

This paper presents a multi-physic modeling of an electromechanical energy scavenging device able to supply energy inside car tires for wireless sensors. A permanent magnet, connected to the inner liner of a tire, is accelerated along a guide by the tire deformation during car motion; by interacting with coils it generates a power which is conditioned by a proper electronic interfaced to an external load. The original approach implemented in this kind of device is the nonlinear dynamic properties designed and controlled: adaptive resonance in function of car velocity is optimized for increasing its global efficiency. The energy conversion process takes into account the simulation of different phenomena such as: non linear dynamic and adaptive resonant behavior of the seismic mass, electromagnetic and magneto-static coupling between moving mass and coils, transfer of the generated power to an external load by means of a nonlinear circuit interface. An integrated model of the cascaded energy steps is developed inside the Simulink/Stateflow environment. A good agreement is found in the comparison between theoretical model and experiments conducted on prototypes produced by means of drawings directly obtained from 3D CAD models. To compare these results to other energy harvesting devices found in Literature, the same device adapted with symmetric configuration is derived. Empirical formulas to measure efficiency are evaluated for this device and compared with Literature results. The accurate modeling of the energy conversion device is a breakthrough in the modeling of these kinds of devices and allows to reach interesting power/volume ratios: small dimensions (about one cubic centimeter) and relatively high power output (more than one milliwatt). Copyright © 2011 SAE International.

This paper presents a very compact electro-mechanical wideband energy harvester optimized for tire applications. The energy conversion process of the device takes into account the simulation of different phenomena like: non linear dynamic and adaptive resonant behavior of the seismic mass, electromagnetic and magneto-static coupling between floating magnetic mass and coils, transfer of the generated power to an external load by means of a nonlinear circuit interface. The paper is focused on the pneumatic effects of the floating magnet sliding into a calibrated guide. A convenient choice of clearance between moving and fixed parts can be used to create an effective air brake preventing or softening shocks with end stops and to modify system dynamic. A block-oriented Simulink®, experimentally validated, model has been realized to predict scavenger device performance and to optimize design parameters. Equivalent linearized stiffness and damping factors due to pneumatic effects have been modeled in the lumped parameters system to get a simplified model and to formalize relations with the geometrical characteristics. Analysis of the effect of several nonlinearities at different vehicle speed have been performed.

Keywords: Adaptive resonance , Electro-mechanical device , Energy scavenger

The paper deals with the investigation of the influence of geometrical and dimensional errors on performance of the Tracta coupling. It is one of the most simple constant-velocity joints which has been used in front-wheel drive automobiles, all-wheel drive military vehicles, heavy vehicles and various other applications. The proposed study is based on building and simulating a parametric spatial multibody model of the full joint. Both kinematic and dynamic behaviour have been investigated. Five different linear and angular errors have been studied. The sensitivity of kinema-tics and dynamics irregularities to these errors has been computed and summarized in design charts. The results can be used in optimal toleran-ce allocation and accurate vehicle system simulation with the coupling joint sub-model.

Keywords: Mechanical error , Multibody model , Tolerance , Tracta joint

Thanks to the high latitude of the location the new scenario of the Svalbard Islands as well as that of the already operative Swedish launch base is very close to becoming a principal launching site for Long Duration Ballooning (LDB) arctic campaigns. LDB flights, rather than mid latitude flights that last several hours have become a suitable framework for all efforts to create low cost campaigns. The scientific world, which uses balloons to record measurements beyond the atmosphere, needs both frequently scheduled campaigns and an optimized organization capable of reducing flight costs. It is obvious that a reducing of general costs means keeping in mind, during all design phases, versatility and the standardization of common facilities such as gondola frame as well as the protection of the solar panels upon landing etc. The multi-user payload is certainly the first step for reducing launch costs. Each balloon is launched as much as possible when its payload hosts a number of experiments that weight just a little less than its maximum lifting capacity, apart from the necessary their mutual compatibility. A second step, concerns the optimization of the gondola frame design. It must manufacture gondolas easy to assemble, transport and as well as be easy to modify in shape in order to host a different combination of a given number of experiments, once these have been selected by a scientific authority for the same balloon. The new concept in designing platform which takes advantage of special mechanical elements that are capable both of jointing different beam lengths and of distributing tensile or compression stress only is proposed. The gondola can be assembled simply by only cutting structural aluminum beams into different lengths. Differences between traditional rigid structures and the new concept of construction are pointed out, as a reduction in the total weight and as an easy way to balance the gondola almost without adding extra weight. An example of how the new mechanical joint works and how its behavior closely approximates to the theoretical one is also demonstrated. The study is devoted to design the platform of one of the next balloon experiments (funded by ASI): The Large Scale Polarization Explorer (LSPE).

Composite materials have increasingly become more common in ground transportation. As this occured thicker panels, as compared to composite panels used in aviation, become necessary in order to withstand high impact loads and day to day degradation. The effectiveness of these panels was often limited by the strength of the joint in which the panel was attached to the frame of the vehicle. Investigating methods of reducing strain concentrations within these joints would increase the effectiveness in using composite materials in ground transportation applications by increasing the load necessary for joint failure to occur. In this study, fiber optic strain gages were embedded in a composite panel along the bearing plane of a thick, single-lap, bolted joint. The gages allow for the strain profile above the hole to be determined experimentally. Several clearance values were then implemented in the bolt to determine their effect on the strain concentrations. Strain increased at every gage, by nearly the same proportion, when clearance was increased from zero to three percent. When clearance was further increased to five percent strain only continued to increase at gages three and four, with one and two remaining similar in value to what was seen at three percent clearance. Ultimately, like in thin composite panels, the zero percent clearance condition was the stiffest. © 2010 Society for Experimental Mechanics Inc.

In this paper the optimization process of a new High Energy Absorption Rear Underrun Protective Device called HEARUPD is discussed. The main objectives of the HEARUPD design optimization process have been related to the reduction in car decelerations (high crashworthiness) and avoiding the car underrun (high structure stability). In the implemented optimization process, the crash between an economy car (GEO Metro) and the rear part of a truck has been simulated by numerical models. A linear function of the decelerations measured on the car has been used as objective to minimize, the main dimensional values of the rear underrun protective device, instead, have been chosen as design variables. The Simplex Method has been used as optimization technique. At the end, a detailed analysis of the optimized model has been also performed. The obtained results have shown the HEARUPD, in comparison with a reference device, is able to dissipate a higher quantity of energy, reducing both the deceleration peaks and the frontal car crushing. © Organizing Committee of TMCE 2010 Symposium.

Keywords: Crash test , Finite element method analyses , Optimization , Rear underrun protective device , Simplex method , Truck

A fully mechanical, infinitely variable transmission (IVT) based on the use of an oscillating inertia is described. The system includes a four-bar linkage mechanism, an epicyclic gear train, and a pair of one-way clutches. The IVT can be used in place of both gearbox and clutch in self-propelled vehicles. A mathematical model is presented. Numerical simulations compare the behavior of a car fitted with a manual gearbox and the same car fitted with the IVT.

Mixed Reality (MR) technologies allow us to create different environments, by merging real and virtual objects, and can be successfully used for the assessment of industrial products during the product development phases. This paper describes the integration of a MR environment including an industrial robotic arm for the ergonomics assessment of the driving seat in the automotive field. The robotic arm has been used to configure the MR environment automatically while guaranteeing the correct merging between real and virtual objects and the repeatability of the testing sessions. The user's presence, near an industrial robot, arises some issues on the safety and on the human-robot interaction that we have been addressed in order to improve the performing of the ergonomic test. Finally, the developed system has been validated through some testing sessions with end users to verify the effectiveness of our solution. © 2010 IEEE.

In the Approach Control Area an important match for reducing aviation environmental impact is played. Aircraft Sequencing Problem (or Aircraft Landing Problem) has been widely studied for the last years in order to find the optimal sequence that maximizes the number of landing aircraft in the time unit. The model we propose is based on no-wait Job- Shop Scheduling with sequence dependent machine set up time and release date. In our model STAR and SID are divided into air segments: runways and air segments of arrival and departure procedures are modeled as machines, airplanes are considered as job with release date. Each machine i processes an Aircraft/Job and produces a cost for the environment. The impact of the pollution in each element of the grid map depends on the related machine. The "green" sensitivity of each grid map element is defined by using numerical models. Starting from existing Job-Shop Scheduling models, by means of elitary Genetic Algorithm, the number of movements in the time unit is optimized to manage the Approach airspace. Finally, an experimental analysis is presented, it has been performed on a case study of Bologna airport terminal area.

Keywords: Aircraft sequencing , Job-shop scheduling

Since 1989 the military scene has substantially changed: There are many nimble and dynamic threats as opposed to the former deployment of each state army. Therefore, this leads to the need of permanent surveillance and monitoring of large areas associated with the capability of a fast combat reaction and this demand is usually performed by deploying both surveillance and ground attack aircrafts. Fighter employment increases the mission costs, because of their oor flight endurance, so it is necessary to use many aircraft; moreover, these vehicles are equested to have a very low radar and infrared signature. On the other hand, surveillance aircraft usually have a very limited attack capability, so there is a dead time between the detection of a threat and the action, with a consequent tactical inefficiency. This paper shows a preliminary analysis referred to an unmanned vehicle with a variable geometry configuration, named VGV (Variable Geometry Vehicle), that aims at matching thehigh endurance capability of surveillance aircrafts with the high performances and survivability of fighter-ground attack aircrafts. The performance analysis of an open and a closed configuration has been undertaken and a conceptual study has been afforded in order to find a mechanical solution to move the outer portion of the wing and inserting it into the trailing edge of the fixed part in order to change the geometry of the aircraft in flight. The proposed design solution is innovative because it matches two different configurations in a unique aircraft. A new unmanned system concept is proposed, with a variable wing geometry which can move from a typical surveillance configuration to a combat one. © 2010 by the International Council of Aeronautical Sciences - ICAS.

Keywords: Morphing aircraft , Preliminary study , UAV

This paper presents a multi-physic modeling of an electromechanical energy scavenging device. A permanent magnet, connected to the inner liner of a tyre, is accelerated along a guide by the tyre deformation during car motion; by interacting with coils it generates a power which is conditioned by a proper electronic interfaced to an external load. The energy conversion process takes into account the simulation of different phenomena like: dynamic behavior of the seismic mass, electromagnetic coupling between moving mass and coils, transfer of the generated power to an external load by means of a nonlinear circuit interface. An integrated model of the cascaded energy steps is developed inside the Simulink environment. A good agreement is found in the comparison between theoretical model and experiments. The accurate modeling of the energy conversion device is a breakthrough in the modeling of these kinds of devices and allows to reach interesting power/volume ratios: small dimensions (about one cubic centimeter) and relatively high power output (more than one milliwatt). © 2006 IEEE.

Keywords: Adaptive resonance , electro-mechanical device , energy scavenger

The big effort spent by researchers towards green vehicles, capable to reduce pollutant emissions and fuel consumption, is directed to the analysis of hybrid electrical vehicles. The design of hybrid vehicles drive train requires a complete system analysis including the control of the energy given from the on board source, the optimization of the electric and electronic devices installed on the vehicle and the design of all the mechanical connections between the different power sources to reach required performances. The aim of this paper is to point out some results obtained from the energetic model and from the experimental tests performed on the plug-in hybrid electrical vehicle (PHEV), realized, in prototypal version, at the Dipartimento di Meccanica of the Politecnico di Milano [1]. In particular the paper focuses the attentions on the benefits achieved with a Start&Stop energy management strategy. © 2010 Springer-Verlag Berlin Heidelberg.

Keywords: Energetic model , Energy control strategy , Plug-in hybrid hev , Pollutant emission

In this paper, the propulsive motility characteristics and the corresponding motion equations of a self-designed sub-mini underwater robot were analyzed. And the disturbance observer was used in propulsive motility control of the underwater robot. According to feedback control principle and dynamic performance index of controlled object, the disturbance observer parameter was designed. Digital simulation of propulsion system indicated that system had a better inhibition effect to the disturbance and the propulsive motility control performance of the underwater robot had also been improved. So all the experimental results showed that the disturbance observer has good robustness, also it is very useful to deal with disturbance rejection, which shows its practical value and good performance in motion control. © 2010 Springer-Verlag Berlin Heidelberg.

Keywords: Disturbance observer , Propulsion control , Simulation platform , Sub-mini underwater robot

This paper presents the results of an extended method of measurement on a tyre for an off-road vehicle 175/82 R16, inserting Prescale paper at the contact with the ground. The experimental analysis of the pressures is carried out, in a cross-sectional direction, in five zones corresponding to the middle of the single dowels that constitute the tread. The results are analysed by means of suitable software so as to refer easily to the value of the pressure. The obtained results are critically analysed and the results are compared with those obtained by the formulae of Rowland and MacLaurin, and by the nominal pressure at the ground, concluding that the expression of MMP for vehicles on wheels is simply to consider a pointer of the performances, in comparison with other vehicles or wheels, rather than a real prediction of the pressure on the ground. Furthermore, a good agreement is found between the tyre deflection calculated and measured experimentally. © IMechE 2009.

Keywords: Behaviour of the tyre , MMP , NGP , Prescale paper

The present paper deals with the manufacturing process of a railway carriage. In the first part of the paper, the authors focus on a "virtual railway factory" that uses a very innovative assembly cycle, if compared to the traditional manufacturing processes in the railway field. The case study refers to a railway carriage consisting of four modules, that are singularly set up of furnishings and other systems in dedicated workplaces. On one hand, the virtual simulation has highlighted several critical aspects to be improved, in order to achieve a greater feasibility and to reduce time and cost. On the other hand, the designers have been able to evaluate the movements of the parts and the assembly sequences of the components, by considering each geometric, functional and technological constraint and also some safety requirements. The second part of the paper deals with the simulation of the assembling operations and the analysis of tolerance chains, which have been performed through a Computer Aided Tolerancing system. In particular, the precision requirements have been also evaluated and we have compared the accumulation of dimensional and geometric deviations when using both rivets and traditional welds to fasten the modules. © 2009 Springer-Verlag.

Keywords: Computer Aided Tolerancing , Train design , Virtual manufacturing

In this paper, an overall description of the design of a robotic hand is discussed, with particular attention to the required sensory subsystem, its integration within the mechanical structure of the hand and the required control architecture. Different solutions for the joint configuration and the structure of the tendon network adopted for the transmission system are present together with three types of sensors applied on the finger and on the actuators. The integrated design of the hand finger and the sensors is reported and the motivations leading to this particular implementation are thoroughly addressed, taking into account both the mechanical constraints and the control requirements.

Keywords: Robot control , Robotic design , Robotic hands , Sensor systems , Sensors integration

A fully mechanical infinitely variable transmission (1VT) based on the use of an oscillating inertia is described. The system includes a four-bar linkage mechanism, an epicyclic gear train and a pair of one-way clutches. The proposed IVT can be used in place of both gear-box and clutch in self-propelled vehicles. A basic model is used for a first attempt sizing of the transmission kinematic parameters. A more accurate model, achieved using Bond Graphs, is used to investigate the dynamic effect of inertias, one-way clutch compliance, and minor design changes in the kinematic parameters. Finally, simulations compare the behavior of a car fitted with a manual gear-box and the same car fitted with the proposed IVT. © 2008 by ASME.