Renzo Capitani

Handling analysis of a two-wheeled vehicle using MSC.ADAMS/motorcycle

In this article, the results of a virtual analysis of a two-wheeled vehicle are described. A virtual prototype of a Piaggio Liberty 150 4T was built to evaluate the handling behavior during some codified maneuvers. The activity was done with the cooperation of Piaggio & C. SpA and MSC Software. The multibody model was built using MSC.Adams/Motorcycle. It reproduces the original vehicle (geometry, inertia, and spring/damper coefficients) and is fully parametrized. The actions between ground and tires are calculated with the ‘Magic Formula’. The multibody model, controlled applying a steering torque to the handlebar, was tested during some maneuvers (turn, ISO lane change, ‘Figure 8’), and the results were compared with the experimental data acquired with an instrumented vehicle during the same maneuvers. Signal comparison gave a good agreement except for the differences due to the input forces: the multibody model is controlled only with the steering torque, but body movements and feet and hand pressures are applied to the instrumented vehicle.

Design of a Semi Active Differential to Improve the Vehicle Dynamics

Suppressing or limiting the differential action of the differential mechanism is the mostly adopted technique to avoid the skidding of a driving wheel of a vehicle riding on a poorly adherent surface. The devices carrying out this function unbalance the traction force distribution in the differential, generating a yaw torque acting on the vehicle as a secondary effect. If the unbalancing action is electronically controlled, this yaw torque can be used to affect the attitude of car as a torque vectoring technique.In this paper, a purpose built differential is presented and its technical features are highlighted, including the electrohydraulic actuation. Moreover, its torque vectoring capabilities are discussed, basing on the numerical simulation campaign performed deploying this device in a 7 DOFs model of a race car with low ground effect.The results of these simulations are compared with the behavior of the same vehicle equipped with a common passive locking differential, to show that the proposed one and its control logic (which relies on only measurable inputs) are able of improving the handling of the vehicle, in terms of both vehicle stability and linearity with the driver’s inputs. Therefore, this system could be considered as a completion of the common ESC (“Electronic Stability Control) systems to control the vehicle attitude when using the brake system is an inefficient solution.Copyright

Numerical and Experimental Testing of Composite Rings for Reciprocating Compressor Valves

Valves are one of the most critical class of components for the reliability of reciprocating compressors. Many failures of reciprocating compressor valves are due to valve ring failure. Investigating the failure mode of rings is complicated because of the ring composite material properties, which randomly and locally range from orthotropic to anisotropic due to the random disposition of the reinforcement, usually consisting of short fibers.In this paper, a cooperation between GE Oil & Gas and the University of Florence, the results of a numerical simulation campaign will be presented, along with its correlation with the experimental evidence arising from a purpose-built test rig. This work guided the design of a new material for rings, whose characteristics have been tailored based on the results of this experimental and numerical campaign.© 2013 ASME

Analysis of the behaviour of biker protection devices for roadside barriers

Existing roadside barriers generally pose a risk for motorcyclist impacts against them; therefore several devices exist and are intended to mitigate the effects of such impacts. The purpose of the study is to investigate the influence of some impact parameters on device behaviour. A numerical crash scenario, according to UNE135900:2008, was built and the effects of three different biker protection devices were simulated. Numerical models were set up and validated against real test data. A simulation campaign was performed investigating the influence of approach angle and speed. Results showed that injury indexes registered by the dummy during the impact rise as approach angle or speed rises. A regression analysis was carried out and the relationship between impact severity, represented by injury indexes, and both the investigated impact parameters proved to be quadratic. An explicative theory is proposed, pointing at that part of kinetic energy that is associated with the component of approach speed orthogonal to the barrier as the most influent parameter on the device performance.

Vehicle Consumption Evaluation Using Simulation Models Reproducing Gear Management Strategies

The object of this article is the study of the estimated consumption of mean class vehicles through the development of a simulation model, which recreates the behavior of the test driver-vehicle on a predefined mission. The aim of such a model is to reproduce the management of the gears on a defined test ground allowing for the realization of a sensibility analysis regarding some vehicle parameters and to determine the optimum ones for the minimization of consumption depending upon the considered vehicle. The provisional model developed has been realized by integrating a simplified model of the dynamic of the vehicle with an expert system based on Artificial Neural Networks. It is able to reproduce logic and strategies of the test driver for the choice of the gear change.Copyright

Design and testing of an innovative electro-hydraulic actuator for a semi-active differential

The performance of semi-active differential systems is deeply influenced by the way in which they are actuated. Conventional semi-active systems are actuated by pressure-controlled hydraulic actuators that, despite their good dynamical behaviour, are relatively inefficient. In this work, the authors propose an innovative controlled hydraulic pump solution that is able to drastically improve the efficiency and to reduce the overall encumbrances, maintaining very high performance in terms of dynamical behaviour and corresponding frequency response. The authors investigate design criteria of the proposed solution, describe a simulation model and validate design and simulation models with experimental data.

A method to assess and model the risk for road accidents using telematics devices

ABSTRACT Road accident risk assessment is a complex topic due to the large number of factors determining it and to the difficulties to collect data. In addition, most exposure factors influencing crash probability, such as environment and driver characteristics, are dependent on each other, so that it is not intuitive to devise a cause–effect scenario. The use of telematics devices, recently spreading among insurance and rental companies, provides new chances to collect exposure data, to define interpretive models of accident risk, and to explain variables relationships. Using global positioning system (GPS) data available through a long term rental company, the authors studied a sample of 900 vehicles. The authors aggregated raw data (e.g., road type covered, time, speed) in exposure metrics and organized them in a relational database. The authors built a number of multivariate logistic regression models, adopting a strategy to progressively refine them. The authors obtained a relatively high model fits (up to pseudo R2 0.301, Hosmer–Lemeshow p value 0.206) acquiring insights about the nonlinear association between explanatory variables and their outcomes. Interactions between variables were also examined. The results are, in general, in accordance with similar studies; regarding certain observed discrepancies, a discussion is provided to explain their origin, starting from the differences in associating predictors, outcome and interaction variables.

Multibody Performance Optimization of a Formula SAE Car

The dynamic behavior optimization of the Formula SAE car built at the Universita degli Studi di Firenze is discussed. A virtual model was built using MSC Adams Motorsports, in order to simulate the kinematics and dynamics of the car. A data acquisition system was mounted on board to record all the data useful to setup the car and the virtual model too. The multibody approach was coupled with a multi objective optimizer to start a design of experiments that was able to find the robust design that maximizes the performance along the Formula SAE track.Copyright

An integrated artificial neural network–unscented Kalman filter vehicle sideslip angle estimation based on inertial measurement unit measurements

Vehicle dynamics stability control systems rely on the amount of so-called sideslip angle and yaw rate. As the sideslip angle can be measured directly only with very expensive sensors, its estimation has been widely studied in the literature. Because of the large non-linearities and uncertainties in the dynamics, model-based methods are not a good solution to estimate the sideslip angle. On the contrary, machine learning techniques require large datasets that cover the entire working range for a correct estimation. In this paper, we propose an integrated artificial neural network and unscented Kalman filter observer using only inertial measurement unit measurements, which can work as a standalone sensor. The artificial neural network is trained solely with numerical data obtained with a Vi-Grade model and outputs a pseudo-sideslip angle which is used as input for the unscented Kalman filter. This is based on a kinematic model making the filter completely transparent to model uncertainty. A direct integration with integral damping and integral reset value allows the estimation of the longitudinal velocity of the kinematic model. A modification strategy of the pseudo-sideslip angle is then proposed to improve the convergence of the filter’s output. The algorithm is tested on both numerical data and experimental data. The results show the effectiveness of the solution.

Development of a real-time steering system model for driving simulators

Driving simulators have boosted the vehicle design with the introduction of human beings in the simulation loop. For a realistic functioning, the steering system must provide an accurate behaviour, since the hand wheel is a crucial human interface. Despite a large diffusion of steering models, this paper deals with the creation of a specific solution for real-time applications, characterized by precise features as numerical stability and low computational cost. The proposed model is based on a physical structure and considers all the key phenomena, such as the system elasticities, the power steering effects and friction hysteresis, making the model more accurate in terms of steering wheel torque and lateral acceleration than other angle-driven models. Its two degrees of freedom design allows a proper behaviour of the power steering sub-model; another key aspect is the friction model: the use of the LuGre formulation greatly improves accuracy and stability in comparison to the lookup table friction models. Compared to the literature reference torque-driven model, it does not need the use of a torque sensor when implemented in driving simulators having an angle-driven formulation (the input of the steering wheel is its angle and the torque needed is its output), hence it is cheaper to implement; nevertheless, its accuracy is close to state-of-art reference. An original parametrization procedure is proposed since a generalized one is not available in literature; using a steering test-rig, all the model variables are defined. The validation phase combines offline and online simulations, assessing objectively and subjectively the model’s capabilities and showing accurate results in terms of steering wheel torque, lateral acceleration and steering feeling. In addition, a minor contribution of this paper shows how different analyses (steering effort evaluation, experimental data comparison or simulator feedback computation) require different output torques.