Poster Presentation

Prof. Roberto Lot, University of Padova, Italy
Prof. Vittore Cossalter, University of Padova, Italy
Mr. Matteo Massaro, University of Padova, Italy
Mr. Giovanni Dalla Torre, University of Padova, Italy

In races, it is essential to adjust the motorcycle setup to different tracks, weather conditions and rider requirements. Vehicle adjustments are usually based on empirical know-how since decisions should be taken quickly and under pressure. Classical multibody tools cannot be adopted for this purpose because they are very complex to manage and simulations are time consuming. This paper presents a non-conventional multibody software specifically designed for this purpose that allows to easily manage and optimize motorcycle parameters such as suspension characteristics, adjustable plates, etc. This tool, called FastBike Race, contains a detailed multibody model of the motorcycle, including non-linear suspensions, a tire model that works at large camber angles and include the geometry and compliance, a flexible chain transmission, frame compliance. The motorcycle model is optimized and makes it possible not only to make time simulations, but also to compute steady state (i.e. inverse dynamics) and stability analysis at different speeds, longitudinal and lateral accelerations. Since the motorcycle model requires many parameters, data input is organized in two different layers. In the first layer, designed for the vehicle development, all the model features are available to the user, which may specify the geometry, inertia, structural compliance, tire properties, etc. At this level many analysis tools are available (steady state, stability, braking, cornering, kick-back, etc.). A second simplified layer is designed for the pit lane: in this layer most motorcycle parameters are hidden, while only adjustable ones are available (e.g. suspensions preload and stiffness, adjustable plates). The analysis tool includes trim and steady state calculation, suspensions optimization, chatter analysis. The peculiarity of trim and steady state analysis is that solution are found almost instantaneously. Indeed, the solution is obtained by solving the equilibrium equations instead of by integrating the dynamic equations as multibody software normally do. In the setup optimization the user first sets its trim target (e.g. wheelbase, normal trail, rake angle, suspensions travel). Then it defines the adjustable parameters (e.g. spring preload and stiffness, length of the rod linkage, size of adjustable plates), finally the software optimizes these parameters. The optimization process requires a lot of trim evaluations at different speeds and accelerations, anyway the results is available in a short time due to the computation efficiency of the model and inverse dynamics approach. The appropriate modeling of the powertrain makes it possible to simulate the presence of the chatter, a self-excited vibration well known on race motorcycles. Chatter is unwanted since the vibration of the rear and front unsprung could reach 5-10 g at a frequency of 17-22 Hz. This software is actually under testing by a racing team involved in the Italian Speed Championship (CIV).

Poster presentation: Simulation and testing