Defining the handling qualities of a motorcycle is not an easy task, because it is a global charateristics , determined by different components of the vehicle. Moreover, there is a strong subjective involvement in the use and rating of the motorcycle on behalf of the driver, according to the driving style and sensitivity. Handling is usually associated to the vehicle's response to the control action. First, a prompt response to the control action is required, in terms of lateral accelaration and yaw rate. Experimental tests supply useful data for the comprehension of the real dynamic behaviour of the vehicle. The motorcycle is assumed as a system with some control quantities as inputs (steering angle and steering torque, forward velocity) and some kinematic and dynamic outputs. The behaviour of the motorcycle is thus described by the logical that links inputs to outputs in performing typical maneuvers, such as SLALOM, LANE-CHANGE, STADY TURNING.
SLALOM TEST
In steady-slaloming condition the rider controls the motorcycle through a periodic action on steering system and the vehicle reacts with periodic roll, yaw and lateral motion. Therefore the slalom test constitutes a study of the forced response of the system, where the forcing exitation is represented by steering torque. Motorcyle's response changes both in amplitude and phase as afuction of the forward speed. To study the behaviour of the vehicle in these condition are analyzed specific frequency response function.
LANE CHANGE TEST
The lane change maneuver represents a typically transient maneuver, and strongly depends on driver's skills and riding style. Vraious driving strategies among pilots differ from each other depending on the initial counter-steer and the lean angle between pilot and motorcycle. In very fast manuvers, riders tend to ally to the steering system not only steeriing torques (i.e. torques parallel to the steering axis), but also rolling torques (i.e. perpendicular to steering axis). The phase between yaw rate and steering torque seems to be the components more highly perceived by the rider when carring out such maneuver. In this case are defined special index to evaluating the effort needed to the rider for this maneuver.
STEADY TURNING TEST
The steady turning tests are demonstrated the more efficient to assesing the handling and the behaviour of the vehicle during a corner. Infact input and output quantities are constant and vehicle's response can be measured in useful and repeatable mode. The quantities describing the driver's control action are the steering torque and the driver lean angle, since both trajectory and forward speed are given. Generally, driver's handling feeling is related to the steering effort needed for a certain maneuver. In this case are defined special index to evaluating both over-neutral-under and counter steering charateristic, and the stable or unstable behaviour.
STANDARD INSTRUMENTATION OF MOTORCYCLE
To proceed to the handling analysis is necessary to install some instrumentation on the vehicle. Some sensors, as steering torque sensor, are created for every single vehicle. For telemetry system is used the 2D DataRecording technology (used in MotoGP) , that supply the GPS system and the inertial platform, to measure both acceleration and the angular velocity.
STABILITY
With the same instrumentation previously described, it can perform the Stability Test. It is determined the frequency of the principal vibration's mode out of plane. Experimentally are determined the Weave (oscillating mode of the rear part of the motorcycle, not self excited, in high and constant speed maneuver) and the Wobble frequency (oscillating mode of the front frame, self excited). In the next picture are shown the telemetry data in Weave test.
STABILITA'
With the same instrumentation previously described, it can perform the Stability Test. It is determined the frequency of the principal vibration's mode out of plane. Experimentally are determined the Weave (oscillating mode of the rear part of the motorcycle, not self excited, in high and constant speed maneuver) and the Wobble frequency (oscillating mode of the front frame, self excited). In the next picture are shown the telemetry data in Weave test.
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The following video shows the wobble vibration obtained in the lab on a bench bank developed by Proff. Stefano Pagano e Domenico De Falco (courtesy of prof. Stefano Pagano - Dipartimento di Ingegneria Meccanica per l' Energetica, Napoli)