Road Simulation Techniques for Reproducing Vehicle Behavior at Motocross Running on a Track 2018-32-0051

A Road Simulator was developed with the aim of reproducing actual vehicle behavior while running on motocross (MX) track in a laboratory. Vehicle behavior while running on an MX track is influenced by various inertial forces, such as jump landing, acceleration at full throttle, reduced speed at full braking and so on, and also load input from the rider to handlebars and footrests. As all influences must be considered, these inertial force and external force should be applied to a vehicle in laboratory tests.

To reproduce various inertial forces such as falling inertia at jump landing, longitudinal inertia during acceleration or deceleration, and rider body action on the vehicle, Active restraint systems must be added instead of the traditional method of Road Simulator that controls wheel axle’s vertical and longitudinal directions with actuators. The number of hydraulic actuator was increased, therefore all actuators must be controlled to eliminate any interaction effect of other actuator load and action. Furthermore, introducing actuator control technology that separated Frequency Response Function (FRF) by each running event, eventually the reproduction of MX running in a laboratory test was successful.

As a result, 5% or less of root mean square (RMS) error value has been accomplished by wheel axis load, acceleration and suspension displacement during the reproduction of MX running. Herewith, accumulated fatigue damage degree of each part of frame has also been reproduced with high accuracy. From the above, we have achieved replicated MX running behavior in indoor laboratory tests, namely we are able to produce stable durability tests without variables of course conditions such as rain, differences caused by rider variations, etc. Moreover the test has been able to run consecutively day and night, so the test period has been shortened. In addition, various mechanisms occurring on vehicle have been able to be understood in detail during the approach to reproduce vehicle behavior and load in laboratory testing.