Abstract
Keywords - Motorcycle, Simulator, Wash-out, Multi-body, Dynamics
Abstract.-.In the next future riding simulators will improve safety of transport on two-wheeled vehicles. This paper deals with the motorcycle riding simulator that has been developed at Department of Mechanical Engineering in order to study man-vehicle interaction in safe conditions. The main design choices are discussed, then the research ad development activities carried out to achieve the expected performance are presented; finally, the validation tests are described and discussed.
The simulator consists of four subsystems: a sensors system that monitors riders control actions; a 5 degree-of-freedom mock motorcycle that generates motion cues; a visual system that generates visual cues; a powerful multi-body code that simulates vehicle dynamics. The whole system is governed by a PC. The sensor system includes the handle-bars equipped with strain-gauges that measure the steering torque and three potentiometers that measure the throttle opening angle and the rotations of brake levers. In the first design the posture angle of riders body was not included among the riders control actions, because it has a lower effect than the steering torque.
The signals from these sensors are the inputs of the dynamic simulation code, which is basedon a 11 degree-of-freedom multi-body model of the vehicle and takes into account details of tire-road interaction. The simulation code every 15 ms processes the riding operations performed by the rider and simulates vehicle motion. According to the simulated motion, the simulator gives to the rider the motion sense by means of motion and visual cues.
Motion cues are generated by the servomotors that drive the 5 axes of the mock motorcycle. The steer axis servomotor generates a torque that simulates the resultant of the moments generated by the forces acting on the front section. The pitch axis servomotor makes it possible to simulate the low frequency components of longitudinal acceleration using components of gravity by tilting the mock motorcycle. The roll axis and the lateral displacement servomotors make it possible to simulate lateral acceleration and to give the sensation of roll rate; a specific washout filter was developed. The high-pass acceleration filter transmits to the lateral displacement servomotor only the high frequency motion signals, since the low frequency signals tend to lead to very large displacements. The low frequency signals are transmitted, through a low-pass filter, to the roll servomotor that tilts the mock motorcycle in order to simulate the low frequency acceleration components using components of gravity. The yaw axis servomotor is used to give the sensation of yaw rate.
The visual system consists of a 2x2 m screen placed in front of the rider and a projector. The forward view is presented from the riders point of view and includes buildings and obstacles in order to improve the riding sense. A specific graphic software linked to the multi-body simulation code was developed.