Characterizing instabilities induced by a four degree-of-freedom all-terrain vehicle simulator

All-terrain vehicles (ATVs) are used widely across the globe for both recreational and occupational purposes. In the U.S. alone, they are associated with approximately 650 deaths and 400,000 total injuries per year. Although specifically designed for off-road use, about three-fifths of ATV-related fatalities occur on public roads, and at least 70% of roadway crashes are not traffic-related. In order to study and better understand the mechanisms that lead to instability and loss of control, a four degree-of-freedom, human in the loop ATV simulator was developed and integrated with a tilt/vibration platform in a real-time interaction. The simulator allowed the study of each individual’s approach to traversing a terrain. Inertial measurement devices were placed on the ATV and platform, and were used to determine acceleration and angular velocity of subjects. The ATV was instrumented with 32 sensors to detect reaction forces applied to the machine at the feet, hands, saddle, and seat. A five-camera motion capture system was used to track posture. Analysis of data showed that a cycle of instability and stability existed as moments of sudden input accelerations caused reactions in the spine and head. Furthermore, component accelerations were analyzed to identify the acceleration of the subject relative to the ATV. The cycle and the time from input acceleration to bracing on the ATV to regain stability served as a baseline for the subject’s reaction to input acceleration and the time between input acceleration and regaining stability. During instability events, peak forces were delayed from the input by as much as 0.5 seconds. In conclusion, a simulator provides a safe, controlled means to study factors that might cause instability. Future investigations comparing data from experienced, adult operators to those with known risk factors could lead to interventions that decrease loss of ATV control and subsequent injury.