Dynamics of Front-and-Rear-Wheel-Independent-Drive-Type Electric Vehicles at the Time of Failure

In this paper, the failsafe performance of front-and-rear-wheel-independent-drive-type electric vehicles (FRID EVs) is clarified from a practical viewpoint through vehicle dynamics analysis under various road conditions and experiments on a running test course. Dynamic analyses at the time of failure were performed under severe road conditions by comparing the vehicle trajectories of FRID EVs with those of conventional EVs, i.e., two- and four-wheel motor drive-type EVs. The analyzed results show that after failure, FRID EVs continue to run safely and stably; all of the conventional EVs deviate from the travel lane in less than 2 s, which is not sufficient time for an ordinary driver to steer the vehicle to safety after being notified about vehicle failure. Using a prototype FRID EV with practical specifications, failsafe performance at the time of failure was evaluated on test courses, including roads having an ultra-low friction coefficient (μ). The experimental results showed that even if failure occurred while cornering and when running on low- μ roads, the FRID EV continued to run stably. These results proved that FRID EVs could ensure safety at the time of failure under practical running conditions.