Investigation Of Human′s Strategy For Aerial Interception In Virtual Reality

Locomotor interception refers to the behavior of an interceptor moving its entire body in space to approach and touch a moving target.During the interception,interceptors use the currently available intercept information to control their locomotion in real time based on the interception strategy.Previous human interception studies have mainly focused on ground interception,with few studies on the aerial interception.However,flying cars are widely discussed and seen as a new direction to alleviate traffic congestion.Therefore,it is worth investigating whether ordinary people can adapt to the aerial environment and control their movement.This study designed a flying interception task in a virtual reality environment to investigate this issue.In the experimental task,participants controlled their yaw in the horizontal direction,and directly moved up and down without any pitch in the vertical direction to intercept a flying target.This study consisted of three sub-studies.Study 1 investigated the interception strategies used by participants when intercepting flying targets moving at different speeds and directions.Results showed that during the interception,participants maintained a constant target-heading()angle in the horizontal direction,which was consistent with the constant target-heading(CTH)strategy,and kept the target in a constant direction relative to their body midline;they maintained the heading()angle,the bearing()angle and the target-heading()angle constant in the vertical direction,which was consistent with the constant bearing(CB)strategy,and kept the target in a constant direction relative to their eye level.Study 2 further investigated whether participants used the ground as a reference frame when using the CB strategy under horizontal and tilted ground conditions.Results replicated the interception strategies of Study 1 and found the vertical bearing angle relative to the ground didn’t remain constant across horizontal and tilted ground conditions,whereas the vertical bearing angle relative to the horizontal eye level changed in the same direction as the participants’ eye level across different ground conditions.This suggests that participants were not using the ground as a reference frame and their interception performance was more consistent with using their eye level as a reference frame.Study 3 investigated why participants used different interception strategies in the horizontal and vertical directions.This study used two control modes of direct control(moving up and down directly without pitch)and rotation control(moving up and down with pitch)in the vertical direction,where participants’ eye level changes with their vertical heading direction in the rotation control mode,but remaining horizontal in the direct control mode.The results showed that participants used the CTH strategy in the horizontal direction;for the vertical direction,they used the CB strategy in the direct control mode,whereas they used the CTH strategy in the rotation control mode.This suggests that different relationships between the body axis and moving direction under different control modes resulted in different interception strategies,and participants’ interception performance was again consistent with using their eye level as a reference frame in the vertical direction.Based on the results of the above sub-studies,this study draws the following conclusions:(1)participants’ performance is consistent with using the body midline as the reference frame in the horizontal direction while using the eye level as the reference frame in the vertical direction;(2)participants’ locomotor control can be unified in a constant egocentric direction(CED)framework,which suggesting that humans use their body axis as a reference frame and keep the target in a constant egocentric direction for successful aerial interception.In summary,this study investigated human’s interception strategies in the aerial environment based on a flying interception task,clarified the reference frames for interception control,found out the influence of the relationship between the body axis and moving direction on interception strategies,and proposed a constant egocentric direction framework.Moreover,the results of this study could also inspire the design of maneuvers for vehicles such as flying cars to make them more compatible with human motion control habits.