Wearable IMU-Derived Kinematic Reference Profiles of Lower-Limb Kick and Wipe Gestures for Contactless Automotive Tailgate Activation.

Contactless automotive tailgate activation relies on recognizing intentional lower-limb gestures near the rear bumper, yet these systems are developed and evaluated from sensor-specific recordings rather than from the underlying human movement, so quantitative, sensor-independent kinematic reference profiles for these gestures are lacking. This study establishes wearable inertial measurement unit (IMU)-derived reference profiles of two tailgate-activation gestures: a forward kick and a lateral wipe. Lower-body motion was recorded in 56 adult participants using a seven-sensor Xsens Awinda configuration under application-oriented conditions, yielding 6879 segmented movements. To the best of our knowledge, this is among the most extensive of such datasets, providing a sensor-independent, joint- and segment-level movement reference. Both gestures shared a common sagittal structure dominated by knee, ankle, and hip flexion/extension, with mean knee flexion/extension of 45.9∘ for kick and 42.3∘ for wipe movements. Wipe gestures differed through markedly larger non-sagittal components, with hip abduction/adduction of 17.2∘ versus 7.7∘ and ankle internal/external rotation of 16.6∘ versus 8.7∘, confirmed in every participant (p<0.001). Foot-segment kinematics showed the highest velocities, with a mean resultant foot velocity of approximately 1.8m/s. These profiles provide a quantitative biomechanical basis for benchmarking gesture-recognition sensor systems, informing detection-window and threshold selection, and enabling standardized, repeatable testing of contactless automotive HMI systems.