School of Aerospace, Transport and Manufacturing, Cranfield University, Cranfield MK43 0AL, UK.
Jaguar Land Rover Limited, University Road, University of Warwick, Coventry CV4 7AL, UK.
Sensors (Basel). 2017 Nov 22;17(11):2692. doi: 10.3390/s17112692.
Although at present legislation does not allow drivers in a Level 3 autonomous vehicle to engage in a secondary task, there may become a time when it does. Monitoring the behaviour of drivers engaging in various non-driving activities (NDAs) is crucial to decide how well the driver will be able to take over control of the vehicle. One limitation of the commonly used face-based head tracking system, using cameras, is that sufficient features of the face must be visible, which limits the detectable angle of head movement and thereby measurable NDAs, unless multiple cameras are used. This paper proposes a novel orientation sensor based head tracking system that includes twin devices, one of which measures the movement of the vehicle while the other measures the absolute movement of the head. Measurement error in the shaking and nodding axes were less than 0.4°, while error in the rolling axis was less than 2°. Comparison with a camera-based system, through in-house tests and on-road tests, showed that the main advantage of the proposed system is the ability to detect angles larger than 20° in the shaking and nodding axes. Finally, a case study demonstrated that the measurement of the shaking and nodding angles, produced from the proposed system, can effectively characterise the drivers' behaviour while engaged in the NDAs of chatting to a passenger and playing on a smartphone.
虽然目前的法规不允许处于 3 级自动驾驶模式的驾驶员从事次要任务，但将来可能会允许。监测从事各种非驾驶活动（NDA）的驾驶员的行为对于确定驾驶员将能够多好地接管车辆的控制至关重要。常用的基于面部的头部跟踪系统（使用摄像头）的一个限制是，必须能够看到面部的足够特征，这限制了头部运动的可检测角度，从而限制了可测量的 NDA，除非使用多个摄像头。本文提出了一种新颖的基于方位传感器的头部跟踪系统，该系统包括两个设备，其中一个设备测量车辆的运动，另一个设备测量头部的绝对运动。在摇晃和点头轴上的测量误差小于 0.4°，而在滚动轴上的误差小于 2°。通过内部测试和道路测试与基于摄像头的系统进行比较，表明所提出系统的主要优势是能够检测到摇晃和点头轴上大于 20°的角度。最后，一个案例研究表明，所提出系统产生的摇晃和点头角度的测量可以有效地描述驾驶员在与乘客聊天和玩手机等 NDA 活动中的行为。
