]ged[ elgnA hctiP0Technical Awards：2022 JSAE Award The Outstanding Technical Paper Award - A Study on Pitch Characteristic to Reduce Line Trace Deviation in Small Steering AngleFig.9 Pitch Sensitivity Experimental Scene4. Hypothesis for reducing variations in line trace deviations using vehicle pitch motion4.2 Hypothesis of pitch characteristics to reduce 91104Fig.10 Driver’s Sensitivity for Pitch Motionvariation in line trace deviationstargeted driving line.In this study, based on the vehicle movements in the six translational and rotational motion directions, the movement to convey to the driver as visual information on behalf of the yaw movement of the vehicle that the vehicle is responding immediately after the start of the yaw movement was examined. First, the roll, pitch, and bounce motions were selected as candidates, excluding the plane motions in the front–back and left–right directions, which directly affect the travel trace of the vehicle, such as the yaw-direction motion. Subsequently, referring to previous studies 2) where human sensitivity was investigated, the motion in the pitch direction, to which it was reported that humans have the same high visual sensitivity as the yaw-direction motion, was fi nally selected.In previous literature 3), 4), it was reported that the feeling of steering, or the equivalent characteristics, could be improved by imparting a downward pitch to the vehicle during steering, as compared to the cases where no pitch motion was provided or an upward pitch was provided. Therefore, in this study, downward pitch motion was imparted to the vehicle during steering.The measurement results are presented in Fig. 10. The experimentally specifi ed pitch rates (eight specifi cations) are provided on the horizontal axis, whereas the pitch angles sensed by the driver at each pitch rate are denoted on the vertical axis. The measurement data obtained from the 25 experimental evaluators (drivers) are indicated by the dots, and the average values are connected by the solid line. For the highest pitch rate of 0.3°/s, the results of the push-button switch operation 4.1 Experiments on driver sensitivity to pitch motionTo determine the minimum pitch motion that a driver can detect, a sensitivity experiment was conducted using a driving simulator. The experimental setup is depicted in Fig. 9. When a constant downward pitch was provided to the vehicle, the drivers were instructed to gaze at the front view of the screen and to press the switch at hand the moment they sensed the pitch movement. A total of eight experiments with different pitch rates, ranging from an extremely low pitch rate of 0.0125°/s to a relatively high pitch rate of 0.3°/s, were conducted fi ve times each, and the pitch angles sensed by the drivers were recorded for each trial.and the evaluation comments confi rmed that all the drivers could feel the pitch movement as soon as it was initiated; therefore, the data in Fig. 10 can be considered as the operational time differences of the drivers between the moment at which the pitch rate of 0.3°/s was generated and the time at which the button was pressed by the individual drivers. The average value (0.51 s) of the operation times for all the drivers was subtracted from all the experimental data for correction.At low angular velocities with pitch rates of 0.05°/s or less, all the drivers sensed the movement at a pitch angle of 0.15°–0.2° (refer to the left side of the graph); the drivers could not sense pitch rates lower than 0.05°/s and the movement was detected for the fi rst time by the size of the integrated pitch angle. By contrast, at a high pitch rate of 0.3°/s, the drivers sensed the movement with almost no pitch angle (see the right side of the graph), which is likely because the drivers could detect the speed at this pitch rate, as described above. The central region between these two regions is considered as the section where the drivers could sense the pitch rate and the pitch angle as a whole; hence, the sensitivity graph presents a downward-sloping line connecting the two regions. Next, using this sensitivity line, the pitch motion that enables drivers to sense the initiation of yaw motion was hypothesized.The pitch characteristics were hypothesized based on the pitch motion required for drivers to recognize a steering input and sense the vehicle response near a steering angle of 1° (at which the yaw motion commences and increases). Although various generated pitch motion patterns can be considered, such as steering angle proportionality, steering wheel angle rate proportionality, and the addition of non-linearity to each, this study aimed to verify the mechanism in the simplest possible manner and selected the pitch angle (downward) proportional to the steering angle, shown in Fig. 11, to formulate a hypothesis of the required proportionality constant. In addition, the experimental results of our Vehicle Pitch Motion0.70.60.50.40.30.20.10-0.1-0.20.050.10.150.2Pitch rate [deg/s]0.250.3No.88 (2022) NISSAN TECHNICAL REVIEW
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