It is widely acknowledged that drivers should remain in the control loop before automated vehicles completely meet real-world operational conditions. This paper presents an "indirect shared control" framework for steer-by-wire vehicles, which allows the control authority to be continuously shared between the driver and automation through an weighted-input-summation method. A "best-response" driver steering model based on model predictive control (MPC) for indirect shared control is proposed. Unlike any conventional driver model for manual driving, this model assumes that drivers can learn and incorporate the controller strategy into their internal model for predictive path following. The analytic solution to the driver model is provided to enable off-line simulations. A driving-simulator experiment was conducted to demonstrate the advantages of the indirect shared control system in a highway lane-keeping task. The result showed that the proposed indirect shared control method was effective to improve the subjects' lane-keeping performance and reduce steering control effort. The proposed driver steering model was also validated by the experiment data, which produced a smaller prediction error than the conventional MPC driver model.

Motion analysis is increasingly applied to spine musculoskeletal models using kinematic constraints to estimate individual intervertebral joint movements, which cannot be directly measured from the skin surface markers. Traditionally, kinematic constraints have allowed a single spinal degree of freedom (DOF) in each direction, and there has been little examination of how different kinematic constraints affect evaluations of spine motion. Thus, the objective of this study was to evaluate the performance of different kinematic constraints for inverse kinematics analysis. We collected motion analysis marker data in seven healthy participants (4F, 3M, aged 27-67) during flexion-extension, lateral bending, and axial rotation tasks. Inverse kinematics analyses were performed on subject-specific models with 17 thoracolumbar joints allowing 51 rotational DOF (51DOF) and corresponding models including seven sets of kinematic constraints that limited spine motion from 3 to 9DOF. Outcomes included: (1) root mean square (RMS) error of spine markers (measured vs. model); (2) lag-one autocorrelation coefficients to assess smoothness of angular motions; (3) maximum range of motion (ROM) of intervertebral joints in three directions of motion (FE, LB, AR) to assess whether they are physiologically reasonable; and (4) segmental spine angles in static ROM trials. We found that RMS error of spine markers was higher with constraints than without (p < 0.0001) but did not notably improve kinematic constraints above 6DOF. Compared to segmental angles calculated directly from spine markers, models with kinematic constraints had moderate to good intraclass correlation coefficients (ICCs) for flexion-extension and lateral bending, though weak to moderate ICCs for axial rotation. Adding more DOF to kinematic constraints did not improve performance in matching segmental angles. Kinematic constraints with 4-6DOF produced similar levels of smoothness across all tasks and generally improved smoothness compared to 9DOF or unconstrained (51DOF) models. Our results also revealed that the maximum joint ROMs predicted using 4-6DOF constraints were largely within physiologically acceptable ranges throughout the spine and in all directions of motions. We conclude that a kinematic constraint with 5DOF can produce smooth spine motions with physiologically reasonable joint ROMs and relatively low marker error.

Spinal intervertebral joints are complex structures allowing motion in multiple directions, and many experimental studies have reported moment-rotation response. However, experimental methods, reporting of results, and levels of the spine tested vary widely, and a comprehensive assessment of moment-rotation response across all levels of the spine is lacking. This review aims to characterize moment-rotation response in a consistent manner for all levels of the human spine. A literature search was conducted in PubMed for moment versus rotation data from mechanical testing of intact human cadaveric intervertebral joint specimens in flexion-extension, lateral bending, and axial rotation. A total of 45 studies were included, providing data from testing of an estimated 1,648 intervertebral joints from 518 human cadavers. We used mixed-effects regression analysis to create 75 regression models of moment-rotation response (25 intervertebral joints × 3 directions). We found that a cubic polynomial model provides a good representation of the moment-rotation behavior of most intervertebral joints, and that compressive loading increases rotational stiffness throughout the spine in all directions. The results allow for the direct evaluation of intervertebral ranges of motion across the whole of the spine for given loading conditions. The random-effects outcomes, representing standard deviations of the model coefficients across the dataset, can aid understanding of normal variations in moment-rotation responses. Overall these results fill a large gap, providing the first realistic and comprehensive representations of moment-rotation behavior at all levels of the spine, with broad implications for surgical planning, medical device design, computational modeling, and understanding of spine biomechanics.

设计了一个实用的模拟驾驶同步装置,该装置的主要部分将Biopac生理仪UIM100C模块输出端产生的方波同时送入该模块输入端、驾驶模拟器输入端,并点亮面部视频视野中的发光二极管.该装置应用于实验教学,为相关人员了解实验环境、合理设计实验提供了便利;该装置应用于科研实验,确保了实验结果的准确性.

The effects of fatigue on a driver's autonomic nervous system (ANS) were investigated through heart rate variability (HRV) measures considering the difference of sex. Electrocardiogram (ECG) data from 18 drivers were recorded during a simulator-based driving experiment. Thirteen short-term HRV measures were extracted through time-domain and frequency-domain methods. First, differences in HRV measures related to mental state (alert or fatigued) were analyzed in all subjects. Then, sex-specific changes between alert and fatigued states were investigated. Finally, sex differences between alert and fatigued states were compared. For all subjects, ten measures showed significant differences (Mann-Whitney U test, p < 0.01) between different mental states. In male and female drivers, eight and four measures, respectively, showed significant differences between different mental states. Six measures showed significant differences between males and females in an alert state, while ten measures showed significant sex differences in a fatigued state. In conclusion, fatigue impacts drivers' ANS activity, and this impact differs by sex; more differences exist between male and female drivers' ANS activity in a fatigued state than in an alert state.

This study seeks to examine human vibration response using a musculoskeletal model that appropriately considers stretch reflex. The stretch reflex is modeled with a feedback control approach, and integrated into a generic musculoskeletal model to study the active muscle forces during seated whole body vibration. The model is used to investigate the effects of stretch reflex gain, vibration frequency and vibration magnitude on transmissibility from the seat to upper body and lower body and on muscle activations. The overall model is validated by comparison with thoracic and lumbar muscle activities measured in human participants during whole body vibration. The simulation results were consistent with the experimental results that the peak transmissibility occurred at resonance frequency of 5-6 Hz, and were in line with other experimental studies that found a primary resonance of 4-6 Hz. Furthermore, the peak normalized Electromyography (EMG) level accorded with the activation level for both thoracic and lumbar regions. What's more, an increase of primary resonance frequency was observed with increasing gains of stretch reflex. In contrary, the peak seat transmissibility of the upper body and lower body had a significant reduction. The major contribution of this model is that the proposed stretch reflex model provides a useful method to consider muscle active response in whole body vibration simulation. This may be used in future studies to better understand how stretch reflex affects spinal loading in a variety of conditions.

Stretch reflex is an important factor that influences the biomechanical response of the human body under whole-body vibration. However, there is a lack of quantitative evaluation at lower frequencies. Thus, the aim of this study was to investigate the effects of vibration on the stretch reflex and, in particular, to explore the quantitative relationship between dynamic muscle responses and low-frequency vibrations. The gastrocnemius muscle of 45 Sprague-Dawley rats was dissected. Sinusoidal vibrations of five discrete frequencies (2~16 Hz) with peak-to-peak amplitudes of 1 mm were applied to the gastrocnemius muscles with 2 mm or 3 mm prelengthening. Variables including dynamic muscle force, vibration acceleration, and displacement were recorded in two conditions, with and without the stretch reflex. Results showed that the dynamic muscle forces decreased by 20% on average for the 2 mm prelengthening group after the stretch reflex was blocked and by 24% for the 3 mm prelengthening group. Statistical analysis indicated that the amplitude of dynamic muscle force in the “with stretch reflex” condition was significantly larger than that in the “without stretch reflex” condition (p<0.001). The tension-length curve was found to be a nonlinear hysteresis loop that changed with frequency. The phase difference between the dynamic muscle force and the length change was affected significantly by vibration frequency (p<0.01), and the minimum frequency was 4–8 Hz. Experimental results of this study could benefit musculoskeletal model by providing a theoretical support to build a stretch reflex model for low-frequency vibration.

To evaluate the effects of driver fatigue on the autonomic nervous system (ANS), Poincare plot indices of heart rate variability (HRV) were investigated. A total of 20 volunteers were recruited to perform a 60-min duration driving experiment on a high-fidelity driving simulator with ECG recorded. The Poincare plot derived from RR intervals of ECG was quantified by measuring SD1, SD2, SD2/SD1, and S. The results showed that all four indices increased significantly (Mann-Whitney U test, p < 0.01) in fatigue state compared to an alert state. Poincare plot indices seem able to distinguish drivers' mental state and have potential prospective in ECG based driving fatigue detection systems.

通过心率变异性(HRV)的非线性特征,研究了疲劳对驾驶入自主神经系统(ANS)的影响.招募被试进行模拟驾驶实验,记录实验过程中的心电信号.通过Poincaré散点图、近似熵和样本熵等非线性方法,提取13个HRV特征.分析所有被试不同精神状态HRV特征的差异,研究特定性别的被试从清醒状态到疲劳状态HRV特征的变化,分别比较清醒和疲劳状态HRV特征的性别差异.对所有被试,5个特征在疲劳状态显著(Mann-Whitney U检验,p＜0.01)上升;男性2个特征在疲劳状态显著上升;女性3个特征在疲劳状态显著上升.清醒状态仅有1个特征在男性与女性之间存在显著性差异,而疲劳状态有5个特征存在显著性差异.驾驶入在疲劳状态ANS的变异性和/或复杂度增加,并且存在性别差异.与清醒状态相比,男性与女性ANS的变异性和/或复杂度在疲劳状态存在更多差异.

Early detection of drowsy driving is an important issue for driving safety. Quantitative electroencephalography (EEG) is an attractive method for detecting brain activity changes. However, further study is still needed to evaluate the feasibility of wearable devices that can detect drowsy driving in real-world settings. This study sought to determine whether convenient EEG recording locations are sensitive in detecting brain activity changes associated with drowsy driving and to characterise these EEG changes. Twenty-two healthy adult subjects were recruited to participate in a car-following task using a driving simulator. EEG data were recorded from four locations, two frontals (Fp1, Fp2) and two temporals (T3, T4) of the brain while driving. The results showed that the increase of activity, decrease of and activity and a decrease of spectral edge frequency at 90% were found in the drowsy state compared to the alert state (paired t-tests, p<0.05). Effect sizes for EEG changes were larger at the temporal locations compared to frontal locations. This suggests temporal locations can be feasible recording locations for wearable monitoring devices to detect drowsy driving.

The characteristics of electroencephalograph (EEG) parameters among drowsy drivers were investigated to deifne physiologic index of driving fatigue. Quantitative EEG (qEEG) analysis techniques were used among 22 subjects using a driving simulator to extractδ band power and 90% spectral edge frequency (SEF90) and to analyze the parameters' changes during drowsy driving and the differences from various recording locations by using binary logistic regression, discriminant classiifcation, and receiver operating characteristic (ROC) curve. The results show that 60 minutes’ mono- environment driving lets to driving drowsiness with increase of relativeδ band power and decrease of SEF90. The EEG quantitative changes recorded at the temporal regions are more than that recorded at the frontal regions. Therefore, the increase of normalizedδ band power can be used as an indicator to discriminate the alert from drowsy state during driving. Decrease of SEM90 can be another indicator to determine the drowsiness during driving.

通过去趋势波动分析（DFA）研究驾驶员疲劳状态的心率变异性信号和脑电信号特征。22名被试在驾驶模拟器上进行模拟驾驶作业,采集驾驶过程中的心率变异性和脑电信号并进行离线分析。Wilcoxon符号秩检验用于分析清醒和疲劳两种状态间DFA标度指数的差异,受试者工作曲线（ROC）分析用于确定DFA区分疲劳驾驶和清醒驾驶的能力。结果表明:疲劳状态时,心率变异性和脑电信号的标度指数显著增加（Wilcoxon符号秩检验,p＜0.01）;心率变异性和脑电信号标度指数的ROC下面积最大分别为0.75和0.78。DFA的标度指数具有应用于驾驶疲劳监测系统的前景。

驾驶员腰部的肌肉力、关节力等负载与驾驶舒适性密切相关,但难以直接测量.本文中建立了驾驶员肌肉骨骼生物力学模型,提出了一种基于Matlab-OpenSim联合仿真的驾驶员与座椅界面接触力和摩擦力计算求解方法,并通过人椅接触压力测试和接触界面摩擦力与腰椎关节压力仿真对上述模型和方法进行验证.结果表明,本文中提出的驾驶员肌肉骨骼生物力学模型和人椅界面接触负载的计算方法可有效解决行驶工况下驾驶员腰部负载的定量评估问题,对驾驶室空间布局和舒适性设计具有重要工程应用价值.

在现有Christophy脊柱肌骨模型的基础上创建了可求解腰部关节力、肌肉载荷的驾驶员生物力学模型,通过Matlab-OpenSim联合仿真求解了驾驶员人椅接触界面接触反力及摩擦力,从关节反力及腰部肌肉负载的角度尝试解释了身高、体质量、腰靠凸起厚度对舒适度影响的内在机理.结果表明:驾驶员腰部载荷随体质量的增加近线性增加,但与身高的相关度较低;4 cm凸起腰靠支撑下的驾驶员较2 cm凸起腰靠支撑下的腰部肌肉群等效载荷平均降低了7.4％,腰部椎间关节力平均降低了18.6％.所提出的仿真方法可以实现不同腰靠支撑下腰部载荷的定量评估,适用于指导人机工程中座椅腰靠的舒适性设计.