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Path planning models are often only founded by geometric calculations and do not consider the vehicle's limitations. In critical situations, path following is crucial, as a departure from the trajectory can have significant consequences. It is therefore necessary to define trajectories which the vehicle has the capacity to follow, i.e. feasible trajectories. This paper presents a framework for feasible trajectory generation for use in minimum time manoeuvres (MTM). The feasibility of trajectories is evaluated against a Quasi-Steady-State (QSS) acceleration envelope and jerk constraints. The vehicle's dynamics feasibility is assessed through a new exact relation of vehicle trajectory curvature that is expressed relative to a track reference line. The physical restriction of these constraints, relative to the vehicle's transient capabilities, implies that QSS feasibility assessments also extend to the transient vehicle. Minimum curvature trajectories are also reviewed. Results are presented for four examples. First, a constant radius example highlights differences in the minimum curvature cost models. The second example compares minimum curvature trajectories against MTM solutions for the Tempelhof Airport Street Circuit (Berlin), resulting in a new minimum curvature objective. The last two examples, straight road and Adria International Raceway, show that the feasible trajectory model is a good predictor of the QSS handling limits, indicating its ability to define feasible trajectories. The maximum spread of results is $ 3.2\% $ 3.2 %. A friction ellipse model is additionally presented for comparison against the Normal-Tangential-Acceleration (NTA) surface. Friction ellipse results showed to be comparable if the acceleration envelope alignment is sufficient. [ABSTRACT FROM AUTHOR]

Lap-time optimisation programs utilising Quasi-Steady-State (QSS) vehicle models are computationally efficient, though inherent simplifications produce inaccuracies. An analysis of the prediction capabilities of a new QSS lap-time optimisation method is presented. A transient vehicle model is formulated with seven degrees-of-freedom (DOF) dynamics. The QSS vehicle model utilises point-mass dynamics, where accelerations are constrained by a bi-quintic piecewise spline surface produced with an identical transient vehicle model. Notable changes to the development of the new QSS model include, evaluation of the acceleration envelope in natural coordinate frame, and the implementation of a normal jerk limit which acts to artificially mimic the yaw inertia resistance during change of direction manoeuvres. Results of the minimum time solution are shown for 90 ∘ left-hand turn, double lane change and full circuit analysis based on Adria International Raceway. An accuracy improvement against previous QSS models is presented. Minimum time results for the new QSS model are within 0.14 % for left turn, 0.24 % for Adria full circuit, and 0.1 % for double lane change. Optimal accelerations, track centreline offset and velocities are presented and compared. [ABSTRACT FROM AUTHOR]

The assimilation of path planning and motion control is a crucial capability for autonomous vehicles. Pure pursuit controllers are a prevalent class of path tracking algorithms for front wheel steering cars. Nonetheless, their performance is rather limited to relatively low speeds. In this paper, we propose a model predictive active yaw control implementation of pure pursuit path tracking that accommodates the vehicle’s steady state lateral dynamics to improve tracking performance at high speeds. A comparative numerical analysis was under taken between the proposed strategy and the traditional pure pursuit controller scheme. Tests were conducted for three different paths at iteratively increasing speeds from 1 m/s up to 20 m/s. The traditional pure pursuit controller was incapable of maintaining the vehicle stable at speeds upwards of 5m/s. The results show that implementing receding horizon strategy for pure pursuit tracking improves their performance. The contribution is apparent by preserving a relatively constant controller effort and consequently maintaining vehicle stability for speeds up to 100Km/h in different scenarios. A Matlab implementation of the proposed controller and datasets of the experimental paths are provided to supplement this work. [ABSTRACT FROM AUTHOR]

This paper describes a novel manoeuvre planning method to attenuate disturbances acting on occupants of autonomous cars as a result of driving behaviour. New research findings suggested that the passengers in autonomous cars might be more prone to motion sickness and thus overall discomfort. The proposed approach is based on a recently developed novel continuous B-spline path smoothing algorithm for car-like steered robots. Two algorithms are designed for urban driving scenarios and steering between two predefined poses. The resulting paths avoid abrupt changes in steering and longitudinal velocity, by maintaining curvature and its high order continuity. We show that this lead to reduced high frequency disturbances in steering and resulting load disturbances on passengers. The presented novel B-spline manoeuvres outperform other planning methods by reducing lateral acceleration and yaw disturbances. New approach was verified by rigorous simulations, numerical and field experimentation. Tests were repeated for a number of different paths and velocities. The reported results are the first spline based parameterisation methods practically applied for autonomous cars planning and re-planning, then validated using both noisy actuation simulations and field experiments. [ABSTRACT FROM AUTHOR]

This paper presents the dynamic behavior of microcantilever-based microresonators and compares their steady state behavior for polarized and nonpolarized systems at different levels of nonlinearities. A microcantilever, equipped with a time-varying capacitor, makes the microresonator system. The capacitor is activated by a constant polarization voltage, and an alternative actuating voltage. The partial differential equation of motion of the vibrating electrode can be reduced to a highly nonlinear parametric second order ordinary differential equation. The steady state behavior of the microresonator has been analyzed with and without polarization voltage. The main characteristic of the non-polarized model is explained by the stability of the system in parameter plane. A set of stability chart is provided to predict the boundary between the stable and unstable domains. Furthermore, the main characteristic of the polarized model is determination by the period-amplitude relationship of the system. Applying perturbation methods, analytical equations are derived to describe the frequency response of the system, which are suitable to be utilized in parameter study and design. [ABSTRACT FROM AUTHOR]

Fault identification using the emitted mechanical noise is becoming an attractive field of research in a variety of industries. It is essential to rank acoustic feature integration functions on their efficiency to classify different types of sound for conducting a fault diagnosis. The Mel frequency cepstral coefficient (MFCC) method was used to obtain various acoustic feature sets in the current study. MFCCs represent the audio signal power spectrum and capture the timbral information of sounds. The objective of this study is to introduce a method for the selection of statistical indicators to integrate the MFCC feature sets. Two purpose-built audio datasets for squeak and rattle were created for the study. Data were collected experimentally to investigate the feature sets of 256 recordings from 8 different rattle classes and 144 recordings from 12 different squeak classes. The support vector machine method was used to evaluate the classifier accuracy with individual feature sets. The outcome of this study shows the best performing statistical feature sets for the squeak and rattle audio datasets. The method discussed in this pilot study is to be adapted to the development of a vehicle faulty sound recognition algorithm.

Although much research has been devoted to the characterization of the effects of whole-body vibration on seated occupants' comfort, drowsiness induced by vibration has received less attention to date. There are also little validated measurement methods available to quantify whole body vibration-induced drowsiness. Here, the effects of vibration on drowsiness were investigated. Twenty male volunteers were recruited for this experiment. Drowsiness was measured in a driving simulator, before and after 30-min exposure to vibration. Gaussian random vibration, with 1-15 Hz frequency bandwidth was used for excitation. During the driving session, volunteers were required to obey the speed limit of 100 kph and maintain a steady position on the left-hand lane. A deviation in lane position, steering angle variability, and speed deviation were recorded and analysed. Alternatively, volunteers rated their subjective drowsiness by Karolinska Sleepiness Scale (KSS) scores every 5-min. Following 30-min of exposure to vibration, a significant increase of lane deviation, steering angle variability, and KSS scores were observed in all volunteers suggesting the adverse effects of vibration on human alertness level., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Although much is known about human body vibration discomfort, there is little research data on the effects of vibration on vehicle occupant drowsiness. A laboratory experimental setup has been developed. Vibration was applied to the volunteers sitting on the vehicle seat mounted on the vibration platform. Seated volunteers were exposed to a Gaussian random vibration, with 1-15 Hz frequency bandwidth at 0.2 ms(-2) r.m.s., for 20-minutes. Two drowsiness measurement methods were used, Psychomotor Vigilance Test (PVT) and Karolinska Sleepiness Scale (KSS). Significant changes in PVT (p<0.05) and KSS (p<0.05) were detected in all eighteen volunteers. Furthermore, a moderate correlation (r>0.4) was observed between objective measurement (PVT) and subjective measurement (KSS). The results suggest that exposure to vibration even for 20-minutes can cause significant drowsiness impairing psychomotor performance. This finding has important implications for road safety.

This paper presents a method to characterize tissue thermal damage by taking into account the thermal-mechanical effect of soft tissues for thermal ablation. This method integrates the bio-heating conduction and non-rigid motion dynamics to describe thermal-mechanical behaviors of soft tissues and further extends the traditional tissue damage model to characterize thermal-mechanical damage of soft tissues. Simulations and comparison analysis demonstrate that the proposed method can effectively predict tissue thermal damage and it also provides reliable guidelines for control of the thermal ablation procedure.

A large number of independent and interacting factors affect seating comfort such as seat shape, stability, lumbar support and seat height. Although many subjective comfort studies have been conducted, few of them considered seating comfort from its subassembly level. This paper analyzed the automotive seat cushion designed with geared four-bar linkage for the seat height adjustment. The operation torque and lift distance of this mechanism was investigated as 2 major comfort factors. Ten cushions with this kind of design in the market were compared and assessed.

Modeling of thermal-induced mechanical behaviors of soft tissues is of great importance for thermal ablation. This paper presents a method by integrating the heating process with thermal-induced mechanical deformations of soft tissues for simulation and analysis of the thermal ablation process. This method combines bio-heat transfer theories, constitutive elastic material law under thermal loads as well as non-rigid motion dynamics to predict and analyze thermal-mechanical deformations of soft tissues. The 3D governing equations of thermal-mechanical soft tissue deformation are discretized by using the finite difference scheme and are subsequently solved by numerical algorithms. Experimental results show that the proposed method can effectively predict the thermal-induced mechanical behaviors of soft tissues, and can be used for the thermal ablation therapy to effectively control the delivered heat energy for cancer treatment.