Analysis of Disengagements in Semi-Autonomous Vehicles: Drivers’ Takeover Performance and Operational Implications

This report analyzes the reactions of human drivers placed in simulated Autonomous Technology disengagement scenarios. The study was executed in a human-in-the-loop setting, within a high-fidelity integrated car simulator capable of handling both manual and autonomous driving. A population of 40 individuals was tested, with metrics for control takeover quantification given by: i) response times (considering inputs of steering, throttle, and braking); ii) vehicle drift from the lane centerline after takeover as well as overall (integral) drift over an S-turn curve compared to a baseline obtained in manual driving; and iii) accuracy metrics to quantify human factors associated with the simulation experiment. Independent variables considered for the study were the age of the driver, the speed at the time of disengagement, and the time at which the disengagement occurred (i.e., how long automation was engaged for). The study shows that changes in the vehicle speed significantly affect all the variables investigated, pointing to the importance of setting up thresholds for maximum operational speed of vehicles driven in autonomous mode when the human driver serves as back-up. The results shows that the establishment of an operational threshold could reduce the maximum drift and lead to better control during takeover, perhaps warranting a lower speed limit than conventional vehicles. With regards to the age variable, neither the response times analysis nor the drift analysis provide support for any claim to limit the age of drivers of semi-autonomous vehicles

Agility Enhancement and Tyre Estimation for Autmotive Vehicles

Every car has its own cornering dynamics, some are oversteered, meaning that they respond more to a steering input, and some are understeered, responding less to a steering input. These dynamics depend on a wide range of parameters, the size and weight of a car and the distribution of the weight to name a few. The main part of this thesis is aimed at controlling the cornering dynamics. More specifically, this thesis deals with increase or decrease the oversteering of a Mercedes car, depending on the situation. This will be achieved by shifting the wheel loads using the Active Body Control, or ABC, of a Mercedes S-class car. During normal driving, an open-loop control scheme will increase the oversteering. As this control scheme will push the car to its limits during cornering, the car might lose control. As the car loses control, the control scheme will shift from increasing the oversteering to decreasing it. When the controller identifies a loss of control, it will shift from the open-loop control scheme to a closed-loop sliding mode controller working to decrease the oversteering. The two controllers require some data which is not measurable. Therefore an observer was used to observe the non-measurable states. The observer used contains a tyre model to be able to calculate the different forces acting on the car. This tyre model contains a parameter set describing the tyres. The last part of this thesis describes a way to choose this parameter set more precisely with least squares estimation of the longitudinal tyre stiffness. This stiffness varies between summer and winter tyres and the estimation of this parameter enables the observer to use different parameter sets for winter and summer tyres

A state-of-the-art review on torque distribution strategies aimed at enhancing energy efficiency for fully electric vehicles with independently actuated drivetrains

© 2019, Levrotto and Bella. All rights reserved. Electric vehicles are the future of private passenger transportation. However, there are still several technological barriers that hinder the large scale adoption of electric vehicles. In particular, their limited autonomy motivates studies on methods for improving the energy efficiency of electric vehicles so as to make them more attractive to the market. This paper provides a concise review on the current state-of-the-art of torque distribution strategies aimed at enhancing energy efficiency for fully electric vehicles with independently actuated drivetrains (FEVIADs). Starting from the operating principles, which include the "control allocation" problem, the peculiarities of each proposed solution are illustrated. All the existing techniques are categorized based on a selection of parameters deemed relevant to provide a comprehensive overview and understanding of the topic. Finally, future concerns and research perspectives for FEVIAD are discussed

Enhanced motorcycle roll stability by use of a reaction wheel actuator

The paper presents a preliminary study on the use of the reaction wheel for improving the roll stability of motorcycles. The development of the controller is based on the dynamics of the reaction wheel pendulum. A feedback linearization approach is employed for the control of the reaction wheel pendulum and the resulting controller is subsequently implemented in a 12 degree-of-freedom non-linear motorcycle model. Simulations reveal the effectiveness of the controller, as well as some problems related to unrealistic power requirements and gyroscopic effects of the reaction wheel during cornering. The latter are treated by introduction of a moving roll-angle reference, while some proposals for reducing the required power to realistic levels are also discussed

Motion Control for a Tracking Fluoroscope System

The tracking fluoroscope system (TFS), patent pending serial No.: 60/606,480; is a vehicle carrying a fluoroscope to take x-rays movies of person’s joints. Fluoroscope, composed by a radiation source and image intensifier, is moved by a total of four servomotors following a subject’s joint. At the same time, vehicle has to follow the subject using two driving-steering servomotor wheels. This thesis is the result of internal research developed at the Mechanical Aerospace Biomedical Engineering Department at the University of Tennessee. The thesis objective is to determine the best control system for TFS subject tracking function in linear translational mode. Kinematic and dynamic models of the system are presented. The kinematic and dynamic control systems are simulated, tested, and compared. A simplified dynamic model is introduced to compare its results with the kinematic model and evaluate if an extensive dynamic model is required. The dynamic model incorporates a tire friction model. Various tests are then carried out to compute the tire model parameters. To overcome some disadvantages presented by the dynamic and kinematic control systems, a stand-off distance controller is introduced and tested. The stand-off distance controller exhibits better performance than the other control systems proposed. Finally, a special setup process is developed and tested to rotate the vehicle in place

Modeling and Control for Vision Based Rear Wheel Drive Robot and Solving Indoor SLAM Problem Using LIDAR

abstract: To achieve the ambitious long-term goal of a feet of cooperating Flexible Autonomous Machines operating in an uncertain Environment (FAME), this thesis addresses several critical modeling, design, control objectives for rear-wheel drive ground vehicles. Toward this ambitious goal, several critical objectives are addressed. One central objective of the thesis was to show how to build low-cost multi-capability robot platform that can be used for conducting FAME research. A TFC-KIT car chassis was augmented to provide a suite of substantive capabilities. The augmented vehicle (FreeSLAM Robot) costs less than $500 but offers the capability of commercially available vehicles costing over$2000. All demonstrations presented involve rear-wheel drive FreeSLAM robot. The following summarizes the key hardware demonstrations presented and analyzed: (1)Cruise (v, ) control along a line, (2) Cruise (v, ) control along a curve, (3) Planar (x, y) Cartesian Stabilization for rear wheel drive vehicle, (4) Finish the track with camera pan tilt structure in minimum time, (5) Finish the track without camera pan tilt structure in minimum time, (6) Vision based tracking performance with different cruise speed vx, (7) Vision based tracking performance with different camera fixed look-ahead distance L, (8) Vision based tracking performance with different delay Td from vision subsystem, (9) Manually remote controlled robot to perform indoor SLAM, (10) Autonomously line guided robot to perform indoor SLAM. For most cases, hardware data is compared with, and corroborated by, model based simulation data. In short, the thesis uses low-cost self-designed rear-wheel drive robot to demonstrate many capabilities that are critical in order to reach the longer-term FAME goal.Dissertation/ThesisDefense PresentationMasters Thesis Electrical Engineering 201

Kinematics-Based Analytical Solution for Wheel Slip Angle Estimation of a RWD Vehicle with Drift

Accurate real-time information of wheel slip angle is essential for various active stability control systems. A number of techniques have been proposed to enhance quality of GPS based estimation. This paper exhibits a novel cost-effective strategy of individual wheel slip angle estimation for a rear-wheel-drive (RWD) vehicle. At any slip condition, the slip angle can be estimated using only measurement of steering angle, front wheel speeds, yaw rate, longitudinal and lateral accelerations, without requiring GPS data. On the basis of zero longitudinal slip at both front tires, the closed-form solutions for direct computation of wheel slip angles were derived via kinematic analysis of a planar four-wheel vehicle, and then primarily verified by computational simulation with prescribed functions of radius of curvature, vehicle speed, sideslip and steering angle. Neither integration nor tire friction model is required for this estimation methodology. In terms of implementation, a 1:10th scaled RWD vehicle was modified so that the steering angle, the front wheel rolling speeds, the vehicle yaw rate and the linear accelerations can be measured. Preliminary experiment was done on extremely random sideslip maneuvers beneath the global positioning using four recording cameras. By comparing with the vision-based reference, the individual wheel slip angles could be well estimated despite extreme tire slip. Other vehicle state variables - radius of curvature, vehicle sideslip and speed - may also be directly obtained from the kinematic relations. This proposed estimation methodology could then be alternatively applied for the full range slip angle estimation in advanced active safety systems