Rollover prevention system dedicated to ATVs on natural ground

In this paper, an algorithm dedicated to light ATVs, which estimates and anticipates the rollover, is proposed. It is based on the on-line estimation of the Lateral Load Transfer (LLT), allowing the evaluation of dynamic instabilities. The LLT is computed thanks to a dynamical model split into two 2D projections. Relying on this representation and a low cost perception system, an observer is proposed to estimate on-line the terrain properties (grip conditions and slope), then allowing to deduce accurately the risk of instability. Associated to a predictive control algorithm, based on the extrapolation of riders action, the risk can be anticipated, enabling to warn the pilot and to consider the implementation of active actions

DETERMINING WHERE INDIVIDUAL VEHICLES SHOULD NOT DRIVE IN SEMIARID TERRAIN IN VIRGINIA CITY, NV

This thesis explored elements involved in determining and mapping where a vehicle should not drive off-road in semiarid areas. Obstacles are anything which slows or obstructs progress (Meyer et al., 1977) or limits the space available for maneuvering (Spenko et al., 2006). This study identified the major factors relevant in determining which terrain features should be considered obstacles when off-road driving and thus should be avoided. These are elements relating to the vehicle itself and how it is driven as well as terrain factors of slope, vegetation, water, and soil. Identification of these in the terrain was done using inferential methods of Terrain Pattern Recognition (TPR), analyzing of remotely sensing data, and Digital Elevation Map (DEM) data analysis. Analysis was further refined using other reference information about the area. Other factors such as weather, driving angle, and environmental impact are discussed. This information was applied to a section of Virginia City, Nevada as a case-study. Analysis and mapping was done purposely without field work prior to mapping to determine what could be assessed using only remote means. Not all findings from the literature review could be implemented in this trafficability study. Some methods and trafficability knowledge could not be implemented and were omitted due to data being unavailable, un-acquirable, or being too coarsely mapped to be useful. Examples of these are Lidar mapping of the area, soil profiling of the terrain, and assessment of plant species present in the area for driven-over traction and tire punctures. The Virginia City section was analyzed and mapped utilizing hyperspectral remotely sensed image data, remote-sensor-derived DEM data was used in a Geographical Information Systems (GIS). Stereo-paired air photos of the study site were used in TPR. Other information on flora, historical weather, and a previous soil survey map were used in a Geographical Information System (GIS). Field validation was used to check findings.The case study's trafficability assessment demonstrated methodologies of terrain analysis which successfully classified many materials present and identified major areas where a vehicle should not drive. The methods used were: Manual TPR of the stereo-paired air photo using a stereo photo viewer to conduct drainage-tracing and slope analysis of the DEM was done using automated methods in ArcMap. The SpecTIR hyperspectral data was analyzed using the manual Environment for Visualizing Images (ENVI) software hourglass procedure. Visual analysis of the hyperspectral data and air photos along with known soil and vegetation characteristics were used to refine analyses. Processed data was georectified using SpecTIR Geographic Lookup Table (GLT) input geometry, and exported to and analyzed in ArcMap with the other data previously listed. Features were identified based on their spectral attributes, spatial properties, and through visual analysis. Inaccuracies in mapping were attributable largely to spatial resolution of Digital Elevation Maps (DEMs) which averaged out some non-drivable obstacles and parts of a drivable road, subjective human and computer decisions during the processing of the data, and grouping of spectral end-members during hyperspectral data analysis. Further refinements to the mapping process could have been made if fieldwork was done during the mapping process.Mapping and field validation found: several manmade and natural obstacles were visible from the ground, but these obstacles were too fine, thin, or small to be identified from the remote sensing data. . Examples are fences and some natural terrain surface roughness - where the terrain's surface deviated from being a smooth surface, exhibiting micro- variations in surface elevation and/or textures. Slope analysis using the 10-meter and 30-meter resolution DEMs did not accurately depict some manmade features [eg. some of the buildings, portions of roads, and fences], evident with a well-trafficked paved road showing in DEM analysis as having too steep a slope [beyond 15°] to be drivable. Some features had been spectrally grouped together during analysis, due to similar spectral properties. Spectral grouping is a process where the spectral class's pixel areas are reviewed and classes which have too few occurrences are averaged into similar classes or dropped entirely. This is done to reduce the number of spectrally unique material classes to those that are most relevant to the terrain mapped. These decisions are subjective and in one case two similar spectral material classes were combined. In later evaluation should have remained as two separate material classes. In field sample collection, some of the determined features; free-standing water and liquid tanks, were found to be inaccessible due to being on private land and/or fence secured. These had to be visually verified - photos were also taken. Further refinements to the mapping could have been made if fieldwork was done during the mapping process. Determining and mapping where a vehicle should not drive in semiarid areas is a complex task which involves many variables and reference data types. Processing, analyzing, and fusing these different references entails subjective manual and automated decisions which are subject to errors and/or inaccuracies at multiple levels that can individually or collectively skew results, causing terrain trafficability to be depicted incorrectly. That said, a usable reference map is creatable which can assist decision makers when determining their route(s)

Unmanned ground vehicles: adaptive control system for real-time rollover prevention

Real-Time Rollover prevention of Unmanned Ground Vehicle (UGV) is very paramount to its reliability and survivability mostly when operating on unknown and rough terrains like mines or other planets.Therefore this research presents the method of real-time rollover prevention of UGVs making use of Adaptive control techniques based on Recursive least Squares (RLS) estimation of unknown parameters, in order to enable the UGVs to adapt to unknown hush terrains thereby increasing their reliability and survivability. The adaptation is achieved by using indirect adaptive control technique where the controller parameters are computed in real time based on the online estimation of the plant’s (UGV) parameters (Rollover index and Roll Angle) and desired UGV’s performance in order to appropriately adjust the UGV speed and suspension actuators to counter-act the vehicle rollover. A great challenge of indirect adaptive control system is online parameter identification, where in this case the RLS based estimator is used to estimate the vehicles rollover index and Roll Angle from lateral acceleration measurements and height of the centre of gravity of the UGV. RLS is suitable for online parameter identification due to its nature of updating parameter estimate at each sample time. The performance of the adaptive control algorithms and techniques is evaluated using Matlab Simulink® system model with the UGV Model built using SimMechanics physical modelling platform and the whole system runs within Simulink environment to emulate real world application. The simulation results of the proposed adaptive control algorithm based on RLS estimation, show that the adaptive control algorithm does prevent or minimize the likely hood of vehicle rollover in real time.Electrical and Mining EngineeringM. Tech. (Electrical Engineering

통합 예측 위험 관리 기반 포텐셜 필드 기법을 이용한 자율 주행 제어 알고리즘 개발

학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 2. 이경수.In recent years, global passenger vehicle sales exceed 60milion units per year. With the increasing number of vehicles on the road, safety has become a focal issue. In order to deal with the safety issue, a number of active safety systems have been developed in passenger vehicles, such as brae assist system (BAS), adaptive cruise control(ACC), lane keeping control(LKS), and collision mitigation(CM). The functionalities of the systems include the assistance in recognizing hazards on roadway e.g. forward vehicles, obstacles, the unexpected lane departure. Beyond the development of each independent safety system, the integrated safety system has been considered nowadays. This dissertation describes design, real-time implementation and test of a fully automated driving algorithm for automated driving in complex urban scenarios and motorways with a satisfactory safety level. The proposed algorithm consists of the following three steps: surround recognition, motion planning, and vehicle control. A full recognition of environment is achieved by data fusion and data interpretation based on the dynamic measurements from the environmental sensors. The recognition of vehicle state including longitudinal, lateral velocity, and position, and driving environment is transformed into a risk potential representation based on probabilistic prediction. The surround recognition system consists of three main modules: object classification, vehicle/non-vehicle tracking and map/lane-based localization. All system modules utilize information from surround sensors close to market such as vision sensors, radars and vehicle sensors. The objective of the motion planning module is to derive an optimal trajectory as a function of time and the surround recognition results. A safety envelope is represented as a complete driving corridor that leads to destination while making sure all objects are either on outside of the left or right corridor bounds. In the case of moving objects such as other traffic participants, their behaviors are anticipated within specific time horizon. The optimal trajectory planning uses the safety envelope as a constraint and computes a trajectory that the vehicle stays in its safe bounds considering drivers pattern and characteristics based on predicted risk potential method. The performance of the proposed algorithm has been verified via computer simulations and vehicle test. From the simulation and vehicle test results, it has been shown that the proposed automated driving control algorithm enhances safety with respect to the potential risk considering driver acceptability.Chapter 1 Introduction 1 1.1 Background and Motivation 1 1.2 Previous Researches 4 1.3 Thesis Objectives 7 1.4 Thesis Outline 9 Chapter 2 Integrated Perception Algorithm 12 2.1 Vehicle Velocity Estimation 15 2.1.1 Longitudinal Velocity Estimation 16 2.1.2 Lateral Velocity Estimation 23 A. Vertical Force Estimation 24 B. Reference Tire Model 25 C. Lateral Velocity Estimation 28 2.2 Perception of Dynamic Driving Environment 33 2.2.1 Vehicle State Prediction 34 2.2.2 Probabilistic Risk Assessment 38 Chapter 3 Development of Integrated Safety Control Algorithm 40 3.1 Integrated Risk Representation 42 3.1.1 Longitudinal and Lateral Collision Risk Indices 44 A. Longitudinal Collision Risk Indices 45 B. Lateral Collision Risk Indices 50 3.1.2 Dynamic Drivable Area Determination via Probabilistic Prediction 56 A. Initial Driving Corridor Decision 56 B. Moving Object Tracking and Prediction 61 C. Dynamic Drivable Area Decision 66 3.2 Desired Motion Determination for Safety Control 70 3.2.1 Potential Field Representation 71 3.2.2 Vehicle Motion Control based on Predictive Risk Potential Energy Function 74 3.2.3 Dynamic Constraints 79 A. Dynamic Constraints of Longitudinal Dynamics 80 B. Dynamic Constraints for lateral stability 81 Chapter 4 Evaluation 86 4.1 Performance Evaluation via Simulation with Multi-traffic Driving Environment 87 4.2 Performance Evaluation via Test Vehicle 91 4.2.1 Test Vehicle Configuration 92 4.2.2 Vehicle Tests 93 Chapter 5 Conclusions and Future Works 103 Bibliography 106 국문초록 113Docto

Robust Control of Nonlinear Systems with applications to Aerial Manipulation and Self Driving Cars

This work considers the problem of planning and control of robots in an environment with obstacles and external disturbances. The safety of robots is harder to achieve when planning in such uncertain environments. We describe a robust control scheme that combines three key components: system identification, uncertainty propagation, and trajectory optimization. Using this control scheme we tackle three problems. First, we develop a Nonlinear Model Predictive Controller (NMPC) for articulated rigid bodies and apply it to an aerial manipulation system to grasp object mid-air. Next, we tackle the problem of obstacle avoidance under unknown external disturbances. We propose two approaches, the first approach using adaptive NMPC with open- loop uncertainty propagation and the second approach using Tube NMPC. After that, we introduce dynamic models which use Artificial Neural Networks (ANN) and combine them with NMPC to control a ground vehicle and an aerial manipulation system. Finally, we introduce a software framework for integrating the above algorithms to perform complex tasks. The software framework provides users with the ability to design systems that are robust to control and hardware failures where preventive action is taken before-hand. The framework also allows for safe testing of control and task logic in simulation before evaluating on the real robot. The software framework is applied to an aerial manipulation system to perform a package sorting task, and extensive experiments demonstrate the ability of the system to recover from failures. In addition to robust control, we present two related control problems. The first problem pertains to designing an obstacle avoidance controller for an underactuated system that is Lyapunov stable. We extend a standard gyroscopic obstacle avoidance controller to be applicable to an underactuated system. The second problem addresses the navigation of an Unmanned Ground Vehicle (UGV) on an unstructured terrain. We propose using NMPC combined with a high fidelity physics engine to generate a reference trajectory that is dynamically feasible and accounts for unsafe areas in the terrain

Applications of MATLAB in Science and Engineering

The book consists of 24 chapters illustrating a wide range of areas where MATLAB tools are applied. These areas include mathematics, physics, chemistry and chemical engineering, mechanical engineering, biological (molecular biology) and medical sciences, communication and control systems, digital signal, image and video processing, system modeling and simulation. Many interesting problems have been included throughout the book, and its contents will be beneficial for students and professionals in wide areas of interest