Informative path planning for scalar dynamic reconstruction using coregionalized Gaussian processes and a spatiotemporal kernel

The proliferation of unmanned vehicles offers many opportunities for solving environmental sampling tasks with applications in resource monitoring and precision agriculture. Informative path planning (IPP) includes a family of methods which offer improvements over traditional surveying techniques for suggesting locations for observation collection. In this work, we present a novel solution to the IPP problem by using a coregionalized Gaussian processes to estimate a dynamic scalar field that varies in space and time. Our method improves previous approaches by using a composite kernel accounting for spatiotemporal correlations and at the same time, can be readily incorporated in existing IPP algorithms. Through extensive simulations, we show that our novel modeling approach leads to more accurate estimations when compared with formerly proposed methods that do not account for the temporal dimension.Comment: Accepted to IROS 202

Advancing Robot Autonomy for Long-Horizon Tasks

Autonomous robots have real-world applications in diverse fields, such as mobile manipulation and environmental exploration, and many such tasks benefit from a hands-off approach in terms of human user involvement over a long task horizon. However, the level of autonomy achievable by a deployment is limited in part by the problem definition or task specification required by the system. Task specifications often require technical, low-level information that is unintuitive to describe and may result in generic solutions, burdening the user technically both before and after task completion. In this thesis, we aim to advance task specification abstraction toward the goal of increasing robot autonomy in real-world scenarios. We do so by tackling problems that address several different angles of this goal. First, we develop a way for the automatic discovery of optimal transition points between subtasks in the context of constrained mobile manipulation, removing the need for the human to hand-specify these in the task specification. We further propose a way to automatically describe constraints on robot motion by using demonstrated data as opposed to manually-defined constraints. Then, within the context of environmental exploration, we propose a flexible task specification framework, requiring just a set of quantiles of interest from the user that allows the robot to directly suggest locations in the environment for the user to study. We next systematically study the effect of including a robot team in the task specification and show that multirobot teams have the ability to improve performance under certain specification conditions, including enabling inter-robot communication. Finally, we propose methods for a communication protocol that autonomously selects useful but limited information to share with the other robots.Comment: PhD dissertation. 160 page

THE ACA-BASED PID CONTROLLER FOR ENHANCING A WHEELED-MOBILE ROBOT

Wall-following control of mobile robot is an important topic in the mobile robot researches. The wall-following control problem is characterized by moving the robot along the wall in a desired direction while maintaining a constants distance to the wall. The existing control algorithms become complicated in implementation and not efficient enough. Ant colony algorithm (ACA), in terms of optimizing parameters, has a faster convergence speed and features that are easy to integrate with other methods. This paper adopts ant colony algorithm to optimize PID controller, and then selects ideal control parameters. The simulation results based on MATLAB show that the control system optimized by ant colony algorithm has higher efficiency than the traditional control systems in term of RMSE

3D Dubins curves for multi-vehicle path planning

This thesis proposes a unified algorithm for target assignment and path planning in 3D space for multiple Autonomous Underwater Vehicles (AUVs) to visit multiple targets. The multi-target assignment and path planning problem is modeled as a multiple Traveling Salesmen Problem (mTSP) and is usually solved by two separate algorithms: the multiple task assignment problem is first solved by the Genetic Algorithm (GA) using Euclidean distances between the targets; then the 3D path planning problem is solved for each assignment by selecting Dubins curves or other continuity curves. In contrast, this paper embeds the 3D Dubins curve selection into the target assignment step and uses the true path lengths rather than Euclidean distances as the fitness value of the GA. The unified algorithm is implemented by three functions: Function 1 designs a 3D Dubins path for a given target assignment sequence and given incoming-outgoing angles by an innovative rotation method extended from the well-known 2D Dubins curves; Function 2 uses the back-propagation algorithm to choose the shortest path among all possible incoming-outgoing angle combinations for a given target assignment sequence; Function 3 uses the true lengths of the 3D Dubins curves in the Genetic Algorithm (GA) to assign target sequence to multiple AUVs. Computer simulations demonstrate that the proposed algorithm provides better G2 continuity in 3D space than the existing linear or spline interpolation methods. The unified algorithm solves the NP-hard integer programming problem with an affordable computational complexity --Abstract, page iii

Adaptive Sampling For Efficient Online Modelling

This thesis examines methods enabling autonomous systems to make active sampling and planning decisions in real time. Gaussian Process (GP) regression is chosen as a framework for its non-parametric approach allowing flexibility in unknown environments. The first part of the thesis focuses on depth constrained full coverage bathymetric surveys in unknown environments. Algorithms are developed to find and follow a depth contour, modelled with a GP, and produce a depth constrained boundary. An extension to the Boustrophedon Cellular Decomposition, Discrete Monotone Polygonal Partitioning is developed allowing efficient planning for coverage within this boundary. Efficient computational methods such as incremental Cholesky updates are implemented to allow online Hyper Parameter optimisation and fitting of the GP's. This is demonstrated in simulation and the field on a platform built for the purpose. The second part of this thesis focuses on modelling the surface salinity profiles of estuarine tidal fronts. The standard GP model assumes evenly distributed noise, which does not always hold. This can be handled with Heteroscedastic noise. An efficient new method, Parametric Heteroscedastic Gaussian Process regression, is proposed. This is applied to active sample selection on stationary fronts and adaptive planning on moving fronts where a number of information theoretic methods are compared. The use of a mean function is shown to increase the accuracy of predictions whilst reducing optimisation time. These algorithms are validated in simulation. Algorithmic development is focused on efficient methods allowing deployment on platforms with constrained computational resources. Whilst the application of this thesis is Autonomous Surface Vessels, it is hoped the issues discussed and solutions provided have relevance to other applications in robotics and wider fields such as spatial statistics and machine learning in general

Path Planning and Performance Evaluation Strategies for Marine Robotic Systems

The field of marine robotics offers many new capabilities for completing dangerous missions such as deep-sea exploration and underwater demining. The harshness of marine environments, however, means that without effective onboard decision-making, vehicle loss or mission failure are likely. Thus, to enable more autonomous operation while building trust that these systems will perform as expected, this thesis develops improved path planning and testing strategies for two different types of marine robotic platforms. The first portion of the research focuses on improved environmental data collection with an autonomous underwater vehicle (AUV). Gaussian process-based modeling is combined with informative path planning to explore an environment, while preferentially collecting data in regions of interest that exhibit extreme sensory measurements. The performance of this adaptive data sampling framework with a torpedo-style AUV is studied in both simulation and field experiments. Results show that the proposed methodology is able to be fielded on an operational platform and collect measurements in regions of interest without sacrificing overall model fidelity of the full sampling area. The second portion of the research then focuses on autonomous surface vessel (ASV) navigation that must comply with international collision avoidance standards and basic ship handling principles. The approach introduces a novel quantification of good seamanship that is used within an ASV path planner to minimize the collision risk with other vessels. This approach generalizes well to both single-vessel and multi-vessel encounters by avoiding rule-based conditions. The performance of this ASV planning strategy is evaluated in simulation against other baseline planners, and the results of on-water testing with a 29-ft ASV demonstrate that the approach is scalable to real systems. Beyond developing improved path planning frameworks, this research also explores methods for improved testing and evaluation of black-box autonomous systems. Statistical learning techniques such as adaptive scenario generation and unsupervised clustering are used to extract the failure modes of the autonomy from large-scale simulation datasets. Subsequently, changes in these failure modes are tracked in a novel form of performance-based regression testing. The effectiveness of this testing framework is demonstrated on the aforementioned ASV planner by discovering several types of unexpected failures

Environmental Monitoring using Autonomous Vehicles: A Survey of Recent Searching Techniques

Autonomous vehicles are becoming an essential tool in a wide range of environmental applications that include ambient data acquisition, remote sensing, and mapping of the spatial extent of pollutant spills. Among these applications, pollution source localization has drawn increasing interest due to its scientific and commercial interest and the emergence of a new breed of robotic vehicles capable of performing demanding tasks in harsh environments without human supervision. In this task, the aim is to find the location of a region that is the source of a given substance of interest (e.g. a chemical pollutant at sea or a gas leakage in air) using a group of cooperative autonomous vehicles. Motivated by fast paced advances in this challenging area, this paper surveys recent advances in searching techniques that are at the core of environmental monitoring strategies using autonomous vehicles