Topological Navigation of Simulated Robots using Occupancy Grid

Formerly I presented a metric navigation method in the Webots mobile robot simulator. The navigating Khepera-like robot builds an occupancy grid of the environment and explores the square-shaped room around with a value iteration algorithm. Now I created a topological navigation procedure based on the occupancy grid process. The extension by a skeletonization algorithm results a graph of important places and the connecting routes among them. I also show the significant time profit gained during the process

Achieving intelligence in mobility

This paper presents an integrated approach to the application of machine learning tasks that can be observed throughout a number of typical applications of mobile robots and puts those tasks into persepective with respect to both existing and newly developed learning techniques. The actual realization of the approach has been carried out on the two mobile robots PRIAMOS and TESEO, which are both operating in a real office environment. In this context, several experimental results are presented. This paper appeared in: IEEE-Expert: Special Track on Intelligent Robotic Systems, Vol. 10, No. 2, April 1995

Policy-Based Planning for Robust Robot Navigation

This thesis proposes techniques for constructing and implementing an extensible navigation framework suitable for operating alongside or in place of traditional navigation systems. Robot navigation is only possible when many subsystems work in tandem such as localization and mapping, motion planning, control, and object tracking. Errors in any one of these subsystems can result in the robot failing to accomplish its task, oftentimes requiring human interventions that diminish the benefits theoretically provided by autonomous robotic systems. Our first contribution is Direction Approximation through Random Trials (DART), a method for generating human-followable navigation instructions optimized for followability instead of traditional metrics such as path length. We show how this strategy can be extended to robot navigation planning, allowing the robot to compute the sequence of control policies and switching conditions maximizing the likelihood with which the robot will reach its goal. This technique allows robots to select plans based on reliability in addition to efficiency, avoiding error-prone actions or areas of the environment. We also show how DART can be used to build compact, topological maps of its environments, offering opportunities to scale to larger environments. DART depends on the existence of a set of behaviors and switching conditions describing ways the robot can move through an environment. In the remainder of this thesis, we present methods for learning these behaviors and conditions in indoor environments. To support landmark-based navigation, we show how to train a Convolutional Neural Network (CNN) to distinguish between semantically labeled 2D occupancy grids generated from LIDAR data. By providing the robot the ability to recognize specific classes of places based on human labels, not only do we support transitioning between control laws, but also provide hooks for human-aided instruction and direction. Additionally, we suggest a subset of behaviors that provide DART with a sufficient set of actions to navigate in most indoor environments and introduce a method to learn these behaviors from teleloperated demonstrations. Our method learns a cost function suitable for integration into gradient-based control schemes. This enables the robot to execute behaviors in the absence of global knowledge. We present results demonstrating these behaviors working in several environments with varied structure, indicating that they generalize well to new environments. This work was motivated by the weaknesses and brittleness of many state-of-the-art navigation systems. Reliable navigation is the foundation of any mobile robotic system. It provides access to larger work spaces and enables a wide variety of tasks. Even though navigation systems have continued to improve, catastrophic failures can still occur (e.g. due to an incorrect loop closure) that limit their reliability. Furthermore, as work areas approach the scale of kilometers, constructing and operating on precise localization maps becomes expensive. These limitations prevent large scale deployments of robots outside of controlled settings and laboratory environments. The work presented in this thesis is intended to augment or replace traditional navigation systems to mitigate concerns about scalability and reliability by considering the effects of navigation failures for particular actions. By considering these effects when evaluating the actions to take, our framework can adapt navigation strategies to best take advantage of the capabilities of the robot in a given environment. A natural output of our framework is a topological network of actions and switching conditions, providing compact representations of work areas suitable for fast, scalable planning.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144073/1/rgoeddel_1.pd

SANTO: Social Aerial NavigaTion in Outdoors

In recent years, the advances in remote connectivity, miniaturization of electronic components and computing power has led to the integration of these technologies in daily devices like cars or aerial vehicles. From these, a consumer-grade option that has gained popularity are the drones or unmanned aerial vehicles, namely quadrotors. Although until recently they have not been used for commercial applications, their inherent potential for a number of tasks where small and intelligent devices are needed is huge. However, although the integrated hardware has advanced exponentially, the refinement of software used for these applications has not beet yet exploited enough. Recently, this shift is visible in the improvement of common tasks in the field of robotics, such as object tracking or autonomous navigation. Moreover, these challenges can become bigger when taking into account the dynamic nature of the real world, where the insight about the current environment is constantly changing. These settings are considered in the improvement of robot-human interaction, where the potential use of these devices is clear, and algorithms are being developed to improve this situation. By the use of the latest advances in artificial intelligence, the human brain behavior is simulated by the so-called neural networks, in such a way that computing system performs as similar as possible as the human behavior. To this end, the system does learn by error which, in an akin way to the human learning, requires a set of previous experiences quite considerable, in order for the algorithm to retain the manners. Applying these technologies to robot-human interaction do narrow the gap. Even so, from a bird's eye, a noticeable time slot used for the application of these technologies is required for the curation of a high-quality dataset, in order to ensure that the learning process is optimal and no wrong actions are retained. Therefore, it is essential to have a development platform in place to ensure these principles are enforced throughout the whole process of creation and optimization of the algorithm. In this work, multiple already-existing handicaps found in pipelines of this computational gauge are exposed, approaching each of them in a independent and simple manner, in such a way that the solutions proposed can be leveraged by the maximum number of workflows. On one side, this project concentrates on reducing the number of bugs introduced by flawed data, as to help the researchers to focus on developing more sophisticated models. On the other side, the shortage of integrated development systems for this kind of pipelines is envisaged, and with special care those using simulated or controlled environments, with the goal of easing the continuous iteration of these pipelines.Thanks to the increasing popularity of drones, the research and development of autonomous capibilities has become easier. However, due to the challenge of integrating multiple technologies, the available software stack to engage this task is restricted. In this thesis, we accent the divergencies among unmanned-aerial-vehicle simulators and propose a platform to allow faster and in-depth prototyping of machine learning algorithms for this drones

A New Approach towards Non-holonomic Path Planning of Car-like Robots using Rapidly Random Tree Fixed Nodes(RRT*FN)

Autonomous car driving is gaining attention in industry and is also an ongoing research in scientific community. Assuming that the cars moving on the road are all autonomous, this thesis introduces an elegant approach to generate non-holonomic collision-free motion of a car connecting any two poses (configurations) set by the user. Particularly this thesis focusses research on "path-planning" of car-like robots in the presence of static obstacles. Path planning of car-like robots can be done using RRT and RRT*. Instead of generating the non-holonomic path between two sampled configurations in RRT, our approach finds a small incremental step towards the next random configuration. Since the incremental step can be in any direction we use RRT to guide the robot from start configuration to end configuration. This "easy-to-implement" mechanism provides flexibility for enabling standard plan- ners to solve for non-holonomic robots without much modifications. Thus, strength of such planners for car path planning can be easily realized. This thesis demon- strates this point by applying this mechanism for an effective variant of RRT called as RRT - Fixed Nodes (RRT*FN). Experiments are conducted by incorporating our mechanism into RRT*FN (termed as RRT*FN-NH) to show the effectiveness and quality of non-holonomic path gener- ated. The experiments are conducted for typical benchmark static environments and the results indicate that RRT*FN-NH is mostly finding the feasible non-holonomic solutions with a fixed number of nodes (satisfying memory requirements) at the cost of increased number of iterations in multiples of 10k. Thus, this thesis proves the applicability of mechanism for a highly constrained planner like RRT*-FN, where the path needs to be found with a fixed number of nodes. Although, comparing the algorithm (RRT*FN-NH) with other existing planners is not the focus of this thesis there are considerable advantages of the mechanism when applied to a planner. They are a) instantaneous non-holonomoic path generation using the strengths of that particular planner, b) ability to modify on-the-fly non-holomic paths, and c) simple to integrate with most of the existing planners. Moreover, applicability of this mechanism using RRT*-FN for non-holonomic path generation of a car is shown for a more realistic urban environments that have typical narrow curved roads. The experiments were done for actual road map obtained from google maps and the feasibility of non-holonomic path generation was shown for such environments. The typical number of iterations needed for finding such feasible solutions were also in multiple of 10k. Increasing speed profiles of the car was tested by limiting max speed and acceleration to see the effect on the number of iterations

준정형화된 환경에서 Look-ahead Point를 이용한 모방학습 기반 자율 내비게이션 방법

학위논문(박사) -- 서울대학교대학원 : 융합과학기술대학원 융합과학부(지능형융합시스템전공), 2023. 2. 박재흥.본 학위논문은 자율주행 차량이 주차장에서 위상지도와 비전 센서로 내비게이션을 수행하는 방법들을 제안합니다. 이 환경에서의 자율주행 기술은 완전 자율주행을 완성하는 데 필요하며, 편리하게 이용될 수 있습니다. 이 기술을 구현하기 위해, 경로를 생성하고 이를 현지화 데이터로 추종하는 방법이 일반적으로 연구되고 있습니다. 그러나, 주차장에서는 도로 간 간격이 좁고 장애물이 복잡하게 분포되어 있어 현지화 데이터를 정확하게 얻기 힘듭니다. 이는 실제 경로와 추종하는 경로 사이에 틀어짐을 발생시켜, 차량과 장애물 간 충돌 가능성을 높입니다. 따라서 현지화 데이터로 경로를 추종하는 대신, 낮은 비용을 가지는 비전 센서로 차량이 주행 가능 영역을 향해 주행하는 방법이 제안됩니다. 주차장에는 차선이 없고 다양한 정적/동적 장애물이 복잡하게 있어, 주행 가능/불가능한 영역을 구분하여 점유 격자 지도를 얻는 것이 필요합니다. 또한, 교차로를 내비게이션하기 위해, 전역 계획에 따른 하나의 갈래 도로만이 주행가능 영역으로 구분됩니다. 갈래 도로는 회전된 바운딩 박스 형태로 인식되며 주행가능 영역 인식과 함께 multi-task 네트워크를 통해 얻어집니다. 주행을 위해 모방학습이 사용되며, 이는 모델-기반 모션플래닝 방법보다 파라미터 튜닝 없이도 다양하고 복잡한 환경을 다룰 수 있고 부정확한 인식 결과에도 강인합니다. 아울러, 이미지에서 제어 명령을 구하는 기존 모방학습 방법과 달리, 점유 격자 지도에서 차량이 도달할 look-ahead point를 학습하는 새로운 모방학습 방법이 제안됩니다. 이 point를 사용함으로써, 모방 학습의 성능을 향상시키는 data aggregation (DAgger) 알고리즘을 별도의 조이스틱 없이 자율주행에 적용할 수 있으며, 전문가는 human-in-loop DAgger 훈련 과정에서도 최적의 행동을 잘 선택할 수 있습니다. 추가로, DAgger 변형 알고리즘들은 안전하지 않거나 충돌에 가까운 상황에 대한 데이터를 샘플링하여 DAgger 성능이 향상됩니다. 그러나, 전체 훈련 데이터셋에서 이 상황에 대한 데이터 비율이 적으면, 추가적인 DAgger 수행 및 사람의 노력이 요구됩니다. 이 문제를 다루기 위해, 가중 손실 함수를 사용하는 새로운 DAgger 훈련 방법인 WeightDAgger 알고리즘이 제안되며, 더 적은 DAgger 반복으로 앞서 언급 것과 유사한 상황에서 전문가의 행동을 더 정확하게 모방할 수 있습니다. DAgger를 동적 상황까지 확장하기 위해, 에이전트와 경쟁하는 적대적 정책이 제안되고, 이 정책을 DAgger 알고리즘에 적용하기 위한 훈련 프레임워크가 제안됩니다. 에이전트는 이전 DAgger 훈련 단계에서 훈련되지 않은 다양한 상황에 대해 훈련될 수 있을 뿐만 아니라 쉬운 상황에서 어려운 상황까지 점진적으로 훈련될 수 있습니다. 실내외 주차장에서의 차량 내비게이션 실험을 통해, 모델-기반 모션 플래닝 알고리즘의 한계 및 이를 다룰 수 있는 제안하는 모방학습 방법의 효용성이 분석됩니다. 또한, 시뮬레이션 실험을 통해, 제안된 WeightDAgger가 기존 DAgger 알고리즘들 보다 더 적은 DAgger 수행 및 사람의 노력이 필요함을 보이며, 적대적 정책을 이용한 DAgger 훈련 방법으로 동적 장애물을 안전하게 회피할 수 있음을 보입니다. 추가적으로, 부록에서는 비전 기반 자율 주차 시스템 및 주차 경로를 빠르게 생성할 수 있는 방법이 소개되어, 비전기반 주행 및 주차를 수행하는 자율 발렛 파킹 시스템이 완성됩니다.This thesis proposes methods for performing autonomous navigation with a topological map and a vision sensor in a parking lot. These methods are necessary to complete fully autonomous driving and can be conveniently used by humans. To implement them, a method of generating a path and tracking it with localization data is commonly studied. However, in such environments, the localization data is inaccurate because the distance between roads is narrow, and obstacles are distributed complexly, which increases the possibility of collisions between the vehicle and obstacles. Therefore, instead of tracking the path with the localization data, a method is proposed in which the vehicle drives toward a drivable area obtained by vision having a low-cost. In the parking lot, there are complicated various static/dynamic obstacles and no lanes, so it is necessary to obtain an occupancy grid map by segmenting the drivable/non-drivable areas. To navigating intersections, one branch road according to a global plan is configured as the drivable area. The branch road is detected in a shape of a rotated bounding box and is obtained through a multi-task network that simultaneously recognizes the drivable area. For driving, imitation learning is used, which can handle various and complex environments without parameter tuning and is more robust to handling an inaccurate perception result than model-based motion-planning algorithms. In addition, unlike existing imitation learning methods that obtain control commands from an image, a new imitation learning method is proposed that learns a look-ahead point that a vehicle will reach on an occupancy grid map. By using this point, the data aggregation (DAgger) algorithm that improves the performance of imitation learning can be applied to autonomous navigating without a separate joystick, and the expert can select the optimal action well even in the human-in-loop DAgger training process. Additionally, DAgger variant algorithms improve DAgger's performance by sampling data for unsafe or near-collision situations. However, if the data ratio for these situations in the entire training dataset is small, additional DAgger iteration and human effort are required. To deal with this problem, a new DAgger training method using a weighted loss function (WeightDAgger) is proposed, which can more accurately imitate the expert action in the aforementioned situations with fewer DAgger iterations. To extend DAgger to dynamic situations, an adversarial agent policy competing with the agent is proposed, and a training framework to apply this policy to DAgger is suggested. The agent can be trained for a variety of situations not trained in previous DAgger training steps, as well as progressively trained from easy to difficult situations. Through vehicle navigation experiments in real indoor and outdoor parking lots, limitations of the model-based motion-planning algorithms and the effectiveness of the proposed method to deal with them are analyzed. Besides, it is shown that the proposed WeightDAgger requires less DAgger performance and human effort than the existing DAgger algorithms, and the vehicle can safely avoid dynamic obstacles with the DAgger training framework using the adversarial agent policy. Additionally, the appendix introduces a vision-based autonomous parking system and a method to quickly generate the parking path, completing the vision-based autonomous valet parking system that performs driving as well as parking.1 INTRODUCTION 1 1.1 Autonomous Driving System and Environments 1 1.2 Motivation 4 1.3 Contributions of Thesis 6 1.4 Overview of Thesis 8 2 MULTI-TASK PERCEPTION NETWORK FOR VISION-BASED NAVIGATION 9 2.1 Introduction 9 2.1.1 Related Works 10 2.2 Proposed Method 13 2.2.1 Bird's-Eye-View Image Transform 14 2.2.2 Multi-Task Perception Network 15 2.2.2.1 Drivable Area Segmentation (Occupancy Grid Map (OGM)) 16 2.2.2.2 Rotated Road Bounding Box Detection 18 2.2.3 Intersection Decision 21 2.2.3.1 Road Occupancy Grid Map (OGMroad) 22 2.2.4 Merged Occupancy Grid Map (OGMmer) 23 2.3 Experiment 25 2.3.1 Experimental Setup 25 2.3.1.1 Autonomous Vehicle 25 2.3.1.2 Multi-task Network Setup 27 2.3.1.3 Model-based Branch Road Detection Method 29 2.3.2 Experimental Results 30 2.3.2.1 Quantitative Analysis of Multi-Task Network 30 2.3.2.2 Comparison of Branch Road Detection Method 31 2.4 Conclusion 34 3 DATA AGGREGATION (DAGGER) ALGORITHM WITH LOOK-AHEAD POINT FOR AUTONOMOUS DRIVING IN SEMI-STRUCTURED ENVIRONMENT 35 3.1 Introduction 35 3.2 Related Works & Background 41 3.2.1 DAgger Algorithms for Autonomous Driving 41 3.2.2 Behavior Cloning 42 3.2.3 DAgger Algorithm 43 3.3 Proposed Method 45 3.3.1 DAgger with Look-ahead Point Composition (State & Action) 45 3.3.2 Loss Function 49 3.3.3 Data-sampling Function in DAgger 50 3.3.4 Reasons to Use Look-ahead Point As Action 52 3.4 Experimental Setup 54 3.4.1 Driving Policy Network Training 54 3.4.2 Model-based Motion-Planning Algorithms 56 3.5 Experimental Result 57 3.5.1 Quantitative Analysis of Driving Policy 58 3.5.1.1 Collision Rate 58 3.5.1.2 Safe Distance Range Ratio 59 3.5.2 Qualitative Analysis of Driving Policy 60 3.5.2.1 Limitations of Tentacle Algorithm 60 3.5.2.2 Limitations of VVF Algorithm 61 3.5.2.3 Limitations of Both Tentacle and VVF 62 3.5.2.4 Driving Results on Noisy Occupancy Grid Map 63 3.5.2.5 Intersection Navigation 65 3.6 Conclusion 68 4 WEIGHT DAGGER ALGORITHM FOR REDUCING IMITATION LEARNING ITERATIONS 70 4.1 Introduction 70 4.2 Related Works & Background 71 4.3 Proposed Method 74 4.3.1 Weighted Loss Function in WeightDAgger 75 4.3.2 Weight Update Process in Entire Training Dataset 78 4.4 Experiments 80 4.4.1 Experimental Setup 80 4.4.2 Experimental Results 82 4.4.2.1 Ablation Study According to τ 82 4.4.2.2 Ablation Study According to ε 83 4.4.2.3 Ablation Study According to α 84 4.4.2.4 Driving Test Results 85 4.4.3 Walking Robot Experiments 86 4.5 Conclusion 87 5 DAGGER USING ADVERSARIAL AGENT POLICY FOR DYNAMIC SITUATIONS 89 5.1 Introduction 89 5.2 Related Works & Background 91 5.2.1 Motion-planning Algorithms for Dynamic Situations 91 5.2.2 DAgger Algorithm for Dynamic Situation 93 5.3 Proposed Method 95 5.3.1 DAgger Training Framework Using Adversarial Agent Policy 95 5.3.2 Applying to Oncoming Dynamic Obstacle Avoidance Task 97 5.3.2.1 Ego Agent Policy 98 5.3.2.2 Adversarial Agent Policy 100 5.4 Experiments 101 5.4.1 Experimental Setup 101 5.4.1.1 Ego Agent Policy Training 102 5.4.1.2 Adversarial Agent Policy Training 103 5.4.2 Experimental Result 103 5.4.2.1 Performance of Adversarial Agent Policy 103 5.4.2.2 Ego Agent Policy Performance Comparisons Trained with / without Adversarial Agent Policy 104 5.5 Conclusion 106 6 CONCLUSIONS 107 Appendix A 110 A.1 Vision-based Re-plannable Autonomous Parking System 110 A.1.1 Parking Spot Detection 112 A.1.2 Re-planning Method 113 A.2 Biased Target-tree* with RRT* Algorithm for Fast Parking Path Planning 115 A.2.1 Introduction 115 A.2.2 Proposed Method 117 A.2.3 Experiments 119 Abstract (In Korean) 143 Acknowledgement 145박

Collective cluster-based map merging in multi robot SLAM

New challenges arise with multi-robotics, while information integration is among the most important problems need to be solved in this field. For mobile robots, information integration usually refers to map merging . Map merging is the process of combining partial maps constructed by individual robots in order to build a global map of the environment. Different approaches have been made toward solving map merging problem. Our method is based on transformational approach, in which the idea is to find regions of overlap between local maps and fuse them together using a set of transformations and similarity heuristic algorithms. The contribution of this work is an improvement made in the search space of candidate transformations. This was achieved by enforcing pair-wise partial localization technique over the local maps prior to any attempt to transform them. The experimental results show a noticeable improvement (15-20%) made in the overall mapping time using our technique

Advances in Robot Navigation

Robot navigation includes different interrelated activities such as perception - obtaining and interpreting sensory information; exploration - the strategy that guides the robot to select the next direction to go; mapping - the construction of a spatial representation by using the sensory information perceived; localization - the strategy to estimate the robot position within the spatial map; path planning - the strategy to find a path towards a goal location being optimal or not; and path execution, where motor actions are determined and adapted to environmental changes. This book integrates results from the research work of authors all over the world, addressing the abovementioned activities and analyzing the critical implications of dealing with dynamic environments. Different solutions providing adaptive navigation are taken from nature inspiration, and diverse applications are described in the context of an important field of study: social robotics