Past, Present, and Future of Simultaneous Localization And Mapping: Towards the Robust-Perception Age

Simultaneous Localization and Mapping (SLAM)consists in the concurrent construction of a model of the environment (the map), and the estimation of the state of the robot moving within it. The SLAM community has made astonishing progress over the last 30 years, enabling large-scale real-world applications, and witnessing a steady transition of this technology to industry. We survey the current state of SLAM. We start by presenting what is now the de-facto standard formulation for SLAM. We then review related work, covering a broad set of topics including robustness and scalability in long-term mapping, metric and semantic representations for mapping, theoretical performance guarantees, active SLAM and exploration, and other new frontiers. This paper simultaneously serves as a position paper and tutorial to those who are users of SLAM. By looking at the published research with a critical eye, we delineate open challenges and new research issues, that still deserve careful scientific investigation. The paper also contains the authors' take on two questions that often animate discussions during robotics conferences: Do robots need SLAM? and Is SLAM solved

A synopsis of test results and knowledge gained from the Phase-0 CSI evolutionary model

The Phase-0 CSI Evolutionary Model (CEM) is a testbed for the study of space platform global line-of-sight (LOS) pointing. Now that the tests have been completed, a summary of hardware and closed-loop test experiences is necessary to insure a timely dissemination of the knowledge gained. The testbed is described and modeling experiences are presented followed by a summary of the research performed by various investigators. Some early lessons on implementing the closed-loop controllers are described with particular emphasis on real-time computing requirements. A summary of closed-loop studies and a synopsis of test results are presented. Plans for evolving the CEM from phase 0 to phases 1 and 2 are also described. Subsequently, a summary of knowledge gained from the design and testing of the Phase-0 CEM is made

Limited Bandwidth Wireless Communication Strategies for Structural Control of Seismically Excited Shear Structures

Structural control is used to mitigate unwanted vibrations in structures when large excitations occur, such as high winds and earthquakes. To increase reliability and controllability in structural control applications, engineers are making use of semi-active control devices. Semi-active control gives engineers greater control authority over structural response versus passive controllers, but are less expensive and more reliable than active devices. However, the large numbers of actuators required for semi-active structural control networks introduce more cabling within control systems leading to increased cost. Researchers are exploring the use of wireless technology for structural control to cut down on the installation cost associated with cabling. However wireless communication latency (time delays in data transmissions) can be a barrier to full acceptance of wireless technology for structural control. As the number of sensors in a control network grows, it becomes increasingly difficult to transmit all sensor data during a single control step over the fixed wireless bandwidth. Because control force calculations rely on accurate state measurements or estimates, the use of strategic bandwidth allocation becomes more necessary to provide good control performance. The traditional method for speeding up the control step in larger wireless networks is to spatially decentralize the network into multiple subnetworks, sacrificing communication for speed. This dissertation seeks to provide an additional approach to address the issue of communication latency that may be an alternative, or even a supplement, to spatial decentralization of the control network. The proposed approach is to use temporal decentralization, or the decentralization of the control network over time, as opposed to space/location. Temporal decentralization is first presented with a means of selecting and evaluating different communication group sizes and wireless unit combinations for staggered temporal group communication that still provide highly accurate state estimates. It is found that, in staggered communication schemes, state estimation and control performance are affected by the network topology used at each time step with some sensor combinations providing more useful information than others. Sensor placement theory is used to form sensor groups that provide consistently high-quality output information to the network during each time step, but still utilize all sensors. If the demand for sensors to communicate data outweighs the available bandwidth, traditional temporal and spatial approaches are no longer feasible. This dissertation examines and validates a dynamic approach for bandwidth allocation relying on an extended, autonomous and controller-aware, carrier sense multiple access with collision detection (CSMA/CD) protocol. Stochastic parameters are derived to strategically alter back-off times in the CSMA/CD algorithm based on nodal observability and output estimation error. Inspired by data fusion approaches, this second study presents two different methods for neighborhood state estimation using a dynamic form of measurement-only fusion. To validate these wireless structural control approaches, a small-scale experimental semi-active structural control testbed is developed that captures the important attributes of a full-scale structure

다중 센서 항법시스템을 위한 연합형 불변 확장칼만필터

학위논문(석사) -- 서울대학교대학원 : 공과대학 항공우주공학과, 2022.2. 박찬국.This thesis presents the federated invariant extended Kalman filter (IEKF) using multiple measurements. IEKF has superior estimation performance compared to EKF through the definition of state variables on matrix Lie group while using the framework of the EKF. The IEKF enables trajectory independent estimation when left- or right-invariant measurements are used with proper invariant error selection. As a result, the IEKF ensures the convergence and accuracy of estimation, even when the estimation error is large. Most IEKF studies assumed the use of single aiding measurement. However, navigation systems often use multiple aiding sensors to improve estimation performance in applications. When left- and right-invariant measurements are used simultaneously, implementing the LIEKF or RIEKF with a centralized filter structure causes some terms of the measurement matrix dependent on the current estimates, which results in IEKF losing its trajectory independent advantage. On the other hand, when a decentralized filter structure, especially a federated filter structure, is applied, the estimation becomes trajectory independent through separate update of each measurement in the local filters. This thesis proposes a fusion method of IEKF using the federated filter structure for simultaneous use of left- and right-invariant measurements. The performance of the proposed fusion method is validated through simulations. The error convergence and accuracy of the proposed method and the centralized IEKF are compared.본 논문에서는 다수의 보정 센서를 사용하는 항법 시스템을 위한 연합형 불변 확장 칼만필터의 구현을 제안한다. 불변 확장 칼만필터는 일반적인 확장 칼만필터의 프레임워크는 그대로 사용하면서 상태변수를 행렬 리 그룹 상에서 정의하여 확장 칼만필터 대비 우수한 추정 성능을 가진다. 좌불변 혹은 우불변 측정치를 사용할 때 이에 적합한 불변 오차 정의를 선택하여 구현한다면 궤적 독립적인 추정이 가능하다. 대부분의 불변 확장 칼만필터에 대한 연구들은 단일 보정 센서의 사용을 가정한다. 그런데 실제 적용에 있어, 항법 시스템은 추정 성능을 향상하기 위해 다수의 보정 센서를 사용하는 경우가 많다. 좌불변 측정치와 우불변 측정치가 모두 사용되는 상황이라면, 중앙집중형 좌불변 확장 칼만필터와 우불변 확장 칼만필터는 모두 추정치에 영향을 받는 측정치 행렬을 사용하게 된다. 이로 인해 불변 확장칼만필터가 갖는 가장 큰 장점인 궤적 독립 특성을 잃는다. 반면에 연합형 필터 구조를 사용하면 각 측정치에 할당된 국소 필터에서 적절한 필터로 각 측정치를 처리할 수 있다. 따라서 이 논문에서는 불변 확장 칼만필터의 연합형 구조 구현을 제안한다. 리 그룹의 성질을 고려하는 적절한 융합 방식을 사용한 구조를 제안하며, 그 성능을 시뮬레이션을 통해 확인한다. 제안한 방식과 중앙집중형 불변 확장 칼만필터를 수렴성과 추정 정확도의 관점에서 비교하였다.Chapter 1 Introduction 1 1.1 Motivation 1 1.2 Objectives and contributions 3 Chapter 2 Related Works 5 2.1 Invariant extended Kalman filter (IEKF) 5 2.2 Federated filter 7 Chapter 3 Framework of invariant EKF 9 3.1 Mathematical preliminaries 9 3.2 States and model 10 3.2.1 Matrix Lie group states 10 3.2.2 Process model 12 3.2.3 Measurement model 15 3.2.4 Adjoint 16 3.3 IEKF for inertial navigation 17 3.3.1 IMU states and error states 17 3.3.2 Process model 20 3.3.3 Measurement model 22 3.3.4 Adjoint transformation 27 Chapter 4 IEKF Using Multiple Measurements 28 4.1 Centralized filter implementation 29 4.1.1 Centralized LIEKF 30 4.1.2 Centralized RIEKF 32 4.2 Federated filter implementation 34 4.2.1 Overall structure 34 4.2.2 Fusion process 39 4.3 Numerical simulations 40 4.3.1 Convergence test 43 4.3.2 Comparison of centralized IEKF and EKF 48 4.3.3 Comparison of IEKF and the proposed method 52 Chapter 5 Conclusion 60 5.1.1 Conclusion and summary 60 5.1.2 Future works 61 Bibliography 62 국문초록 68석

Cyber-Physical Codesign of Wireless Structural Control System

Structural control systems play a critical role in protecting civil infrastructure from natural hazards such as earthquakes and extreme winds. Utilizing wireless sensors for sensing, communication and control, wireless structural control systems provide an attractive alternative for structural vibration mitigation. Although wireless control systems have advantages of flexible installation, rapid deployment and low maintenance cost, there are unique challenges associated with them, such as wireless network induced time delay and potential data loss. These challenges need to be considered jointly from both the network (cyber) and control (physical) perspectives. This research aims to develop a framework facilitating cyber-physical codesign of wireless control system. The challenges of wireless structural control are addressed through: (1) a numerical simulation tool to realistically model the complexities of wireless structural control systems, (2) a codesign approach for designing wireless control system, (3) a sensor platform to experimentally evaluate wireless control performance, (4) an estimation method to compensate for the data loss and sensor failure, and (5) a framework for fault tolerance study of wireless control system withreal-time hybrid simulation. The results of this work not only provide codesign tools to evaluate and validate wireless control design, but also the codesign strategies to implement on real-world structures for wireless structural control

Uncertainty Modelling of High-precision Trajectories for Industrial Real-time Measurement Applications

Within the field of large volume metrology, kinematic tasks such as the movement of an industrial robot have been measured using laser trackers. In spite of the kinematic applications, to date most research has focused on static measurements. It is crucial to have a reliable uncertainty of kinematic measurements in order to assess spatiotemporal path deviations of a robot. With this in mind an approach capable of real-time was developed, to determine the uncertainties of kinematic measurements