Earthquakes, fire, and floods often cause structural collapses of buildings. The inspection of damaged buildings poses a high risk for emergency forces or is even impossible, though. We present three recent selected missions of the Robotics Task Force of the German Rescue Robotics Center, where both ground and aerial robots were used to explore destroyed buildings. We describe and reflect the missions as well as the lessons learned that have resulted from them. In order to make robots from research laboratories fit for real operations, realistic test environments were set up for outdoor and indoor use and tested in regular exercises by researchers and emergency forces. Based on this experience, the robots and their control software were significantly improved. Furthermore, top teams of researchers and first responders were formed, each with realistic assessments of the operational and practical suitability of robotic systems.

近年来，无人驾驶汽车（UAV）用于众多检查和视频捕获任务。但是，在障碍附近手动控制无人机是具有挑战性的，并且构成了高风险。即使对于自动飞行，全球导航计划也可能太慢，无法应对新感知的障碍。诸如风之类的干扰可能会导致与计划中的轨迹偏离。在这项工作中，我们提出了一种快速的预测障碍方法，该方法不取决于更高级别的本地化或映射，并保持无人机的动态飞行功能。它直接在LIDAR范围内实时运行，并通过计算范围图像内的角电位字段来调整当前飞行方向。随后根据轨迹预测和接触时间估计来确定速度幅度。使用硬件式模拟评估我们的方法。它可以使无人机保持安全距离，同时允许比以前直接在传感器数据上运行的反应性障碍物方法更高的飞行速度。

Mohamed Bin Zayed国际机器人挑战（MBZIRC）2020为无人机（无人机）构成了不同的挑战。我们提供了四个量身定制的无人机，专门为MBZIRC的单独空中机器人任务开发，包括自定义硬件和软件组件。在挑战1中，使用高效率，车载对象检测管道进行目标UAV，以捕获来自目标UAV的球。第二个UAV使用类似的检测方法来查找和流行散落在整个竞技场的气球。对于挑战2，我们展示了一种能够自主空中操作的更大的无人机：从相机图像找到并跟踪砖。随后，将它们接近，挑选，运输并放在墙上。最后，在挑战3中，我们的UAV自动发现使用LIDAR和热敏摄像机的火灾。它用船上灭火器熄灭火灾。虽然每个机器人都具有任务特定的子系统，但所有无人机都依赖于为该特定和未来竞争开发的标准软件堆栈。我们介绍了我们最开源的软件解决方案，包括系统配置，监控，强大无线通信，高级控制和敏捷轨迹生成的工具。为了解决MBZirc 2020任务，我们在多个研究领域提出了机器视觉和轨迹生成的多个研究领域。我们介绍了我们的科学贡献，这些贡献构成了我们的算法和系统的基础，并分析了在阿布扎比的MBZIRC竞赛2020年的结果，我们的系统在大挑战中达到了第二名。此外，我们讨论了我们参与这种复杂的机器人挑战的经验教训。

微型航空车（MAV）具有很高的信息收集任务的潜力，以支持搜索和救援方案中的情况意识。在这种情况下，手动控制MAV需要经验丰富的飞行员，并且容易出错，尤其是在真正紧急情况的压力下。灾难情景的条件对于自动MAV系统也充满挑战。通常不知道环境，GNSS可能并不总是可用。我们介绍了一个不依赖全球定位系统的未知环境中自动MAV航班的系统。该方法在多个搜索和救援方案中进行评估，即使在室内和室外区域之间过渡时，也可以进行安全的自动飞行。

The performance of inertial navigation systems is largely dependent on the stable flow of external measurements and information to guarantee continuous filter updates and bind the inertial solution drift. Platforms in different operational environments may be prevented at some point from receiving external measurements, thus exposing their navigation solution to drift. Over the years, a wide variety of works have been proposed to overcome this shortcoming, by exploiting knowledge of the system current conditions and turning it into an applicable source of information to update the navigation filter. This paper aims to provide an extensive survey of information aided navigation, broadly classified into direct, indirect, and model aiding. Each approach is described by the notable works that implemented its concept, use cases, relevant state updates, and their corresponding measurement models. By matching the appropriate constraint to a given scenario, one will be able to improve the navigation solution accuracy, compensate for the lost information, and uncover certain internal states, that would otherwise remain unobservable.

We consider infinite horizon Markov decision processes (MDPs) with fast-slow structure, meaning that certain parts of the state space move "fast" (and in a sense, are more influential) while other parts transition more "slowly." Such structure is common in real-world problems where sequential decisions need to be made at high frequencies, yet information that varies at a slower timescale also influences the optimal policy. Examples include: (1) service allocation for a multi-class queue with (slowly varying) stochastic costs, (2) a restless multi-armed bandit with an environmental state, and (3) energy demand response, where both day-ahead and real-time prices play a role in the firm's revenue. Models that fully capture these problems often result in MDPs with large state spaces and large effective time horizons (due to frequent decisions), rendering them computationally intractable. We propose an approximate dynamic programming algorithmic framework based on the idea of "freezing" the slow states, solving a set of simpler finite-horizon MDPs (the lower-level MDPs), and applying value iteration (VI) to an auxiliary MDP that transitions on a slower timescale (the upper-level MDP). We also extend the technique to a function approximation setting, where a feature-based linear architecture is used. On the theoretical side, we analyze the regret incurred by each variant of our frozen-state approach. Finally, we give empirical evidence that the frozen-state approach generates effective policies using just a fraction of the computational cost, while illustrating that simply omitting slow states from the decision modeling is often not a viable heuristic.

In the present work we propose an unsupervised ensemble method consisting of oblique trees that can address the task of auto-encoding, namely Oblique Forest AutoEncoders (briefly OF-AE). Our method is a natural extension of the eForest encoder introduced in [1]. More precisely, by employing oblique splits consisting in multivariate linear combination of features instead of the axis-parallel ones, we will devise an auto-encoder method through the computation of a sparse solution of a set of linear inequalities consisting of feature values constraints. The code for reproducing our results is available at https://github.com/CDAlecsa/Oblique-Forest-AutoEncoders.

When robots learn reward functions using high capacity models that take raw state directly as input, they need to both learn a representation for what matters in the task -- the task ``features" -- as well as how to combine these features into a single objective. If they try to do both at once from input designed to teach the full reward function, it is easy to end up with a representation that contains spurious correlations in the data, which fails to generalize to new settings. Instead, our ultimate goal is to enable robots to identify and isolate the causal features that people actually care about and use when they represent states and behavior. Our idea is that we can tune into this representation by asking users what behaviors they consider similar: behaviors will be similar if the features that matter are similar, even if low-level behavior is different; conversely, behaviors will be different if even one of the features that matter differs. This, in turn, is what enables the robot to disambiguate between what needs to go into the representation versus what is spurious, as well as what aspects of behavior can be compressed together versus not. The notion of learning representations based on similarity has a nice parallel in contrastive learning, a self-supervised representation learning technique that maps visually similar data points to similar embeddings, where similarity is defined by a designer through data augmentation heuristics. By contrast, in order to learn the representations that people use, so we can learn their preferences and objectives, we use their definition of similarity. In simulation as well as in a user study, we show that learning through such similarity queries leads to representations that, while far from perfect, are indeed more generalizable than self-supervised and task-input alternatives.

While the capabilities of autonomous systems have been steadily improving in recent years, these systems still struggle to rapidly explore previously unknown environments without the aid of GPS-assisted navigation. The DARPA Subterranean (SubT) Challenge aimed to fast track the development of autonomous exploration systems by evaluating their performance in real-world underground search-and-rescue scenarios. Subterranean environments present a plethora of challenges for robotic systems, such as limited communications, complex topology, visually-degraded sensing, and harsh terrain. The presented solution enables long-term autonomy with minimal human supervision by combining a powerful and independent single-agent autonomy stack, with higher level mission management operating over a flexible mesh network. The autonomy suite deployed on quadruped and wheeled robots was fully independent, freeing the human supervision to loosely supervise the mission and make high-impact strategic decisions. We also discuss lessons learned from fielding our system at the SubT Final Event, relating to vehicle versatility, system adaptability, and re-configurable communications.

Deep learning models are known to put the privacy of their training data at risk, which poses challenges for their safe and ethical release to the public. Differentially private stochastic gradient descent is the de facto standard for training neural networks without leaking sensitive information about the training data. However, applying it to models for graph-structured data poses a novel challenge: unlike with i.i.d. data, sensitive information about a node in a graph cannot only leak through its gradients, but also through the gradients of all nodes within a larger neighborhood. In practice, this limits privacy-preserving deep learning on graphs to very shallow graph neural networks. We propose to solve this issue by training graph neural networks on disjoint subgraphs of a given training graph. We develop three random-walk-based methods for generating such disjoint subgraphs and perform a careful analysis of the data-generating distributions to provide strong privacy guarantees. Through extensive experiments, we show that our method greatly outperforms the state-of-the-art baseline on three large graphs, and matches or outperforms it on four smaller ones.