Reviewerly/exHarmony huggingface dataset:
Global and Reactive Motion Generation with Geometric Fabric Command Sequences

Motion generation seeks to produce safe and feasible robot motion from start to goal. Various tools at different levels of granularity have been developed. On one extreme, sampling-based motion planners focus on completeness - a solution, if it exists, would eventually be found. However, produced paths are often of low quality, and contain superfluous motion. On the other, reactive methods optimise the immediate cost to obtain the next controls, producing smooth and legible motion that can quickly adapt to perturbations, uncertainties, and changes in the environment. However, reactive methods are highly local, and often produce motion that become trapped in non-convex regions of the environment. This paper contributes, Geometric Fabric Command Sequences, a method that lies in the middle ground. It can produce globally optimal motion that is smooth and intuitive, while being also reactive. We model motion via a reactive Geometric Fabric policy that ingests a sequence of attractor states, or commands, and then apply global optimisation over the space of commands. We postulate that solutions for different problems and scenes are highly transferable when conditioned on environmental features. Therefore, an implicit generative model is trained on solutions from optimisation and environment features in a self-supervised manner. That is, faced with multiple motion generation problems, the learning and optimisation are contained within the same loop: the optimisation generates labels for learning, while the learning improves the optimisation for the next problem, which in turn provides higher quality labels. We empirically validate our method in both simulation and on a real-world 6-DOF JACO arm.
Reinforcement Learning-Based Optimal Multiple Waypoint Navigation

In this paper, a novel method based on Artificial Potential Field (APF) theory is presented, for optimal motion planning in fully-known, static workspaces, for multiple final goal configurations. Optimization is achieved through a Reinforcement Learning (RL) framework. More specifically, the parameters of the underlying potential field are adjusted through a policy gradient algorithm in order to minimize a cost function. The main novelty of the proposed scheme lies in the method that provides optimal policies for multiple final positions, in contrast to most existing methodologies that consider a single final configuration. An assessment of the optimality of our results is conducted by comparing our novel motion planning scheme against a RRT* method.
Task-Driven Graph Attention for Hierarchical Relational Object Navigation

Embodied AI agents in large scenes often need to navigate to find objects. In this work, we study a naturally emerging variant of the object navigation task, hierarchical relational object navigation (HRON), where the goal is to find objects specified by logical predicates organized in a hierarchical structure-objects related to furniture and then to rooms-such as finding an apple on top of a table in the kitchen. Solving such a task requires an efficient representation to reason about object relations and correlate the relations in the environment and in the task goal. HRON in large scenes (e.g. homes) is particularly challenging due to its partial observability and long horizon, which invites solutions that can compactly store the past information while effectively exploring the scene. We demonstrate experimentally that scene graphs are the best-suited representation compared to conventional representations such as images or 2D maps. We propose a solution that uses scene graphs as part of its input and integrates graph neural networks as its backbone, with an integrated task-driven attention mechanism, and demonstrate its better scalability and learning efficiency than state-of-the-art baselines.
RPGD: A Small-Batch Parallel Gradient Descent Optimizer with Explorative Resampling for Nonlinear Model Predictive Control

Nonlinear model predictive control often involves nonconvex optimization for which real-time control systems require fast and numerically stable solutions. This work proposes RPGD, a Resampling Parallel Gradient Descent optimizer designed to exploit small-batch parallelism of modern hardware like neural accelerators or multithreaded microcontrollers. After initialization, it continuously maintains a small population of good control trajectory solution candidates and improves them using gradient information, followed by selection of elite candidates and resampling of the others. In simulation on a cartpole, the OpenAI Gym mountain car, a Dubins car with obstacles, and a high input dimensional 2D arm, it produces similar or lower MPC costs than benchmark cross-entropy and path integral methods. On a physical cartpole, it performs swing-up and cart target following of the pole, using either a differential equation or multilayer perceptron as dynamics model. RPGD drives an F1TENTH simulated race car at near-optimal lap times and a real F1TENTH car in laps around a cluttered room. We study alterations of RPGD's building blocks to justify its composition. RPGD compute time in Python with TensorFlow optimization running on CPU is 2 to 4 times slower than the FORCESPRO commercial embedded solver.
Improved Event-Based Dense Depth Estimation via Optical Flow Compensation

Event cameras have the potential to overcome the limitations of classical computer vision in real-world applications. Depth estimation is a crucial step for high-level robotics tasks and has attracted much attention from the community. In this paper, we propose an event-based dense depth estimation architecture, Mixed-EF2DNet, which firstly predicts inter-grid optical flow to compensate for lost temporal information, and then estimates multiple contextual depth maps that are fused to generate a robust depth estimation map. To supervise the network training, we further design a smoothing loss function used to smooth local depth estimates and facilitate estimating reasonable depth for pixels without events. In addition, we introduce SE-resblocks in the depth network to enhance the network representation by selecting feature channels. Experimental evaluations on both real-world and synthetic datasets show that our method performs better in terms of accuracy when compared to state-of-the-art algorithms, especially in scene detail estimation. Besides, our method demonstrates excellent generalization in cross-dataset tasks.
Towards Consistent Batch State Estimation Using a Time-Correlated Measurement Noise Model

In this paper, we present an algorithm for learning time-correlated measurement covariances for application in batch state estimation. We parameterize the inverse measurement covariance matrix to be block-banded, which conveniently factorizes and results in a computationally efficient approach for correlating measurements across the entire trajectory. We train our covariance model through supervised learning using the groundtruth trajectory. In applications where the measurements are time-correlated, we demonstrate improved performance in both the mean posterior estimate and the covariance (i.e., improved estimator consistency). We use an experimental dataset collected using a mobile robot equipped with a laser rangefinder to demonstrate the improvement in performance. We also verify estimator consistency in a controlled simulation using a statistical test over several trials.
S*: On Safe and Time Efficient Robot Motion Planning

As robots and humans increasingly share the same workspace, the development of safe motion plans becomes paramount. For real-world applications, nonetheless, it is critical that safety solutions are achieved without compromising performance. The computation of safe, time-efficient trajectories, however, usually requires rather complex often decoupled planning and optimization methods which degrades the nominal performance. In this work, instead, we cast the problem as a graph search-based scheme that enables us to solve the problem efficiently. The graph search is guided by an informed cost balance criterion. In this context we present the S* algorithm which minimizes the total planning time by equilibrising shortest time-efficient paths and paths with higher safe velocities. The approach is compatible with standards and validated both in rigorous simulation trials on a 6 DoF UR5 robot as well as real world experiments on a Franka Emika 7 DoF research robot.
Data-Driven Stochastic Motion Evaluation and Optimization with Image by Spatially-Aligned Temporal Encoding

This paper proposes a probabilistic motion prediction method for long motions. The motion is predicted so that it accomplishes a task from the initial state observed in the given image. While our method evaluates the task achievability by the Energy-Based Model (EBM), previous EBMs are not designed for evaluating the consistency between different domains (i.e., image and motion in our method). Our method seamlessly integrates the image and motion data into the image feature domain by spatially-aligned temporal encoding so that features are extracted along the motion trajectory projected onto the image. Furthermore, this paper also proposes a data-driven motion optimization method, Deep Motion Optimizer (DMO), that works with EBM for motion prediction. Different from previous gradient-based optimizers, our self-supervised DMO alleviates the difficulty of hyper-parameter tuning to avoid local minima. The effectiveness of the proposed method is demonstrated with a variety of experiments with similar SOTA methods.
Gradient-Based Trajectory Optimization With Learned Dynamics

Trajectory optimization methods have achieved an exceptional level of performance on real-world robots in recent years. These methods heavily rely on accurate analytical models of the dynamics, yet some aspects of the physical world can only be captured to a limited extent. An alternative approach is to leverage machine learning techniques to learn a differentiable dynamics model of the system from data. In this work, we use trajectory optimization and model learning for performing highly dynamic and complex tasks with robotic systems in absence of accurate analytical models of the dynamics. We show that a neural network can model highly nonlinear behaviors accurately for large time horizons, from data collected in only 25 minutes of interactions on two distinct robots: (i) the Boston Dynamics Spot and an (ii) RC car. Furthermore, we use the gradients of the neural network to perform gradient-based trajectory optimization. In our hardware experiments, we demonstrate that our learned model can represent complex dynamics for both the Spot and Radio-controlled (RC) car, and gives good performance in combination with trajectory optimization methods.
Integrated vector field and backstepping control for quadcopters

In this work, we present an Integrated Guidance and Controller (IGC) scheme to drive quadcopters in path-following tasks with obstacle avoidance and constant uncertainty rejection. This scheme is based on the combination of a time-varying artificial vector field and Backstepping with integral action control. The vector field switches between two behaviors: (i) path-following; and (ii) obstacle circumnavigation to allow collision avoidance. This vector field is then integrated into a nonlinear controller designed via Backstepping with Integral Action to deal with the quadcopter vehicle dynamics and reject constant uncertainties. The considered vehicle model is based on quaternion algebra. The control inputs are considered to be the total thrust and torques. Stability is proved by using Lyapunov's Theory and Matrosov's Theorem.
Learning-based Initialization of Trajectory Optimization for Path-following Problems of Redundant Manipulators

Trajectory optimization (TO) is an efficient tool to generate a redundant manipulator's joint trajectory following a 6-dimensional Cartesian path. The optimization performance largely depends on the quality of initial trajectories. However, the selection of a high-quality initial trajectory is non-trivial and requires a considerable time budget due to the extremely large space of the solution trajectories and the lack of prior knowledge about task constraints in configuration space. To alleviate the issue, we present a learning-based initial trajectory generation method that generates high-quality initial trajectories in a short time budget by adopting example-guided reinforcement learning. In addition, we suggest a null-space projected imitation reward to consider null-space constraints by efficiently learning kinematically feasible motion captured in expert demonstrations. Our statistical evaluation in simulation shows the improved optimality, efficiency, and applicability of TO when we plug in our method's output, compared with three other baselines. We also show the performance improvement and feasibility via real-world experiments with a seven-degree-of-freedom manipulator.
Safety-Constrained Policy Transfer with Successor Features

In this work, we focus on the problem of safe policy transfer in reinforcement learning: we seek to leverage existing policies when learning a new task with specified constraints. This problem is important for safety-critical applications where interactions are costly and unconstrained exploration can lead to undesirable or dangerous outcomes, e.g., with physical robots that interact with humans. We propose a Constrained Markov Decision Process (CMDP) formulation that simultaneously enables the transfer of policies and adherence to safety constraints. Our formulation cleanly separates task goals from safety considerations and permits the specification of a wide variety of constraints. Our approach relies on a novel extension of generalized policy improvement to constrained settings via a Lagrangian formulation. We devise a dual optimization algorithm that estimates the optimal dual variable of a target task, thus enabling safe transfer of policies derived from successor features learned on source tasks. Our experiments in simulated domains show that our approach is effective; it visits unsafe states less frequently and outperforms alternative state-of-the-art methods when taking safety constraints into account.
Autotuning Symbolic Optimization Fabrics for Trajectory Generation

In this paper, we present an automated parameter optimization method for trajectory generation. We formulate parameter optimization as a constrained optimization problem that can be effectively solved using Bayesian optimization. While the approach is generic to any trajectory generation method, we showcase it using optimization fabrics. Optimization fabrics are a geometric trajectory generation method based on non-Riemannian geometry. By symbolically pre-solving the structure of the tree of fabrics, we obtain a parameterized trajectory generator, called symbolic fabrics. We show that autotuned symbolic fabrics reach expert-level performance in a few trials. Additionally, we show that tuning transfers across different robots, motion planning problems and between simulation and real world. Finally, we qualitatively showcase that the framework could be used for coupled mobile manipulation.
Using Memory-Based Learning to Solve Tasks with State-Action Constraints

Tasks where the set of possible actions depend discontinuously on the state pose a significant challenge for current reinforcement learning algorithms. For example, a locked door must be first unlocked, and then the handle turned before the door can be opened. The sequential nature of these tasks makes obtaining final rewards difficult, and transferring information between task variants using continuous learned values such as weights rather than discrete symbols can be inefficient. Our key insight is that agents that act and think symbolically are often more effective in dealing with these tasks. We propose a memory-based learning approach that leverages the symbolic nature of constraints and temporal ordering of actions in these tasks to quickly acquire and transfer high-level information. We evaluate the performance of memory-based learning on both real and simulated tasks with approximately discontinuous constraints between states and actions, and show our method learns to solve these tasks an order of magnitude faster than both model-based and model-free deep reinforcement learning methods.
Towards Robust Reference System for Autonomous Driving: Rethinking 3D MOT

With the rapid development of autonomous driving, the need for auto-labeling reference systems is becoming increasingly urgent. 3D multiple object tracking (MOT) is one of the most critical components of the reference system. In this work, we reviewed and rethought the common failure sources and limitations of the SOTA 3D MOT methods. We propose a set of innovative 3D MOT post-processing modules as a unified framework based on the observation. First, we design a self-learning-based detector to eliminate the outliers in each tracklet. Then a novel post-processing module, GGTrajRec, will recover the breakpoints and ID switches in the trajectories. Finally, a confidence-guided trajectory optimizer is implemented to ensure each trajectory's consistency. Extensive experiments on KITTI and nuScenes show that our method can improve the SOTA methods on most evaluation metrics by a remarkable margin. Currently, our results are second ranking on the KITTI tracking leaderboard. Specifically, our method offers the lowest FPs, highest DetRe, and AssRe values among all methods, which can significantly contribute to a stable and robust reference system for ADAS.
Limit Cycle Generation with Pneumatically Driven Physical Reservoir Computing

One of the recent developments in physical reservoir computing, which uses the complex dynamics of a physical system as a computational resource, is the use of a pneumatic pipeline system as a computational resource. This uses the dynamics of air for computation, and because it is lightweight and power-saving, it is used for gait-assist control using a soft exoskeleton with pneumatic rubber artificial muscles. In this study, we verified that by feeding back the estimated information to a pneumatic pipeline system, the pneumatic physical reservoir computing can generate periodic pressure changes as a stable limit cycle, such as those seen in walking. A pneumatic reservoir with feedback loops was modeled to generate limit cycles in the simulation, and it was confirmed that the system could generate limit cycles with high accuracy even from initial positions far from the target limit cycle. This system is expected to be applied to assist walking movements with a soft exoskeleton with a lightweight computational device.
Depth Is All You Need for Monocular 3D Detection

A key contributor to recent progress in 3D detection from single images is monocular depth estimation. Existing methods focus on how to leverage depth explicitly, by generating pseudo-pointclouds or providing attention cues for image features. More recent works leverage depth prediction as a pretraining task and fine-tune the depth representation while training it for 3D detection. However, the adaptation is limited in scale by manual labels. In this work, we propose further aligning the depth representation with the target domain in an unsupervised fashion. Our methods leverage commonly available LiDAR or RGB videos during training time to fine-tune the depth representation, which leads to improved 3D detectors. Especially when using RGB videos, we show that our two-stage training by first generating depth pseudo-labels is critical, because of the inconsistency in loss distribution between the two tasks. With either type of reference data, our multi-task learning approach improves over the state of the art on both KITTI and NuScenes, while matching the test-time complexity of its single-task sub-network. Source code and pretrained models are available on https://github.com/TRI-ML/DD3D.
Radar Velocity Transformer: Single-scan Moving Object Segmentation in Noisy Radar Point Clouds

The awareness about moving objects in the surroundings of a self-driving vehicle is essential for safe and reliable autonomous navigation. The interpretation of LiDAR and camera data achieves exceptional results but typically requires to accumulate and process temporal sequences of data in order to extract motion information. In contrast, radar sensors, which are already installed in most recent vehicles, can overcome this limitation as they directly provide the Doppler velocity of the detections and, hence incorporate instantaneous motion information within a single measurement. In this paper, we tackle the problem of moving object segmentation in noisy radar point clouds. We also consider differentiating parked from moving cars, to enhance scene understanding. Instead of exploiting temporal dependencies to identify moving objects, we develop a novel transformer-based approach to perform single-scan moving object segmentation in sparse radar scans accurately. The key to our Radar Velocity Transformer is to incorporate the valuable velocity information throughout each module of the network, thereby enabling the precise segmentation of moving and non-moving objects. Additionally, we propose a transformer-based upsampling, which enhances the performance by adaptively combining information and over-coming the limitation of interpolation of sparse point clouds. Finally, we create a new radar moving object segmentation benchmark based on the RadarScenes dataset and compare our approach to other state-of-the-art methods. Our network runs faster than the frame rate of the sensor and shows superior segmentation results using only single-scan radar data.
FDLNet: Boosting Real-time Semantic Segmentation by Image-size Convolution via Frequency Domain Learning

This paper proposes a novel real-time semantic segmentation network via frequency domain learning, called FDLNet, which revisits the segmentation task from two critical perspectives: spatial structure description and multilevel feature fusion. We first devise an image-size convolution (IS-Conv) as a global frequency-domain learning operator to capture long-range dependency in a single shot. To model spatial structure information, we construct the global structure representation path (GSRP) based on IS-Conv, which learns a unified edge-region representation with affordable complexity. For efficient and lightweight multi-level feature fusion, we propose the factorized stereoscopic attention (FSA) module, which alleviates semantic confusion and reduces feature redundancy by introducing level-wise attention before channel and spatial attention. Combining the above modules, we propose a concise semantic segmentation framework named FDLNet. We experimentally demonstrate the effectiveness and superiority of the proposed method. FDLNet achieves state-of-the-art performance on the Cityscapes, which reports 76.32% mIoU at 150+ FPS and 79.0% mIoU at 41+ FPS. The code is available at https://github.com/qyan0131/FDLNet.