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IEEE Transactions on Evolutionary Computation 2022年第5期26卷 1144-1156页

作者： Shirazi, Abolfazl Ceberio, Josu Lozano, Jose A. Basque Center for Applied Mathematics Machine Learning Group Bilbao48009 Spain University of the Basque Country Intelligent Systems Group Computer Science and Artificial Intelligence Department Donostia-San Sebastian20018 Spain University of the Basque Country Department of Computer Science Donostia-San Sebastian20018 Spain

Handling nonlinear constraints in continuous optimization is challenging, and finding a feasible solution is usually a difficult task. In the past few decades, various techniques have been developed to deal with linear and nonlinear constraints. However, reaching feasible solutions has been a challenging task for most of these methods. In this article, we adopt the framework of estimation of distribution algorithms (EDAs) and propose a new algorithm (EDA++) equipped with some mechanisms to deal with nonlinear constraints. These mechanisms are associated with different stages of the EDA, including seeding, learning, and mapping. It is shown that, besides increasing the quality of the solutions in terms of objective values, the feasibility of the final solutions is guaranteed if an initial population of feasible solutions is seeded to the algorithm. The EDA with the proposed mechanisms is applied to two suites of benchmark problems for constrained continuous optimization and its performance is compared with some state-of-the-art algorithms and constraint-handling methods. Conducted experiments confirm the speed, robustness, and efficiency of the proposed algorithm in tackling various problems with linear and nonlinear constraints. © 1997-2012 IEEE.

关键词： Computation theory

ST-RRT*: Asymptotically-Optimal Bidirectional Motion Planning through Space-Time

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arXiv 2022年

作者： Grothe, Francesco Hartmann, Valentin N. Orthey, Andreas Toussaint, Marc Learning and Intelligent Systems Group TU Berlin Germany Machine Learning & Robotics Lab University of Stuttgart Germany

We present a motion planner for planning through space-time with dynamic obstacles, velocity constraints, and unknown arrival time. Our algorithm, Space-Time RRT* (ST-RRT*), is a probabilistically complete, bidirectional motion planning algorithm, which is asymptotically optimal with respect to the shortest arrival time. We experimentally evaluate ST-RRT* in both abstract (2D disk, 8D disk in cluttered spaces, and on a narrow passage problem), and simulated robotic path planning problems (sequential planning of 8DoF mobile robots, and 7DoF robotic arms). The proposed planner outperforms RRT-Connect and RRT* on both initial solution time, and attained final solution cost. The code for ST-RRT* is available in the Open Motion Planning Library (OMPL). Copyright © 2022, The Authors. All rights reserved.

关键词： Motion planning

Control-Tree Optimization: an approach to MPC under discrete Partial Observability

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Control-Tree Optimization: an approach to MPC under discrete...

IEEE International Conference on Robotics and Automation (ICRA)

作者： Camille Phiquepal Marc Toussaint Machine Learning & Robotic Lab University of Stuttgart Germany Learning and Intelligent Systems Lab TU Berlin Germany

This paper presents a new approach to Model Predictive Control for environments where essential, discrete variables are partially observed. Under this assumption, the belief state is a probability distribution over a finite number of states. We optimize a control-tree where each branch assumes a given state-hypothesis. The control-tree optimization uses the probabilistic belief state information. This leads to policies more optimized with respect to likely states than unlikely ones, while still guaranteeing robust constraint satisfaction at all times. We apply the method to both linear and non-linear MPC with constraints. The optimization of the control-tree is decomposed into optimization subproblems that are solved in parallel leading to good scalability for high number of state-hypotheses. We demonstrate the real-time feasibility of the algorithm on two examples and show the benefits compared to a classical MPC scheme optimizing w.r.t. one single hypothesis.

关键词： Automation Scalability Conferences Probabilistic logic Real-time systems Probability distribution Observability

learning to execute: Efficiently learning universal plan-conditioned policies in robotics

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arXiv 2021年

作者： Schubert, Ingmar Driess, Danny Oguz, Ozgur S. Toussaint, Marc Learning and Intelligent Systems Group Tu Berlin Germany Machine Learning and Robotics Lab University of Stuttgart Germany

Applications of Reinforcement learning (RL) in robotics are often limited by high data demand. On the other hand, approximate models are readily available in many robotics scenarios, making model-based approaches like planning a data-efficient alternative. Still, the performance of these methods suffers if the model is imprecise or wrong. In this sense, the respective strengths and weaknesses of RL and modelbased planners are complementary. In the present work, we investigate how both approaches can be integrated into one framework that combines their strengths. We introduce learning to Execute (L2E), which leverages information contained in approximate plans to learn universal policies that are conditioned on plans. In our robotic manipulation experiments, L2E exhibits increased performance when compared to pure RL, pure planning, or baseline methods combining learning and planning. © 2021, CC BY.

关键词： Robot programming

learning to execute: efficiently learning universal plan-conditioned policies in robotics 21

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Learning to execute: efficiently learning universal plan-con...

Proceedings of the 35th International Conference on Neural Information Processing systems

作者： Ingmar Schubert Danny Driess Ozgur S. Oguz Marc Toussaint Learning and Intelligent Systems Group TU Berlin Germany Machine Learning and Robotics Lab University of Stuttgart Germany

ISBN: (纸本)9781713845393

Applications of Reinforcement learning (RL) in robotics are often limited by high data demand. On the other hand, approximate models are readily available in many robotics scenarios, making model-based approaches like planning a data-efficient alternative. Still, the performance of these methods suffers if the model is imprecise or wrong. In this sense, the respective strengths and weaknesses of RL and model-based planners are complementary. In the present work, we investigate how both approaches can be integrated into one framework that combines their strengths. We introduce learning to Execute (L2E), which leverages information contained in approximate plans to learn universal policies that are conditioned on plans. In our robotic manipulation experiments, L2E exhibits increased performance when compared to pure RL, pure planning, or baseline methods combining learning and planning.

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Deep visual reasoning: learning to predict action sequences for task and motion planning from an initial scene image

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arXiv 2020年

作者： Driess, Danny Ha, Jung-Su Toussaint, Marc Machine Learning and Robotics Lab University of Stuttgart Germany Max-Planck Institute for Intelligent Systems Stuttgart Germany Learning and Intelligent Systems Group TU Berlin Germany

In this paper, we propose a deep convolutional recurrent neural network that predicts action sequences for task and motion planning (TAMP) from an initial scene image. Typical TAMP problems are formalized by combining reasoning on a symbolic, discrete level (e.g. first-order logic) with continuous motion planning such as nonlinear trajectory optimization. Due to the great combinatorial complexity of possible discrete action sequences, a large number of optimization/motion planning problems have to be solved to find a solution, which limits the scalability of these approaches. To circumvent this combinatorial complexity, we develop a neural network which, based on an initial image of the scene, directly predicts promising discrete action sequences such that ideally only one motion planning problem has to be solved to find a solution to the overall TAMP problem. A key aspect is that our method generalizes to scenes with many and varying number of objects, although being trained on only two objects at a time. This is possible by encoding the objects of the scene in images as input to the neural network, instead of a fixed feature vector. Results show runtime improvements of several magnitudes. Video: https://***/i8yyEbbvoEk Copyright © 2020, The Authors. All rights reserved.

关键词： Motion planning

Plan-based relaxed reward shaping for goal-directed tasks

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arXiv 2021年

作者： Schubert, Ingmar Oguz, Ozgur S. Toussaint, Marc Learning and Intelligent Systems Group TU Berlin Germany Max Planck Institute for Intelligent Systems Stuttgart Germany Machine Learning and Robotics Lab University of Stuttgart Germany

In high-dimensional state spaces, the usefulness of Reinforcement learning (RL) is limited by the problem of exploration. This issue has been addressed using potential-based reward shaping (PB-RS) previously. In the present work, we introduce Final-Volume-Preserving Reward Shaping (FV-RS). FV-RS relaxes the strict optimality guarantees of PB-RS to a guarantee of preserved long-term behavior. Being less restrictive, FV-RS allows for reward shaping functions that are even better suited for improving the sample efficiency of RL algorithms. In particular, we consider settings in which the agent has access to an approximate plan. Here, we use examples of simulated robotic manipulation tasks to demonstrate that plan-based FV-RS can indeed significantly improve the sample efficiency of RL over plan-based PB-RS. © 2021, CC BY.

关键词： Efficiency

Solving partially observable reinforcement learning problems with recurrent neural networks

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Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 2012年 7700 LECTURE NO卷 709-733页

作者： Duell, Siegmund Udluft, Steffen Sterzing, Volkmar Siemens AG Corporate Technology Intelligent Systems and Control Germany Berlin University of Technology Machine Learning Germany

ISBN: (纸本)9783642352881

The aim of this chapter is to provide a series of tricks and recipes for neural state estimation, particularly for real world applications of reinforcement learning. We use various topologies of recurrent neural networks as they allow to identify the continuous valued, possibly high dimensional state space of complex dynamical systems. Recurrent neural networks explicitly offer possibilities to account for time and memory, in principle they are able to model any type of dynamical system. Because of these capabilities recurrent neural networks are a suitable tool to approximate a Markovian state space of dynamical systems. In a second step, reinforcement learning methods can be applied to solve a defined control problem. Besides the trick of using a recurrent neural network for state estimation, various issues regarding real world problems such as, large sets of observables and long-term dependencies are addressed. © Springer-Verlag Berlin Heidelberg 2012.

关键词： Recurrent neural networks

Integrating document clustering and topic modeling

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Integrating document clustering and topic modeling

29th Conference on Uncertainty in Artificial Intelligence, UAI 2013

作者： Xie, Pengtao Xing, Eric P. State Key Laboratory on Intelligent Technology and Systems Department of Computer Science and Technology Tsinghua University Beijing 100084 China Machine Learning Department Carnegie Mellon University Pittsburgh PA 15213 United States

Document clustering and topic modeling are two closely related tasks which can mutually benefit each other. Topic modeling can project documents into a topic space which facilitates effective document clustering. Cluster labels discovered by document clustering can be incorporated into topic models to extract local topics specific to each cluster and global topics shared by all clusters. In this paper, we propose a multi-grain clustering topic model (MGCTM) which integrates document clustering and topic modeling into a unified framework and jointly performs the two tasks to achieve the overall best performance. Our model tightly couples two components: a mixture component used for discovering latent groups in document collection and a topic model component used for mining multi-grain topics including local topics specific to each cluster and global topics shared across clusters. We employ variational inference to approximate the posterior of hidden variables and learn model parameters. Experiments on two datasets demonstrate the effectiveness of our model.

关键词： Cluster analysis

Walk-the-Talk: LLM driven pedestrian motion generation

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Walk-the-Talk: LLM driven pedestrian motion generation

IEEE Symposium on intelligent Vehicle

作者： Mohan Ramesh Fabian B. Flohr Intelligent Vehicles Lab Institute for Applications of Machine Learning and Intelligent Systems Munich University of Applied Sciences Germany

ISBN: (数字)9798350348811

ISBN: (纸本)9798350348828

In the field of autonomous driving, a key challenge is the "reality gap": transferring knowledge gained in simulation to real-world settings. Despite various approaches to mitigate this gap, there’s a notable absence of solutions targeting agent behavior generation which are crucial for mimicking spontaneous, erratic, and realistic actions of traffic participants. Recent advancements in Generative AI have enabled the representation of human activities in semantic space and generate real human motion from textual descriptions. Despite current limitations such as modality constraints, motion sequence length, resource demands, and data specificity, there’s an opportunity to innovate and use these techniques in the intelligent vehicles domain. We propose Walk-the-Talk, a motion generator utilizing Large Language Models (LLMs) to produce reliable pedestrian motions for high-fidelity simulators like CARLA. Thus, we contribute to autonomous driving simulations by aiming to scale realistic, diverse long-tail agent motion data - currently a gap in training datasets. We employ Motion Capture (MoCap) techniques to develop the Walk-the-Talk dataset, which illustrates a broad spectrum of pedestrian behaviors in street-crossing scenarios, ranging from standard walking patterns to extreme behaviors such as drunk walking and near-crash incidents. By utilizing this new dataset within a LLM, we facilitate the creation of realistic pedestrian motion sequences, a capability previously unattainable (cf. Figure 1). Additionally, our findings demonstrate that leveraging the Walk-the-Talk dataset enhances cross-domain generalization and significantly improves the Fréchet Inception Distance (FID) score by approximately 15% on the HumanML3D dataset. https://***/publications/w-the-t/

关键词： Legged locomotion Training Pedestrians Generative AI Large language models Semantics Motion capture