Constraint-Based Reasoning
Bridging the Gap: Representation Spaces in Neuro-Symbolic AI
However, although the cooperation between these two seems natural, the difference in their representation is obviously not negligible. Prof. Henry Kautz proposed a taxonomy of Neuro-Symbolic Systems in the AAAI 2020. In addition, many researchers have conducted relevant reviews of the recent neuro-symbolic AI from different perspectives. As Fig.1 shows, Acharya et al. [1] proposed a new classification method, which classified and discussed the application of existing neuro-symbolic AI by the role of neural and symbolic parts: learning for reasoning, reasoning for Learning, and learning-reasoning. Garcez et al. [73] proposed a taxonomy that includes sequential, nested, cooperative, and compiled neuro-symbolic AI based on the six types introduced by Henry Kautz. In addition, some reviews focus on cross-field integration and applications. For example, Berlot-Attwell [27] reviewed neuro-symbolic VQA (visual question answering) from the perspectives of AGI (artificial general intelligence) desiderata. Marra [128] conducted a comprehensive review on integrating neuro-symbolic and statistical relational artificial intelligence based on seven dimensions.
Heterogeneous Multi-robot Task Allocation for Long-Endurance Missions in Dynamic Scenarios
We present a framework for Multi-Robot Task Allocation (MRTA) in heterogeneous teams performing long-endurance missions in dynamic scenarios. Given the limited battery of robots, especially in the case of aerial vehicles, we allow for robot recharges and the possibility of fragmenting and/or relaying certain tasks. We also address tasks that must be performed by a coalition of robots in a coordinated manner. Given these features, we introduce a new class of heterogeneous MRTA problems which we analyze theoretically and optimally formulate as a Mixed-Integer Linear Program. We then contribute a heuristic algorithm to compute approximate solutions and integrate it into a mission planning and execution architecture capable of reacting to unexpected events by repairing or recomputing plans online. Our experimental results show the relevance of our newly formulated problem in a realistic use case for inspection with aerial robots. We assess the performance of our heuristic solver in comparison with other variants and with exact optimal solutions in small-scale scenarios. In addition, we evaluate the ability of our replanning framework to repair plans online.
Guided Game Level Repair via Explainable AI
Procedurally generated levels created by machine learning models can be unsolvable without further editing. Various methods have been developed to automatically repair these levels by enforcing hard constraints during the post-processing step. However, as levels increase in size, these constraint-based repairs become increasingly slow. This paper proposes using explainability methods to identify specific regions of a level that contribute to its unsolvability. By assigning higher weights to these regions, constraint-based solvers can prioritize these problematic areas, enabling more efficient repairs. Our results, tested across three games, demonstrate that this approach can help to repair procedurally generated levels faster.
Towards Geometry-Preserving Reductions Between Constraint Satisfaction Problems (and other problems in NP)
Reductions are the fundamental tool of computational complexity. They allow classification of computational problems into families (somewhat resembling those in biology), with problems in the same class sharing common features (in particular NP-complete problems being isomorphic versions of a single problem, if we believe that the Berman-Hartmanis conjecture [6] holds). A significant concern in the literature on complexity-theoretic reductions is to make the theory of reductions more predictive. This means that we should aim to better connect the structural properties of the two problems that the given reduction is connecting. For instance the notion of pasimonious reduction attempts to preserve the total number of solutions between instances.
Tensegrity Robot Proprioceptive State Estimation with Geometric Constraints
Tong, Wenzhe, Lin, Tzu-Yuan, Mi, Jonathan, Jiang, Yicheng, Ghaffari, Maani, Huang, Xiaonan
Tensegrity robots, characterized by a synergistic assembly of rigid rods and elastic cables, form robust structures that are resistant to impacts. However, this design introduces complexities in kinematics and dynamics, complicating control and state estimation. This work presents a novel proprioceptive state estimator for tensegrity robots. The estimator initially uses the geometric constraints of 3-bar prism tensegrity structures, combined with IMU and motor encoder measurements, to reconstruct the robot's shape and orientation. It then employs a contact-aided invariant extended Kalman filter with forward kinematics to estimate the global position and orientation of the tensegrity robot. The state estimator's accuracy is assessed against ground truth data in both simulated environments and real-world tensegrity robot applications. It achieves an average drift percentage of 4.2%, comparable to the state estimation performance of traditional rigid robots. This state estimator advances the state of the art in tensegrity robot state estimation and has the potential to run in real-time using onboard sensors, paving the way for full autonomy of tensegrity robots in unstructured environments.
Towards Fast Algorithms for the Preference Consistency Problem Based on Hierarchical Models
George, Anne-Marie, Wilson, Nic, O'Sullivan, Barry
Such order relations can be, e.g., comparing alternatives by the values of the evaluation functions In this paper, we construct and compare algorithmic approaches lexicographically [15], by Pareto order, weighted sums [6], to solve the Preference Consistency Problem for based on hierarchical models [16] or by conditional preferences preference statements based on hierarchical models. Instances structures as CP-nets [2] and partial lexicographic preference of this problem contain a set of preference statements that are trees [11]. Here, the choice of the order relation can direct comparisons (strict and non-strict) between some alternatives, lead to stronger or weaker inferences and can make solving and a set of evaluation functions by which all alternatives PDP computationally more or less challenging. In a recommender can be rated. An instance is consistent based on hierarchical system or in a multi-objective decision making scenario, preference models, if there exists an hierarchical model the user should only be presented with a relatively small on the evaluation functions that induces an order relation on number of solutions, hence, a strong order relation is required.
Efficient Inference and Computation of Optimal Alternatives for Preference Languages Based On Lexicographic Models
Wilson, Nic, George, Anne-Marie
We analyse preference inference, through consistency, for general preference languages based on lexicographic models. We identify a property, which we call strong compositionality, that applies for many natural kinds of preference statement, and that allows a greedy algorithm for determining consistency of a set of preference statements. We also consider different natural definitions of optimality, and their relations to each other, for general preference languages based on lexicographic models. Based on our framework, we show that testing consistency, and thus inference, is polynomial for a specific preference language LpqT, which allows strict and non-strict statements, comparisons between outcomes and between partial tuples, both ceteris paribus and strong statements, and their combination. Computing different kinds of optimal sets is also shown to be polynomial; this is backed up by our experimental results.
An Efficient Representation of Whole-body Model Predictive Control for Online Compliant Dual-arm Mobile Manipulation
Du, Wenqian, Long, Ran, Moura, João, Wang, Jiayi, Samadi, Saeid, Vijayakumar, Sethu
Dual-arm mobile manipulators can transport and manipulate large-size objects with simple end-effectors. To interact with dynamic environments with strict safety and compliance requirements, achieving whole-body motion planning online while meeting various hard constraints for such highly redundant mobile manipulators poses a significant challenge. We tackle this challenge by presenting an efficient representation of whole-body motion trajectories within our bilevel model-based predictive control (MPC) framework. We utilize B\'ezier-curve parameterization to represent the optimized collision-free trajectories of two collaborating end-effectors in the first MPC, facilitating fast long-horizon object-oriented motion planning in SE(3) while considering approximated feasibility constraints. This approach is further applied to parameterize whole-body trajectories in the second MPC for whole-body motion generation with predictive admittance control in a relatively short horizon while satisfying whole-body hard constraints. This representation enables two MPCs with continuous properties, thereby avoiding inaccurate model-state transition and dense decision-variable settings in existing MPCs using the discretization method. It strengthens the online execution of the bilevel MPC framework in high-dimensional space and facilitates the generation of consistent commands for our hybrid position/velocity-controlled robot. The simulation comparisons and real-world experiments demonstrate the efficiency and robustness of this approach in various scenarios for static and dynamic obstacle avoidance, and compliant interaction control with the manipulated object and external disturbances.
VLMimic: Vision Language Models are Visual Imitation Learner for Fine-grained Actions
Chen, Guanyan, Wang, Meiling, Cui, Te, Mu, Yao, Lu, Haoyang, Zhou, Tianxing, Peng, Zicai, Hu, Mengxiao, Li, Haizhou, Li, Yuan, Yang, Yi, Yue, Yufeng
Visual imitation learning (VIL) provides an efficient and intuitive strategy for robotic systems to acquire novel skills. Recent advancements in Vision Language Models (VLMs) have demonstrated remarkable performance in vision and language reasoning capabilities for VIL tasks. Despite the progress, current VIL methods naively employ VLMs to learn high-level plans from human videos, relying on pre-defined motion primitives for executing physical interactions, which remains a major bottleneck. In this work, we present VLMimic, a novel paradigm that harnesses VLMs to directly learn even fine-grained action levels, only given a limited number of human videos. Specifically, VLMimic first grounds object-centric movements from human videos, and learns skills using hierarchical constraint representations, facilitating the derivation of skills with fine-grained action levels from limited human videos. These skills are refined and updated through an iterative comparison strategy, enabling efficient adaptation to unseen environments. Our extensive experiments exhibit that our VLMimic, using only 5 human videos, yields significant improvements of over 27% and 21% in RLBench and real-world manipulation tasks, and surpasses baselines by over 37% in long-horizon tasks. Code and videos are available at our home page.
DAGE: DAG Query Answering via Relational Combinator with Logical Constraints
He, Yunjie, Xiong, Bo, Hernández, Daniel, Zhu, Yuqicheng, Kharlamov, Evgeny, Staab, Steffen
Predicting answers to queries over knowledge graphs is called a complex reasoning task because answering a query requires subdividing it into subqueries. Existing query embedding methods use this decomposition to compute the embedding of a query as the combination of the embedding of the subqueries. This requirement limits the answerable queries to queries having a single free variable and being decomposable, which are called tree-form queries and correspond to the $\mathcal{SROI}^-$ description logic. In this paper, we define a more general set of queries, called DAG queries and formulated in the $\mathcal{ALCOIR}$ description logic, propose a query embedding method for them, called DAGE, and a new benchmark to evaluate query embeddings on them. Given the computational graph of a DAG query, DAGE combines the possibly multiple paths between two nodes into a single path with a trainable operator that represents the intersection of relations and learns DAG-DL from tautologies. We show that it is possible to implement DAGE on top of existing query embedding methods, and we empirically measure the improvement of our method over the results of vanilla methods evaluated in tree-form queries that approximate the DAG queries of our proposed benchmark.