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Generalized Guarantees for Variational Inference in the Presence of Even and Elliptical Symmetry

Margossian, Charles C., Saul, Lawrence K.

arXiv.org Machine Learning

We extend several recent results providing symmetry-based guarantees for variational inference (VI) with location-scale families. VI approximates a target density~$p$ by the best match $q^*$ in a family $Q$ of tractable distributions that in general does not contain $p$. It is known that VI can recover key properties of $p$, such as its mean and correlation matrix, when $p$ and $Q$ exhibit certain symmetries and $q^*$ is found by minimizing the reverse Kullback-Leibler divergence. We extend these guarantees in two important directions. First, we provide symmetry-based guarantees for a broader family of divergences, highlighting the properties of variational objectives under which VI provably recovers the mean and correlation matrix. Second, we obtain further guarantees for VI when the target density $p$ exhibits even and elliptical symmetries in some but not all of its coordinates. These partial symmetries arise naturally in Bayesian hierarchical models, where the prior induces a challenging geometry but still possesses axes of symmetry. We illustrate these theoretical results in a number of experimental settings.


TARMAC: A Taxonomy for Robot Manipulation in Chemistry

Huang, Kefeng, Pipe, Jonathon, Martin, Alice E., Wang, Tianyuan, Franklin, Barnabas A., Tyrrell, Andy M., Fairlamb, Ian J. S., Zhu, Jihong

arXiv.org Artificial Intelligence

Chemistry laboratory automation aims to increase throughput, reproducibility, and safety, yet many existing systems still depend on frequent human intervention. Advances in robotics have reduced this dependency, but without a structured representation of the required skills, autonomy remains limited to bespoke, task-specific solutions with little capacity to transfer beyond their initial design. Current experiment abstractions typically describe protocol-level steps without specifying the robotic actions needed to execute them. This highlights the lack of a systematic account of the manipulation skills required for robots in chemistry laboratories. To address this gap, we introduce TARMAC - a Taxonomy for Robot Manipulation in Chemistry - a domain-specific framework that defines and organizes the core manipulations needed in laboratory practice. Based on annotated teaching-lab demonstrations and supported by experimental validation, TARMAC categorizes actions according to their functional role and physical execution requirements. Beyond serving as a descriptive vocabulary, TARMAC can be instantiated as robot-executable primitives and composed into higher-level macros, enabling skill reuse and supporting scalable integration into long-horizon workflows. These contributions provide a structured foundation for more flexible and autonomous laboratory automation. More information is available at https://tarmac-paper.github.io/


Approximation-free Control of Unknown Euler-Lagrangian Systems under Input Constraints

Das, Ratnangshu, Jagtap, Pushpak

arXiv.org Artificial Intelligence

In this paper, we present a novel funnel-based tracking control algorithm for robotic systems with unknown dynamics and prescribed input constraints. The Euler-Lagrange formulation, a common modeling approach for robotic systems, has been adopted in this study to address the trade-off between performance and actuator safety. We establish feasibility conditions that ensure tracking errors evolve within predefined funnel bounds while maintaining bounded control efforts, a crucial consideration for robots with limited actuation capabilities. We propose two approximation-free control strategies for scenarios where these conditions are violated: one actively corrects the error, and the other stops further deviation. Finally, we demonstrate the robust performance and safety of the approach through simulations and experimental validations. This work represents a significant advancement in funnel-based control, enhancing its applicability to real-world robotics systems with input constraints.


Mobile Video Diffusion

Yahia, Haitam Ben, Korzhenkov, Denis, Lelekas, Ioannis, Ghodrati, Amir, Habibian, Amirhossein

arXiv.org Artificial Intelligence

Video diffusion models have achieved impressive realism and controllability but are limited by high computational demands, restricting their use on mobile devices. This paper introduces the first mobile-optimized video diffusion model. Starting from a spatio-temporal UNet from Stable Video Diffusion (SVD), we reduce memory and computational cost by reducing the frame resolution, incorporating multi-scale temporal representations, and introducing two novel pruning schema to reduce the number of channels and temporal blocks. Furthermore, we employ adversarial finetuning to reduce the denoising to a single step. Our model, coined as MobileVD, is 523x more efficient (1817.2 vs. 4.34 TFLOPs) with a slight quality drop (FVD 149 vs. 171), generating latents for a 14x512x256 px clip in 1.7 seconds on a Xiaomi-14 Pro. Our results are available at https://qualcomm-ai-research.github.io/mobile-video-diffusion/


PiP-X: Online feedback motion planning/replanning in dynamic environments using invariant funnels

Jaffar, Mohamed Khalid M, Otte, Michael

arXiv.org Artificial Intelligence

Computing kinodynamically feasible motion plans and repairing them on-the-fly as the environment changes is a challenging, yet relevant problem in robot-navigation. We propose a novel online single-query sampling-based motion re-planning algorithm - PiP-X, using finite-time invariant sets - funnels. We combine concepts from sampling-based methods, nonlinear systems analysis and control theory to create a single framework that enables feedback motion re-planning for any general nonlinear dynamical system in dynamic workspaces. A volumetric funnel-graph is constructed using sampling-based methods, and an optimal funnel-path from robot configuration to a desired goal region is then determined by computing the shortest-path subtree in it. Analysing and formally quantifying the stability of trajectories using Lyapunov level-set theory ensures kinodynamic feasibility and guaranteed set-invariance of the solution-paths. The use of incremental search techniques and a pre-computed library of motion-primitives ensure that our method can be used for quick online rewiring of controllable motion plans in densely cluttered and dynamic environments. We represent traversability and sequencibility of trajectories together in the form of an augmented directed-graph, helping us leverage discrete graph-based replanning algorithms to efficiently recompute feasible and controllable motion plans that are volumetric in nature. We validate our approach on a simulated 6DOF quadrotor platform in a variety of scenarios within a maze and random forest environment. From repeated experiments, we analyse the performance in terms of algorithm-success and length of traversed-trajectory.


Funnel-based Reward Shaping for Signal Temporal Logic Tasks in Reinforcement Learning

Saxena, Naman, Sandeep, Gorantla, Jagtap, Pushpak

arXiv.org Artificial Intelligence

Signal Temporal Logic (STL) is a powerful framework for describing the complex temporal and logical behaviour of the dynamical system. Numerous studies have attempted to employ reinforcement learning to learn a controller that enforces STL specifications; however, they have been unable to effectively tackle the challenges of ensuring robust satisfaction in continuous state space and maintaining tractability. In this paper, leveraging the concept of funnel functions, we propose a tractable reinforcement learning algorithm to learn a time-dependent policy for robust satisfaction of STL specification in continuous state space. We demonstrate the utility of our approach on several STL tasks using different environments.


Data-Guided Regulator for Adaptive Nonlinear Control

Rahimi, Niyousha, Mesbahi, Mehran

arXiv.org Artificial Intelligence

A critical aspect of autonomous operations in safety-critical scenarios is learning from available data for quick adaptation to new environments while maintaining safety. Examples include aircraft emergency landing scenarios in adverse weather conditions and agile quadrotor flights through low clearance gates in the presence of dynamic and strong wind conditions [1]. From a system theoretic perspective, this system feature maps to having the autonomous agent handle parametric model uncertainties and disturbances with control-theoretic guarantees such as stability and tracking error convergence, common in adaptive control settings [2, 3]. A rich body of literature has analyzed classical adaptive control algorithms' stability and convergence properties for continuous-time dynamical systems. Such studies include the use of PI (proportional integral) controllers [4] for a class of linear time-varying systems to guarantee (I) infinite-time convergence of the tracking error to zero, i.e., the difference between actual and nominal states () = () (), for any constant exogenous disturbance (denoted by), (II) infinite-time convergence of the tracking error () to a bound which is proportional to the bound on the magnitude of the rate of the exogenous signal ().


Kinodynamic Motion Planning via Funnel Control for Underactuated Unmanned Surface Vehicles

Lapandić, Dženan, Verginis, Christos K., Dimarogonas, Dimos V., Wahlberg, Bo

arXiv.org Artificial Intelligence

We develop an algorithm to control an underactuated unmanned surface vehicle (USV) using kinodynamic motion planning with funnel control (KDF). KDF has two key components: motion planning used to generate trajectories with respect to kinodynamic constraints, and funnel control, also referred to as prescribed performance control, which enables trajectory tracking in the presence of uncertain dynamics and disturbances. We extend prescribed performance control to address the challenges posed by underactuation and control-input saturation present on the USV. The proposed scheme guarantees stability under user-defined prescribed performance functions where model parameters and exogenous disturbances are unknown. Furthermore, we present an optimization problem to obtain smooth, collision-free trajectories while respecting kinodynamic constraints. We deploy the algorithm on a USV and verify its efficiency in real-world open-water experiments.


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