INTERACT: Intuitive Interaction for Robots among Humans

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People

Saray Bakker - PhD candidate
Andreu Matoses Gimenez - PhD candidate
Dr. Clarence Chen - Postdoctoral researcher
Max Spahn - Postdoctoral researcher
Dr. Nils Wilde - Postdoctoral researcher
Tomas Merva - Visiting PhD candidate
Prof. Wendelin Bohmer - Key collaborator
Prof. Chris Pek - Key collaborator
Prof. Javier Alonso-Mora

Funding

This project has received funding from the European Union through an ERC Starting Grant.

More Links
Github: Fabrics Implementation Github: multi-agent fabrics

About the Project

INTERACT aims to equip mobile robots with the ability to navigate and operate safely in human-populated environments. Leveraging advancements in motion planning, multi-robot task assignment, and machine learning, this project seeks to overcome the challenges of modeling intuition and ensuring safety in complex, uncertain settings. By developing intuitive models from past interactions and integrating them into novel optimization methods, INTERACT will enable robots to perform seamless, interaction-aware navigation and task planning. This foundational work paves the way for a new era of automation in both industrial and urban settings, where robots and humans can coexist harmoniously.

One recent contribution from this project has been development of task and motion planning (TAMP) algorithms which are used in robotic systems to autonomously decide the high-level actions along with the associated motions. Previous research into TAMP algorithms have several simplifications and often do not account for robot dynamics or issues with low-level controllers. This project uses GPU based physics simulators to find high-quality realizations which can be directly implemented in the real system as it accounts for robot dynamics. Experimental results validated the effectiveness of this algorithm for a pick and place task while finding low-cost feasible solutions in 1-2 minutes.

Another problem addressed in this project is that of real-time motion planning for multiple robotic manipulators in close proximity of each other. A novel method called multi-robot dynamics fabrics(MRDF) is developed which uses dynamic fabrics that rely on differential equations to solve for local motion planning. This method enables higher replanning frequencies and makes it useful for complex systems in dynamic environments. An online local motion planning algorithm is built that can enable multiple manipulators to operate in a shared workspace. The method is then validated in several pick-and-place scenarios obtaining high success rates and a real-time performance.

Project Demonstrations

Funding & Partners

This project has received funding from the European Union through ERC, INTERACT, under Grant 101041863. Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.

Topology-Driven Parallel Trajectory Optimization in Dynamic Environments
Oscar de Groot, Laura Ferranti, Dariu M. Gavrila, Javier Alonso-Mora. In IEEE Transaction on Robotics (T-RO), 2024.

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Ground robots navigating in complex, dynamic environments must compute collision-free trajectories to avoid obstacles safely and efficiently. Nonconvex optimization is a popular method to compute a trajectory in real-time. However, these methods often converge to locally optimal solutions and frequently switch between different local minima, leading to inefficient and unsafe robot motion. In this work, we propose a novel topology-driven trajectory optimization strategy for dynamic environments that plans multiple distinct evasive trajectories to enhance the robot's behavior and efficiency. A global planner iteratively generates trajectories in distinct homotopy classes. These trajectories are then optimized by local planners working in parallel. While each planner shares the same navigation objectives, they are locally constrained to a specific homotopy class, meaning each local planner attempts a different evasive maneuver. The robot then executes the feasible trajectory with the lowest cost in a receding horizon manner. We demonstrate, on a mobile robot navigating among pedestrians, that our approach leads to faster trajectories than existing planners.
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Safe and stable motion primitives via imitation learning and geometric fabrics
Saray Bakker, Rodrigo Pérez-Dattari, Cosimo Della Santina, Wendelin Böhmer, Javier Alonso-Mora. In Robotics: Science and Systems, Workshop on Structural Priors as Inductive Biases for Learning Robot Dynamics, 2024.

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Using the language of dynamical systems, Imitation learning (IL) provides an intuitive and effective way of teaching stable task-space motions to robots with goal convergence. Yet, these techniques are affected by serious limitations when it comes to ensuring safety and fulfillment of physical constraints. With this work, we propose to solve this challenge via TamedPUMA, an IL algorithm augmented with a recent development in motion planning called geometric fabrics. We explore two variations of this approach, which we name the forcing policy method and the compatible potential method. Making these combinations possible requires two enabling factors: the possibility of learning second-order dynamical systems by imitation and the availability of a potential function that is compatible with the learned dynamics. In this paper, we show how these conditions can be met when using an IL strategy called PUMA. The result is a stable imitation learning strategy within which we can seamlessly blend geometrical constraints like collision avoidance and joint limits. Beyond providing a theoretical analysis, we demonstrate TamedPUMA with simulated and real-world tasks, including a 7-degree-of-freedom manipulator that is trained to pick a tomato from a crate in the presence of obstacles.

Reactive grasp and motion planning for adaptive mobile manipulation among obstacles
Tomas Merva, Saray Bakker, Max Spahn, Ivan Virgala, Javier Alonso-Mora. In Robotics: Science and Systems, Workshop on Frontiers of Optimization for Robotics, 2024.

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Mobile manipulators are susceptible to situations in which the precomputed grasp pose is not reachable as the result of conflicts between collision avoidance behaviour and the manipulation task. In this work, we address this issue by combining real-time grasp planning with geometric motion planning for decentralized multi-agent systems, referred to as Reactive Grasp Fabrics (RGF). We optimize the precomputed grasp pose candidate to account for obstacles and the robot's kinematics. By leveraging a reactive geometric motion planner, specifically geometric fabrics, the grasp optimization problem can be simplified, resulting in a fast, adaptive framework that can resolve deadlock situations in pick-and-place tasks. We demonstrate the robustness of this approach by controlling a mobile manipulator in both simulation and real-world experiments in dynamic environments.

Evaluating Dynamic Environment Difficulty for Obstacle Avoidance Benchmarking
Moji Shi, Gang Chen, Alvaro Serra-Gomez, Siyuan Wu, Javier Alonso-Mora. In IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2024.

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Dynamic obstacle avoidance is a popular research topic for autonomous systems, such as micro aerial vehicles and service robots. Accurately evaluating the performance of dynamic obstacle avoidance methods necessitates the establishment of a metric to quantify the environment's difficulty, a crucial aspect that remains unexplored. In this paper, we propose four metrics to measure the difficulty of dynamic environments. These metrics aim to comprehensively capture the influence of obstacles' number, size, velocity, and other factors on the difficulty. We compare the proposed metrics with existing static environment difficulty metrics and validate them through over 1.5 million trials in a customized simulator. This simulator excludes the effects of perception and control errors and supports different motion and gaze planners for obstacle avoidance. The results indicate that the survivability metric outperforms and establishes a monotonic relationship between the success rate, with a Spearman's Rank Correlation Coefficient (SRCC) of over 0.9. Specifically, for every planner, lower survivability leads to a higher success rate. This metric not only facilitates fair and comprehensive benchmarking but also provides insights for refining collision avoidance methods, thereby furthering the evolution of autonomous systems in dynamic environments.
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Physically Grounded Optimal Realizations of Symbolic Plans
Andreu Matoses Gimenez, Nils Wilde, Chris Pek, Javier Alonso-Mora. In Robotics: Science and Systems (RSS), Workshop on Frontiers of Optimization for Robotics, 2024.

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Robot autonomy often involves planning high-level discrete decisions and continuous motion planning to realize each decision. Task and Motion Planning (TAMP) algorithms solve these hybrid problems jointly while considering constraints between the discrete symbolic actions, i.e., the task plan, and their continuous geometric realization. Previous TAMP algorithms have mostly focused on computational performance, completeness, or optimality. However, due to the required simplifications and abstractions, the resulting plans often do not account for robot dynamics, nor complex contacts. They also often ignore the effect of the low-level controllers on the optimality and/or feasibility of the plan's realizations. This work investigates the use of a parallelized physics simulator to compute realizations of the plan with a motion controller, realistic dynamics, and considering contacts with the environment. Using cross-entropy optimization, we sample the parameters used by the controllers, or actions, to obtain low-cost solutions. The resulting realized plan is straightforward to implement in the real system, as the robot uses the same controllers. We test our approach for a pick and place task, where our method is capable of finding low-cost feasible solutions in 1-2 min.
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Multi-Modal MPPI and Active Inference for Reactive Task and Motion Planning
Yuezhe Zhang, Corrado Pezzato, Elia Trevisan, Chadi Salmi, Carlos Hernández Corbato, Javier Alonso-Mora. In IEEE Robotics and Automation Letters (RA-L), 2024.

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Task and Motion Planning (TAMP) has made strides in complex manipulation tasks, yet the execution robustness of the planned solutions remains overlooked. In this work, we propose a method for reactive TAMP to cope with runtime uncertainties and disturbances. We combine an Active Inference planner (AIP) for adaptive high-level action selection and a novel Multi-Modal Model Predictive Path Integral controller (M3P2I) for low-level control. This results in a scheme that simultaneously adapts both high-level actions and low-level motions. The AIP generates alternative symbolic plans, each linked to a cost function for M3P2I. The latter employs a physics simulator for diverse trajectory rollouts, deriving optimal control by weighing the different samples according to their cost. This idea enables blending different robot skills for fluid and reactive plan execution, accommodating plan adjustments at both the high and low levels to cope, for instance, with dynamic obstacles or disturbances that invalidate the current plan. We have tested our approach in simulations and real-world scenarios.
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Decentralized Multi-Agent Trajectory Planning in Dynamic Environments with Spatiotemporal Occupancy Grid Maps
Siyuan Wu, Gang Chen, Moji Shi, Javier Alonso-Mora. In IEEE Int. Conf. on Robotics and Automation (ICRA), 2024.

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This paper proposes a decentralized trajectory planning framework for the collision avoidance problem of mul- tiple micro aerial vehicles (MAVs) in environments with static and dynamic obstacles. The framework utilizes spatiotemporal occupancy grid maps (SOGM), which forecast the occupancy status of neighboring space in the near future, as the environ- ment representation. Based on this representation, we extend the kinodynamic A* and the corridor-constrained trajectory optimization algorithms to efficiently tackle static and dynamic obstacles with arbitrary shapes. Collision avoidance between communicating robots is integrated by sharing planned tra- jectories and projecting them onto the SOGM. The simulation results show that our method achieves competitive performance against state-of-the-art methods in dynamic environments with different numbers and shapes of obstacles. Finally, the proposed method is validated in real experiments.

Auto-Encoding Bayesian Inverse Games
Xinjie Liu, Lasse Peters, Javier Alonso-Mora, Ufuk Topcu, David Fridovich-Keil. In 16th Workshop on the Algorithmic Foundations of Robotics (WAFR), 2024.

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When multiple agents interact in a common environment, each agent's actions impact others' future decisions, and noncooperative dynamic games naturally capture this coupling. In interactive motion planning, however, agents typically do not have access to a complete model of the game, e.g., due to unknown objectives of other players. Therefore, we consider the inverse game problem, in which some properties of the game are unknown a priori and must be inferred from observations. Existing maximum likelihood estimation (MLE) approaches to solve inverse games provide only point estimates of unknown parameters without quantifying uncertainty, and perform poorly when many parameter values explain the observed behavior. To address these limitations, we take a Bayesian perspective and construct posterior distributions of game parameters. To render inference tractable, we employ a variational autoencoder (VAE) with an embedded differentiable game solver. This structured VAE can be trained from an unlabeled dataset of observed interactions, naturally handles continuous, multi-modal distributions, and supports efficient sampling from the inferred posteriors without computing game solutions at runtime. Extensive evaluations in simulated driving scenarios demonstrate that the proposed approach successfully learns the prior and posterior game parameter distributions, provides more accurate objective estimates than MLE baselines, and facilitates safer and more efficient game-theoretic motion planning.

Contingency Games for Multi-Agent Interaction
Lasse Peters, Andrea Bajcsy, Chih-Yuan Chiu, David Fridovich-Keil, Forrest Laine, Laura Ferranti, Javier Alonso-Mora. In Robotics and Automation Letters (RA-L), 2024.

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Contingency planning, wherein an agent generates a set of possible plans conditioned on the outcome of an uncertain event, is an increasingly popular way for robots to act under uncertainty. In this work we take a game-theoretic perspective on contingency planning, tailored to multi-agent scenarios in which a robot’s actions impact the decisions of other agents and vice versa. The resulting contingency game allows the robot to efficiently interact with other agents by generating strategic motion plans conditioned on multiple possible intents for other actors in the scene. Contingency games are parameterized via a scalar variable which represents a future time when intent uncertainty will be resolved. By estimating this parameter online, we construct a game-theoretic motion planner that adapts to changing beliefs while anticipating future certainty. We show that existing variants of game-theoretic planning under uncertainty are readily obtained as special cases of contingency games. Through a series of simulated autonomous driving scenarios, we demonstrate that contingency games close the gap between certainty-equivalent games that commit to a single hypothesis and non-contingent multi-hypothesis games that do not account for future uncertainty reduction.
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Learning to Play Trajectory Games Against Opponents with Unknown Objectives
X. Liu, L. Peters, J. Alonso-Mora. In IEEE Robotics and Automation Letters (RA-L), 2023.

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Many autonomous agents, such as intelligent ve- hicles, are inherently required to interact with one another. Game theory provides a natural mathematical tool for robot motion planning in such interactive settings. However, tractable algorithms for such problems usually rely on a strong assumption, namely that the objectives of all players in the scene are known. To make such tools applicable for ego-centric planning with only local information, we propose an adaptive model-predictive game solver, which jointly infers other players’ objectives online and computes a corresponding generalized Nash equilibrium (GNE) strategy. The adaptivity of our approach is enabled by a differentiable trajectory game solver whose gradient signal is used for maximum likelihood estimation (MLE) of opponents’ objectives. This differentiability of our pipeline facilitates direct integration with other differentiable elements, such as neural networks (NNs). Furthermore, in contrast to existing solvers for cost inference in games, our method handles not only partial state observations but also general inequality constraints. In two simulated traffic scenarios, we find superior performance of our approach over both existing game-theoretic methods and non- game-theoretic model-predictive control (MPC) approaches. We also demonstrate our approach’s real-time planning capabilities and robustness in two-player hardware experiments.

RAST: Risk-Aware Spatio-Temporal Safety Corridors for MAV Navigation in Dynamic Uncertain Environments
G. Chen, S. Wu, M. Shi, W. Dong, H. Zhu, J. Alonso-Mora. In IEEE Robotics and Automation Letters (RA-L), 2023.

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Autonomous navigation of Micro Aerial Vehicles (MAVs) in dynamic and unknown environments is a complex and challenging task. Current works rely on assumptions to solve the problem. The MAV’s pose is precisely known, the dynamic obstacles can be explicitly segmented from static ones, their number is known and fixed, or they can be modeled with given shapes. In this paper, we present a method for MAV navigation in dynamic uncertain environments without making any of these assumptions. The method employs a particle-based dynamic map to represent the local environment and predicts it to the near future. Collision risk is defined based on the predicted maps and a series of risk-aware spatio-temporal (RAST) safety corridors are constructed, which are finally used to optimize a dynamically- feasible collision-free trajectory for the MAV. We compared our method with several state-of-the-art works in 12000 simulation tests in Gazebo with the physical engine enabled. The results show that our method has the highest success rate at different uncertainty levels. Finally, we validated the proposed method in real experiments.

Multi-Robot Local Motion Planning Using Dynamic Optimization Fabrics
Saray Bakker, Luzia Knoedler, Max Spahn, Wendelin Boehmer, Javier Alonso-Mora. In Proc. IEEE International Symposium on Multi-Robot and Multi-Agent Systems, 2023.

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In this paper, we address the problem of real-time motion planning for multiple robotic manipulators that operate in close proximity. We build upon the concept of dynamic fabrics and extend them to multi-robot systems, referred to as Multi-Robot Dynamic Fabrics (MRDF). This geometric method enables a very high planning frequency for high-dimensional systems at the expense of being reactive and prone to deadlocks. To detect and resolve deadlocks, we propose Rollout Fabrics where MRDF are forward simulated in a decentralized manner. We validate the methods in simulated close-proximity pick-and-place scenarios with multiple manipulators, showing high success rates and real-time performance.