Publications
Sean Bone, Luca Bartolomei, Florian Kennel-Maushart, Margarita Chli
IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) - September 2023
Autonomous robotic systems are useful in automating tasks such as inspection and surveying of unknown areas, where speed is often an important factor. In order to effectively reduce the time required to complete missions, an efficient exploration and coordination strategy is needed. In this spirit, this work proposes an approach based on the Monte Carlo Tree Search (MCTS) algorithm to guide robots during exploration missions. Our method first expands a search tree of possible actions from the robot's position towards unknown regions, and then selects the sequence of movements that best drive the exploration process forward with respect to a given reward function. The proposed approach, which is able to balance short- and long-term decision-making, is then extended to accommodate the presence of multiple robots, in a bid to push the efficiency of exploration further. Our method allows for the coordination of the robots' movements in a decentralized manner, relying on point-to-point communication. This results in an efficient strategy, which we refer to as Decentralized Monte Carlo Exploration (DMCE). The experimental results demonstrate that our pipeline outperforms a greedy exploration approach, as well as state-of-the-art planners, with up to 30% reduction in exploration times in a series of real-world maps.
Ziqi Wang, Florian Kennel-Maushart, Yijiang Huang, Bernhard Thomaszewski, Stelian Coros
ACM Transactions on Graphics, presented at ACM SIGGRAPH - July 2023
We present a computational framework for planning the assembly sequence of bespoke frame structures. Frame structures are one of the most commonly used structural systems in modern architecture, providing resistance to gravitational and external loads. Building frame structures requires traversing through several partially built states. If the assembly sequence is planned poorly, these partial assemblies can exhibit substantial deformation due to self-weight, slowing down or jeopardizing the assembly process. Finding a good assembly sequence that minimizes intermediate deformations is an interesting yet challenging combinatorial problem that is usually solved by heuristic search algorithms. In this paper, we propose a new optimization-based approach that models sequence planning using a series of topology optimization problems. Our key insight is that enforcing temporal coherent constraints in the topology optimization can lead to sub-structures with small deformations while staying consistent with each other to form an assembly sequence. We benchmark our algorithm on a large data set and show improvements in both performance and computational time over greedy search algorithms. In addition, we demonstrate that our algorithm can be extended to handle assembly with static or dynamic supports. We further validate our approach by generating a series of results in multiple scales, including a real-world prototype with a mixed reality assistant using our computed sequence and a simulated example demonstrating a multi-robot assembly application.
Florian Kennel-Maushart, Roi Poranne, Stelian Coros
IEEE International Conference on Robotics and Automation (ICRA) - May 2023
Visualization by Beat Reichenbach
Mobile robots are becoming safer and more affordable, and their presence in the workspace is increasing. However, many tasks that involve reasoning, long-term planning or human preferences are still hard to automate. While some solutions in specialised areas slowly emerge, an alternative to full autonomy can be to actively leverage intuition and experience of human operators. To do this, suitable interfaces and modes of interaction have to be explored. Inspired by Real-Time Strategy games, we implement a Mixed Reality interface that can be used with either a Microsoft HoloLens 2 headset or a tablet. The interface allows users to interact with multiple mobile robots simultaneously. We conduct a user study to compare the headset and tablet versions of the interface in different scenarios inspired by a real-world construction setting. We show that while performance and preference of interface are dependent on the task and the complexity of the required interaction, users are able to solve non-trivial tasks on both platforms using our system.
Florian Kennel-Maushart, Roi Poranne, Stelian Coros
IEEE International Conference on Robotics and Automation (ICRA) - May 2022
Many tasks can be performed better by a multi-robot system than by a single robot. Carrying a large payload is one such task, which is often required on construction sites and in warehouses. Working together, multiple robots can carry these large payloads, while providing more speed and stability and while costing less than a single, specialized robot. Ideally, an operator would only need to specify where to take the payload from, and where to place it, e.g. for installation or storage. However, real environments are generally complex and dynamic, and might require constant attention from the operator. Additionally, directly controlling multiple arms and keeping an overview over their individual and collective motion places a significant cognitive burden on the operator. For example, these systems are sensitive to singular configurations, which can result in dangerous, fast motions. To reduce mental strain for the operator and increase security, it is necessary that, while carrying out the task, the multi-robot system automatically avoids these configurations. We present a mixed reality control interface that allows the operator to specify the payload target poses in real-time, while effectively keeping the system away from bad configurations. To this end, we solve the inverse kinematics problem for each arm individually and leverage available degrees of freedom to optimize for a secondary objective. Using the manipulability index as a secondary objective in particular, allows us to significantly improve the tracking and singularity avoidance capabilities of our multi-robot system in comparison to the unoptimized scenario. We test our approach on different setups and over different input trajectories, and show that the method works well when deployed on to a two-armed ABB YuMi robot.
Florian Kennel-Maushart, Roi Poranne, Stelian Coros
IEEE International Conference on Robotics and Automation (ICRA) - June 2021
Teleoperation provides a way for human operators to guide robots in situations where full autonomy is challenging or where direct human intervention is required. It can also be an important tool to teach robots in order to achieve autonomous behaviour later on. The increased availability of collaborative robot arms and Virtual Reality (VR) devices, provides ample opportunity for development of novel teleoperation methods. Since robot arms are often kinematically different from human arms, mapping human motions to a robot in real-time is not trivial. Additionally, a human operator might steer the robot arm toward singularities or its workspace limits, which can lead to undesirable behaviour. This is further accentuated for the orchestration of multiple robots. In this paper, we present a VR interface targeted to multi-arm payload manipulation, which can closely match real-time input motion. Allowing the user to manipulate the payload rather than mapping their motions to individual arms we are able to simultaneously guide multiple collaborative arms. By releasing a single rotational degree of freedom, and by using a local optimization method, we can improve each arm’s manipulability index, which in turn lets us avoid kinematic singularities and workspace limitations. We apply our approach to predefined trajectories as well as real-time teleoperation on different robot arms and compare performance in terms of end-effector position error and relevant joint motion metrics.
Florian Maushart, Amanda Prorok, M. Ani Hsieh, Vijay Kumar
IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) - September 2017
We present a novel framework for integrity analysis of swarm robotic systems using the symmetric Kullback-Leibler Divergence. The objective is to understand a robot swarm's vulnerability to malicious intrusion and to develop the necessary computational tools that would detect the presence of malicious agents within the swarm. Using ensemble approaches for modeling and analyzing stochastic task allocation, we analyze the performance of the proposed strategy subject to different system parameters, and show how different design choices can facilitate early intrusion detection. We further evaluate the performance of our method in realistic scenarios through stochastic simulations for different team sizes. The main contribution is an analysis framework whose output can be used to avoid system-inherent design flaws and to decrease the damage that can be inflicted by an undetected attacker.
