New Zealand


Robots learning from observations in the real world using inverse reinforcement learning (IRL) may encounter objects or agents in the environment, other than the expert, that cause nuisance observations during the demonstration. These confounding elements are typically removed in fully-controlled environments such as virtual simulations or lab settings. When complete removal is impossible the nuisance observations must be filtered out. However, identifying the source of observations when large amounts of observations are made is difficult. To address this, we present a hierarchical Bayesian process that models both the expert&#39;s and the confounding elements&#39; observations thereby explicitly modeling the diverse observations a robot may receive. We extend an existing IRL algorithm originally designed to work under partial occlusion of the expert to consider the diverse and noisy observations. In a simulated robotic sorting domain containing both occlusion and confounding elements, we demonstrate the model&#39;s effectiveness. In particular, our technique outperforms several other comparative methods, second only to having perfect knowledge of the subject&#39;s trajectory.

AAMAS 2022

A Hierarchical Bayesian Process for Inverse RL in Partially-Controlled Environments

produce sorting

cobots

uncertainty

maximum entropy

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Robots learning from observations in the real world using inverse reinforcement learning (IRL) may encounter objects or agents in the environment, other than the expert, that cause nuisance observations during the demonstration. These confounding elements are typically removed in fully-controlled environments such as virtual simulations or lab settings. When complete removal is impossible the nuisance observations must be filtered out. However, identifying the source of observations when large amounts of observations are made is difficult. To address this, we present a hierarchical Bayesian process that models both the expert's and the confounding elements' observations thereby explicitly modeling the diverse observations a robot may receive. We extend an existing IRL algorithm originally designed to work under partial occlusion of the expert to consider the diverse and noisy observations. In a simulated robotic sorting domain containing both occlusion and confounding elements, we demonstrate the model's effectiveness. In particular, our technique outperforms several other comparative methods, second only to having perfect knowledge of the subject's trajectory.

technical paper

AAMAS (International Conference on Autonomous Agents and Multiagent Systems) is the largest and most influential conference in the area of agents and multiagent systems. The aim of the conference is to bring together researchers and practitioners in all areas of agent technology and to provide a single, high-profile, internationally renowned forum for research in the theory and practice of autonomous agents and multiagent systems. AAMAS is the flagship conference of the non-profit International Foundation for Autonomous Agents and Multiagent Systems (IFAAMAS).

The AAMAS conference series was initiated in 2002 in Bologna, Italy as a joint event comprising the 6th International Conference on Autonomous Agents (AA), the 5th International Conference on Multiagent Systems (ICMAS), and the 9th International Workshop on Agent Theories, Architectures, and Languages (ATAL).

Subsequent AAMAS conferences have been held in Melbourne, Australia (July 2003), New York City, NY, USA (July 2004), Utrecht, The Netherlands (July 2005), Hakodate, Japan (May 2006), Honolulu, Hawaii, USA (May 2007), Estoril, Portugal (May 2008), Budapest, Hungary (May 2009), Toronto, Canada (May 2010), Taipei, Taiwan (May 2011), Valencia, Spain (June 2012), Minnesota, USA (May 2013), Paris, France (May 2014), Istanbul, Turkey (May 2015), Singapore (May 2016), São Paulo (2017) and Stockholm, Sweden (2018), Montreal (May 2019), Auckland (May 2020, Virtual), London (May 2021, Virtual).
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AAMAS (International Conference on Autonomous Agents and Multiagent Systems) is the largest and most influential conference in the area of agents and multiagent systems. The aim of the conference is to bring together researchers and practitioners in all areas of agent technology and to provide a single, high-profile, internationally renowned forum for research in the theory and practice of autonomous agents and multiagent systems. AAMAS is the flagship conference of the non-profit International Foundation for Autonomous Agents and Multiagent Systems (IFAAMAS).


Many research works in computational social choice assume a fixed set of voters in an election, and study the resistance of different voting rules against electoral manipulation. In recent years, however, a new technique known as {\it random sample voting} has been adopted in many multi-agent systems. One of the most prominent examples is blockchain. Many proof-of-stake based blockchain systems like Algorand will randomly select a subset of participants of the system to form a committee, and only the committee members will be involved in the decision of some important system parameters. This can be viewed as running an election where the voter committee (i.e., the voters whose votes will be counted) is randomly selected. It is generally expected that the introduction of such randomness should make the election more resistant to electoral manipulation, despite the lack of theoretical analysis. In this paper, we present a systematic study on the resistance of an election with a randomly selected voter committee against bribery. Since the committee is randomly generated, by bribing any fixed subset of voters, the designated candidate may or may not win. Consequently, we consider the problem of finding a feasible solution that maximizes the winning probability of the designated candidate. We show that for most voting rules, this problem becomes extremely difficult for the briber as even finding any non-trivial solution with non-zero objective value becomes NP-hard. However, for plurality and 1-veto, there exists a polynomial time approximation scheme which computes a near-optimal solution efficiently. The algorithm builds upon a novel integer programming formulation together with techniques from $n$-fold integer programming, which may be of separate interest.

How Hard is Bribery in Elections with Randomly Selected Voters


Sampling-based motion planners such as RRT* and BIT*, when applied to kinodynamic motion planning, rely on steering functions to generate time-optimal solutions connecting sampled states. Implementing exact steering functions requires either analytical solutions to the time-optimal control problem, or nonlinear programming (NLP) solvers to solve the boundary value problem given the system's kinodynamic equations. Unfortunately, analytical solutions are unavailable for many real-world domains, and NLP solvers are prohibitively computationally expensive, hence fast and optimal kinodynamic motion planning remains an open problem. We provide a solution to this problem by introducing State Supervised Steering Function (S3F), a novel approach to learn time-optimal steering functions. S3F is able to produce near-optimal solutions to the steering function orders of magnitude faster than its NLP counterpart. Experiments conducted on three challenging robot domains show that RRT* using S3F significantly outperforms state-of-the-art planning approaches on both solution cost and runtime. We further provide a proof of probabilistic completeness of RRT* modified to use S3F.

State Supervised Steering Function for Sampling-based Kinodynamic Planning


Wireless Rechargeable Sensor Networks (WRSNs) are especially promising in large-area monitoring tasks that are previously impossible to complete by traditional Wireless Sensor Networks (WSNs). Mobile Chargers (MCs) in WRSNs are to cooperatively charge battery drained sensor nodes high efficiently and with a guarantee of sensors survival. Considering the unpredictability and high dynamics of WRSNs during the charging process, Multi-Agent Reinforcement Learning (MARL) is an attractive alternative to schedule the cooperation among MCs. However, most existing MARL methods based on Dec-POMDP only work for scenarios that agents make decisions at the same time step. Nevertheless, MCs in WRSNs perform charging asynchronously since the charging time of each sensor node varies. To address this problem, we first formulate an Asynchronous Dec-POMDP (AD-POMDP) for asynchronous decision-making. We propose an algorithm called Asynchronous and Scalable Multi-Agent PPO (ASM-PPO) which is a multi-agent PPO variant that allows asynchronous decision-making in AD-POMDP. Furthermore, ASM-PPO takes advantage of the translation invariance in WRSNs to avoid the huge input space dimensions caused by centralized training. The evaluation results not only indicate that our method achieves much charging efficiency and the longer lifetime of sensor nodes, but also demonstrate that ASM-PPO has advantages in terms of stability and scalability over existing methods.

ASM-PPO: Asynchronous and Scalable Multi-Agent PPO for Cooperative Charging


Agile software development is a popular and widely adopted practice due to its flexible and iterative nature that facilitates rapid prototyping. Recent work presented an agile approach to capturing requirements in agent systems via user and system stories. User and system stories present the requirements from the user and system perspective, respectively. Each story contains a set of acceptance criteria , which are a set of statements that identify the conditions under which the system behaviour can be accepted by the users or stakeholders. In this paper, we present a novel approach to testing the requirements that are specified via User and System stories in an agent system. We do this by developing a systematic approach to validating the execution traces output by the system against the specified acceptance criteria for each story. The approach identifies acceptance criterion that are met successfully in execution and those that fail. We present a fault model that categorises the failures providing insight to the developers to address the failed cases. We classify three kinds of faults for a given acceptance criteria: (a) the trigger condition is never met; (b) when the trigger occurs the preconditions are not met; or (iii) the trigger and preconditions are met but the resulting actions are not as expected. The motivating application of our work, which is also the test-bed for evaluation, is an agent-based simulation application for modelling the behaviours of civilians in a bushfire emergency scenario that is used in practice. We show our approach is able to successfully test and uncover requirements that were not met in this application.

Testing requirements via User and System Stories in Agent Systems


Decentralized cooperation in partially-observable multi-agent systems requires effective communications among agents. To support this effort, this work focuses on the class of problems where global communications are available but may be unreliable, thus precluding differentiable communication learning methods. We introduce FCMNet, a reinforcement learning based approach that allows agents to simultaneously learn a) an effective multi-hop communications protocol and b) a common, decentralized policy that enables team-level decision-making. Specifically, our proposed method utilizes the hidden states of multiple directional recurrent neural networks as communication messages among agents. Using a simple multi-hop topology, we endow each agent with the ability to receive information sequentially encoded by every other agent at each time step, leading to improved global cooperation. We demonstrate FCMNet on a challenging set of StarCraft II micromanagement tasks with shared rewards, as well as a collaborative multi-agent pathfinding task with individual rewards. There, our comparison results show that FCMNet outperforms state-of-the-art communication-based reinforcement learning methods in all StarCraft II micromanagement tasks, and value decomposition methods in certain tasks. We further investigate the robustness of FCMNet under realistic communication disturbances, such as random message loss or binarized messages (i.e., non-differentiable communication channels), to showcase FMCNet’s potential applicability to robotic tasks under a variety of real-world conditions.

FCMNet: Full Communication Memory Net for Team-Level Cooperation in Multi-Agent Systems


A protocol specifies interactions between roles, which together constitute a multiagent system (MAS).
Existing protocol-based approaches simply assume that the MAS is instantiated; that is, that the roles are bound.
However, practical applications must bind their roles to enact a protocol. 

Pippi addresses this problem of MAS instantiation.
It proposes the notion of a metaprotocol, enacting which instantiates a MAS suitable for enacting a given protocol.
Pippi demonstrates the subtleties involved in instantiating MAS arising from protocol composition, correlation, and decentralization.
To address these subtleties, and further support practical application patterns, we introduce an enhanced protocol language, with support for semantic names and namespaces, parameter types (including role and protocol typed parameters, for metaprotocols), interface flexibility, and binding constraints.
We discuss the realization of our approach through an extended agent architecture, including the novel concept of a MAS adapter for contact management.
We evaluate Pippi's expressiveness by demonstrating common patterns for agent discovery.

Pippi: Practical Protocol Instantiation


This paper is about modeling and verifying quantitative group trust. We present a formal analysis of this concept that allows us to express and reason about trust in multi-agent systems in a quantitative setting. We introduce GTL, the graded branching temporal logic that includes operators for quantitative aspects of trust within a group. A two-stage verification procedure of the logic is presented. The first stage is a transformation procedure, and the second stage is an indirect procedure that makes use of an existing model checking algorithm. Theoretical results about the soundness, completeness and complexity of the procedure are presented.

Quantitative Group Trust: A Two-Stage Verification Approach


Given a Markov decision process (MDP) and a linear-time ($\omega$-regular or Linear Temporal Logic) specification, the controller synthesis problem aims to compute the optimal policy that satisfies the specification. Recently, problems that reason over the asymptotic behavior of systems have been proposed through the lens of steady-state planning. This entails finding a control policy for an MDP such that the Markov chain induced by the solution policy satisfies a given set of constraints on its steady-state distribution. This paper studies a generalization of the controller synthesis problem for a linear-time specification under steady-state constraints on the asymptotic behavior. We present an algorithm to find a deterministic policy satisfying omega-regular and steady-state constraints by characterizing the solutions as an integer linear program, and experimentally evaluate our approach.

Controller Synthesis for Omega-Regular and Steady-State Specifications


With the rising demand of deploying robot teams in autonomous warehouses and factories, the Multi-agent Path Finding (MAPF) problem has drawn more and more attention. However, the classical MAPF problem focuses on navigating agent teams to reach single goal locations while avoiding collisions, and thus it cannot plan the case in which each agent is associated with a sequence of goal locations, and precedence constraints across goal sequences should be respected. Planning with these goal sequences and precedence constraints is important in real-world multi-agent systems. For example, a mobile robot needs to move an inventory pod to several stations for delivering different packages, which is captured by a sequence of goal locations, and another robot can only pick up a package after it has been delivered to the corresponding station, which can be modeled as precedence constraints across goal sequences. In this paper, we formalize the Multi-Agent Path Finding with Precedence Dependency (MAPF-PD) problem along with two algorithms to systematically solve this problem: Conflict-Based Search with Precedence Dependency (CBS-PD) is a complete and optimal algorithm; and Priority-Based Search with Precedence Dependency (PBS-PD) is an incomplete and suboptimal algorithm but shows great scalability and obtains near-optimal solutions in practice. Our experimental results show that our algorithms can scale to dozens of agents with hundreds of goal locations and precedence constraints.

Multi-Agent Path Finding for Precedence-Constrained Goal Sequences


This extended abstract summarises the contributions from the journal article "Enabling BDI group plans with coordination middleware: semantics and implementation".

A Hierarchical Bayesian Process for Inverse RL in Partially-Controlled Environments

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