Efficient learning of sequential tasks for collaborative robots: a neurodynamic approach

Dissertação de mestrado integrado em Engenharia Eletrónica, Industrial e ComputadoresIn the recent years, there has been an increasing demand for collaborative robots able to interact and co operate with ordinary people in several human environments, sharing physical space and working closely with people in joint tasks, both within industrial and domestic environments. In some scenarios, these robots will come across tasks that cannot be fully designed beforehand, resulting in a need for flexibility and adaptation to the changing environments. This dissertation aims to endow robots with the ability to acquire knowledge of sequential tasks using the Programming by Demonstration (PbD) paradigm. Concretely, it extends the learning models - based on Dynamic Neural Fields (DNFs) - previously developed in the Mobile and Anthropomorphic Robotics Laboratory (MARLab), at the University of Minho, to the collaborative robot Sawyer, which is amongst the newest collaborative robots on the market. The main goal was to endow Sawyer with the ability to learn a sequential task from tutors’ demonstrations, through a natural and efficient process. The developed work can be divided into three main tasks: (1) first, a previously developed neuro-cognitive control architecture for extracting the sequential structure of a task was implemented and tested in Sawyer, combined with a Short-Term Memory (STM) mechanism to memorize a sequence in one-shot, aiming to reduce the number of demonstration trials; (2) second, the previous model was extended to incorporate workspace information and action selection in a Human-Robot Collaboration (HRC) scenario where robot and human co worker coordinate their actions to construct the structure; and (3) third, the STM mechanism was also extended to memorize ordinal and temporal aspects of the sequence, demonstrated by tutors with different behavior time scales. The models implemented contributed to a more intuitive and practical interaction with the robot for human co-workers. The STM model made the learning possible from few demonstrations to comply with the requirement of being an efficient method for learning. Moreover, the recall of the memorized information allowed Sawyer to evolve from being in a learning position to be in a teaching one, obtaining the capability of assisting inexperienced co-workers.Nos últimos anos, tem havido uma crescente procura por robôs colaborativos capazes de interagir e cooperar com pessoas comuns em vários ambientes, partilhando espaço físico e trabalhando em conjunto, tanto em ambientes industriais como domésticos. Em alguns cenários, estes robôs serão confrontados com tarefas que não podem ser previamente planeadas, o que resulta numa necessidade de existir flexibilidade e adaptação ao ambiente que se encontra em constante mudança. Esta dissertação pretende dotar robôs com a capacidade de adquirir conhecimento de tarefas sequenciais utilizando técnicas de Programação por Demonstração. De forma a continuar o trabalho desenvolvido no Laboratório de Robótica Móvel e Antropomórfica da Universidade do Minho, esta dissertação visa estender os modelos de aprendizagem previamente desenvolvidos ao robô colaborativo Sawyer, que é um dos mais recentes no mercado. O principal objetivo foi dotar o robô com a capacidade de aprender tarefas sequenciais por demonstração, através de um processo natural e eficiente. O trabalho desenvolvido pode ser dividido em três tarefas principais: (1) em primeiro lugar, uma arquitetura de controlo baseada em modelos neurocognitivos, desenvolvida anteriormente, para aprender a estrutura de uma tarefa sequencial foi implementada e testada no robô Sawyer, conjugada com um mecanismo de Short Term Memory que permitiu memorizar uma sequência apenas com uma demonstração, para reduzir o número de demonstrações necessárias; (2) em segundo lugar, o modelo anterior foi estendido para englobar informação acerca do espaço de trabalho e seleção de ações num cenário de Colaboração Humano-Robô em que ambos coordenam as suas ações para construir a tarefa; (3) em terceiro lugar, o mecanismo de Short-Term Memory foi também estendido para memorizar informação ordinal e temporal de uma sequência de passos demonstrada por tutores com comportamentos temporais diferentes. Os modelos implementados contribuíram para uma interação com o robô mais intuitiva e prática para os co-workers humanos. O mecanismo de Short-Term Memory permitiu que a aprendizagem fosse realizada a partir de poucas demonstrações, para cumprir com o requisito de ser um método de aprendizagem eficiente. Além disso, a informação memorizada permitiu ao Sawyer evoluir de uma posição de aprendizagem para uma posição em que é capaz de instruir co-workers inexperientes.This work was carried out within the scope of the project “PRODUTECH SIF - Soluções para a Indústria do Futuro”, reference POCI-01-0247-FEDER-024541, cofunded by “Fundo Europeu de Desenvolvimento Regional (FEDER)”, through “Programa Operacional Competitividade e Internacionalização (POCI)”

Neuro-symbolic Rule Learning in Real-world Classification Tasks

Neuro-symbolic rule learning has attracted lots of attention as it offers better interpretability than pure neural models and scales better than symbolic rule learning. A recent approach named pix2rule proposes a neural Disjunctive Normal Form (neural DNF) module to learn symbolic rules with feed-forward layers. Although proved to be effective in synthetic binary classification, pix2rule has not been applied to more challenging tasks such as multi-label and multi-class classifications over real-world data. In this paper, we address this limitation by extending the neural DNF module to (i) support rule learning in real-world multi-class and multi-label classification tasks, (ii) enforce the symbolic property of mutual exclusivity (i.e. predicting exactly one class) in multi-class classification, and (iii) explore its scalability over large inputs and outputs. We train a vanilla neural DNF model similar to pix2rule's neural DNF module for multi-label classification, and we propose a novel extended model called neural DNF-EO (Exactly One) which enforces mutual exclusivity in multi-class classification. We evaluate the classification performance, scalability and interpretability of our neural DNF-based models, and compare them against pure neural models and a state-of-the-art symbolic rule learner named FastLAS. We demonstrate that our neural DNF-based models perform similarly to neural networks, but provide better interpretability by enabling the extraction of logical rules. Our models also scale well when the rule search space grows in size, in contrast to FastLAS, which fails to learn in multi-class classification tasks with 200 classes and in all multi-label settings.Comment: Accepted at AAAI-MAKE 202