Seyed Reza Ahmadzadeh

Towards Autonomous Robotic Valve Turning

Abstract In this paper an autonomous intervention robotic task to learn the skill of grasping and turning a valve is described. To resolve this challenge a set of different techniques are proposed, each one realizing a specific task and sending information to the others in a Hardware-In-Loop (HIL) simulation. To improve the estimation of the valve position, an Extended Kalman Filter is designed. Also to learn the trajectory to follow with the robotic arm, Imitation Learning approach is used. In addition, to perform safely the task a fuzzy system is developed which generates appropriate decisions. Although the achievement of this task will be used in an Autonomous Underwater Vehicle, for the first step this idea has been tested in a laboratory environment with an available robot and a sensor.

Autonomous robotic valve turning: A hierarchical learning approach

Autonomous valve turning is an extremely challenging task for an Autonomous Underwater Vehicle (AUV). To resolve this challenge, this paper proposes a set of different computational techniques integrated in a three-layer hierarchical scheme. Each layer realizes specific subtasks to improve the persistent autonomy of the system. In the first layer, the robot acquires the motor skills of approaching and grasping the valve by kinesthetic teaching. A Reactive Fuzzy Decision Maker (RFDM) is devised in the second layer which reacts to the relative movement between the valve and the AUV, and alters the robots movement accordingly. Apprenticeship learning method, implemented in the third layer, performs tuning of the RFDM based on expert knowledge. Although the long-term goal is to perform the valve turning task on a real AUV, as a first step the proposed approach is tested in a laboratory environment.

Learning symbolic representations of actions from human demonstrations

In this paper, a robot learning approach is proposed which integrates Visuospatial Skill Learning, Imitation Learning, and conventional planning methods. In our approach, the sensorimotor skills (i.e., actions) are learned through a learning from demonstration strategy. The sequence of performed actions is learned through demonstrations using Visuospatial Skill Learning. A standard action-level planner is used to represent a symbolic description of the skill, which allows the system to represent the skill in a discrete, symbolic form. The Visuospatial Skill Learning module identifies the underlying constraints of the task and extracts symbolic predicates (i.e., action preconditions and effects), thereby updating the planner representation while the skills are being learned. Therefore the planner maintains a generalized representation of each skill as a reusable action, which can be planned and performed independently during the learning phase. Preliminary experimental results on the iCub robot are presented.

Online Discovery of AUV Control Policies to Overcome Thruster Failures

We investigate methods to improve fault-tolerance of Autonomous Underwater Vehicles (AUVs) to increase their reliability and persistent autonomy. We propose a learning-based approach that is able to discover new control policies to overcome thruster failures as they happen. The proposed approach is a model-based direct policy search that learns on an on-board simulated model of the AUV. The model is adapted to a new condition when a fault is detected and isolated. Since the approach generates an optimal trajectory, the learned fault-tolerant policy is able to navigate the AUV towards a specified target with minimum cost. Finally, the learned policy is executed on the real robot in a closed-loop using the state feedback of the AUV. Unlike most existing methods which rely on the redundancy of thrusters, our approach is also applicable when the AUV becomes under-actuated in the presence of a fault. To validate the feasibility and efficiency of the presented approach, we evaluate it with three learning algorithms and three policy representations with increasing complexity. The proposed method is tested on a real AUV, Girona500.

Visuospatial skill learning for object reconfiguration tasks

We present a novel robot learning approach based on visual perception that allows a robot to acquire new skills by observing a demonstration from a tutor. Unlike most existing learning from demonstration approaches, where the focus is placed on the trajectories, in our approach the focus is on achieving a desired goal configuration of objects relative to one another. Our approach is based on visual perception which captures the objects context for each demonstrated action. This context is the basis of the visuospatial representation and encodes implicitly the relative positioning of the object with respect to multiple other objects simultaneously. The proposed approach is capable of learning and generalizing multi-operation skills from a single demonstration, while requiring minimum a priori knowledge about the environment. The learned skills comprise a sequence of operations that aim to achieve the desired goal configuration using the given objects. We illustrate the capabilities of our approach using three object reconfiguration tasks with a Barrett WAM robot.

Multi-objective reinforcement learning for AUV thruster failure recovery

This paper investigates learning approaches for discovering fault-tolerant control policies to overcome thruster failures in Autonomous Underwater Vehicles (AUV). The proposed approach is a model-based direct policy search that learns on an on-board simulated model of the vehicle. When a fault is detected and isolated the model of the AUV is reconfigured according to the new condition. To discover a set of optimal solutions a multi-objective reinforcement learning approach is employed which can deal with multiple conflicting objectives. Each optimal solution can be used to generate a trajectory that is able to navigate the AUV towards a specified target while satisfying multiple objectives. The discovered policies are executed on the robot in a closed-loop using AUVs state feedback. Unlike most existing methods which disregard the faulty thruster, our approach can also deal with partially broken thrusters to increase the persistent autonomy of the AUV. In addition, the proposed approach is applicable when the AUV either becomes under-actuated or remains redundant in the presence of a fault. We validate the proposed approach on the model of the Girona500 AUV.

Learning reactive robot behavior for autonomous valve turning

A learning approach is proposed for the challenging task of autonomous robotic valve turning in the presence of active disturbances and uncertainties. The valve turning task comprises two phases: reaching and turning. For the reaching phase the manipulator learns how to generate trajectories to reach or retract from the target. The learning is based on a set of trajectories demonstrated in advance by the operator. The turning phase is accomplished using a hybrid force/motion control strategy. Furthermore, a reactive decision making system is devised to react to the disturbances and uncertainties arising during the valve turning process. The reactive controller monitors the changes in force, movement of the arm with respect to the valve, and changes in the distance to the target. Observing the uncertainties, the reactive system modulates the valve turning task by changing the direction and rate of the movement. A real-world experiment with a robot manipulator mounted on a movable base is conducted to show the efficiency and validity of the proposed approach.

Interactive robot learning of visuospatial skills

This paper proposes a novel interactive robot learning approach for acquiring visuospatial skills. It allows a robot to acquire new capabilities by observing a demonstration while interacting with a human caregiver. Most existing learning from demonstration approaches focus on the trajectories, whereas in our approach the focus is placed on achieving a desired goal configuration of objects relative to one another. Our approach is based on visual perception which captures the objects context for each demonstrated action. The context embodies implicitly the visuospatial representation including the relative positioning of the object with respect to multiple other objects simultaneously. The proposed approach is capable of learning and generalizing different skills such as object reconfiguration, classification, and turn-taking interaction. The robot learns to achieve the goal from a single demonstration while requiring minimum a priori knowledge about the environment. We illustrate the capabilities of our approach using four real world experiments with a Barrett WAM robot.

Visuospatial Skill Learning

This chapter introduces Visuospatial Skill Learning (VSL) , which is a novel interactive robot learning approach. VSL is based on visual perception that allows a robot to acquire new skills by observing a single demonstration while interacting with a tutor. The focus of VSL is placed on achieving a desired goal configuration of objects relative to another. VSL captures the object’s context for each demonstrated action. This context is the basis of the visuospatial representation and encodes implicitly the relative positioning of the object with respect to multiple other objects simultaneously. VSL is capable of learning and generalizing multi-operation skills from a single demonstration, while requiring minimum a priori knowledge about the environment. Different capabilities of VSL such as learning and generalization of object reconfiguration, classification, and turn-takinginteraction are illustrated through both simulation and real-world experiments.

Robot Learning for Persistent Autonomy

Autonomous robots are not very good at being autonomous. They work well in structured environments, but fail quickly in the real world facing uncertainty and dynamically changing conditions. In this chapter, we describe robot learning approaches that help to elevate robot autonomy to the next level, the so-called ‘persistent autonomy’. For a robot to be ‘persistently autonomous’ means to be able to perform missions over extended time periods (e.g. days or months) in dynamic, uncertain environments without need for human assistance. In particular, persistent autonomy is extremely important for robots in difficult-to-reach environments such as underwater, rescue, and space robotics. There are many facets of persistent autonomy, such as: coping with uncertainty, reacting to changing conditions, disturbance rejection, fault tolerance, energy efficiency and so on. This chapter presents a collection of robot learning approaches that address many of these facets. Experiments with robot manipulators and autonomous underwater vehicles demonstrate the usefulness of these learning approaches in real world scenarios.