Retour au site du LAAS-CNRS

Abstract

Planning for real world applications, with explicit temporal representation and a robust execution is a very challenging problem. To tackle it, the planning community has proposed a number of original and successful approaches. However, there are other paradigms "outside" the Automated Planning field which may prove to be successful with respect to this objective. This paper presents a comparison of two "planning" approaches dealing with temporal and/or discrete uncertainties and with a strong emphasis on robust execution. The first approach is based on chronicles and constraint satisfaction techniques; it relies on a causal link partial order temporal planner, in our case IXTET. The second approach is based on timed game automata and reachability analysis, and uses the UPPAAL-TIGA system. The comparison is both qualitative (the kind of problems modeled and the properties of plans obtained) and quantitative (experimental results on a real example). To make this comparison possible, we propose a general scheme to translate a subset of IXTET planning problems into UPPAAL-TIGA game-reachability problems. A direct consequence of this automated process would be the possibility to apply validation and verification techniques available in the timed automata community.

Abstract

Autonomous robots offer alluring perspectives in numerous application domains: space rovers, satellites, medical assistants, tour guides, etc. However, a severe lack of trust in their dependability greatly reduces their possible usage. In particular, autonomous systems make extensive use of decisional mechanisms that are able to take complex and adaptative decisions, but are very hard to validate. This paper proposes a fault tolerance approach for decisional planning components, which are almost mandatory in complex autonomous systems. The proposed mechanisms focus on development faults in planning models and heuristics, through the use of diversification. The paper presents an implementation of these mechanisms on an existing autonomous robot architecture, and evaluates their impact on performance and reliability through the use of fault injection.

Abstract

Autonomous robots offer alluring perspectives in numerous application domains: space rovers, satellites, medical assistants, tour guides, etc. However, a severe lack of trust in their dependability greatly reduces their possible usage. In particular, autonomous systems make extensive use of decisional mechanisms that are able to take complex and adaptative decisions, but are very hard to validate. This paper proposes a fault tolerance approach for decisional planning components, which are almost mandatory in complex autonomous systems. The proposed mechanisms focus on development faults in planning models and heuristics, through the use of diversi ication. The paper presents an implementation of these mechanisms on an existing autonomous robot architecture, and evaluates their impact on performance and reliability through the use of fault injection.

Mots-Clés / Keywords

Abstract

Autonomous robots make extensive use of decisional mechanisms, such as planning. These mechanisms are able to take complex and adaptative decisions, but are notoriously hard to validate. This paper reports an investigation of how redundant, diversi ied models can be used to tolerate residual design faults in such mechanisms. A fault-tolerant temporal planner has been designed and implemented using diversity, and its effectiveness demonstrated experimentally through fault injection. The pa- per describes the implementation of the fault-tolerant planner and discusses the results obtained. The results indicate that diversi ication provides a noticeable improvement in planning reliability with a negligible performance overhead. However, further improvements in reliability will require implementation of a on-line checking mechanism for assessing plan validity before execution.

Mots-Clés / Keywords

Abstract

In the immediate future, metrics related to safety and dependability have to be found in order to successfully introduce robots in everyday environments. The crucial issues needed to tackle the problem of a safe and dependable physical human-robot interaction (pHRI) were addressed in the EURON Perspective Research Project PHRIDOM (Physical Human- Robot Interaction in Anthropic Domains), aimed at charting the new territory of pHRI. While there are certainly also cognitive issues involved, due to the human perception of the robot (and vice versa), and other objective metrics related to fault detection and isolation, the discussion in this paper will focus on the peculiar aspects of physical interaction with robots. In particular, safety and dependability will be the underlying evaluation criteria for mechanical design, actuation, and control architectures. Mechanical and control issues will be discussed with emphasis on techniques that provide safety in an intrinsic way or by means of control components. Attention will be devoted to dependability, mainly related to sensors, control architectures, and fault handling and tolerance. After PHRIDOM, a novel research project has been launched under the Information Society Technologies Sixth Framework Programme of the European Commission. This Specific Targeted Research or Innovation project is dedicated to Physical Human-Robot Interaction: depENDability and Safety (PHRIENDS). PHRIENDS is about developing key components of the next generation of robots, including industrial robots and assist devices, designed to share the environment and to physically interact with people. The philosophy of the project proposes an integrated approach to the co-design of robots for safe physical interaction with humans, which revolutionizes the classical approach for designing industrial robots  rigid design for accuracy, active control for safety  by creating a new paradigm: design robots that are intrinsically safe, and control them to deliver performance. This paper presents the state of the art in the field as surveyed by the PHRIDOM project, as well as it enlightens a number of challenges that will be undertaken within the PHRIENDS project.

Mots-Clés / Keywords