Emilia Villani

A proposal and verification of a software architecture based on LabVIEW for a multifunctional robotic end-effector

This paper proposes a software architecture based on LabVIEW for controlling discrete event systems. The proposed architecture is an adaptation of the producer-consumer design pattern. This work uses the control software of a multifunctional robotic end-effector as a test-bed for analyzing the applicability of the software architecture and its limitations and advantages. This case study demonstrates the effectiveness of the architecture for dealing with the integration of multiple functionalities in the control system. For this case study, the validation of the architecture is performed using two verification techniques: (1) a formal verification using timed automata and the UPPAAL model checker and (2) the CoFI (Conformance and Fault Injection) method for defining the set of test cases to check the software product. Both verification techniques identified errors that were introduced into the control system during the programming phase.

Contributions of model checking and CoFI methodology to the development of space embedded software

The role of embedded software in the last space accidents highlights the importance of verification and validation techniques for the development of space embedded software. In this context, this work analyses the contribution of two verification techniques applied to the onboard data handling software of space products. The first technique is model checking. The system is modeled by a set of timed automata and the verification of safety and liveness properties is performed using UPPAAL model checker. The verified model is then used to generate the embedded software. The second technique analyzed in this work is model based approach for the generation of test cases. The Conformance and Fault Injection (CoFI) testing methodology is used to guide the development of a set of Finite State Machine (FSM) models from the software specification. The test suite is automatically generated from the FSM models. The contributions of the two methodologies are analyzed based on the results provided by an experiment. Two software products are used as case study, each one implementing two services of the Packet Utilization Standard (PUS). These services represent the functionalities offered by a satellite onboard data handling computer. One of the products is developed with the aid of model checking, while the other is developed according to the practices currently used at the Instituto Nacional de Pesquisas Espaciais (INPE). Both software products are tested by the CoFI methodology. The experiment highlights the advantages and vulnerable points of model checking. It also demonstrates that the main contribution of CoFI testing methodology is to highlight problems related to situations that have not been considered in the software specification, such as the occurrence of inopportune events. This analysis helps to understand how different techniques can be integrated in the design of critical embedded software.

Errors on Space Software Requirements: A Field Study and Application Scenarios

This paper presents a field study on real errors found in space software requirements documents. The goal is to understand and characterize the most frequent types of requirement problems in this critical application domain. To classify the software requirement errors analyzed we initially used a well-known existing taxonomy that was later extended in order to allow a more thorough analysis. The results of the study show a high rate of requirement errors (9.5 errors per each 100 requirements), which is surprising if we consider that the focus of the work is critical embedded software. Besides the characterization of the most frequent types of errors, the paper also proposes a set of operators that define how to inject realistic errors in requirement documents. This may be used in several scenarios, including: evaluating and training reviewers, estimating the number of requirement errors in real specifications, defining checklists for quick requirement verification, and defining benchmarks for requirements specifications.

A platform for distributed modeling and simulation of productive systems based on Petri nets and object-oriented paradigm

The increasing complexity of productive systems associated with the geographical dispersion of industries motivates new demands and the adoption of new design tools. In this context the purpose of this work is to introduce a new platform for distributed modeling and analyses of productive systems. The platform is based on Petri net as a modeling formalism and on the label-ring protocol for managing the distributed simulation. The focus of this paper is on the platform communication algorithm. An example is presented in order to illustrate the proposal

A comparison of industrial robots interface: force guidance system and teach pendant operation

Purpose This paper aims to propose an evaluation method to compare two different Human–Robot Interaction (HRI) solutions that can be used for on-line programming in an industrial context: a force guidance system and the traditional teach pendant operation. Design/methodology/approach The method defines three evaluation criteria (agility, accuracy and learning) and describes an experimental approach based on the analysis of variance to verify the performance of guidance systems according to these criteria. This method is used in this paper to compare the traditional teach pendant interface with an implementation of a force guidance system based on the use of an external force/torque sensor. Findings The application of the proposed method to an off-the-shelf industrial robot shows that the force guidance system has a better performance according to the agility criterion. Both solutions have a similar performance for the accuracy criterion, with a limit of about 2 mm in the achieved position accuracy. Regarding the learning criterion, the authors cannot affirm that any of the methods has an improved agility when the operator repeats the tasks. Practical implications This work supports the selection of guidance systems to be used in on-line programming of industrial applications. It shows that the force guidance system is an option potentially faster than the teach pendant when the required positioning accuracy is greater than 2 mm. Originality/value The new method proposed in this paper can be applied to a large range of robots, not being limited to commercial available collaborative robots. Furthermore, the method is appropriate to accomplish further investigations in HRI not only to compare programming methods but also to evaluate guidance systems approaches or robot control systems.

Benchmarking software requirements documentation for space application

Poorly written requirements are a common source of software defects. In application areas like space systems, the cost of malfunctioning software can be very high. This way, assessing the quality of software requirements before coding is of utmost importance. This work proposes a systematic procedure for assessing software requirements for space systems that adopt the European Cooperation for Space Standardization (ECSS) standards. The main goal is to provide a low-cost, easy-to-use benchmarking procedure that can be applied during the software requirements review to guarantee that the requirements specifications comply with the ECSS standards. The benchmark includes two checklists that are composed by a set of questions to be applied to the requirements specification. It was applied to the software requirements specification for one of the services described in the ECSS Packet Utilization Standard (PUS). Results show that the proposed benchmark allows finding more with a low effort.

A Comparative Analysis of two Verification Techniques for DEDS: Model Checking versus Model-based Testing

Abstract This paper presents a comparative analysis of two verification techniques: (1) formal verification of the system specification and (2) execution of FSM-derived test cases on the delivered product. It uses as a testbench a didactic example of a coffee machine and a work team composed of post-graduation students. The purpose is to analyze the advantages and drawbacks of each technique, define the kind of errors detect by each one and highlight the contributions to the development process.

Modeling of hybrid supervisory systems using UML and Petri nets

In this work, a new approach for the design of supervisory systems is introduced. It focuses on how supervisory systems can improve global system performance through the use of efficient local controller switching configuration policies. For this purpose, a modeling approach is developed that can represent the integration of different hierarchical levels of the control architecture and different dynamic behavior. UML, Petri nets and differential equation systems are merged in order to provide a framework with flexibility for representing the abstractions that emerge when considering supervisory system design.

Avaliação metrológica de um robô industrial para montagem estrutural de aeronaves

The aircraft fuselage assembly process is too labor intensive and highly manual within the Brazilian aircraft industry. Foreign companies of this industrial segment started the adoption of automated solutions in the last two decades. Their automated solutions are very product dependent as well as very expensive. This kind of solution is inadequate for the Brazilian aircraft industry. This paper shows the preliminary results of a flexible, low cost automated system specially designed to fit the Brazilian requirements. This is based upon the usage of industrial robots for general purposes. In order to check the feasibility of such a solution, the process requirements are expressed in terms of accuracy, repeatability and resolution of the robots. These characteristics are measured by two independent, state-of-art measurement systems, namely, Indoor GPS and photogrammetry device. The initial results allow one to conclude that the robot can be used for the purpose described herein as long as it is assisted by correction process based upon the very measurement systems used to acquire its operational characteristics

UNCERTAINTY IN HYBRID SYSTEMS AND THE FIRE MANAGEMENT SYSTEM DESIGN

Abstract This paper approaches the problem of analysing control strategies in the case of fire in a building. The elements of this problem present behaviours of different nature and therefore the use of a hybrid modelling formalism is necessary. Petri nets are used to model the discrete aspects and differential equation systems are used for the continuous ones. In order to realistically evaluate the safeness provided by the fire management system, faults, failures and other uncertainties, such as people behaviour, should be included in the model. Due to the model complexity, results are obtained using Monte Carlo simulation.