Browsing by Author "Hietala, Jani"

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  • Comparison of REST and GraphQL Interfaces for OPC UA
    (2022-05) Ala-Laurinaho, Riku; Mattila, Joel; Autiosalo, Juuso; Hietala, Jani; Laaki, Heikki; Tammi, Kari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Industry 4.0 and Cyber-physical systems require easy access to shop-floor data, which allows the monitoring and optimization of the manufacturing process. To achieve this, several papers have proposed various ways to make OPC UA (Open Platform Communications Unified Architec-ture), a standard protocol for industrial communication, RESTful (Representational State Transfer). As an alternative to REST, GraphQL has recently gained popularity amongst web developers. This paper compares the characteristics of the REST and GraphQL interfaces for OPC UA and conducts measurements on reading and writing data. The measurements show that GraphQL offers better performance than REST when multiple values are read or written, whereas REST is faster with single values. However, using OPC UA directly outperforms both REST and GraphQL interfaces. As a conclusion, this paper recommends using a GraphQL interface alongside an OPC UA server in smart factories to simultaneously yield easy data access, the best performance, and maximum interoperability.
  • GraphQL Interface for OPC UA
    (2020-06-10) Hietala, Jani; Ala-Laurinaho, Riku; Autiosalo, Juuso; Laaki, Heikki
     A4 Artikkeli konferenssijulkaisussa
    Industrial Cyber-Physical Systems consist of multi-ple machines working together and demand efficient and flexiblecommunication methods to function as intended. The protocolsused in industrial operations and web applications are oftencontradictory in regards to the latency and security characteris-tics. Due to these differences, the intersection of operation andinformation technologies is a challenging area. But the rewards insmoother information flow are also high, providing a fruitful areafor development. This paper introduces a general wrapper appli-cation to enable the use of the industrial OPC UA server throughan interface implemented with web technology GraphQL. Theresults demonstrate sufficient performance for the middleware tobe used in an overhead crane control application, bringing theagility of web development to industrial environments.
  • Kodin automaattiset turvajärjestelmät
    (2015-04-29) Hietala, Jani
     Insinööritieteiden korkeakoulu | Bachelor's thesis
  • Real-time two-way data transfer with a digital twin via web interface
    (2020-03-16) Hietala, Jani
     Insinööritieteiden korkeakoulu | Master's thesis
    Technological advancements in industry have paved way for the fourth industrial revolution called Industry 4.0. One critical aspect of this revolution is the usage of digital twins in product design, production, and service. A common depiction of a digital twin consists of three parts: a physical twin, its digital twin, and the data exchanged between them. In industry, one common solution for the data exchange between the digital twin and its physical twin is OPC Unified Architecture (OPC UA) communication protocol. The protocol provides a solution to collect data from devices along an entire production line. Communication with OPC UA servers requires carefully studying the protocol specification, which can deter new developers from creating applications with the data collected by the servers. The goal of this thesis is to develop a web-based application program interface (API) that simplifies transferring data with an OPC UA server. The API is intended to be made with a popular technology that is already widely known among developers. It would lower the learning curve for utilizing the data on OPC UA servers. Thus, more developers can be tempted to start developing applications with the data. As the API is web-based, it is accessible by any web capable device bringing the data available to virtually any programming language and platform. Requirements for the API beyond the functionalities concern its efficiency and capability of handling real-time data exchange situations. To test the API’s performance, a case study is made: a web-based control application. The control application uses the API in real-time to both write control signals to and read sensor values from the OPC UA server. The API performance is evaluated by measuring its request completion time in both controlled environment and real use cases. The developed API was considered to be fast enough for user-based input and even applications that required fast synchronisation of values from different data sources. However, the API did add considerable latency compared using the OPC UA server directly which might be a problem in some applications that require extremely time sensitive data from the data server.