WebLab of a DC motor speed control didactical experiment

摘要

Purpose - Weblabs are an additional resource in the execution of experiments in control engineering education, making learning process more flexible both in time, by allowing extra class laboratory activities, and space, bringing the learning experience to remote locations where experimentation facilities would not be available. The purpose of this paper is to investigate and report on a weblab project where the speed of a DC motor is controlled in closed loop, being the control system parameters set by the remote user (student). Design/methodology/approach - The engine control experiments are run and on-line transmitted by videoconference over the internet, from a didactical plant physically located at the Systems and Automation Laboratory of the Control and Automation Engineering department of the Pontifical Catholic University of Parana. The system response (transient motor speed) to the user's choice of parameters is evaluated through performance indices (IAE, ITAE), which are used to qualify the ability of the student to tune PID and RTS control algorithms. There is an option to run experiments in open loop, so the student can perform preliminary analysis to identify the system dynamic model and then apply mathematical models and computational methods, learned in theoretical classes, to define best performance control parameters. A simulation function was implemented, to further help the student in the problem solution. Virtual instrumentation resources were used to implement the Weblab, using the DC motor of a laboratory didactical plant. A local server runs a LabVIEWTM application, which can be remotely accessed in the client side through a web browser, where the system front panel is reproduced. This remote interface is directly originated at the LabVIEWTM application, through an embedded web server. At the user request, the control of the remote system is granted. The user interface is cognitive, with motor speed, control signal, set point and all the pertinent information displayed in evolving charts and indicators. Microsoft™ Skype is used to establish a videoconference with the laboratory where the plant is located. Results of the user experiments are stored in local files, which can be e-mailed to the user at his command by the end of the session. Findings - Used as a platform in weblab projects, Lab VIEW combined with Skype provides a suitable solution for the necessary software/hardware integration for communications with data acquisition systems and advanced connectivity resources. In virtual instrumentation Skype has proved to be efficient in establishing the right environment without the need for developing complex software for teaching practical control engineering concepts. Research limitations/implications - The level of performance (speed of acquisition, accuracy and number of parameters that could be evaluated) of the current system would need to be evaluated compared to some existing systems. The implication is the changes brought to the adopted approach to the development of, access to and the overall cost of producing virtual laboratory systems used for science, engineering and technology education. Practical implications - With further effort, the current and similar systems could be further upgraded with user login control and server, so that results can be submitted to the tutor, thus acting as a learning evaluation instrument. Originality/value - The originality of this research lies in the innovative integration of technology in education, which involves the implementation of a carefully designed, cost-effective virtual laboratory for teaching and learning of concepts in control engineering.