Jesus Chacon

Virtual and remote robotic laboratory using EJS, MATLAB and LabVIEW.

This paper describes the design and implementation of a virtual and remote laboratory based on Easy Java Simulations (EJS) and LabVIEW. The main application of this laboratory is to improve the study of sensors in Mobile Robotics, dealing with the problems that arise on the real world experiments. This laboratory allows the user to work from their homes, tele-operating a real robot that takes measurements from its sensors in order to obtain a map of its environment. In addition, the application allows interacting with a robot simulation (virtual laboratory) or with a real robot (remote laboratory), with the same simple and intuitive graphical user interface in EJS. Thus, students can develop signal processing and control algorithms for the robot in simulation and then deploy them on the real robot for testing purposes. Practical examples of application of the laboratory on the inter-University Master of Systems Engineering and Automatic Control are presented.

EJS, JIL Server, and LabVIEW: An Architecture for Rapid Development of Remote Labs

Designing and developing web-enabled remote laboratories for pedagogical purposes is not an easy task. Often, developers (generally, educators who know the subjects they teach but lack of the technical and programming skills required to build Internet-based educational applications) end up discarding the idea of exploring these new teaching and learning experiences mainly due to the technical issues that must be mastered. To tackle this problem, authors present a novel technique that allows developers to create remote labs in a quick, didactical, and straightforward way. This framework is based on the use of two well-known software tools in the scope of engineering education, Easy Java Simulations and LabVIEW. The development exploits a new feature of Easy Java Simulations known as EJS-elements that enables Java developers to create and integrate their own authoring libraries (elements) into EJS, thus increasing its application possibilities. Particularly, the EJS element here presented allows to LabVIEW programs be controlled from EJS applications through a communication network. This paper presents the element creation details and how this can be used to create web-enabled experimentation environments for educational purposes. A step by step example of development of a remote lab for automatic control education is described.

Experimental analysis of a remote event-based PID controller in a flexible link system

In this work a virtual and remote lab developed to explore the properties of event-based PID controllers in a flexible link system is presented. The architecture is based on the decomposition of the system in three tiers or layers: the server, the client, and a middleware. The server layer is directly connected to the plant, the client side implements the controller and the graphical interface, and the middle-tier acts as interface between client and server. The implementation of the remote lab allows the control of a flexible link plant through a generic network. The platform is used to evaluate, with a particular case, the effectiveness of an algorithm that allows the user to find numerically the limit cycles in control schemes where the feedback is done through a level crossing sampling, and which can be applied to LTI systems with delay.

An Experimental Framework to Analyze Limit Cycles Generated by Event-Based Sampling

Abstract In this work a remote lab developed to explore the properties of event-based controllers is presented. The architecture is based on the decomposition of the system in three tiers. The server layer is directly connected to the plant, the client side implements the controller and the graphical interface, and the middle-tier acts as interface between client and server. The implementation of the remote lab allows the control of a Coupled Tank plant through a generic network. The platform is used to evaluate the effectiveness of an algorithm that allows the user to find numerically the limit cycles in control schemes where the feedback is done through a level crossing sampling, and which can be applied to LTI systems with delay.

Design of a Low-Cost Air Levitation System for Teaching Control Engineering

Air levitation is the process by which an object is lifted without mechanical support in a stable position, by providing an upward force that counteracts the gravitational force exerted on the object. This work presents a low-cost lab implementation of an air levitation system, based on open solutions. The rapid dynamics makes it especially suitable for a control remote lab. Due to the system’s nature, the design can be optimized and, with some precision trade-off, kept affordable both in cost and construction effort. It was designed to be easily adopted to be used as both a remote lab and as a hands-on lab.

Developing web & TwinCAT PLC-based remote Control laboratories for modern web-browsers or mobile devices

This paper describes a new approach to develop remote Control laboratories accessible from modern web-browsers and student devices (PCs, laptops, tablets and smartphones) based on TwinCAT Programmable Controllers (PLCs), Easy JavaScript Simulations (EJsS) webpages, and a Node.js laboratory web-server. On the one hand, implementing the laboratory back-end application (responsible of closing the feedback loop over the plant under study) using a TwinCAT PLC provides the laboratory controllers with standard/industrial automation methodologies, real-time support and connectivity to a wide range of input/output signals. On the other hand, defining the controller front-end (graphical/interactive interface used by the students to parametrize the PLC behavior and observe the evolution of the plant and PLC signals) with EJsS facilitates the organization of its visual/interactive elements and allows the generation of a JavaScript and HTML5 webpage that is accessible from modern web-browsers and various types of students devices running different operating systems. Last, but not least, developing the laboratory web-server (in charge of managing the student access to the lab and of hosting its different webpages, including the controller frontend) within the JavaScript development and runtime platform Node.js ensures a lightweight behavior of the remote lab, provides a robust connectivity to the students, and supports efficient (real-time) communication between the controller back & front-ends. This paper also shows how the new strategy is used to update and overcome the current accessibility limitations of some existing (and published) experiences with Proportional/Integral/Differential (PIDs) and Estimator and State Feedback (ESF) Controllers based on TwinCAT PLCs and Easy Java Simulations (EJS) applets front-ends.

A virtual and remote lab of the two electric coupled drives system in the University Network of Interactive Laboratories

This paper describes all the details on the latest addition to the University Network of Interactive Laboratories: a virtual and a remote laboratory of a two electric coupled drives system. This two new activities allow performing control practices in a 2×2 MIMO system. The virtual and the remote labs are accessible for anyone in a new open course that contains several other experiments in the automatic control field.

Building process control simulations with Easy Java Simulations elements

Abstract This work presents a library of Java classes and Easy Java Simulation (EJS) elements, developed to provide a framework to allow an easy building of a wide range of process control related simulations. The potentiality of the framework is illustrated with an application example built by combining several elements of the library: the simulation of control loops composed of a SISO process and a PID controller with send-on-delta sampling. The framework has been designed to be somewhat similar to a block diagram editor, where the user can create a control loop simply by adding the constructive elements and interconnecting them as needed. The model creation is thus made much more intuitive and robust, mainly because the lines of code needed are reduced, if not at all, depending on the complexity of the simulation. The library provides the user with the implementation of the most frequently used control elements, such as a system described by state-space expressions, PID controllers, non-linear systems, etc. In addition, an extension mechanism is provided for advanced users, which can extend the functionality of the built-in blocks either by adapting them or by defining completely new blocks.A device laboratory was designed to create a commanded disturbance to the Furuta inverted pendulum. This pendulum was modified by adding a second inverted pendulum coupled to the main one by means of a semi-rigid spring. The induced motion on the second inverted pendulum causes displacement of the center of mass of the system, producing a kind of perturbation similar to that presented on mobile inverted pendulum transportation units. A linear matrix inequality (LMI) controller is designed from the unperturbed model (based on the main pendulum without the second inverted one) and implemented to our system. Then, experimentally, the behaviour of the whole closed-loop system and the controller performance was analysed. According to the laboratory test, the LMI controller is robust enough in front of perturbation induced on the second pendulum.

Design of an event-based feedforward strategy for SOPTD processes

An event-based method to perform the set-point following task for second order processes with time delay (SOPTD) is investigated in this work. The aim of the research is to extend an event-based controller that has been tested previously in processes responding to the first-order with time delay (FOPTD) model. The controller is based on feedforward and feedback actions to do the two main tasks of a controller, set-point following and disturbances rejection, with an event triggered paradigm. This work is mainly focused on the feedforward part of the controller, with the goal of establishing a method to calculate the control signal and the conditions that must be satisfied to update it.

Optimal Control for Aperiodic Dual-Rate Systems With Time-Varying Delays

In this work, we consider a dual-rate scenario with slow input and fast output. Our objective is the maximization of the decay rate of the system through the suitable choice of the n-input signals between two measures (periodic sampling) and their times of application. The optimization algorithm is extended for time-varying delays in order to make possible its implementation in networked control systems. We provide experimental results in an air levitation system to verify the validity of the algorithm in a real plant.