CNC machine laboratory stand with H-Bot parallel kinematics using the EtherCAT bus

This paper presents an H-Bot kinematics machine control system. The H-Bot machine accuracy depends on the servo drives' synchronous operation and mechanical design. Therefore, the mechanical axes' movement quality is influenced by the communication bus and the ability to detect backlash and elasticity in the machine axes. EtherCAT – an industrial bus will be used for communication between the controller and other machine control system elements. Each mechanical axis at the H-Bot machine is equipped with a position measurementsystem. The laboratory stand was equipped with accelerometers. It is planned to perform research in the Predictive Maintenance and Trajectory Optimization field

Real-Time Ethernet Networks: a practical approach to cycle time influence in control applications

Vivemos num mundo cada vez mais digital e informatizado onde existe uma constante necessidade de interligação entre tudo e todos. Os sistemas robóticos modernos não escapam a esta necessidade e, por isso, é preciso adaptá-los. Existem no mercado várias soluções de redes de comunicação de tempo real, já bem estabelecidas, mas em todas se encontra a mesma lacuna: a escassez de material educativo acerca delas. Este documento pretende apresentar as duas soluções propostas para colmatar um pouco esta lacuna na rede EtherCAT e demonstrar o trabalho de pesquisa e estudo preliminar efetuado para suportar e servir de ponto de partida para o desenvolvimento aprofundado de uma das soluções. Nos capítulos seguintes será explicitado o contexto e motivação para a realização deste projeto, os objetivos que propomos alcaçar, uma descrição do problema incluindo a sua caraterização, uma apresentação não exaustiva da tecnologia por detrás da rede EtherCAT, a explicação das soluções propostas e, por fim, um planeamento de tarefas e objetivos com calendarização dos mesmos

Neural network contour error prediction of a bi-axial linear motor positioning system

In the article a method of predicting contour error using artificial neural network for a bi-axial positioning system is presented. The machine consists of two linear stages with permanent magnet linear motors controlled by servo drives. The drives are controlled from a PC with real-time operating system via EtherCAT fieldbus. A randomly generated Non-Uniform Rational B-Spline (NURBS) trajectory is used to train offline a NARX-type artificial neural network for each axis. These networks allow prediction of following errors and contour errors of the motion trajectory. Experimental results are presented that validate the viability of the neural network based contour error prediction. The presented contour error predictor will be used in predictive control and velocity optimization algorithms of linear motor based CNC machines

A Scalable, High-Performance, Real-Time Control Architecture with Application to Semi-Autonomous Teleoperation

A scalable and real-time capable infrastructure is required to enable high-performance control and haptic rendering of systems with many degrees-of-freedom. The specific platform that motivates this thesis work is the open research platform da Vinci ReResearch Kit (dVRK). For the system architecture, we propose a specialized IEEE-1394 (FireWire) broadcast protocol that takes advantage of broadcast and peer-to-peer transfers to minimize the number of transactions, and thus the software overhead, on the control PC, thereby enabling fast real-time control. It has also been extended to Ethernet via a novel Ethernet-to-FireWire bridge protocol. The software architecture consists of a distributed hardware interface layer, a real-time component-based software framework, and integration with the Robot Operating System (ROS). The architecture is scalable to support multiple active manipulators, reconfigurable to enable researchers to partition a full system into multiple independent subsystems, and extensible at all levels of control. This architecture has been applied to two semi-autonomous teleoperation applications. The first application is a suturing task in Robotic Minimally Invasive Surgery (RMIS), that includes the development of virtual fixtures for the needle passing and knot tying sub-tasks, with a multi-user study to verify their effectiveness. The second application concerns time-delayed teleoperation of a robotic arm for satellite servicing. The research contribution includes the development of a line virtual fixture with augmented reality, a test for different time delay configurations and a multi-user study that evaluates the effectiveness of the system

Controllo di robot omnidirezionale tramite Ethercat

La tesi tratta lo sviluppo del software di controllo della piattaforma omnidirezionale del Barcellona Mobile Manipulator. Lo sviluppo del progetto ha richiesto: a) lo studio della comunicazione EtherCAT tra il PC di controllo e i driver dei motori; b) lo sviluppo di un opportuno master EtherCAT; c ) lo sviluppo di software sia per il controllo in tempo reale mediante un joystick che per il tracking di una traiettoria pianificat

Movement Detection with Event-Based Cameras: Comparison with Frame-Based Cameras in Robot Object Tracking Using Powerlink Communication

Event-based cameras are not common in industrial applications despite the fact that they can add multiple advantages for applications with moving objects. In comparison with frame-based cameras, the amount of generated data is very low while keeping the main information in the scene. For an industrial environment with interconnected systems, data reduction becomes very important to avoid network congestion and provide faster response time. However, the use of new sensors as event-based cameras is not common since they do not usually provide connectivity to industrial buses. This work develops a network node based on a Field Programmable Gate Array (FPGA), including data acquisition and tracking position for an event-based camera. It also includes spurious reduction and filtering algorithms while keeping the main features at the scene. The FPGA node also includes the stack of the network protocol to provide standard communication among other nodes. The powerlink IEEE 61158 industrial network is used to communicate the FPGA with a controller connected to a self-developed two-axis servo-controlled robot. The inverse kinematics model for the robot is included in the controller. To complete the system and provide a comparison, a traditional frame-based camera is also connected to the controller. Response time and robustness to lighting conditions are tested. Results show that, using the event-based camera, the robot can follow the object using fast image recognition achieving up to 85% percent data reduction providing an average of 99 ms faster position detection and less dispersion in position detection (4.96 mm vs. 17.74 mm in the Y-axis position, and 2.18 mm vs. 8.26 mm in the X-axis position) than the frame-based camera, showing that event-based cameras are more stable under light changes. Additionally, event-based cameras offer intrinsic advantages due to the low computational complexity required: small size, low power, reduced data and low cost. Thus, it is demonstrated how the development of new equipment and algorithms can be efficiently integrated into an industrial system, merging commercial industrial equipment with new devices

LinuxCNC – Napredni sustav CNC upravljanja: primjena i kritički osvrt

Ovaj rad prikazuje osvrt na implementaciju upravljačkog sustava otvorene arhitekture, tzv. Enhanced Machine Controller-a (EMC2), koji je primijenjen na glodalici kao ispitnom postavu. Razvoj ispitnog postava motiviran je edukacijskim i istraživačkim potrebama, osobito u području razvoja i analize algoritama za nadzor i upravljanje procesima obrade odvajanjem. EMC2 sustav je razmatran s obzirom na kompatibilne hardverske komponente i mogućnosti prilagodbe specifičnostima obradnog stroja, kao i mogućnostima za industrijsku primjenu. U radu su također prikazane tehničke karakteristike ispitnog postava i upravljačkog sustava

A new method for motion synchronization among multivendor’s programmable controllers

This paper is aimed at increasing the number of possible architectures of distributed control systems by investigating and developing novel methods for the synchronization of axes between PLCs and iPCs of different vendors. In order to find a global solution to this problem, particular attention has been focused on programmable controllers that can manage axes by means of point-by-point control or motion instructions. Two synchronization algorithms have been developed and validated for real and virtual axes; they differ in computational load so that they can be used with programmable controllers having high or low computational performances