Real-Time Jerk Limited Feedrate Profiling and Interpolation for Linear Motor Multiaxis Machines Using NURBS Toolpaths

In this article, a NURBS toolpath feedrate profile generation algorithm for a biaxial linear motor control system is presented. High achievable velocities and accelerations of linear motor machines present new computational challenges in implementing feedrate generation and toolpath interpolation algorithms in real-time controllers. The proposed algorithm is capable of online generation of the feedrate profile with axial acceleration and jerk constraints. Each stage of the feedrate profiling algorithm is described with attention being given to both performance and implementation aspects. Furthermore, an alternative to the commonly used Taylor series interpolation method is also tested to ensure minimal interpolation errors. The feedrate profiling and interpolation algorithms’ implementation in a PC-based controller with real-time Linux kernel is described. Experimental results are presented that confirm that the algorithm is capable of limiting acceleration and jerk in the machine’s axes and it is low computation time enables real-time on-line operation in a PC-based CNC controller

PSO based feedrate optimization with contour error constraints for NURBS toolpaths

Paper presented at MMAR 2016 conference (Międzyzdroje, Poland, 29 Aug.-1 Sept. 2016)Generation of a time-optimal feedrate profile for CNC machines has received significant attention in recent years. Most methods focus on achieving maximum allowable feedrate with constrained axial acceleration and jerk without considering manufacturing precision. Manufacturing precision is often defined as contour error which is the distance between desired and actual toolpaths. This paper presents a method of determining the maximum feedrate for NURBS toolpaths while constraining velocity, acceleration, jerk and contour error. Contour error is predicted during optimization by using an artificial neural-network. Optimization is performed by Particle Swarm Optimization with Augmented Lagrangian constraint handling technique. Results of a time-optimal feedrate profile generated for an example toolpath are presented to illustrate the capabilities of the proposed method

Neural Network Contour Error Predictor in CNC Control Systems

Paper presented as poster presentation at MMAR 2016 conference (Międzyzdroje,Poland, 29 Aug.-1 Sept. 2016)This article presents a method for predicting contour error using artificial neural networks. Contour error is defined as the minimum distance between actual position and reference toolpath and is commonly used to measure machining precision of Computerized Numerically Controlled (CNC) machine tools. Offline trained Nonlinear Autoregressive networks with exogenous inputs (NARX) are used to predict following error in each axis. These values and information about toolpath geometry obtained from the interpolator are then used to compute the contour error. The method used for effective off-line training of the dynamic recurrent NARX neural networks is presented. Tests are performed that verify the contour error prediction accuracy using a biaxial CNC machine in a real-time CNC control system. The presented neural network based contour error predictor was used in a predictive feedrate optimization algorithm with constrained contour error

Stanowisko badawcze układów sterowania wieloosiowego napędami liniowymi poprzez magistralę EtherCAT

W artykule przedstawiono stanowisko badawcze przeznaczone do badania wieloosiowych układów sterowania z serwonapędami liniowymi. Stanowisko składa się z komputera pełniącego rolę sterownika nadrzędnego, serwosterowników oraz silników liniowych. Sterownik pracuje pod kontrolą systemu Linux z jądrem czasu rzeczywistego. Zaimplementowano również programowy stos EtherCAT do komunikacji z napędami. Przedstawiono budowę układu sterowania oraz strukturę oprogramowania sterownika. Przedstawiono również planowane badania, które będą realizowane na stanowisku dotyczące metod generacji optymalnych trajektorii ruchu, implementacji algorytmów regulacji położenia i prędkości w sterowniku oraz wpływu magistrali EtherCAT na jakość sterowania

Application of Ethernet Powerlink for communication in a Linux RTAI open CNC control system

In computerized numerical control (CNC) systems, the communication bus between the controller and axis servo drives must offer high bandwidth, noise immunity, and time determinism. More and more CNC systems use real-time Ethernet protocols such as Ethernet Powerlink (EPL). Many modern controllers are closed costly hardware-based solutions. In this paper, the implementation of EPL communication bus in a PC-based CNC system is presented. The CNC system includes a PC, a software CNC controller running under Linux Real-Time Application Interface real-time operating system and servo drives communicating via EPL. The EPL stack was implemented as a real-time kernel module. Due to software-only implementation, this system is a cost-effective solution for a broad range of applications in machine control. All software systems are based on GNU General Public License or Berkeley Software Distribution licenses. Necessary modifications to the EPL stack, Linux configurations, computer basic input/output system, and motherboard configurations were presented. Experimental results of EPL communication cycle jitter on three different PCs were presented. The results confirm good performance of the presented system

Układ sterowania CNC bazujący na komputerze PC z magistralą EtherCAT

W artykule przedstawiono układ sterowania numerycznego maszyn zbudowany na bazie komputera PC, komunikujący się z serwonapędami i układami wejścia/wyjścia sterującymi wyposażeniem maszyny poprzez magistralę komunikacyjną EtherCAT. W komputerze zaimplementowano system operacyjny czasu rzeczywistego Linux RTAI wraz ze zmodyfikowanym oprogramowaniem sterującym LinuxCNC. Opracowano programowy moduł komunikacyjny magistrali EtherCAT i zintegrowano go z oprogramowaniem LinuxCNC. Opracowany moduł EtherCAT umożliwia komunikację z serwonapędami zgodnie ze standardem CiA 402 oraz modułami wejść/wyjść zgodnie ze standardem CiA 401. Opracowany układ sterowania cechuje się prostą budową i łatwym montażem. Pozwala na bardzo szybką dwukierunkową komunikację z napędami i układami wejścia/wyjścia. Jest układem elastycznym, który można łatwo zaimplementować do sterowania maszynami wieloosiowymi o różnej konfiguracji

Hybrid MPI/Open-MP acceleration approach for high-order schemes for CFD

The paper presents a hybridMPI+OpenMP (Message Passing Interface/Open Multi-Processor) algorithm used for parallel programs based on the high-order compact method.The main tools used to implement parallelism in computations are OpenMP andMPI whichdiffer in terms of memory on which they are based. OpenMP works on shared-memory and the MPIon distributed-memory whereas the hybrid model is based on a combination of those methods. The tests performed and described in this paper present significant advantages provided by a combination of the MPI/OpenMP approach. The test computations needed for verifying possibilities ofMPI, Open-MP and Hybrid of both tools were carried out using anacademic high-order SAILORsolver. The obtained results seem to be very promising to accelerate simulations of fluid flows as well as for application using high order methods