Krystian Erwinski

Application of Ethernet Powerlink for Communication in a Linux RTAI Open CNC 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.

PSO based feedrate optimization with contour error constraints for NURBS toolpaths

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.

Accelerating PSO based feedrate optimization for NURBS toolpaths using parallel computation with OpenMP

Over the last few years generation of a time-optimal feedrate profile for CNC machines has recieved significant attention. This is a difficult optimization problem usually requiring long computation time. In the proposed solution, optimization is performed by parallel Particle Swarm Optimization with Augmented Lagrangian constraint handling technique. In order to decrease computation time the authors previously developed algorithm was reimplemented using Open Multi-processing. OpenMP utilizes the ability of modern CPUS to run multiple threads and reduce the algorithms runtime by using parallel processing. The performance gain (speed-up) of the algorithm parallelized on a multi-core system has been tested. The experimental results of a time-optimal feedrate profile generated using an example toolpath are presented to illustrate the capabilities of parallel computation to improve the algorithms performance.

Neural network contour error predictor in CNC control systems

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.

PC based CNC control system with EtherCAT fieldbus

Przemyslowy Instytut Automatyki i Pomiarow - Oddzial Badawczo Rozwojowy Ukladow Sterowania Napedow (PIAP-OBRUSN)