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PEOPLE@HES-SO – Directory and Skills inventory

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Herzog Raoul

Herzog Raoul

Professeur HES associé

Main skills

Régulation de processus

Optimisation de trajectoires

Model predictive control

Mécatronique

Realtime software

  • Contact

  • Research

  • Publications

  • Conferences

Main contract

Professeur HES associé

Phone: +41 24 557 61 93

Desktop: C31

Haute école d'Ingénierie et de Gestion du Canton de Vaud
Route de Cheseaux 1, 1400 Yverdon-les-Bains, CH
HEIG-VD
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Ongoing

OpenCN

Role: Collaborator

Description du projet :

OpenCN is a high performance opensource framework for machine control including trajectory planning algorithms with jerk control.

It is a joint development of 3 institutes at HEIG-VD : comatec, REDS, and iAi.

https://www.youtube.com/watch?v=WGHzkGgXEdI

Research team within HES-SO: Herzog Raoul

Statut: Ongoing

2019

Optimal G2 Hermite interpolation for 3D curves
Scientific paper ArODES

Raoul Herzog, Philippe Blanc

Computer-Aided Design,  2019, vol. 117, art. no. 102752

Link to the publication

Summary:

We consider a Hermite interpolation problem for a 3D curve where the functional to be minimized is defined as the integral of squared norm of the third parametric derivative, subject to continuity constraints at the end points. The first order necessary optimality condition of the variational problem leads to a parametric transition curve with quintic polynomials. The determination of coefficients is given by a polynomial system with 2 unknowns. Stationary points correspond to positive roots of the resultant which is a degree 9 polynomial. Although the formulated variational problem is non-convex, the proposed approach leads to the global solution, which can be computed in a reliable and fast manner.

2018

Spline-based trajectory generation for CNC machines
Scientific paper ArODES

Tim Mercy, Nicolas Jacquod, Raoul Herzog, Goele Pipeleers

IEEE Transactions on Industrial Electronics,

Link to the publication

Summary:

Manufacturing of workpieces with CNC machines requires computing machine tool trajectories that fast and accurately track the desired workpiece contour. This paper presents a novel B-spline trajectory generation method for machine tools. The method solves an optimal control problem to minimize the motion time of the tool, while taking into account the velocity, acceleration and jerk limits of the tool axes. Furthermore, it directly includes the allowed workpiece tolerance, by constraining the trajectory to lie inside a tube around the nominal geometry contour. This allows exploring the trade-off between accuracy and productivity, while computing near-optimal trajectories. The presented method creates fluent connections between segments that build up the contour by simultaneously optimizing trajectories for multiple segments. On the other hand, limiting the amount of simultaneously optimized segments and using an efficient problem formulation keeps the computation time acceptable. The trajectory generation method is validated in simulation by comparison with industrial benchmarks, showing a reduction in machining time of more than 10%. The comparison to a state-of-the-art corner smoothing approach shows that the presented method obtains similar or slightly faster trajectories, at a computation time that is up to 45 times lower. In addition, the method is validated experimentally on a 3-axis micro-milling machine. To easily generate trajectories for different workpieces and machines, the method is included in a user-friendly open-source software toolbox.

2023

OpenCN :
Conference ArODES
an open-source CNC with new trajectory optimization for high performance milling

Raoul Herzog

Proceedings of SAMCE 2023, 21 September 2023, Neuchâtel, Switzerland

Link to the conference

2022

OpenCN :
Conference ArODES
une commande numérique ouverte pour des applications à haute performance

Raoul Herzog, Alain Schorderet, Daniel Rossier

Actes de la conférence Manufacturing'21, 19-20 octobre 2022, Paris, France

Link to the conference

Summary:

Les commandes numériques (CNC) du marché sont des boîtes noires où l'utilisateur n'a quasiment aucun accès aux algorithmes de planification de trajectoires. LinuxCNC est une commande libre et ouverte, mais pas adaptée pour l'usinage à haute performance, car sans contrôle du jerk. OpenCN surmonte ces limitations avec une optimisation de trajectoires en deux étapes : 1. optimisations géométriques comprenant entre autres un lissage optimal des transitions avec une continuité géométrique de type G2 . 2. optimisation temporelle avec contrôle du jerk, basée sur un problème d'optimisation convexe de type LP appliqué sur un horizon reculant. Les algorithmes sont codés et testés sur Matlab avec une génération automatique du code embarqué C/C++. Le framework OpenCN est constitué d’un environnement de type Linux asymétrique (AMP), avec un noyau récent, et d’une version revisitée de l’extension temps-réel Xenomai/Cobalt. Les plateformes HW supportées sont x86, Raspberry Pi, Zynq® Ultrascale+, et QEMU/virt64 offrant ainsi la possibilité d’exécuter le framework dans un environnement émulé. Un maître EtherCAT libre est inclus, permettant la transmission fiable de consignes aux drives avec une cadence de 10 kHz grâce à l'horloge distribuée (DC). Une validation fonctionnelle de OpenCN est présentée sur une mini fraiseuse 3 axes très performante, dont la première fréquence propre est supérieure à 180 Hz. Les tests ont été effectués sur des pièces fraisées en laiton jusqu'à des vitesses d'avance de F9000. Un module cinématique pour des machines 5 axes est en cours de développement.

2019

Productivity increase of high precision micro-milling by trajectory optimization
Conference ArODES

Alain Schorderet, Raoul Herzog, Nicolas Jacquod, Yoan Marchand, Christophe Prongué

MM Science Journal ; Proceedings of 15th International Conference on High Speed Machining, 8-9 October 2019, Prague, Czech Republic

Link to the conference

Summary:

Milling parts for watch, medical, aircraft or molds industries is a compromise between time and precision or surface quality. The latter is very often related to machine vibrations during the process. This paper summarizes results obtained with two approaches aiming at reducing machine vibrations caused by axes accelerations. Both are control model based, taking into account the machine's modal behavior. The first algorithm optimizes the acceleration profile, while the second manages the axes cross-talk vibrations. A high-end 5-axis machine tool was used to mill 8 mm square pockets in brass with a 1 mm diameter tool and using a 0.05 mm depth of cut. Standard CNC parameters as well as vibration reduction options were evaluated. Then the two proposed algorithms were implemented on the same machine-tool using a laboratory Matlab based CNC. This paper describes the significant improvements provided by the algorithms when compared to a high end CNC. In the case of milling reference square pockets, up to 90% vibration amplitude reduction were achieved for a given feed rate, and a 5-fold decrease in the pockets machining time was obtained for the same surface quality.

2012

Fe2.7Si, Fe50Ni and Fe50Co soft ferromagnetic materials by powder injection moulding
Conference ArODES

Efrain Carreno-Morelli, Mikel Rodriguez Arbaizar, Hervé Girard, Hazimeh Hussein, Raoul Herzog

Proceedings of Powder Metallurgy World Congress PM2012, 14-18 october 2012, Yokohama, Japan

Link to the conference

Summary:

Powder injection moulding is an enabling technology for the production of soft ferromagnetic components, which bring solutions and open the way for new applications. In this work, square toroid parts have been injection moulded for three typical soft magnetic alloy compositions. Fe2.7Si, Fe50Ni and Fe50Co feedstocks were produced by mixing elemental powders and a multicomponent binder. The green parts were first solvent debinded in a heptane bath. Then, thermal debinding under nitrogen atmosphere and sintering under hydrogen atmosphere were performed in a single step in a retort furnace. The sintered parts were characterized by measurements of B‐H hysteresis cycles and optical metallography. The results were compared with literature values obtained from powder metallurgy processes.

Fe2.7Si, Fe50Ni and Fe50Co Soft Ferromagnetic Materials by Powder Injection Moulding
Conference

Girard Hervé, Carreno-Morelli Efrain, Rodriguez Arbaizar Mikel, Herzog Raoul, Hamdam Hussein

Powder Metallurgy World Congress PM2012, 14.10.2012 - 18.10.2012, Yokohama, Japan

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