Browsing by Author "Verl, Alexander"

Now showing 1 - 13 of 13

Open Access
Acceleration-based disturbance compensation for elastic rack-and-pinion drives
(2021) Brenner, Felix; Lechler, Armin; Verl, Alexander
Rack-and-pinion drives are mainly used for large machine tools and are often operated with indirect position control. Due to the lack of state information on the output side, this results in reduced accuracy regarding the table position. In addition, the system can only react inadequately to disturbances outside the control loop, meaning that often insufficient results can be achieved in typical application scenarios such as milling. To meet the increasing dynamic and accuracy requirements of the modern manufacturing industry, this paper presents a highly dynamic acceleration-based disturbance compensation method. For this purpose, the table acceleration is estimated using a dynamical model of the drive train and compared to the signal from an additional acceleration sensor attached to the machine table. Based on the resulting difference, an additional compensation torque is provided, which suppresses the disturbance in counterphase. The approach is tested experimentally on an open control platform with industrial drive components and the behavior is investigated based on compliance frequency responses and externally applied milling forces. At the same time, a standardized parametrization methodology is developed and the robustness is evaluated by varying table masses. In summary, a considerable improvement of the dynamic disturbance behavior can be achieved compared to the conventional system without compensator.
Open Access
Efficient combination of topology and parameter optimization
(2014) Lin, Yusheng; Sun, Zheng; Dadalau, Alexandru; Verl, Alexander
This paper presents a combination method of Particle Swarm Optimization (PSO) and topology optimization. With this method a better result can be achieved compared with the sequential ap-plication of the two optimization methods. It inherits the ability in finding global optimum from PSO and also suits for discretized design domain. Some special schemes are used in order to provide higher computation efficiency. This method has only been tested with a convex optimization problem. The application in case of a concave problem will be a future study.
Open Access
Experimental investigation into the implications of transmission errors for rack-and-pinion drives
(2021) Steinle, Lukas; Lechler, Armin; Neubauer, Michael; Verl, Alexander
Rack-and-pinion drives are the preferred option in the machine tool sector when long ranges of motion and high loads are involved. However, their shortcomings particularly include deficiencies in the achievable positioning and path accuracy. The backlash as one of the main issues is well described in the literature and numerous solutions to reduce its negative effects exist. In contrast, there is a lack of literature regarding the scientific and systematic analysis of the transmission errors in rack-and-pinion drives. In this paper, the displacements originating in the drive train of a system with industrial components are measured under different operating conditions. The observed transmission errors are thoroughly analyzed in no-load operation and their sources are discussed. Subsequent investigations show significant load-dependent alterations of the transmission errors and direction-dependent characteristics, the causes of which are explained. It is shown, that transmission errors negatively affect the path accuracy of position controlled drives, which is amplified by excitation of the machine structure in certain operating conditions. To address this issue, different error compensation concepts are presented.
Open Access
Fehlertolerante Sicherheitssteuerung aus der Cloud : Softwarebasierte Sicherheitssteuerungen
(2023) Fischer, Marc; Walker, Moritz; Lechler, Armin; Riedel, Oliver; Verl, Alexander
Open Access
Hybrid manufacturing of topology optimized machine tool parts through a layer laminated manufacturing method : practical validation using the example of a bearing block
(2021) Helfesrieder, Nico; Neubauer, Michael; Lechler, Armin; Verl, Alexander
Load-oriented lightweight structures are commonly designed based on topology optimization. For machine tool parts, they enable the reduction of moving masses and therefore increase the resource and energy efficiency of production systems. However, this usually results in complex part structures that are difficult or impossible to produce using conventional manufacturing methods. In this paper, a hybrid layer laminated manufacturing (LLM) method is proposed enabling manufacturing of topology-optimized machine tool parts. The method is referred to as hybrid, as the subtractive structuring of metal sheets is combined with the additive joining of the sheets by adhesive bonding. This enables enclosed inner cavities without support structures, which are used to approximate the optimal density distribution from a topology optimization via manufacturing. The proposed LLM method is validated on the basis of a bearing block of a ball screw feed drive. A experimental study in the time and frequency domain on a test rig confirms the principle suitability of the LLM method for the production of industrial applicable lightweight components.
Open Access
Impact-based feed drive actuator for discontinuous motion profiles
(2020) Zahn, Peter; Schulte, Alexander; Verl, Alexander
This paper discusses an approach to enable step-wise velocity changes in machine tool feed drives while reducing the reaction force of the drive on structural machine components. The implementation is based on an additional actuator that transmits well-defined impulses on the table via mechanical impacts. Possible applications are seen in processes as beam processing or handling. The approach is introduced by means of a multi-body model and afterwards experimental results are shown. On the one hand, the reduction of the tracking error while following discontinuous velocity profiles is analyzed, on the other hand, the reduced excitation of the machine structure is shown. The experimental verification of the functional principle is performed on a single axis setup where the fundamental parameters in design, material and control are quantified. Concluding, a short outlook on remaining research topics regarding the shown approach is given.
Open Access
iWindow - Intelligentes Maschinenfenster
(Düsseldorf : VDI Verlag, 2018) Sommer, Philipp; Verl, Alexander; Kiefer, Manuel; Rahäuser, Raphael; Müller, Sebastian; Brühl, Jens; Gras, Michael; Berckmann, Eva; Stautner, Marc; Schäfer, D.; Schotte, Wolfgang; Do-Khac, Dennis; Neyrinck, Adrian; Eger, Ulrich; Sommer, Philipp
Das Verbundforschungsprojekt iWindow: Intelligentes Maschinenfenster beschäftigte sich mit der visuellen Unterstützung von Maschinenbedienern an Werkzeugmaschinen. Diese konnten bisher nur auf wenige bis keine Systeme, die sie bei ihren täglichen Aufgaben direkt an der Werkzeugmaschine unterstützen, zurückgreifen. Das Forschungsprojekt verbindet reale und virtuelle Welt in der Werkzeugmaschine durch Technologien wie Virtual und Augmented Reality, digitaler Zwilling, Simulation und Mehrwertdienste. Durch Nutzung jeweils für die aktuelle Arbeitssituation passender Dienste, werden Mitarbeiter befähigt, sich an die steigende Individualisierung der Produkte und die flexiblere Produktion anzupassen. Kunden und Geschäftspartner werden durch die Möglichkeit eigene mehrwertgenerierende Dienste zu entwickeln und anderen Anwendern zur Verfügung zu stellen in den Wertschöpfungsprozess eingebunden. Diese Publikation beleuchtet die im Rahmen des Forschungsprojekts erarbeiteten Ergebnisse hinsichtlich für ein intelligentes Maschinenfenster benötigter Technologien und Entwicklungen.
Open Access
Konzept zur Testfallgenerierung mittels Mixed Reality : Erweiterung der Testautomatisierung um Methoden der Mixed-Reality-in-the-Loop-Simulation (MRiLS)
(2023) Hönig, Jana; Littfinski, Daniel; Schnierle, Marc; Röck, Sascha; Verl, Alexander
Open Access
Model predictive control for compliant feed drives with offset-free tracking behavior
(2023) Leipe, Valentin; Hinze, Christoph; Lechler, Armin; Verl, Alexander
Industrial machine tool feed drives are predominantly controlled by cascade control due to their low tuning complexity and inherent robustness. However, the cascaded structure requires the inner cascades to have higher dynamics than the outer cascades, which limits the achievable dynamic accuracy. Direct control approaches, which substitute the position and velocity cascade, offer the potential to utilize the unused potential. A promising approach is model predictive control (MPC), which optimizes the manipulated variable with a plant model along a prediction horizon. However, model uncertainties between the nominal model and the real plant lead to tracking errors. Therefore, this paper presents, a linear MPC (LMPC) and an adaptive MPC (AMPC) with an additional integral action to robustly compensate for model mismatches. Both controllers use a compliant model, are real-time capable with a sample rate of 2kHzand consider state and input space constraints. The AMPC accounts for position-varying stiffness and friction. The controllers are experimentally compared with classical P-PI cascaded control on a ball screw drive. They show a tracking error reduction of 37%(LMPC) and 44%(AMPC) during a high speed motion profile and an increase in bandwidth of 180%(LMPC) and 184%(AMPC), resulting in significantly improved dynamic accuracy.
Open Access
Parameter identification for fault analysis of permanent magnet synchronous motors based on transient processes
(2024) Wu, Chaoqiang; Verl, Alexander
As the market for hybrid and electric vehicles expands, electric motor production and testing technology must be continuously improved to meet the cost and quality requirements of mass production. In order to detect faults in motors during the production process, a condition monitoring tool is used for the motor end line. During most condition monitoring, the motor operates in a static state where the speed of the motor remains constant and the voltage/current is recorded for a certain period. This process usually takes a long time and requires a loader to drag the motor to a standstill at a constant speed. In this paper, various transient process testing methods are introduced. For these processes, only transient operation of the motor, such as acceleration, loss, or a short circuit, is required. By analyzing the measurement results and simulation results of motor models, unhealthy motors can be detected more effectively.
Open Access
Process-integrated computerized numerical control : an analysis on process-machine coupling and feed scheduling
(2024) Elser, Anja; Lechler, Armin; Verl, Alexander
Computerized numerical controls (CNCs) have been invented for the automation of industrial processes. They are used, when the process to be automated is required to be exact and fast with repeatable quality. Originally, the use of CNCs was primarily focused on milling and drilling processes. Today, CNCs are utilized in a wide range of industrial processes due to the growing importance of automation. However, the integration of process information or adaptation to the needs of these processes to achieve advanced manufacturing with CNCs is difficult: Industrial CNCs are rather closed real-time machining systems. Today, process integration is possible, when the interaction between the process and the machine is decoupled in view of the bandwidth of machine dynamics and process dynamics. There are interfaces that allow for process-motivated control loops that are realized on top of the machine control loop (e.g. chatter control). Then, machine-integrated real-time control is not the focus. Besides, it is often possible to change desired values inside the control loop (position, velocity, acceleration) on an axes basis. In this case, adaptation to the process can be realized in each computation cycle. However, process dynamics and machine axes dynamics are generally treated separately. The same holds for extra actuators (e.g., in the spindle) for position control. This paper has two goals. First, it wants to create an understanding for different levels of process-machine coupling. Second, the problem of direct coupling of process dynamics and machine dynamics is focused. Machining systems design propositions as well as some examples for the coupling of process and machine dynamics in the CNC are given.
Open Access
Prozessmodellierung für das Rührreibschweißen : semi-analytisches Prozessmodell für das roboterbasierte Rührreibschweißen
(2023) Kamm, Valentin; Mesmer, Patrick; Lechler, Armin; Verl, Alexander
Unknown
Universal and automated approaches for optimising the processing order of geometries in a CAM tool for redundant galvanometer scanner-based systems
(2024) Kurth, Daniel; Reiff, Colin; Jiang, Yujiao; Verl, Alexander
The combination of highly dynamic systems with a limited work envelope with a less dynamic system with a larger working envelope promises to combine the advantages of both systems while eliminating the disadvantages. For these systems, separation algorithms determine the trajectories based on the target geometries. However, arbitrary processing orders of these result in inefficient trajectories because successive geometries may be geometrically far apart. This causes the dynamic system to operate below its potential. Current planning tools do not optimise the processing order for such redundant systems. The aim is to design and implement a planning tool for the application of laser marking. The tool considers the processing order of the 2D geometries from a geometric point of view. The resulting sequenced path data can then be used by trajectory generation algorithms to make full use of the potential of redundant systems. The approach analyses literature on Travelling Salesman Problems (TSP), which is then transferred to the given application. A heuristic and a genetic algorithm are developed and integrated into a planning tool. The results show the heuristic algorithm being faster while still producing solutions whose total path length is similar to that of the genetic algorithm. Even though the solutions don’t meet any optimality standards, the presented automated approaches are superior to manual approaches and are to be seen as a starting point for further research.