Position control of an industrial robot using an optical measurement system for machining purposes

A series of mechanical properties and disturbances limit the accuracy achievable in robotic applications. External control of the end effector position is commonly known as being an appropriate mean to increase accuracy. This paper presents an approach for position control of industrial robots using the pass-through between an industrial CNC and servomotors. A CNC-controlled robot is used together with an external optical measurement system to close the feedback loop of robot end effector and robot controller in order to improve robot accuracy. For short cycle times and implementation reasons a PLC is used for signal processing and control implementation. The relevance of the approach is outlined in experiments. The robot behaviour in free space motion and in machining application is analysed with the optical measurement system and a CMM

Introduction of an industrial transfer learning use case systematization for machine tools

Traditional intelligent systems such as fault detection are mainly developed for isolated use on single machines and are mostly trained individually. A cross-machine knowledge transfer of intelligent systems holds an immense potential and can reduce implementation effort of intelligent systems. To enable a structured analysis of real-world transfer problems, an industry-relevant, far-reaching systematization of typical machine tool use cases is developed. This provides the overview over different typical use case classes from the industrial use case perspective. Based on the derived transfer criteria of each use case class, a conceptual approach of concrete transfer methods is proposed

Robot machining of thin-walled workpieces with automatically reconfigurable fixturing through feature analysis

Machining of large scale thin-walled workpieces pose high requirements for fixturing because of large stiffness changes due to material removal. Automatically reconfigurable fixtures that allow in-process reconfiguration are a promising approach. In this paper, an efficient approach based on feature analysis is proposed for fixture reconfiguration planning. For this, material removal is simulated. At discrete points in time, feature analysis is performed and an approximated local stiffness map is calculated with weight functions derived from the features’ parameterizations. Viable fixture configurations are then identified through root finding and validated through simulation in Ansys and experimentally with a fixture jig. In both validations, workpiece deformation for drilling operations could be reduced to an acceptable level enabling the implementation\u27s future use in industrial application

Parameter identification for fault analysis of permanent magnet synchronous motors based on transient processes

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.This research received no external funding

Impact-based feed drive actuator for discontinuous motion profiles

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.Deutsche ForschungsgemeinschaftProjekt DEA

Acceleration-based disturbance compensation for elastic rack-and-pinion drives

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.Deutsche ForschungsgemeinschaftProjekt DEA

Simulative Optimierung der Steuerungsparameter eines Materialflusslayouts mit Bandförderern

Moderne Fertigungssysteme sind komplexe, umfangreiche Systeme. Eine sorgfältige Planung des gesamten Fertigungssys- tems ist erforderlich, um langfristig effektiv zu produzieren und Gewinne zu erzielen. Bei der Layoutplanung dieser Systeme muss berücksichtigt werden, dass der Materialfluss zwischen einzelnen Stationen zuverlässig und reibungslos funktioniert. Die virtuelle Inbetriebnahme (VIBN) ermöglicht es, das Zusammenspiel von Anlagenlayout und Steuerungssystem, wel- ches das optimale Design der Anlage wesentlich beeinflusst, frühzeitig zu testen. Konzeptionsfehler und Engpässe, die die Performance beeinflussen, können im Voraus erkannt und behoben werden. Für die VIBN wird die reale Anlage durch ein Simulationsmodell ersetzt, um im Zusammenspiel mit dem realen Steuerungssystem Tests durchführen zu können. In dieser Arbeit wird ein Vorgehensmodell entworfen, anhand dessen die Leistungsfähigkeit von Maschinen und Anlagen mit besonders hohem Materialflussaufkommen analysiert und das Layout bewertet werden kann. Wichtige Leistungskenn- größen wie die Taktzeit und Auslastung einzelner Bestandteile des Fertigungssystem können hinsichtlich ihrer Realisier- barkeit überprüft werden. Durch Testläufe an einem Simulationsmodell des Materialflusses werden Fehler und Engpässe, welche die Performance der Anlage negativ beeinflussen, frühzeitig erkannt. Zur Verbesserung des Layouts wird dabei ein Flussmodell basierend auf einer Erhaltungsgleichung eingesetzt. Das neue Simulationsmodell ermöglicht insbesondere die Simulation großer Mengen an Materialien bei gleichzeitig geringer Berechnungsdauer. Für die Validierung der Ergebnisse werden Parameter festgelegt, die als Indikator für die Leistung von Materialflusssystemen dienen und in einer ingenieurs- technischen Simulation gemessen werden können. Das enge Zusammenspiel verschiedener Simulationen ermöglicht die Validierung und effiziente Verbesserung des Layouts

Hybrid manufacturing of topology optimized machine tool parts through a layer laminated manufacturing method : practical validation using the example of a bearing block

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.Deutsche ForschungsgemeinschaftProjekt DEA