This contribution concerns about a problem that often arises in vision based control, when a camera is used as a sensor for fast control applications, or more precisely, when the sample rate of the control loop is higher than the frame rate of the camera. In control applications for mechanical axes, e.g. in robotics or automated production, a camera and some image processing can be used as a sensor to detect positions or angles. The sample time in these applications is typically in the range of a few milliseconds or less and this demands the use of a camera with a high frame rate up to 1000 fps.The presented solution is a special state observer that can work with a slower and therefore cheaper camera to estimate the state variables at the higher sample rate of the control loop. To simplify the image processing for the determination of positions or angles and make it more robust, some LED markers are applied to the plant. Simulation and experimental results show that the concept can be used even if the plant is unstable like the inverted pendulum.

Injection molded plastic parts are often influenced with the surface defect tiger stripes, which dramatically reduce the visual quality. Tiger stripes are known as alternating bands of bright and dull regions normally to the molded flow direction. This defect highly depends on the injection time and on the formation of the plastic compound. In the last years, the intensity of the tiger stripes defect was controlled visually. For quantifying the tiger strip defect a new, efficient, repeatable, reliable and nondestructive optical measurement system is proposed. To evaluate the dependency of the injection time, a number of five DIN-A5 plastic specimens are molded. Each of the five plates consists of the same material but they have different injection times. For the measurement, one specimen is put into the specimen holder, which is placed on the drawer of a closed cabinet. In this inside black painted cabinet a LED light source and a CCD Camera are mounted. The beams of the LED light are diffuse reflected on the surface of the specimen. To catch only parallel beams by the lens of the camera a large distance between specimen and camera is realized by two justified mirrors in the cabinet. The bright and dull regions of the tiger stripe defect have different diffuse reflection parameters. Thus in a picture of defined brightness the visibility of this defect is very good. To enhance the repeatability the failure of the camera noise and of the light oscillation is reduced by mends of averaging multiple images. Next, the surface structure is filtered out of the image and a representing number of horizontal grey-value lines are extracted. The so called tiger line signal is the difference between the grey line and a calculated polynomial function (degree of 6) and shows the surface defect of each line oscillating on the zero x-axis. For each tiger line signal the mean squared error is evaluated. To calculate a quantitative value of the whole surface, all line errors are averaged to the so called MSE-value. Measurements and comparisons show, that this MSE-value represents surface defects and especially the intensity of tiger stripes very good. The repeating error is lower than 1 %. Experiments for showing unknown effects of normal and of accelerated aging and weathering of plastic surfaces were done successfully.

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Zusammenfassung Dieser Beitrag diskutiert die Wahlmöglichkeiten hinsichtlich der konstanten Führungsgrößenaufschaltung, um einen bestehenden Zustandsregler für allgemeine d. h. auch sprungfähige sowohl zeitkontinuierliche als auch zeitdiskrete LTI-SISO-Systeme um einen Integralanteil auf einen sogenannten PI-Zustandsregler zu erweitern. Der Fokus dieser Arbeit liegt in einer systemanalytischen Interpretation der charakteristischen Fälle. Infolge des konstruktiven Zugangs können Methoden präsentiert werden, wie ein bestehender Zustandsregler ohne vollständigen Neuentwurf um einen Integralanteil erweitert werden kann. Dies ermöglicht prinzipiell eine ressourcenschonende online Umparametrierung bzw. Zu- und Abschaltung des I-Anteils. Von besonderem Interesse ist dabei die Möglichkeit, durch dezidierte Wahl der Vorfilterkonstante sogar die Invarianz des gesamten Führungsverhaltens des ursprünglichen Zustandsreglers zu erzielen. Dies wird durch systematische Abspaltung eines nicht erreichbaren Teilsystems erzwungen. Weiters wird hierfür die direkte Äquivalenz zu einem reduzierten Störgrößenbeobachter gezeigt. Eine andere Parametrierung erlaubt, rampenförmigen Führungssignalen asymptotisch exakt zu folgen bzw. derartige Ausgangsstörungen zu unterdrücken. Die Demonstration der wesentlichen präsentierten Methoden an einem Simulationsmodell mit integrierendem Verhalten schließt diesen Beitrag.