Direkte Mensch-Roboter-Kooperation in der Kleinteilemontage mit einem SCARA-Roboter

Abstract

Die Arbeitsräume des Menschen und des Roboters sind bisher aus Sicherheitsgründen getrennt. Eine solche Trennung ist gerade in Anwendungsgebieten wie der Montage, wo beide Kapazitäten gebraucht werden und ein stetiger Wechsel von manuellen und automatischen Tätigkeiten verlangt wird, oft nicht mehr sinnvoll. Ziel der vorliegenden Arbeit war es, die strikte sicherheitstechnisch bedingte Trennung von Werker und Roboter in der Produktion aufzuheben und hierfür wissenschaftliche Erkenntnisse eines benutzerzentrierten Sytemdesigns für eine direkte Mensch-Roboter-Kooperation in der Kleinteilemontage mit einem SCARA-Roboter zu erarbeiten, das an die individuellen menschlichen Eigenschaften angepasst werden kann. Hierfür wurden in experimentellen Untersuchungen der wichtigsten Einflussparameter auf die menschliche Wahrnehmung und Empfindung ermittelt. Bei der Wahrnehmung wurden vor allem die zum Menschen relativen Bewegungsgrößen des Roboters, wie Abstand, Annäherungswinkel, Geschwindigkeit und Beschleunigung untersucht. Anschließend wurde der Einfluss dieser Bewegungsgrößen auf das individuelle Sicherheitsempfinden des Menschen ermittelt. Um diese Größe quantifizieren zu können, wurde als Begriff das Kooperationsvermögen und der damit verbundene Kooperationsfaktor k eingeführt. Das Kooperationsvermögen stellt die individuelle Fähigkeit und Bereitschaft des Werkers zur Zusammenarbeit mit dem Roboter und dem System dar. Entsprechend der Konzeption und auf Datenbasis der experimentellen Untersuchungen wurden Verfahren zur Überwachung der Mensch-Roboter-Kooperation entwickelt. Zum einen eine Kollosionsüberwachung über einen kinematischen Ansatz, die der Geschwindigkeit des Roboters eindeutige und scharfte Grenzen setzt, um eine Verletzung des Werkers zu verhindern. Zum anderen eine Ergonomieüberwachung über ein Neuro-Fuzzy-System, die die Robotergeschwindigkeit anpasst, um dem Werker das absolute Gefühl der Sicherheit und der Kontrolle über den Roboter zu vermitteln, aber trotzdem die Produktivität des Systems gewährleistet. Da das menschliche Empfinden von Mensch zu Mensch stark variiert, kann das Roboterverhalten über den Kooperationsfaktor individuell eingestellt werden.

The beginning of a man-robot-cooperation requires a complete ergonomic review around to develop an efficient system. In order to reach an acceptance of man-robot-cooperation, the developments must always take place under the aspect of security and the individual safety senses of humans. The goal is a user-centred system design, which can be adapted to the individual human characteristics. Alternative approaches for the following subsystems were developed in a morphologic proceeding and the optimal concepts are selected: · Work routine of man-robot-cooperation · Ergonomic robot behaviour · Control system, consisting of sensor technology and procedures · Cooperation station and its integration into existing assembly systems By looking at the overlapping work space, three different operating modes for the work routine of man-robot-cooperation result from the variation of local and temporal separation from humans and robot. From the analysis of the possible downtime situations of the robot, the worker and due to the dependence in cooperation and general recovery steps, appropriate manipulation modes can be derived. The worker has at any time and in the normal program mode the possibility to intervene in the work routine of the robot and to manipulate it. For an ergonomic robot attitude the "Continuous Path" procedure is selected. Straight approach paths are selected, up to the flexible point of transferring into the common work space. The flexible points of transferring are always arranged perpendicularly to the working location, in order to signal the worker clearly the goal of the robot movement. To set an ergonomic speed an ergonomic control is developed, which can be adapted to the most different experience degrees and safety feeling of the workers. Sensor technology CCD cameras are selected and connected with an appropriate colour image processing system. The high measuring accuracy, due to the dissolution of the cameras, and the low costs compared to infrared cameras is decisive for the use of CCD cameras and a colour image processing system. In order to fulfil the requirements to security, a control system is developed, which can optimally react on each possible situation by appropriate definitions of cases. Due to the simple 4-axis kinetics of the SCARA robot, the total movement of the robot can be divided into two phases: main axis movement and vertical axis movement. This subdivision of the total movements corresponds also to the crucial endangerments pushing, crushing and shearing from the hazards analysis. The cooperation station is designed in such a way that man and robot stand opposite each other, the work piece lies stationary in the centre and the torso of the worker is in the normal work stance outside of the work space of the robot. Thus both interaction partners have unrestricted access to the work piece and nevertheless can move as freely as possible. In order to achieve a user-centred system design, experimental investigations of the most important parameters on the human perception and senses were carried out. With the perception above all motion quantities of the robot like distance, approach angle, speed and acceleration were examined. Subsequently, the influence of these motion quantities on the individual safety sense of humans were determined. In order to be able to quantify this size the cooperation ability and the associated cooperation factor were introduced. The cooperation ability represents the individual ability and readiness of the worker to cooperate with the robot and the system. The cooperation ability varies with the practice extent and the experience of the worker and is subjected to daily individual performance and motivation fluctuations. Procedures for the control of man-robot-cooperation were developed. On the one hand a collision control with a kinematic approach, which sets clear and sharp limits to the speed of the robot, in order to prevent an injury of the worker. On the other hand an ergonomic control over a Neuro-Fuzzy system, which adapts the robot speed to give the worker the absolute feeling of security and control of the robot, but although ensures the productivity of the system. Since human feelings strongly vary from human to human the robot behaviour can be individually adjusted by the cooperation factor. As proof of the technical feasibility and for the verification of the theoretical results a pilot system for a direct man-robot-cooperation in assembly systems was realised and tested by an example product. On the one hand the benefit of a direct man-robot-cooperation for a standard application in the small products assembly was proven. On the other hand the applicability of the control procedures was shown, in which the temporal progress of an assembly job, the learning curve and the adjustment of the cooperation factor of the test persons were measured.