Page - 55 - in Joint Austrian Computer Vision and Robotics Workshop 2020

screwingandstoringtasksareallocatedbetweenfour resources, i.e. human, two robots and a mobile ma- nipulator. Theworksystemisdesignedinaway, that the position of peripheral appliances is variable and safety devices can be changed. Hence, the collabo- rative work system consists of (a) a Universal Robot UR10 on a linear axis for workpiece handling, (b) a feeder and a conveyor belt for workpiece supply, (c) a Universal Robot UR3 for workpiece assembly, (d) ahumanoperator forworkpieceassemblyandwork- piece removal, (e) a mobile manipulator for work- piece manipulation and (f) external safety devices, such as light curtains and laser scanners, for person safeguarding. See Figure 1 for the layout sketch of the workplace. 2.2.ModificationDimensions in theUseCase Thelaboratoryusecaseoffers thepossibilityof13 modification dimensions, which either influence the layout, the task allocation or the motion parameters of the involved resources. • Product: Two different products can be assem- bled on the work system - either in mixed or unmixed production. The change of the assem- bled product influences the workpiece supply, the task allocation as well as the motion paths of the robots. • Position during collaboration (end effector height): The end effector height indicates the position where human and robot assemble the product at the same time. It can be changed ac- cording to theergonomicheightof theoperator. • Positionduringcollaboration(robotbasepo- sition): The Universal Robot UR10 is mounted on a linear axis so to easily change its base po- sition. This might be necessary due to reacha- bility reasons when the layout of the work sys- tem changes or when new collision points arise on the anticipated robot paths due to changes in the task allocation. A choice of the robot’s base position during the collaboration is possi- bleandinfluencesthesensitivityandstiffnessof the armdue to theaccording robotposture. • Resource allocation for trestle feed: The sup- ply of workpieces can either be implemented in terms of a feeder, directly coming from the previous manufacturing machine on a conveyor belt or by a human operator. The change of the supplyunit influencesnotonly the layoutof the work system but also the robot paths and op- tionally the resource allocation (depending on thepicking requirements). • Resource allocation for screwing: The screw- ing process can be either done by the Universal RobotUR3,by thehumanorby themobilema- nipulator. A change in resource allocation for a specific task influences the temporal andspatial proximity of humans and robots and thus may influence the safetyconcept. • Safety function: The safety function can ei- ther be implemented as force limitation or as distance monitoring. Based on the safety func- tion, the safety devices are defined as well as the layout of the work system in terms of space requirements and the motion behaviour of the resources. • Type of safety device for distance monitor- ing: The distance monitoring can either be implemented by a separating safety fence or by non-separating safety devices such as light curtains, laser scanners, safety mats, software- based workspace limitations or a combination of those. • Position of safety device for distance moni- toring: Depending on the type of safety device and the space requirements of the work system, the mounting distance of the safety devices is defined and thus the velocity of the robots. In general these safeguarding distances are regu- lated by the standard ISO 13855:2010 - Posi- tioning of safeguards with respect to the ap- proachspeedsofpartsof thehumanbody. Modification dimensions lead to system variants ofausecasewhicharenecessaryfor theflexibilityof acollaborativeworksystem. Inorder toalreadycon- sider desired variants of a human-robot work system in the planning and design phase, a Morphological Box is introduced. 3.Morphological Box A morphological analysis is a creative heuristic method introduced by the Swiss astrophysicist Fritz Zwickywhichismostlyappliedforfullyunderstand- ing complex problem areas and considering all pos- sible solutions without prejudice [12]. The resulting 55