The aim of the OAS is to support employees in carrying out manual assembly activities in terms of efficiency, process reliability and error prevention. The system is equipped with an image processing unit. 2D markers, which employees wear on their wrists like a watch, recognize gripping movements and compare them with predefined target processes. This transforms the system into an intelligent inspection technology that reduces production costs by minimizing errors, complaints and expensive re-production. The OAS was developed in collaboration with the Fraunhofer Institute for Factory Operation and Automation (IFF) in Magdeburg.

Clearly structured processes
The OAS further streamlines assembly and creates a clearly structured work process with step-by-step instructions. This also benefits the employee. The strain on their concentration is greatly reduced. In future, all other Treston workbench solutions - such as Concept, LMT, WB, Towerline or TP - will also be able to be optionally extended with the OAS and benefit from the stable, secure process. Depending on the intended use, the solution adapts to different assembly applications because the operator can define individual work processes themselves.

Depth image sensors localize gripping movements
An OAS system consists of an assembly monitoring unit (AMU), two 2D markers, each measuring 4.5 x 4.5 centimetres and weighing 30 grams, a touchscreen and a computer. The AMU is mounted vertically above the workstation on the Moduline superstructure, for example. From there, a depth image sensor built into the AMU analyzes and monitors the hand and gripping movements of the employee taking place beneath it. This monitoring is made possible by the continuous, image-based identification and localization of 2D markers, which the employee wears on their wrists like a watch. It is possible to grip with the right, left or both hands.

The depth image sensor (left), which is installed above the workstation, and the 2D markers for the wrist are core components with which the OAS performs a hand-based (grasping) analysis. © Fraunhofer IFF

Step-by-step to the finished product
The work steps at the two workstations are predefined and stored in a database. When the employee starts the assembly process at a workstation via the touchscreen, the individual work instructions for each work step are displayed there. As soon as the OAS identifies a work step as "ok", it completes the work step and calls up the next work step with the associated work instructions. If the work step is declared "not ok" - due to a gripping error, for example - the system prompts the employee to correct the error and repeat the work step. The system is also equipped with a documentation function that creates a photo after each completed work step and enables sustainable and consistent quality management.

In order to carry out these process steps, the OAS must perform a continuous hand-based analysis. It compares the actual hand movements per work step with the predefined target hand movements. In this way, the OAS can draw intelligent conclusions and make decisions as to whether the work step is "ok" or "not ok". In the future, the OAS will have further levels of analysis. An area-based and an object-based analysis are planned, which in turn will trigger certain functions as soon as the 2D marker enters certain pre-defined work zones. In this way, further documentation and measurement functions are to be initiated and specific requirements of other industries are to be developed.

Electrical assembly, shipping and logistics
OAS is suitable for continuous use in non-automated, manual assembly processes that are characterized by small order volumes and frequent product changes. It is a good fit for applications in the electrical industry, for packing processes in shipping and logistics and for manual assembly in toolmaking and mechanical engineering. Installation, application-specific adaptation and process programming of the system are simple and can be carried out without training; commissioning takes just a few hours. pb