Robots based on parallel kinematic structures are known to have a small workspace compared to their installation space. To tackle this drawback a workspace enlargement approach using several workspaces going along with different working and assembly modes has been introduced in earlier publications. Robot structures designed for this approach are able to change their assembly modes. Using the drives' position feedback systems these assembly modes cannot be distinguished, which is necessary at least after startup of the robot control to correctly solve the structure's kinematic models. In this paper different approaches for a detection of the actual assembly mode of a kinematic structure are presented. Using the example of a Triglide-robot one of the approaches is demonstrated in more detail. It is based on a comparison of measured drive forces, necessary to hold the structure against gravity, with theoretical holding forces, calculated for all possible assembly modes. Experimental results show the effectiveness of the approach.