Hardware
The system is based on a four wheeled mobile platform which was originally built by the Technical University of Munich / Institute of Automatic Control Engineering (LSR). We changed the wheels control electronic part to integrate the platform into our control architecture. Therefore the platform and the arm can be controlled as a 10 axis system for manipulation tasks. To navigate the system through the lab, the platform can be controlled on its own over a trajectory interface. The platform is omni directional, but non holonomic.
To give the system extended manipulation potential, the DLR Lightweight Arm II with the DLR Hand is mounted on the platform. All systems are real-time controlled by PowerPC Boards running under VxWorks in a VME-Bus Rack. For the non real-time software components, like navigation, scene analysis, collision avoidance, a laptop running Linux is also attached to the system. All computers are connected by Wireless LAN to the lab infrastructure.
Vision applications are supported through a Digiclops Stereo Vision System mounted on a PanTilt unit on the platform. Digiclops provides wide angle video images as well as a 2 ½D point cloud (Depth Image).
The robot can be interactively driven through the lab either with the push sensor built on top of the platform or a space mouse.
Software
The software part of the system consists of the control software for the platform, arm and hand and a task oriented programming system which allows to command the real-time control blocks.
Complex manipulation tasks can be composed of small sensor based operations easily within this system. The use of sensor information allows the real world to be slightly different from the model based view in the system. Therefore smaller changes in the environment do not result in the reprogramming of the whole task.
To obtain a representation of the environment scene-analysis software based on stereo images is integrated. This system can recognize and localize a set of known objects. Before activating any manipulation task, a so called World Model Update is executed with this scene-analysis component.