Lena Kredel suffers from multiple sclerosis. She cannot move her arms and legs, but nevertheless she is working. The literary scholar originates from Bad Segeberg, Germany and is undertaking an apprenticeship as a librarian at the University of Bremen. Lena is using a service robot ‘FRIEND’ and its Schunk lightweight arm as a tool to support everyday tasks to allow autonomous environmental interaction. Now, the robot specialists from the Institute for Automation Technology (IAT) Bremen have modified the mechatronic helper so that Lena Kredel can independently catalog the books in the university’s library.
Lena Kredel says: “Friend is a stroke of luck for me.” The abbreviation ‘FRIEND’ stands for ‘functional robot arm with user-friendly interface for disabled people’. At a first glance the unit looks somewhat bulky. The electrically powered wheelchair is equipped with a monitor, multiple sensor systems and as a central element, a lightweight arm from Schunk. With a joystick at her head and via voice recognition, Lena Kredel controls her assisting robot to record books with standard software for libraries using an internet browser for research. In the course of time, ‘FRIEND’ really did become a true friend for Lena. Using ‘FRIEND’ has brought a great deal of pleasure, and it is obvious that Lena enjoys the freedom and independence that the system brings.
Since 1997, the IAT Bremen has conducted research on robot-supported assisting systems, and the system used by Lena Kredel today is the fourth generation. The system is based on a concept of shared autonomy. Things that can be independently solved by the robot, are done by the robot itself. If it reaches its limits, the user intervenes for correcting the gripping position or if unforeseen disturbances occur. According to Torsten Heyer, project manager at IAT, presently about 95 per cent of all processes can be solved this way without any external help.
For ensuring perfect teamwork, the environmental conditions are autonomously recorded via a three-dimensional camera and an infrared camera that are positioned over the head of the user. When Lena Kredel starts the system, the camera locates the bookshelf, the books and the storage position automatically. Then, the Schunk lightweight arm approaches the determined position autonomously. Markers and coloured markings are used by the system as a point of reference. The control of the whole gripping system is carried out by Lena Kredel. For this purpose, the system has been equipped with numerous features that allow assessment and control of the gripping process. A camera on the robot gripper continuously transmits live pictures of the gripping process. These are immediately visible for the user on a monitor. At the same time the camera can be used as a reading lens that makes even small print readable. If the system should approach its limits, Lena Kredel intervenes.
Versatile lightweight arm
The central element of the assisting robot is the LWA 3.10 lightweight arm from Schunk, a modularly integrated gripping arm with seven degrees of freedom. The system uses three degrees for orientation, three for positioning and one for bypassing obstacles. In contrast to classic industrial robots, the lightweight arm is designed for automating the direct environment of a human. This includes inspection and assembly tasks and also the use of assistance systems.
A permanently high repeatability of +/-0.1mm ensures optimum conditions for precise gripping operations. The maximum payload of the gripping arm amounts to 10kg. At a battery-servable power supply of 24V, the average power requirement is below 3A. If no socket should be available, or if the system is used completely mobile, the assistance robot may be self-sufficiently operated by the standard wheelchair battery for about 2–3 hours. In order to exclude the risk of injury, the IAT has equipped the assistance robots with force-moment and spatial monitoring sensors.
As the drive amplifier and controller are directly integrated in the lightweight arm, the system does not require a control cabinet. The complete control and regulation electronics are integrated in the joint drive. Position, speed, and torque can be flexibly adjusted. With integrated intelligence, universal communication interfaces and cable technology for data transmission and power supply, the arm can be quickly and easily integrated into existing concepts. Moreover, it is controlled via an embedded personal computer.
As the assisting robot has to cover a gripping radius of 180cm, it appears bulky at first glance. Thanks to the consistent modular program from Schunk, Torsten Heyer says that changing to the more compact Powerball lightweight arm LWA 4.6 is now possible.
The lightweight arm is programmed via the Schunk interface. The individual movement strategies were developed by IAT. According to Christos Fragkopoulos, at the IAT, programming has been easy: “We control the speed or current via the interface. How the modules are working with each other depends on the individual program. This belongs to the scientific work carried out by IAT.”
At the beginning, the pure handling time for an individual book was 17 minutes; now Lena Kredel requires between five and seven minutes for handling and 15 minutes for cataloguing. In the next step, reliability will be increased. The aim is to achieve a success rate of 99.9 per cent over the course of time. According to Torsten Heyer, the ‘ReIntegraRob’ project sponsored by the Integration Office in Bremen with €400,000, shows the hidden potentials of assisting robots.
For further information about robots and the LWA 3.10 lightweight arm from Schunk, go to www.gb.schunk.com/.