Robot-assisted automation can be very expensive. Depending on the application, a modern robot cell can cost anywhere from 100,000 to over 500,000 euros. Only a comparatively small proportion of this is spent on the actual arm structure. Around two thirds of the costs are usually incurred for peripherals such as assembly devices, conveyor belts and safety fences as well as grippers or tools. Such high costs are particularly problematic when it comes to a highly specialized system that is only used to a limited extent. An obvious solution is to use less specialized, more universal robots. In the field of stationary robots, however, this is not readily possible, as only a certain amount of peripherals can be accommodated in the robot's working area and because the various requirements of the different processes can rarely be met economically by just one robot.

Mobile robots ensure efficiency and flexibility

This is where mobile robotics can help. Mobile robots can move flexibly through production and therefore have an almost unlimited workspace. At the same time, they reduce the need for feeding and transport equipment. Another advantage of mobile robots is that several robots can work together. As part of the SCALE research project - Scalable Production Systems of the Future - the Institute of Assembly Technology (match) is developing methods to enable several mobile robots to perform the task of a larger robot together. This cooperation between several universally deployable small robot units enables them to perform tasks that would be impossible for a single unit. As many mobile robots as are required for the task in question are always combined. This makes the so-called multi-robot systems extremely versatile and highly scalable.

The match's research focus in mobile robotics is on solving application-related problems in the areas of programming, control and regulation as well as task planning and distribution. A particular research challenge is the degree of freedom of the overall system and the associated complexity in modeling and identification. In addition to the mobile robot platform, which can already move freely in space, each mobile unit also has a manipulator with six or seven joints. If several so-called mobile manipulators, as shown in the illustrations, are working on a common object, all the drives of both robots must be moved in precise coordination with each other.

Without the precise coordination of all drives, there will be tension in the object and in the robots, which can cause mechanical damage. In view of this, it is a particular challenge that communication between the mobile platforms must be wireless in order to maintain the autonomy and flexibility of the individual robots. For this reason, the match is researching the use of 5G communication in order to be able to exchange data with the lowest possible latency. In addition, methods are being developed to detect errors and the resulting component stresses at an early stage and to cushion them through the compliant behavior of the manipulator.

Precise process planning

Correct planning of the process sequence is just as important as controlling the manipulators. In particular, it must be determined which robots are to be used, how many and in what arrangement. The number and arrangement of robots is crucial for the distribution of weight and process forces to the individual robots. When determining the optimum arrangement, a number of boundary conditions must be taken into account. On the one hand, the points at which the existing grippers can grip the component must be taken into account. Secondly, collisions between the robots must be avoided.

In addition to the problems mentioned above, match also deals with general problems of mobile robotics such as localization and path planning. The institute thus covers a large part of industrial mobile robotics both in terms of research and application.