Control of link-elastic serial kinematic chains with multiple bending planes for safe, dependable and efficient physical human-machine-interaction

• Applicant: Professor Dr.-Ing. Torsten Bertram
• Subject Area: Automation, Mechatronics, Control Systems, Intelligent Technical Systems, Robotics
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 289939442

The proposed project aims at the development of control concepts for the oscillation damping, positioning and force regulation of kinematic chains with link elasticity emerging in multiple planes of a robot mechanism. In future small batch production chains, the manufacturing expert is envisioned to become a herdsman, who is responsible for an entire herd of robots. With his knowledge about the manufacturing process, the expert instructs the robots for a particular manufacturing task. While each and every robot of the herd is processing its individual task, the herdsman is free to instruct other robots for new tasks. The demographic change motivates the conceptual extension of a flexible and physically interactive production assistant to universal service robots in household environments. Such artificial butlers disburden us from tedious tasks of the daily grind. They enable us to retain independence and self-determination up to an old age. The key to the realization is to ensure intrinsic safety and dependability of the physical interaction between humans and robots. This implicates a paradigm shift from conventional highly accurate but stiff and massive robot designs towards the application of so called Soft-Robotics methods. In first place, such methods strive to reduce the overall robot mass. In the next step, passive elastic components are intentionally introduced into the structure in series with the actuators. Undesired structural oscillations and deflections must be compensated by novel controllers. Existing prototypes realize the passive elasticity solely in the robot joints. Here the elastic effects are collocated about the joint axis of actuation. Novel composite materials or substantial mechanical construction efforts are considered to ensure lightweight but stiff link bodies. If the link bodies are elastic, the elastic properties are distributed along the link structure, so that the attenuation of undesired oscillations and deflections becomes a more difficult control challenge. Robust control concepts can relax the strict requirement for rigidity in the links of robots and comparable machinery. The reduction of the overall mechanism mass can hence be accomplished with simpler link geometries, conventional materials and thinner wall thicknesses. This yields a lighter and more efficient and affordable class of robots. Smaller and less powerful actuators can be employed, which further improves safety and dependability with respect to physical human robot interaction. This is the reason why the proposer sees an increased demand for the development of novel control concepts for link elastic multi body systems following the Soft-Robotics design paradigm. The few experimental studies reported in literature are limited to the elasticity being present in just a single plane. With the investigations particularly focusing on link elasticity in multiple planes of the mechanism, the proposed project consequently extends the state of science.

• DFG Programme: Research Grants
• International Connection: Italy
• Cooperation Partner: Dr.-Ing. Jörn Malzahn