Tobias Bellmann

The DLR Robot Motion Simulator Part I: Design and setup

In recent years a new generation of motion simulators, based on serial kinematics industrial robots, emerged as alternative to the currently prevalent Steward-platforms. This paper presents the newest addition to this: The DLR Robot Motion Simulator.

The DLR Robot Motion Simulator Part II: Optimization based path-planning

In Part I of this paper, a novel motion simulator platform is presented, the DLR Robot Motion Simulator with 7 degrees of freedom (DOF). In this Part II, a path-planning algorithm for mentioned platform will be discussed. By replacing the widely used hexapod kinematics by an antropomorhic, industrial robot arm mounted on a standard linear axis, a comparably larger workspace at lower hardware costs can be achieved. But the serial, redundant kinematics of the industrial robot system also introduces challenges for the path-planning as singularities in the workspace, varying movability of the system and the handling of robot systems kinematical redundancy. By solving an optimization problem with constraints in every sampling step, a feasible trajectory can be generated, fulfilling the task of motion cueing, while respecting the robots dynamic constraints.

Proof of concept simulator demonstration of a physics based self-preserving flight envelope protection algorithm

This article discusses the development of an adaptive protection algorithm which is based on a physical approach, with the purpose to keep a closed loop aircraft with manual control laws within the actual safe flight envelope, even in the presence of failures or disturbances. Adaptive estimation of the flight envelope guarantees that not only flap changes, but also damage (e.g. icing) and external disturbances such as wind can be taken into account. This method is robust with respect to uncertainties in the estimates for the aerodynamic properties. This updated information makes the flight control laws more self-preserving and prevents loss of control in flight. This development can extend the functional envelope of the nominal law and reduce the need to switch from nominal to alternate law in the presence of certain failures. This algorithm has been applied on a simulation model of a medium range passenger aircraft and the setup has been implemented and evaluated in the DLR Robotic Motion Simulator at the German Aerospace Center as a proof of concept demonstration. Adaptive flight envelope protections prevent loss of control for damaged aircraft in certain scenarios.Flight control laws become more self-preserving with improved autonomy thanks to these adaptive protections.The developed method is robust with respect to uncertainties in estimates of the aerodynamic properties.The functional envelope of the nominal law is extended and the need to switch to alternate law for certain failures is reduced.A proof of concept demonstration has been given in the robotic motion simulator at DLR.

Worst Case Braking Trajectories for Robotic Motion Simulators

Motion simulators based on industrial robots can produce high dynamic accelerations and velocities compared to classical hydraulic hexapod systems. In case of emergency stops, large and possibly harmful accelerations can occur. This paper aims to provide an optimization procedure to generate worst case trajectories in order to test for these harmful accelerations, by maximizing the kinetic energy prior the emergency stop. The dynamical and mechanical limits of the robot are considered as constraints of the optimization criterion. An exemplary worst case trajectory is simulated using a braking model and the resulting Head Injury Criterion (HIC) is calculated and compared with older tests, using non-optimized trajectories. A significant higher, yet with the current robot dynamics not harmful HIC value can be generated.

Aircraft Upset and Recovery Simulation with the DLR Robot Motion Simulator

Aiming at providing a more accessible alternative platform for upset recovery training and research, the feasibility of adapting the German Aerospace Center (DLR)s Robot Motion Simulator is studied with use of the Fokker 100 extended flight dynamics model developed earlier. Adjustments are made to the S-function in the simulation software setup for better preserving the dynamic motions in stall and post-stall conditions. The configuration of the simulator with a cabin located on the top of a KUKA industrial robot arm provides seven axis of movement freedom, greatly enlarging the motion capability in comparison to the conventional hexapod simulators. Virtually all nominal ight conditions can be simulated well with the current setup; and with a slight modification of one axis for continuous rotations, the simulator shows good capability of reproducing the motions experienced in aircraft upset conditions and recovery maneuvers.