Speaker
Dr
Matthias Reiner
(DLR)
Description
Studies have shown that the population of large objects has become a problem in Low Earth Orbit (LEO). The danger of collisions is higher than ever before and important objects are at high risk of major damage. One proposed solution for this problem is Active Debris Removal (ADR) using a robotic arm mounted on a spacecraft.
A gripper or another adequate tool installed on the robot arm could capture almost every debris part (target) that endangers other satellites in the orbit. Once a connection (docking) is established, the chaser spacecraft can be used to safely deorbit the target by transferring it to a disposal orbit.
To analyze this approach, a GNC simulation tool for Active Debris Removal with a robot arm was developed. A realistic benchmark scenario based on the capturing of the inactive Envisat satellite was chosen for a simulation study. The scenario considers uncertainties in the mechanical parameters and measurement noise. It focuses on the most critical phases of an ADR mission. In particular, the rendezvous phase, the capture phase as well as the GNC controlled de-orbiting phase.
The tool is used to design and simulate the GNC algorithms, satellite dynamics, kinematics and environment as well as the robot arm control.
The developed control system consists of multiple parts at different hierarchical levels. A trajectory planning module coordinates different controllers of chaser satellite and robotic arm and provides reference trajectories for a successful docking of the two satellites.
An optimization based approach trajectory was designed using an inverse satellite model of the chaser and the robotic arm. The results are used as the feed-forward control part of the two degree of freedom control approach.
The trajectory design plays an important role to avoid a collision between the rotating passive target and the chaser satellite.
Due to the rapid rotation of the target satellite, a simultaneous combined control of the chaser satellite together with the mounted robot arm is necessary, and considering actuator limits is crucial.
The feed-back controller synthesis for the thrusters, reaction wheels and robot joint control was implemented using multi-case and multi-objective optimization with parameterizable models generated by the newly developed tool. This results in a robust control setup that is able to handle mechanical uncertainties and sensor noise.
The simulation tool can also be used to visualize the ADR scenario, based on CAD models of the satellite and the robot arm. The object-oriented design allows the change of modular components and parameters of the simulation.
Simulation results show that the suggested ADR benchmark scenario can be successfully completed using the developed control algorithms.
The object-oriented GNC simulation tool for active debris removal with a robot arm allows the comprehensive design and analysis of an ADR scenario. It can be used to develop and verify the required GNC of the satellite and the control of the robot arm.
| Applicant type | First author |
|---|
Primary author
Dr
Matthias Reiner
(DLR)
