DLR's Advancements in Space Robotic Manipulation

5, 4, 3, 2, 1, solid rocket ignition and liftoff, liftoff of Columbia on a voyage to the future. Robotics is becoming a key technology for ensuring sustainability in space operations in the years to come. We have the situation that with increasing number of satellites in orbit, with the huge constellations, we need the capability to repair, to refuel, to inspect, to maintain and even to assemble large structures in orbit. And robotics technology, compliance robots, which are able to assemble, to be tele-operated, but also to interact with astronauts, is going to be a game changer in this area. The starting shot for Germany's participation in space robotics and automation was the Rotex mission in 1993. We tested a small 6-axis robot arm inside the space shuttle with the D2 Space Lab mission. We performed different prototypical tasks, including capturing a free-floating object, which is a precursor to our final goal of capturing a Tombril satellite in space. The gripper was endowed with different sensing modalities and we tested different control approaches, including tele-manipulation, shared autonomy and full autonomy modes. Our next experiment was Rokbis, launched in 2004. We launched a robot with two joint units and installed it on the outer wall of the Russian module on the ISS. With this robot, we tested the performance of the total control joint units under the harsh conditions of the space environment. Building on the success of previous space robotic missions, the Caesar Space Manipulator was presented in 2018. It is currently undergoing space qualification. It's a larger robot, 3 meters long to be precise. It also exhibits improved performance and high dexterity. One of Caesar's key features is that it exhibits sensitive compliant behavior. This is made possible thanks to the impedance controller, which ensures that the robot interacts and reacts with forces that it experiences as it moves through the environment. This is important when the robot interacts with other objects, in particular in safety-critical space applications. When we created the Caesar robot arm, we faced a particular challenge. As the robot arm is developed to operate in zero gravity, its motors are not able to lift its own weight under Earth's environment. So, how do we test the robot arm in our labs? The motion suspension system is a gravity compensation mechanism. It is based on a cable robot, which consists of ropes, which are connected to the ceiling and motors. It computes an optimal suspension force that reduces the torques acting on the joints. Now, with the motion suspension system, we can test and qualify all types of applications in 3D space. DLR is now on a good track to finish the verification and validation of the robot arm technology, which will be a key component of the upcoming servicing mission in the next few years.