On-orbit servicing involves a new class of space missions in which a servicer spacecraft is launched into the orbit of a target spacecraft, the client. The servicer navigates to the client with the intention of manipulating it, using a robotic arm. Within this framework, this work presents a new robotic experimental facility which was recently built at the DLR to support the development and experimental validation of such orbital servicing robots. The facility allows reproducing a closeproximity scenario under realistic three-dimensional orbital dynamics conditions. Its salient features are described here, to include a fully actuated macro-micro system with multiple sensing capabilities, and analyses on its performance including the amount of space environment volume that can be simulated.
Position-based force control is presented, incorporating compliance in the robot joints and possibly in a force-/ torque-sensor and/or the environment. First, the total compliance is identified. Then, in the control phase, the desired pose of the tool center point is computed from the force control error. Thus standard position control may be applied. This leads to an inherently stable control scheme, even with a low sampling rate of the sensor interface and unknown environmental compliance. The method is designed for applications of industrial robots, e.g. assembly tasks. Parallel control considers the existence of a reference trajectory which allows feedforward in force controlled directions. The paper further examines couplings between forces and torques, which are important for partially constrained configurations. A possible impact force is considered when colliding with an unexpected object.
Despite the progress since the first attempts of mankind to explore space, it appears that sending man in space remains challenging. While robotic systems are not yet ready to replace human presence, they provide an excellent support for astronauts during maintenance and hazardous tasks. This paper presents the development of a space qualified multi-fingered robotic hand and highlights the most interesting challenges. The design concept, the mechanical structure, the electronics architecture and the control system are presented throughout this overview paper.
MMX (Martian Moons eXploration) is a robotic sample return mission of JAXA (Japan Aerospace Exploration Agency), CNES (Centre National d' Études Spatiales), and DLR (German Aerospace Center) with the launch planned for 2024. The mission aims to answer the question of the origin of Phobos and Deimos, which will also help to understand the material transport in the earliest period of our solar system, and of how was water brought to Earth. Besides JAXA's MMX mothership, which is responsible for sampling and sample return to Earth, a small rover which is built by CNES and DLR to land on Phobos for in-situ measurements, similar to MASCOT (Mobile Asteroid Surface Scout) on Ryugu. The MMX rover is a fourwheel driven autonomous system with a size of 41 cm x 37 cm x 30 cm and a weight of approximately 25 kg. Multiple science instruments and cameras are integrated in the rover body. The rover body has the form of a rectangular box. Attached at the sides are four legs with one wheel per leg. When the rover is detached from the mothership, the legs are folded together at the side of the rover body. When the rover has landed passively (no parachute or braking rockets) on Phobos, the legs are autonomously maneuvered to bring the rover in an upright orientation. One Phobos day lasts 7.65 earth hours, which yields about 300 extreme temperature cycles for the total mission time of three earth months. These cycles and the wide span of surface temperature between day and night are the main design drivers for the rover. This paper gives a detailed view on the development of the MMX rover locomotion subsystem
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