Contact Dynamics Simulation for Space Robotics Applications

Abstract—The subject of this paper are contact dynamics simulation methods for two different examples of space robotics applications: Satellite docking in GEO and rover locomotion on planetary surfaces. The according modeling techniques include contact dynamics computation a) between two polygonal surfaces according to the elastic foundation model theory and b) between digital elevation grid surfaces and point cloud surfaces with application of Bekker’s empirical terramechanics functions. The presented simulation results, which are taken from two ongoing projects, SMART-OLEV with satellite docking simulations and ExoMars with rover drawbar pull simulations, demonstrate that contact dynamics simulations can provide helpful inputs in terms of mission feasibility assessment and system design. I

Lunar Rover with Multiple Science Handling Capability

A rover design study was undertaken for exploration of the Moon. Rovers that have been launched in the past carried a suite of science payload either onboard its body or on the robotic arm’s end. No rover has so far been launched and tasked with “carrying and deploying” a payload on an extraterrestrial surface. This paper describes a lunar rover designed for deploying payload as well as carrying a suite of instruments onboard for conventional science tasks. The main consideration during the rover design process was the usage of existing, in-house technology for development of some rover systems. The manipulation subsystem design was derived from the technology of Light Weight Robot, a dexterous arm originally developed for terrestrial applications. Recent efforts have led to definition of a mission architecture for exploration of the Moon with such a rover. An outline of its design, the manipulating arm technology and the design decisions that were made has been presented

Control Strategy of Hardware-in-the-Loop Simulator EPOS 2.0 for Autonomous Docking Verification

This paper briefly describes the hybrid simulator system called European Proximity Operation Simulator (EPOS 2.0) and the development of the hardware-in-the-loop (HIL) docking simulation concept. A critical requirement for the docking simulation of this HIL simulator is that the 6-DOF robots in the loop have to exactly mimic the dynamic response of the two satellites during a contact operation. The main challenges to meet this requirement are in the stiffness of the robots, which is unlike that of the satellites, as well as the time delay in the HIL simulator. The paper mainly presents the impedance parameter identification concept for matching the impedance between the satellites impact model and the EPOS robots. In addition it presents the contact dynamics model used, and the control strategies to meet the requirements of the docking simulator. Finally it presents the preliminary results and future work

MOSAR : Modular spacecraft assembly and reconfiguration demonstrator

With rapid development of space systems in recent years and their limited lives, it is imperative that a sustainable space development approach is developed to support more affordable access to space for all stakeholders. The European Commission hence funded the MOSAR project which aims to create a new paradigm technology to address this increasing challenge. This paper provides an overview of this technology’s preliminary development to enable on-orbit servicing. Building on five successful projects which collectively created all required common building blocks for both planetary explorations and in-orbit missions, a novel architecture is proposed to create a walking manipulator to demonstrate its unique capability in both space system assembly and on-orbit servicing. Preliminary design concepts of a walking manipulator and spacecraft modules are shown. A dedicated simulator is also developed to evaluate the proposed novel architecture for these targeted applications

GWAS meta-analysis of over 29,000 people with epilepsy identifies 26 risk loci and subtype-specific genetic architecture

Epilepsy is a highly heritable disorder affecting over 50 million people worldwide, of which about one-third are resistant to current treatments. Here we report a multi-ancestry genome-wide association study including 29,944 cases, stratified into three broad categories and seven subtypes of epilepsy, and 52,538 controls. We identify 26 genome-wide significant loci, 19 of which are specific to genetic generalized epilepsy (GGE). We implicate 29 likely causal genes underlying these 26 loci. SNP-based heritability analyses show that common variants explain between 39.6% and 90% of genetic risk for GGE and its subtypes. Subtype analysis revealed markedly different genetic architectures between focal and generalized epilepsies. Gene-set analyses of GGE signals implicate synaptic processes in both excitatory and inhibitory neurons in the brain. Prioritized candidate genes overlap with monogenic epilepsy genes and with targets of current antiseizure medications. Finally, we leverage our results to identify alternate drugs with predicted efficacy if repurposed for epilepsy treatment

Multibody and Contact Dynamics: From Satellite Capturing to Planetary Rover Terrainability

This paper gives a short overview of the multibody and contact dynamics based modelling and simulation activities performed at the German Aerospace Center. These cover two different applications, one in the orbital satellite servicing field and a second one in planetary explorations with rovers, specifically on Mars and Moon. Both topics require efficient and reliable contact dynamics modelling for both, satellite grasping and capturing and for the interaction between rover wheels and soft and hard planetary soils, i.e. the power transmission from the wheel actuators to the ground. Although the two applications areas, at first glance, are not necessarily common to each other, the contact dynamics modelling approach for both areas can rely on the same algorithms