Driving in Milli-G: The Flight Model of the MMX Rover Locomotion Subsystem and its Integration & Testing in the Rover

IDEFIX is a 25 kg four-wheeled rover that will explore the surface of the Martian Moon Phobos in 2027. The rover is jointly developed by the German Aerospace Center (DLR) and the Centre National d'Etudes Spatiales (CNES) and will be brought to Phobos within the Japan Aerospace Exploration Agency's (JAXA) Martian Moon eXploration (MMX) mission. Being the world's first wheeled system to drive in milli-gravity, IDEFIX's locomotion deserves special attention. This paper gives an overview of the locomotion subsystem (LSS) of the rover, which is entirely developed and built by the Robotics and Mechatronics Center of DLR (DLR-RMC). A representative LSS, mounted on an IDEFIX prototype, is shown in Figure 1. The LSS is tailored to the needs for the IDEFIX rover and the most important, sizing challenges and functional requirements are summarized. It is then shown how the final flight model (FM) design answers to these requirements. The assembly, integration and testing (AIT) with respect to the LSS consists of several steps of integration and testing at different facilities as well as a comprehensive test sequence once the rover is mostly integrated. Since the LSS is an important, interconnected and the functionally most complex subsystem of the rover, some functionalities could only be tested once the LSS was integrated into IDEFIX. These AIT aspects are therefore summarized in this paper as well

Fault Detection, Isolation and Recovery in the MMX Rover Locomotion Subsystem

In any mechatronic system, faults can occur. Likewise also in the MMX rover, which is a wheeled rover mutually developed by CNES (Centre national d'études spatiales) and DLR (German Aerospace Center), intended to land on Phobos. An essential part of the MMX rover is the locomotion subsystem which includes several sensors and eight motors actuating the four legs and the four wheels. In each of these components and their interfaces, there is a possibility that faults arise and lead to subsystem failures, which would mean that the rover cannot move anymore. To reduce this risk, the possible faults of the MMX locomotion subsystem were identified in a FMECA study and their criticality was classified, which is presented in here. During this examination, the criticality was graded depending on different mission phases. With the help of this study, the hardware, firmware and software design were enhanced. Fur- ther, certain fault detection, isolation and recovery strategies were implemented in the locomotion firmware and software as well as in the full rover software

MMX Rover Locomotion Subsystem - Development and Testing towards the Flight Model

Wheeled rovers have been successfully used as mobile landers on Mars and Moon and more such missions are in the planning. For the Martian Moon eXploration (MMX) mission of the Japan Aerospace Exploration Agency (JAXA), such a wheeled rover will be used on the Marsian Moon Phobos. This is the first rover that will be used under such low gravity, called milli-g, which imposes many challenges to the design of the locomotion subsystem (LSS). The LSS is used for unfolding, standing up, driving, aligning and lowering the rover on Phobos. It is a entirely new developed highly-integrated mechatronic system that is specifically designed for Phobos. Since the Phase A concept of the LSS, which was presented two years ago [1], a lot of testing, optimization and design improvements have been done. Following the tight mission schedule, the LSS qualification and flight models (QM and FM) assembly has started in Summer 2021. In this work, the final FM design is presented together with selected test and optimization results that led to the final state. More specifically, advances in the mechanics, electronics, thermal, sensor, firmware and software design are presented. The LSS QM and FM will undergo a comprehensive qualification and acceptance testing campaign, respectively, in the first half of 2022 before the FM will be integrated into the rove

Valenzgebundene Elemente und logisch-semantische Tiefenstruktur

Eines der Hauptprobleme bei der Erstellung einer Verbvalenzgrammatik besteht darin, Kriterien zu formulieren, die es erlauben, eindeutig zwischen valenzgebundenen und nicht valenzgebundenen Elementen des einfachen Verbalsatzes zu unterscheiden. Es hat sich gezeigt, daß die Kriterien der “Weglaßbarkeit” zur Identifizierung der freien Elemente und der “verbspezifischen Erwartungswahrscheinlichkeit” zur Bestimmung der Verbergänzungen nicht ausreichen. Daher wird seit einigen Jahren in steigendem Maße die Frage diskutiert, ob die Abhängikeitsverhältnisse zwischen dem Prädikat und seinen Ergänzungen nicht nur als oberflächensyntaktische Vorkommensrelationen zu beschreiben, sondern primär in einer Tiefenstruktur anzusetzen sind, als deren Reflex sie sich an der Oberfläche niederschlagen. Auf diesem Hintergrund hat G. Helbig ein operationalisiertes Verfahren entwickelt, das das Problem der valenzgebundenen Elemente auf der Ebene einer syntaktischen Tiefenstruktur entscheiden soll. Der folgende Beitrag setzt sich kritisch mit Helbigs Vorschlag auseinander und stellt ihm eine Alternative auf der Basis der von K. Heger2a entwickelten Aktantenmodelle entgegen

Upscreening of Infineon Hall Effect Sensors for the MMX rover locomotion subsystem

The MMX (Martian Moons eXploration mission), conducted by JAXA (Japan Aerospace Exploration Agency) aims to explore both Mars moons Phobos and Deimos. This mission is supported by a small rover intended to land on Phobos, jointly developed by CNES (Centre national d'etudes spatiales) and DLR (German Aerospace Center). An essential part of this rover is the locomotion subsystem, which includes several sensors and eight motors actuating four legs, and the four wheels mount on them. In each of the BLDC (Brushless DC) motors are three industrial Hall effect sensors mounted, used for incremental position sensing and motor commutation in parallel. Smaller form factor and high accuracy are two key requirements for the selection of the Infinion TLE4945L Hall effect sensors. Since the motors are not located in the insulated inner compartment of the rover, they must withstand extreme temperature ranges of -75°C to +85°C (non operational). This goes beyond the temperature range of industrial electronics and space grade electronics. Therefore, an up-screening campaign was performed, where the radiation and the temperature performance of the Hall effect sensors were measured. This paper highlights the most important results of the conducted tests

Development of zinc-air flow batteries by investigating compact zinc deposition and improving air electrode cycling stability

The growing number of electric vehicles worldwide demands increasing electricity generation from renewable sources such as wind and solar in order to render these vehicles CO2 neutral. However, these systems are very intermittent and need to be coupled with high capacity and fast responding energy storage systems. Zinc-air flow batteries are designed for this stationary application, using the inexpensive, safe and abundant metal zinc as active storing material. In the project Luziflow all battery components are investigated and improved regarding the efficiency during cycling and the long-term stability during operation. On the negative zinc electrode, new insights have been gained on dendrite-free zinc deposition during charging and with flowing electrolyte. On the positive air electrode stable bifunctional electrode designs with high catalytic activity have been applied in long-term operation. The final aim of the project Luziflow will be the scale-up to 100 cm² and full cell operation

Dexhand : a Space qualified multi-fingered robotic hand

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