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 - development of a rover locomotion system for Phobos

The MMX mission (Martian Moons eXploration) is a robotic sample return mission of the JAXA (Japan Aerospace Exploration Agency), CNES (Centre National d'Etudes Spatiales ) and DLR (German Aerospace Center) for launch in 2024. The mission aims to answer the question on the origin of Phobos and Deimos which will also help to understand the material transport in the earliest period of our solar system and the most important question how was the water brought on Earth. Besides the MMX mothership (JAXA) which is responsible for sampling and sample return to Earth a small rover which is built by CNES and DLR shall land on Phobos for in-situ measurements similar to MASCOT (Mobile Asteroid Surface Scout) on Ryugu. The MMX rover is a four wheel driven autonomous system with a size of 41 cm x 37 cm x 30 cm and a weight of approx. 25 kg. Multiple science instruments and cameras are integrated in the rover body. The rover body is basically 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, braking rockets) on Phobos, the legs are autonomously controlled to bring the rover in an upright orientation. One Phobos day lasts 7 earth hours, which gives for the total mission time of 3 earth months, the number of about 300 extreme temperature cycles. These cycles and the wide span of surface temperature between day and night are main design drivers for the rover. This paper gives a short overview on the MMX mission, the MMX rover and a detailed view on the development of the MMX rover locomotion subsystem

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

Raver, Rapper, Punks, Skinheads und viele andere. Beobachtungen aus jugendkulturellen Szenen

Der Autor setzt sich mit folgenden Aspekten der Jugendkulturen auseinander: 1. Jugendkulturen beginnen in der Familie. 2. Es gibt eine Vielzahl von Jugendkulturen. 3. Jugendkulturen sind zunehmend auch Kulturen junger Erwachsener. 4. Jugendkulturen sind Alltagskulturen und zugleich Eigensinn-Kulturen. 5. Jugendkulturen sind "ästhetische und symbolische" Orientierungsfelder. 6. Jugendkulturen sind Stil-Kulturen. 7. Jugendkulturen sind Medien- und Weltkulturen. 8. Jugendkulturen sind keine Gewalt- und Drogenszenen. Jugendkulturen sind Peer-Kulturen und landen wiederum in der Familie. (DIPF/Sch.

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

Qualification of the MMX Rover Locomotion Subsystem for the Martian Moon Phobos

Planetary rovers have proven their function and value for the Earth moon as well as Mars in the past decades. While these celestial bodies have a gravity of the same order of magnitude as the Earth, wheeled locomotion has never been performed on a body with much lower gravity. Within the Japanese Martian Moon eXploration (MMX) mission, a wheeled rover will land on the Martian Moon Phobos with a gravity of about 1/2000 of the Earth gravity. The Robotic and Mechatronics Center of the German Aerospace Center (DLR-RMC) has designed and built the locomotion subsystem (LSS) for this rover. As the first ever driving gear for milli-gravity, the LSS needed to undergo a comprehensive qualification campaign. Due to the very challenging timeline of this project, the extent of the campaign needed to be carefully tailored to the needs of the mission. This work describes the concept of the verification including some crucial tailoring choices that have been made. The individual domains of verification are then described in detail with their scope, setup, procedure and results. The goal of this publication is to give a good overview and a detailed insight into the verification of the LSS for milli-gravity. Besides follow-up missions to Phobos, this work is also a good foundation for the qualification of future driving gears for low gravity environments or small rovers in general