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

Abstract

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 rover.

MMX Rover Simulation - Robotic Simulations for Phobos Operations

“…Introduction-To assist the development of the locomotion subsystem, see [5], different simulations in the theme of driving were conducted. These simulations range from answering simple aspects like the maximum safe rover acceleration to more complex questions like an analysis of the rover's As the rover has no steered wheels, it has to rely on differential steering to navigate.…”

“…One of the critical parts of the rover is its locomotion subsystem, consisting of four individually driven wheels attached to four individually actuated legs [5]. The legs allow the rover to be put into a stowed configuration during transit.…”

“…We chose a hybrid approach for the tool selection. The implementation of the Modelica 4 modeling language in the Dymola 5 simulation framework and IDE builds the basis. On top of it are various in-house developed libraries for visualization or contact dynamics.…”

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

“…Furthermore, the milli-gravity on this moon -around 0.004 − 0.007m/s 2 -and the unknown surface properties make it difficult to develop a locomotion subsystem that ensures a proper movement of the rover on Phobos. More details about the mission and the locomotion subsystem development can be found in [1], [2] and [3]. A simulation view of the MMX rover on the surface of Phobos can be seen in Fig.…”

“…The external shoulder side and the legs with wheels can be seen. Credits: [3], Copyright ©2022, IEEE Fig. 2.…”