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’études 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 $-75^{\circ} C$ to $+85^{\circ} C$ (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.

I. Introduction

The MMX rover, jointly developed by CNES and DLR, shall be deployed on the Martian Moon Phobos. During the mission, the rover aims to explore the surface of Phobos, which is still unknown in detail. The environment on the Martian Moon is challenging, with the expected temperatures of up to (non-operating) at the motors - which are not located in the warmer inner compartment (E-Box) of the rover. During operation, the temperatures are heated up to as minimum, which is acceptable for space qualified parts, but still challenging for industrial parts. Furthermore, the milli-gravity on this moon - around - 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. 1.