A multidisciplinary design tool for robotic systems involved in sampling operations on planetary bodies

Abstract

The analysis of robotic systems (e.g. landers and rovers) involved in sampling operations on planetary bodies is crucial to ensure mission success, since those operations generate forces that could affect the stability of the robotic system. This paper presents MISTRAL (MultIdisciplinary deSign Tool for Robotic sAmpLing), a novel tool conceived for trade space exploration during early conceptual and preliminary design phases, where a rapid and broad evaluation is required for a very high number of configurations and boundary conditions. The tool rapidly determines the preliminary design envelope of a sampling apparatus to guarantee the stability condition of the whole robotic system. The tool implements a three-dimensional analytical model capable to reproduce several scenarios, being able to accept various input parameters, including the physical and geometrical characteristics of the robotic system, the properties related to the environment and the characteristics related to the sampling system. This feature can be exploited to infer multidisciplinary high-level requirements concerning several other elements of the investigated system, such as robotic arms and footpads. The presented research focuses on the application of MISTRAL to landers. The structure of the tool and the analysis model are presented. Results from the application of the tool to real mission data from NASA's Phoenix Mars lander are included. Moreover, the tool was adopted for the definition of the high-level requirements of the lander for a potential future mission to the surface of Saturn's moon Enceladus, currently under investigation at NASA Jet Propulsion Laboratory. This case study was included to demonstrate the tool's capabilities. MISTRAL represents a comprehensive, versatile, and powerful tool providing guidelines for cognizant decisions in the early and most crucial stages of the design of robotic systems involved in sampling operations on planetary bodies.

Keywords: Design tool; Lander; Planetary exploration; Robotic systems; Sampling.

Fig. 1

Block diagram of the tool

Fig. 2

Free body diagram (XY plane view) for the 3-legged lander. Qualitative scheme, not to scale

Fig. 3

Main geometric parameters (XY plane view) for the 3-legged lander. Qualitative scheme, not to scale

Fig. 4

Free body diagram and main geometric parameters (XZ plane view) for the 3-legged lander. Qualitative scheme, not to scale

Fig. 5

Free body diagram and main geometric parameters (YZ plane view) for the 3-legged lander. Qualitative scheme, not to scale

Fig. 6

Free body diagram (XY plane view) for the 4-legged lander. Qualitative scheme, not to scale

Fig. 7

Main geometric parameters (XY plane view) for the 4-legged lander. Qualitative scheme, not to scale

Fig. 8

Free body diagram and main geometric parameters (XZ plane view) for the 4-legged lander. Qualitative scheme, not to scale

Fig. 9

Free body diagram and main geometric parameters (YZ plane view) for the 4-legged lander. Qualitative scheme, not to scale

Fig. 10

Vectors joining the lander’s footpads for the 3-legged lander. Qualitative scheme, not to scale

Fig. 11

Vectors joining the lander’s footpads for the 4-legged lander. Qualitative scheme, not to scale

Fig. 12

Example of convex objective functions

Fig. 13

Some sampling system configurations that might be explored by changing the $\beta$ angle

Fig. 14

Engineering model of the Phoenix lander RA and ISAD. Credits: NASA/University of Arizona

Fig. 15

Phoenix lander worst-case configuration. The lander is inclined about the Y axis and pulled downhill during backhoe operations. Qualitative scheme, not to scale

Fig. 16

Phoenix lander configuration. The sampling spot lies in the green area. Qualitative scheme, not to scale

Fig. 17

DE of the Phoenix lander together with the mission data points

Fig. 18

Enceladus lander worst-case configuration. The lander is inclined about the Y axis and pushed downhill during scooping operations. Qualitative scheme, not to scale

Fig. 19

3-legged lander configuration for the Enceladus lander case study. The sampling spot is aligned along the X axis. Qualitative scheme, not to scale

Fig. 20

4-legged lander configuration for the Enceladus lander case study. The sampling spot is aligned along the X axis. Qualitative scheme, not to scale

Fig. 21

DE of the 3-legged lander for the Enceladus lander case study. The ground slope is reported in absolute value for convenience

Fig. 22

DE of the 4-legged lander for the Enceladus lander case study. The ground slope is reported in absolute value for convenience

Fig. 23

Use of the DE for general systems design. Example for the 3-legged lander configuration