Workspace and Reachability Analysis of a Robotic Arm for Sample Cache Retrieval from a Mars Rover

The return of Martian samples to earth could require extraction of a sample cache from the proposed Mars 2020 mission rover by a follow-up mission that would include a retrieval rover and robotic arm. Several major parameters that govern the design required to accomplish this goal include the length, mounting height, and degrees of freedom (DoF) of the robotic arm, the size of the rover it is mounted to, and the sample cache stowage location on the Mars 2020 mission rover. To assess the feasibility of this objective and begin understanding the architectural trade-space, a set of analyses was developed that explores the impact of these variables on cache accessibility. A software tool was developed that uses kinematics and collision detection to determine cache accessibility in the area around Mars 2020 through variation in the aforementioned parameters, as well as the robustness in retrieval rover approach angle at these locations. The results demonstrate that the minimum size arm needed to retrieve the cache from all possible locations and mounting heights is approximately two meters in length. A comparison of single versus double elbow arm configurations reveals that having a double elbow results in up to 30% improvement in reachable space.