A report discusses the design of a rover lift mechanism (RLM) — a major subsystem of each of the Mars Exploration Rover vehicles, which were landed on Mars in January 2004. The RLM had to satisfy requirements to (1) be foldable as part of an extremely dense packing arrangement and (2) be capable of unfolding itself in a complex, multistep process for disengaging the rover from its restraints in the lander, lifting the main body of the rover off its landing platform, and placing the rover wheels on the platform in preparation for driving the rover off the platform. There was also an overriding requirement to minimize the overall mass of the rover and lander. To satisfy the combination of these and other requirements, it was necessary to formulate an extremely complex design that integrated components and functions of the RLM with those of a rocker-bogie suspension system, the aspects of which have been described in several prior NASA Tech Briefs articles. In this design, suspension components also serve as parts of a 4- bar linkage in the RLM.
This work was done by Joseph Melko, Theodore Iskenderian, Brian Harrington, and Christopher Voorhees of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Mechanics category. NPO-40875
This Brief includes a Technical Support Package (TSP).
Lifting Mechanism for the Mars Explorer Rover;
(reference NPO-40875) is currently available for download from the TSP library.
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Overview
The document discusses the engineering and design challenges faced during the development of NASA's Mars Exploration Rovers (MER), which were launched in 2003 and landed on Mars in early 2004. The project was characterized by stringent constraints on schedule, volume, and mass, necessitating an integrated approach to system design. This integration led to complex engineering issues but ultimately resulted in a robust and efficient deployment mechanism.
A key focus of the document is the Rover Lift Mechanism (RLM), which played a crucial role in the rover's deployment process, particularly during the "standup" phase. The RLM utilized a four-bar linkage system that incorporated existing components of the rover's structure, such as the Warm Electronics Box (WEB) and the suspension system. This design minimized the number of additional parts and devices required for lifting the rover, thereby adhering to the mission's mass and volume restrictions.
The RLM operated in two distinct modes. In the first mode, it provided the necessary force to lift the rover while controlling both vertical motion and pitch rotation. In the second mode, as the rover reached its deployment apex, the mechanism transitioned to controlling only vertical motion, allowing for a more rigid structure as the deployment progressed. This innovative design approach was informed by a trade study that favored linear actuators over torque-actuated joints, which would have added unacceptable mass and complexity.
The document also highlights the importance of modularity in design, allowing for quick replacements and modifications of key components. This flexibility proved beneficial in addressing unforeseen challenges during the development process. The lessons learned from the MER project emphasize the need for foresight in design, accommodating potential uncertainties and enabling multiple approaches to achieve mission objectives.
Overall, the document serves as a testament to the collaborative efforts of the engineering team and the successful implementation of complex mechanisms that enabled the MERs to operate effectively on Mars. The insights gained from this project contribute to the broader field of aerospace engineering and provide valuable lessons for future missions.
