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In recent decades, the exploration of celestial bodies has moved to surface-based landers and rovers designed to perform experiments on the ground. The presented research focuses on legged ...

Recent exploration missions to celestial bodies have shown an increasing demand for surface based landers and rovers designed to perform experiments on the ground, rather than relying purely on traditional orbiting observatories. Many of the scientifically interesting locations have proven hazardous and difficult to reach and traverse, driving the need for different methods of locomotion. Some of these locations lie in deep, permanently shadowed craters or in rocky, highly uneven landscapes. Various wheeled, flying, jumping, and legged rovers have been proposed. Those chosen for development have experienced both success and problems alike. Even stationary landers, such as the Philae lander which attempted to perform a controlled landing onto a comet surface, encountered unforgiving terrain causing it to bounce multiple times due to the ineffectiveness of its two on-board anchoring mechanisms. A new generation of legged rovers and landers is envisioned to utilize dynamic anchors on the feet of its legs to claw into the surface, engaging and disengaging with each step or landing. A method for simulating and evaluating the performance of these dynamic anchors is proposed to aid in-progress surface missions with relatively quick response to new target data. Discrete Element Method software is used to simulate a lunar-like regolith medium and the interaction of a dynamic anchor with this medium. The engagement, holding, and disengagement forces are recorded during this simulation. Physical testing was performed by using a robotic arm to engage a series of anchors with a lunar regolith simulant while measuring the same three forces as the simulation. The actual test data efficient anchor geometry as determined during testing is compared to predicted data to evaluate the simulation accuracy. Calibration testing to determine suitable simulation parameters is also presented. Results show the applicable forces can be predicted well within an order of magnitude, but improvements are possible to predict soil behavior more accurately.

In situ Resource Utilization (ISRU) facilitates planetary exploration by drawing needed resources, such as water, from the local environment. However, the extreme nature of these environments require the development of advanced unmanned space systems integrated with sample-capture devices to achieve the ultimate goal of prospecting these resources. This paper presents the design, development and Hardware-in-the-Loop (HIL) simulation testing of guidance and tracking control laws for an autonomous small marsupial free-flyer prospector system. The control laws are based on an extended non-linear dynamic inversion (NLDI) approach and its implementation is illustrated through HIL simulation using a mathematical model of an autonomous vehicle research platform developed by NASA Kennedy Space Center. This vehicle has been designed to support the development, testing and validation of algorithms for safe, reliable, and scalable control space missions with minimal need for human intervention in complex, unstructured environments. The main objective of the control laws is to minimize 3-axis distances with respect to a desired trajectory and maintain stability and adequate performance in the presence of uncertainties. The performance of the control laws is evaluated during autonomous flight in terms of trajectory tracking errors, real-time execution on board the flight computer, and control activity at nominal and dynamically-changing conditions. The results show that for all mission cases investigated the control laws approach has desirable capabilities and is reliable for in-flight testing operation as a next step towards the validation and verification of this configuration.

This paper investigates vision-aided navigation strategies for an autonomous free-flying robotic vehicle designed to explore interplanetary bodies, such as moons or asteroids, for the purposes of In Situ Resource Utilization (ISRU). ISRU has the potential to facilitate planetary exploration by drawing needed resources, such as water, from the local environment. The realization of ISRU requires the development of advanced unmanned space systems integrated with sample-capture devices and guidance, navigation, and control systems capable of supporting autonomous exploration of challenging environments such as craters and lava tubes. Navigation on interplanetary bodies is challenging due to the unavailability of traditional navigation sesnors such as GPS and magnetometers. This paper focuses on the use of one or more vision sensors to augment an onboard inertial measurement unit, which is composed of accelerometers and rate gyros, in order to provide vision-aided navigation solutions for the free-flyer robotic system. In this study, a vision-aided navigation strategy is considered that entails using object detection and tracking algorithms to identify known landmarks in the scene, which provides information that can be used to estimate the position of the vehicle within the environment. Vision-aided navigation filters are developed for a stereo implementation of landmark detection and tracking, and the algorithms are implemented on video obtained from flights of a quadrotor UAV at the Hazard Field at the NASA Kennedy Space Center.