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At least 253 records · Page 14

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NASA NTRS2001

A Framework for Distributed Rover Control and Three Sample Applications

In order to develop quality control software for multiple robots, a common interface is required. By developing components in a modular fashion with well-defined boundaries, roboticists can write code to program a generic rover, and only require very simple modifications to run on any robot with a properly implemented framework. The proposed framework advances a Generic Rover that could be any rover, from Real World Interface's All Terrain Robot Vehicle Jr. series to the Fido-class rovers from the Jet Propulsion Laboratory to any other research robot. Using these generic hardware interfaces, software designers and engineers can concentrate on the actual code, and not have to worry about hardware details. In addition to the hardware support framework, three sample applications have been developed to demonstrate the flexibility and extensibility of the framework.

McGuire, Steve↗

NASA NTRS2003

An Automated Approach for Acquiring Onboard Rover Science

Rover traverse distances are increasing at a faster rate than downlink capacity is increasing. As this trend continues, the quantity of data that can be returned to Earth per meter traversed is reduced. The capacity of the rover to collect data, however, remains high. This circumstance leads to an opportunity to increase mission science return by carefully selecting the data with the highest science interest for downlink. We have developed an onboard science analysis technology for increasing science return from missions. Our technology evaluates the geologic data gathered by the rover. This analysis is used to prioritize the data for transmission, so that the data with the highest science value is transmitted to Earth. In addition, the onboard analysis results are used to identify additional science gathering opportunities. A planning and scheduling component of the system enables the rover to take advantage of the identified science opportunity.

Anderson, R. C.↗

NASA NTRS2004

Preliminary Results of a New Type of Surface Property Measurement Ideal for a Future Mars Rover Mission

The success of the recent rover missions to Mars has stressed the importance of acquiring the maximum amount of geological information with the least amount of data possible. We have designed, tested and implemented special sensors mounted on a rover s wheel capable of detecting minute changes in surface topology thus eliminating the need for specially- made science platforms. These sensors, based on the previously designed, flight qualified Mars Environmental Compatibility Assessment (MECA) Electrometer, measure the static electricity (triboelectricity) generated between polymer materials and the Martian regolith during rover transverses. The sensors are capable of detecting physical changes in the soil that may not be detectable by other means, such as texture, size and moisture content. Although triboelectricity is a surface phenomenon, the weight of a rover will undoubtedly protrude the sensors below the dust covered layers, exposing underlying regolith whose properties may not be detectable through other means.

Buhler, C. R.↗

NASA NTRS2004

Deployment Process, Mechanization, and Testing for the Mars Exploration Rovers

NASA's Mar Exploration Rover (MER) robotic prospectors were produced in an environment of unusually challenging schedule, volume, and mass restrictions. The technical challenges pushed the system s design towards extensive integration of function, which resulted in complex system engineering issues. One example of the system's integrated complexity can be found in the deployment process for the rover. Part of this process, rover "standup", is outlined in this paper. Particular attention is given to the Rover Lift Mechanism's (RLM) role and its design. Analysis methods are presented and compared to test results. It is shown that because prudent design principles were followed, a robust mechanism was created that minimized the duration of integration and test, and enabled recovery without perturbing related systems when reasonably foreseeable problems did occur. Examples of avoidable, unnecessary difficulty are also presented.

Iskenderian, Ted↗

NASA NTRS2004

The Challenges of Designing the Rocker-Bogie Suspension for the Mars Exploration Rover

Over the past decade, the rocker-bogie suspension design has become a proven mobility application known for its superior vehicle stability and obstacle-climbing capability. Following several technology and research rover implementations, the system was successfully flown as part of Mars Pathfinder s Sojourner rover. When the Mars Exploration Rover (MER) Project was first proposed, the use of a rocker-bogie suspension was the obvious choice due to its extensive heritage. The challenge posed by MER was to design a lightweight rocker-bogie suspension that would permit the mobility to stow within the limited space available and deploy into a configuration that the rover could then safely use to egress from the lander and explore the Martian surface. This paper will describe how the MER rocker-bogie suspension subsystem was able to meet these conflicting design requirements while highlighting the variety of deployment and latch mechanisms employed in the design.

Harrington, Brian D.↗

NASA NTRS2005

An Overview of Wind-Driven Rovers for Planetary Exploration

The use of in-situ propulsion is considered enabling technology for long duration planetary surface missions. Most studies have focused on stored energy from chemicals extracted from the soil or the use of soil chemicals to produce photovoltaic arrays. An older form of in-situ propulsion is the use of wind power. Recent studies have shown potential for wind driven craft for exploration of Mars, Titan and Venus. The power of the wind, used for centuries to power wind mills and sailing ships, is now being applied to modern land craft. Efforts are now underway to use the wind to push exploration vehicles on other planets and moons in extended survey missions. Tumbleweed rovers are emerging as a new type of wind-driven science platform concept. Recent investigations by the National Aeronautics and Space Administration (NASA) and Jet Propulsion Laboratory (JPL) indicate that these light-weight, mostly spherical or quasi-spherical devices have potential for long distance surface exploration missions. As a power boat has unique capabilities, but relies on stored energy (fuel) to move the vessel, the Tumbleweed, like the sailing ships of the early explorers on earth, uses an unlimited resource the wind to move around the surface of Mars. This has the potential to reduce the major mass drivers of robotic rovers as well as the power generation and storage systems. Jacques Blamont of JPL and the University of Paris conceived the first documented Mars wind-blown ball in 1977, shortly after the Viking landers discovered that Mars has a thin CO2 atmosphere with relatively strong winds. In 1995, Jack Jones, et al, of JPL conceived of a large wind-blown inflated ball for Mars that could also be driven and steered by means of a motorized mass hanging beneath the rolling axis of the ball. A team at NASA Langley Research Center started a biomimetic Tumbleweed design study in 1998. Wind tunnel and CFD analysis were applied to a variety of concepts to optimize the aerodynamic characteristics of the Tumbleweed Rovers. Bare structures, structures carrying sails and a tumbleweed plant (of the Salsola genus) were tested in Langley's wind tunnels. Thomas Estier of the Swiss Federal Institute of Technology developed a memory metal collapsible structure, the Windball. Numerous other researchers have also suggested spherical rovers.

Hajos, Gregory A.↗

NASA NTRS2005

Exploration Rover Concepts and Development Challenges

This paper presents an overview of exploration rover concepts and the various development challenges associated with each as they are applied to exploration objectives and requirements for missions on the Moon and Mars. A variety of concepts for surface exploration vehicles have been proposed since the initial development of the Apollo-era lunar rover. This paper provides a brief description of the rover concepts, along with a comparison of their relative benefits and limitations. In addition, this paper outlines, and investigates a number of critical development challenges that surface exploration vehicles must address in order to successfully meet the exploration mission vision. These include: mission and environmental challenges, design challenges, and production and delivery challenges. Mission and environmental challenges include effects of terrain, extreme temperature differentials, dust issues, and radiation protection. Design methods are discussed that focus on optimum methods for developing highly reliable, long-life and efficient systems. In addition, challenges associated with delivering a surface exploration system is explored and discussed. Based on all the information presented, modularity will be the single most important factor in the development of a truly viable surface mobility vehicle. To meet mission, reliability, and affordability requirements, surface exploration vehicles, especially pressurized rovers, will need to be modularly designed and deployed across all projected Moon and Mars exploration missions.

Zakrajsek, James J.↗

NASA NTRS2005

The Mars Exploration Rover Cameras: A Status Report

With more than 68,000 images returned from the surface of Mars to date, the Mars Exploration Rover (MER) camera suite continues to perform extremely well. Image signal to noise ratios (SNRs) are greater than 200:1, flat fields remain stable, and single-pixel degradation has been negligible. Acting as the eyes of the robotic field geologists, the 18 MER cameras continue to play a leading role in major scientific findings at both Gusez Crater and Meridiana Planum. All 4 types of cameras, the hazard avoidance (Hazcam), navigation (Navcam), the color panoramic (Pancam) and the microscopic imager (MI), continue to return data from the Martian surface from both Rovers. In addition to the rover cameras, each lander utilized a descent imager (DI) to help facilitate safe landing and provide landing site context. The Pancam and MI are part of the scientific instrument payload of the rovers. In addition to gathering gathering science image data, the Pacams also support sun finding and measure atmospheric dust optical depth. The Hazcam and Navcam stereo pairs are used for traverse planning, autonomous navigation and general imaging.

Schwochert, M. A.↗

NASA NTRS2005

Coordinating Multi-Rover Systems: Evaluation Functions for Dynamic and Noisy Environments

This paper addresses the evolution of control strategies for a collective: a set of entities that collectively strives to maximize a global evaluation function that rates the performance of the full system. Directly addressing such problems by having a population of collectives and applying the evolutionary algorithm to that population is appealing, but the search space is prohibitively large in most cases. Instead, we focus on evolving control policies for each member of the collective. The fundamental issue in this approach is how to create an evaluation function for each member of the collective that is both aligned with the global evaluation function and is sensitive to the fitness changes of the member, while relatively insensitive to the fitness changes of other members. We show how to construct evaluation functions in dynamic, noisy and communication-limited collective environments. On a rover coordination problem, a control policy evolved using aligned and member-sensitive evaluations outperfoms global evaluation methods by up to 400%. More notably, in the presence of a larger number of rovers or rovers with noisy and communication limited sensors, the proposed method outperforms global evaluation by a higher percentage than in noise-free conditions with a small number of rovers.

Turner, Kagan↗

NASA NTRS2005

Cerebellum Augmented Rover Development

Bio-Inspired Technologies and Systems (BITS) are a very natural result of thinking about Nature's way of solving problems. Knowledge of animal behaviors an be used in developing robotic behaviors intended for planetary exploration. This is the expertise of the JFL BITS Group and has served as a philosophical model for NMSU RioRobolab. Navigation is a vital function for any autonomous system. Systems must have the ability to determine a safe path between their current location and some target location. The MER mission, as well as other JPL rover missions, uses a method known as dead-reckoning to determine position information. Dead-reckoning uses wheel encoders to sense the wheel's rotation. In a sandy environment such as Mars, this method is highly inaccurate because the wheels will slip in the sand. Improving positioning error will allow the speed of an autonomous navigating rover to be greatly increased. Therefore, local navigation based upon landmark tracking is desirable in planetary exploration. The BITS Group is developing navigation technology based upon landmark tracking. Integration of the current rover architecture with a cerebellar neural network tracking algorithm will demonstrate that this approach to navigation is feasible and should be implemented in future rover and spacecraft missions.

King, Matthew↗

NASA NTRS2004

Planning for rover opportunistic science

The Mars Exploration Rover Spirit recently set a record for the furthest distance traveled in a single sol on Mars. Future planetary exploration missions are expected to use even longer drives to position rovers in areas of high scientific interest. This increase provides the potential for a large rise in the number of new science collection opportunities as the rover traverses the Martian surface. In this paper, we describe the OASIS system, which provides autonomous capabilities for dynamically identifying and pursuing these science opportunities during longrange traverses. OASIS uses machine learning and planning and scheduling techniques to address this goal. Machine learning techniques are applied to analyze data as it is collected and quickly determine new science gods and priorities on these goals. Planning and scheduling techniques are used to alter the behavior of the rover so that new science measurements can be performed while still obeying resource and other mission constraints. We will introduce OASIS and describe how planning and scheduling algorithms support opportunistic science.

artificial intelligence↗

NASA NTRS2005

Attitude and position estimation on the Mars Exploration Rovers

NASA/JPL 's Mars Exploration Rovers acquire their attitude upon command and autonomously propagate their attitude and position. The rovers use accelerometers and images of the sun to acquire attitude, autonomously searching the sky for the sun with a pointable camera. To propagate the attitude and position the rovers use either accelerometer and gyro readings or gyro readings and wheel odometiy, depending on the nature of the movement ground operators are commanding. Where necessary, visual odometry is performed on images to fine tune the position updates, particularly in high slip environments. The capability also exists for visual odometry attitude updates. This paper describes the techniques used by the rovers to acquire and maintain attitude and position knowledge, the accuracy which is obtainable, and lessons learned after more than one year in operation.

attitude estimation↗

NASA NTRS2007

Mars Exploration Rover Pancam Multispectral Imaging of Rocks, Soils, and Dust at Gusev Crater and Meridiani Planum

Multispectral imaging from the Panoramic Camera (Pancam) instruments on the Mars Exploration Rovers Spirit and Opportunity has provided important new insights about the geology and geologic history of the rover landing sites and traverse locations in Gusev crater and Meridiani Planum. Pancam observations from near-UV to near-IR wavelengths provide limited compositional and mineralogic constraints on the presence abundance, and physical properties of ferric- and ferrous-iron bearing minerals in rocks, soils, and dust at both sites. High resolution and stereo morphologic observations have also helped to infer some aspects of the composition of these materials at both sites. Perhaps most importantly, Pancam observations were often efficiently and effectively used to discover and select the relatively small number of places where in situ measurements were performed by the rover instruments, thus supporting and enabling the much more quantitative mineralogic discoveries made using elemental chemistry and mineralogy data. This chapter summarizes the major compositionally- and mineralogically-relevant results at Gusev and Meridiani derived from Pancam observations. Classes of materials encountered in Gusev crater include outcrop rocks, float rocks, cobbles, clasts, soils, dust, rock grindings, rock coatings, windblown drift deposits, and exhumed whitish/yellowish salty soils. Materials studied in Meridiani Planum include sedimentary outcrop rocks, rock rinds, fracture fills, hematite spherules, cobbles, rock fragments, meteorites, soils, and windblown drift deposits. This chapter also previews the results of a number of coordinated observations between Pancam and other rover-based and Mars-orbital instruments that were designed to provide complementary new information and constraints on the mineralogy and physical properties of martian surface materials.

Bell, J. F., III↗

NASA NTRS2006

A Strategy to Integrate Probabilistic Risk Assessment into Design and Development Processes for Aerospace Based pon Mars Exploration Rover Experiences

This paper will discuss the Probabilistic Risk Assessment (PRA) effort and its involvement with related activities during the development of the Mars Exploration Rover (MER). The Rovers were launched 2003.June.10 (Spirit) and 2003.July.7 (Opportunity), and both have proven very successful. Although designed for a 90-day mission, the Rovers have been operating for over two earth years. This paper will review aspects of how the MER project integrated PRA into the design and development process. A companion paper (Development of the Mars Exploration Rover PRA) will describe the MER PRA and design changes from those results.

Probabilistic Risk Assessment (PRA)↗

NASA NTRS2005

High Gain Antenna Pointing on the Mars Exploration Rovers

This paper describes the algorithm used to point the high gain antennae on NASA/JPL's Mars exploration rovers. Each rover's gimballed antenna must track the Earth as it moves across the Martian sky during communication sessions. The pointing algorithm accounts for obstacles to the line-of-sight posed by (1) features on the rover and in the surrounding environment (2) gimbal range limitations, and (3) kinematic singularities in the gimbal mechanism. The algorithm treats all obstacles with a generalized approach that computes the intercept-times to each obstacle. Where possible, the algorithm takes advantage of pairs of joint-space solutions arising from the mechanism design. The algorithm chooses the solution that provides the longest obstruction-free tracking time. Upon encountering an obstacle, the algorithm automatically switches to the other solution if it is not also obstructed. This algorithm has successfully provided obstruction-free pointing for both rovers throughout the mission.

inverse kinematics↗

NASA NTRS2008

Mars Science Laboratory Rover Mobility Bushing Development

NASA s Mars Science Laboratory (MSL) Project will send a six-wheeled rover to Mars in 2009. The rover will carry a scientific payload designed to search for organic molecules on the Martian surface during its primary mission. This paper describes the development and testing of a bonded film lubricated bushing system to be used in the mobility system of the rover. The MSL Rover Mobility System contains several pivots that are tightly constrained with respect to mass and volume. These pivots are also exposed to relatively low temperatures (-135 C) during operation. The combination of these constraints led the mobility team to consider the use of solid film lubricated metallic bushings and dry running polymeric bushings in several flight pivot applications. A test program was developed to mitigate the risk associated with using these materials in critical pivots on the MSL vehicle. The program was designed to characterize bushing friction and wear performance over the expected operational temperature range (-135 C to +70 C). Seven different bushing material / lubricant combinations were evaluated to aid in the selection of the final flight pivot bushing material / lubricant combination.

Riggs, Benjamin↗

NASA NTRS2006

Lunar Surface Scenarios: Habitation and Life Support Systems for a Pressurized Rover

Pressurized rovers will be a critical component of successful lunar exploration to enable safe investigation of sites distant from the outpost location. A pressurized rover is a complex system with the same functions as any other crewed vehicle. Designs for a pressurized rover need to take into account significant constraints, a multitude of tasks to be performed inside and out, and the complexity of life support systems to support the crew. In future studies, pressurized rovers should be given the same level of consideration as any other vehicle occupied by the crew.

Anderson, Molly↗

NASA NTRS2008

Visual Target Tracking on the Mars Exploration Rovers

Visual target tracking (VTT) software has been incorporated into Release 9.2 of the Mars Exploration Rover (MER) flight software, now running aboard the rovers Spirit and Opportunity. In the VTT operation (see figure), the rover is driven in short steps between stops and, at each stop, still images are acquired by actively aimed navigation cameras (navcams) on a mast on the rover (see artistic rendition). The VTT software processes the digitized navcam images so as to track a target reliably and to make it possible to approach the target accurately to within a few centimeters over a 10-m traverse.

Kim, Won↗