1,489 research outputs found
A manipulator arm for zero-g simulations
A 12-ft counterbalanced Slave Manipulator Arm (SMA) was designed and fabricated to be used for resolving the questions of operational applications, capabilities, and limitations for such remote manned systems as the Payload Deployment and Retrieval Mechanism (PDRM) for the shuttle, the Free-Flying Teleoperator System, the Advanced Space Tug, and Planetary Rovers. As a developmental tool for the shuttle manipulator system (or PDRM), the SMA represents an approximate one-quarter scale working model for simulating and demonstrating payload handling, docking assistance, and satellite servicing. For the Free-Flying Teleoperator System and the Advanced Tug, the SMA provides a near full-scale developmental tool for satellite servicing, docking, and deployment/retrieval procedures, techniques, and support equipment requirements. For the Planetary Rovers, it provides an oversize developmental tool for sample handling and soil mechanics investigations. The design of the SMA was based on concepts developed for a 40-ft NASA technology arm to be used for zero-g shuttle manipulator simulations
A survey of planning and scheduling research at the NASA Ames Research Center
NASA Ames Research Center has a diverse program in planning and scheduling. This paper highlights some of our research projects as well as some of our applications. Topics addressed include machine learning techniques, action representations and constraint-based scheduling systems. The applications discussed are planetary rovers, Hubble Space Telescope scheduling, and Pioneer Venus orbit scheduling
Potential field based navigation for planetary rovers using internal states
The work in this paper aims to introduce analysis and applications for the internal state model which is a new model for a swarm of rovers interacting via pair-wise attractive and repulsive potentials. The internal state model updates the state of the art in overcoming the local minima problem through solving the problem with comparatively lower computation cost than other methods. The simulations results show that using the internal state model, a swarm of planetary rovers, rather than moving in a static potential field, are able to manipulate the potential according to their estimation of whether they are moving towards or away from the goal, which allows them to escape from and maneuver around a local minimum in the potential field to reach a goal. An application of a swarm of rovers to solve the problem for different shaped obstacles is introduced to show the efficiency of the model. The model proves stable convergence to a goal and provides similarities with the behaviour of real groups of animals
Development Environment for Optimized Locomotion System of Planetary Rovers
This paper addresses the first steps that have been undergone to set up the development environement w.r.t optimization and to modelling and simulation of overall dynamics of the rover driving behaviour under all critical surface terrains, like soft and hard soils, slippage, bulldozing effect and digging in soft soil. Optimization is based on MOPS (Multi-Objective Prameter Synthesis), that is capable for handling several objective functions such as mass reduction, motor power reduction, increase of traction forces, rover stability guarantee, and more. The tool interferes with Matlab/Simulink and with Modelica/Dymola for dynamics model implementation. For modelling and simulation of the overall rover dynamics and terramechanical behaviour in all kind of soils we apply a Matlab based tool that takes advantage of the multibody dynamics tool Simpack. First results of very promising rover optimizations 6 wheels are presented that improve ExoMars rover type wheel suspension systems. Performance of driveability behaviour in different soils is presented as well. The next steps are discusses in order to achieve the planned overall development environment
Efficient Autonomous Navigation for Planetary Rovers with Limited Resources
Rovers operating on Mars are in need of more and more autonomous features to ful ll their
challenging mission requirements. However, the inherent constraints of space systems make
the implementation of complex algorithms an expensive and difficult task. In this paper
we propose a control architecture for autonomous navigation. Efficient implementations of
autonomous features are built on top of the current ExoMars navigation method, enhancing
the safety and traversing capabilities of the rover. These features allow the rover to detect
and avoid hazards and perform long traverses by following a roughly safe path planned by
operators on ground. The control architecture implementing the proposed navigation mode
has been tested during a field test campaign on a planetary analogue terrain. The experiments
evaluated the proposed approach, autonomously completing two long traverses while
avoiding hazards. The approach only relies on the optical Localization Cameras stereobench,
a sensor that is found in all rovers launched so far, and potentially allows for computationally
inexpensive long-range autonomous navigation in terrains of medium difficulty
Planetary rovers and data fusion
This research will investigate the problem of position estimation for planetary rovers.
Diverse algorithmic filters are available for collecting input data and transforming
that data to useful information for the purpose of position estimation process. The
terrain has sandy soil which might cause slipping of the robot, and small stones and
pebbles which can affect trajectory.
The Kalman Filter, a state estimation algorithm was used for fusing the sensor data
to improve the position measurement of the rover. For the rover application the
locomotion and errors accumulated by the rover is compensated by the Kalman
Filter. The movement of a rover in a rough terrain is challenging especially with
limited sensors to tackle the problem. Thus, an initiative was taken to test drive
the rover during the field trial and expose the mobile platform to hard ground and
soft ground(sand). It was found that the LSV system produced speckle image and
values which proved invaluable for further research and for the implementation of
data fusion.
During the field trial,It was also discovered that in a at hard surface the problem
of the steering rover is minimal. However, when the rover was under the influence
of soft sand the rover tended to drift away and struggled to navigate.
This research introduced the laser speckle velocimetry as an alternative for odometric
measurement. LSV data was gathered during the field trial to further simulate under
MATLAB, which is a computational/mathematical programming software used for
the simulation of the rover trajectory. The wheel encoders came with associated
errors during the position measurement process. This was observed during the
earlier field trials too. It was also discovered that the Laser Speckle Velocimetry
measurement was able to measure accurately the position measurement but at the
same time sensitivity of the optics produced noise which needed to be addressed as
error problem.
Though the rough terrain is found in Mars, this paper is applicable to a terrestrial
robot on Earth. There are regions in Earth which have rough terrains and regions
which are hard to measure with encoders. This is especially true concerning icy
places like Antarctica, Greenland and others.
The proposed implementation for the development of the locomotion system is to
model a system for the position estimation through the use of simulation and collecting data using the LSV. Two simulations are performed, one is the differential
drive of a two wheel robot and the second involves the fusion of the differential drive
robot data and the LSV data collected from the rover testbed. The results have
been positive. The expected contributions from the research work includes a design
of a LSV system to aid the locomotion measurement system.
Simulation results show the effect of different sensors and velocity of the robot. The
kalman filter improves the position estimation process
Machine vision for space telerobotics and planetary rovers
Machine vision allows a non-contact means of determining the three-dimensional shape of objects in the environment, enabling the control of contact forces when manipulation by a telerobot or traversal by a vehicle is desired. Telerobotic manipulation in Earth orbit requires a system that can recognize known objects in spite of harsh lighting conditions and highly specular or absorptive surfaces. Planetary surface traversal requires a system that can recognize the surface shape and properties of an unknown and arbitrary terrain. Research on these two rather disparate types of vision systems is described
Design and evaluation of a toroidal wheel for planetary rovers
The inverted toroidal wheel concept was perceived, mathematically quantified, and experimentally verified. The wheel design has a number of important characteristics, namely; (1) the low footprint pressures required for Mars exploration (0.5 to 1.0 psi); (2) high vehicle weight to wheel weight ratios capable of exceeding 10:1; (3) extremely long cyclic endurances tending towards infinite life; and (4) simplicity of design. The concept, in combination with appropriate materials such as titanium or composites, provides a planetary roving vehicle with a very high degree of exploratory mobility, a substantial savings in weight and a high assurity of mission success. Design equations and computation procedures necessary to formulate an inverted wheel are described in detail
Automated construction of lightweight, simple, field-erected structures
The feasibility of automation of construction processes which could result in mobile construction robots is examined. The construction of a large photovoltaic power plant with a peak power output of 100 MW is demonstrated. The reasons to automate the construction process, a conventional construction scenario as the reference for evaluation, and a list of potential cost benefits using robots are presented. The technical feasibility of using robots to construct SPS ground stations is addressed
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