Biologically Inspired Autonomous Rover Control

Robotic missions beyond 2013 will likely be precursors to a manned habitat deployment on Mars. Such missions require robust control systems for long duration activities. Current single rover missions will evolve into deployment of multiple, heterogeneous cooperating robotic colonies. This paper describes the map-making memory and action selection mechanism of BISMARC ( iologically nspired ystem for ap-based utonomous over ontrol) that is currently under development at the Jet Propulsion Laboratory in Pasadena, CA (Huntsberger and Rose, Neutral Networks, 11(7/8):1497–1510). BISMARC is an integrated control system for long duration missions involving robots performing cooperative tasks.     

Color edge detection

The detection of visually significant edges and boundaries in a natural color image is complicated by inherent noise and correlation between color coordinates. In this letter we present a color edge detector which uses fuzzy set theory to model this imprecision.     

Improved Rover State Estimation in Challenging Terrain

Given ambitious mission objectives and long delay times between command-uplink/data-downlink sessions, increased autonomy is required for planetary rovers. Specifically, NASA's planned 2003 and 2005 Mars rover missions must incorporate increased autonomy if their desired mission goals are to be realized. Increased autonomy, including autonomous path planning and navigation to user designated goals, relies on good quality estimates of the rover's state, e.g., its position and orientation relative to some initial reference frame. The challenging terrain over which the rover will necessarily traverse tends to seriously degrade a dead-reckoned state estimate, given severe wheel slip and/or interaction with obstacles. In this paper, we present the implementation of a complete rover navigation system. First, the system is able to adaptively construct semi-sparse terrain maps based on the current ground texture and distances to possible nearby obstacles. Second, the rover is able to match successively constructed terrain maps to obtain a vision-based state estimate which can then be fused with wheel odometry to obtain a much improved state estimate. Finally the rover makes use of this state estimate to perform autonomous real-time path planning and navigation to user designated goals. Reactive obstacle avoidance is also implemented for roaming in an environment in the absence of a user designated goal. The system is demonstrated in soft soil and relatively dense rock fields, achieving state estimates that are significantly improved with respect to dead reckoning alone (e.g., 0.38 m mean absolute error vs. 1.34 m), and successfully navigating in multiple trials to user designated goals.     

Dynamic optimization of N‐joint robotic limb deployments

We describe an approach using a stochastic optimization framework (SOF) for operating complex mobile systems with several degrees of freedom (DOFs), such as robotic limbs with N joints, in environments that can contain obstacles. As part of the SOF, we have employed an efficient simulated annealing algorithm normally used in computationally highly expensive optimization and search problems such as the traveling salesman problem and protein design. This algorithm is particularly suited to run onboard industrial robots, robots in telemedicine, remote spacecraft, planetary landers, and rovers, i.e., robotic platforms with limited computational capabilities. The robotic limb deployment optimization approach presented here offers an alternative to time‐intensive robotic arm deployment path planning algorithms in general and in particular for robotic limb systems in which closed‐form solutions do not exist. Application examples for a (N = 4)‐DOF arm on a planetary exploration rover are presented. © 2009 Wiley Periodicals, Inc.     

An Architecture for Distributed Environment Sensing with Application to Robotic Cliff Exploration

Future planetary exploration missions will use cooperative robots to explore and sample rough terrain. To succeed robots will need to cooperatively acquire and share data. Here a cooperative multi-agent sensing architecture is presented and applied to the mapping of a cliff surface. This algorithm efficiently repositions the systems' sensing agents using an information theoretic approach and fuses sensory information using physical models to yield a geometrically consistent environment map. This map is then distributed among the agents using an information based relevant data reduction scheme. Experimental results for cliff face mapping using the JPL Sample Return Rover (SRR) are presented. The method is shown to significantly improve mapping efficiency over conventional methods.     

Planetary Rover Developments Supporting Mars Exploration, Sample Return and Future Human-Robotic Colonization

We overview our recent research on planetary mobility. Products of this effort include the Field Integrated Design & Operations rover (FIDO), Sample Return Rover (SRR), reconfigurable rover units that function as an All Terrain Explorer (ATE), and a multi-Robot Work Crew of closely cooperating rovers (RWC). FIDO rover is an advanced technology prototype; its design and field testing support NASA's development of long range, in situ Mars surface science missions. Complementing this, SRR implements autonomous visual recognition, navigation, rendezvous, and manipulation functions enabling small object pick-up, handling, and precision terminal docking to a Mars ascent vehicle for future Mars Sample Return. ATE implements on-board reconfiguration of rover geometry and control for adaptive response to adverse and changing terrain, e.g., traversal of steep, sandy slopes. RWC implements coordinated control of two rovers under closed loop kinematics and force constraints, e.g., transport of large payloads, as would occur in robotic colonies at future Mars outposts. RWC is based in a new extensible architecture for decentralized control of, and collective state estimation by multiple heterogeneous robotic platforms—CAMPOUT; we overview the key architectural features. We have conducted experiments with all these new rover system concepts over variable natural terrain. For each of the above developments, we summarize our approach, some of our key experimental results to date, and our future directions of planned development.     

Local enhancement of compressed images

We develop a simple focusing technique for wavelet decompositions. This allows us to single out interesting parts of an image and obtain variable compression rates over the image. We also study similar techniques for image enhancement.Partially supported by U.S. Air Force Office of Scientific Research grant 89-0455 and Defense Advanced Research Projects Agency grant AFOSR 89-0455.     

Characterization of mechanical properties of thermoplastic films by creep measurements

Plasticized poly(methyl methacrylate) and methyl methacrylate/acrylate copolymer films were examined by isothermal creep at low loads measured at several temperatures from ～T_g to T_g + 15°C. Viscosity calculated using η = σ/3\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document} was plotted vs temperature giving precise values for T_g based on a viscosity criterion of η = 10¹³ poises. Creep fracture data at various temperatures below T_g were interpreted using the maximum apparent viscosity measured at the minima of strain rate vs strain curves. Plots of η_max VS stress at several temperatures gave values of ΔT_g/Δσ of ?1° to 2°C/10⁶ N/m² in agreement with treatment of ΔT_g/Δσ based on free volume. Fracture occurred at low elongations when η_max was ≥10¹³ poises, and at higher elongations when η_max was <10¹³ poises supporting the concept that fracture is related to the lowering of T_g under stress. Plots of log σ VS log ε_b (the elongation at fracture) had the same form as that for crosslinked elastomers above T_g reported by T. L. Smith. Plots of log \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}_b VS log ε_b also had the same form supporting proposals on the rate sensitivity of fracture.     

Technique for using microencapsulated terpenes in lepidopteran artificial diets

We have developed and tested a technique to microencapsulate terpene compounds by forming gelatin-walled microcapsules around the terpene essential oils. Eight terpenes that are common constituents of Douglas fir (Pseudotsuga menziesii) oleoresin were encapsulated, including five monoterpenes (-pinene,-pinene, camphene, myrcene, and limonene) and three oxygenated monoterpenes (bornyl acetate, linalool, and-citronellol). The encapsulated terpenes were mixed into artificial diets to determine the effects they had on western spruce budworm (Choristoneura occidentalis) survival and reproduction, using a three-generation bioassay. We describe the technique and present data from preliminary bioassays with seven of the terpenes to demonstrate thatC. occidentalis larvae would consume diets fortified with microencapsulated terpenes. The technique is useful because it helps to reduce the rate at which terpenes volatilize from the diets and it packages the terpenes in a manner more closely resembling the way they are present in the resin canals of plant foliage. Many scientists investigating the biological importance of terpenes in mediating plant-herbivore interactions may find that microencapsulated terpenes are useful in both laboratory diet studies and field and greenhouse experiments with plant material.