Impacts of hydrologic soil properties on drought detection with MODIS thermal data

Remote sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS), a climatic water budget model, and the STATSGO database were used within a GIS environment to determine the influences of hydrologic soil properties on soil moisture and thermal emission in western-central Kansas for a dry year, 2000. Two important variables, water-holding capacity (WHC) and hydrologic soil group (HSG), were controlled in our water budget experiment to evaluate their impacts on soil moisture content (SMC) changes throughout the period. Results showed that HSG affected drought detection and occurrence very little, but WHC variations explained most local variations of soil moisture content. As a strong indicator of relative soil moisture deficit, the Standardized Thermal Index (STI) patterns were also influenced by WHC. Generally, the earlier the soil moisture content drops below 40%, the earlier the STI reaches a threshold value of 0.2 or higher. Vegetation responses to thermal detection lagged behind the STI by up to 8 weeks, which was computed by comparing the STI and Normalized Difference Vegetation Index (NDVI) deviation from a 10-year mean. The spatial pattern of lag-times was not apparent, but lag-times were correlated with a WHC component.     

Designing Stable Finite State Machine Behaviors Using Phase Plane Analysis and Variable Structure Control

This paper discusses how phase plane analysis can be used to describe the overall behavior of single and multiple autonomous robotic vehicles with finite state machine rules. The importance of this result is that we can begin to design provably stable group behaviors from a set of simple control laws and appropriate switching points with decentralized variable structure control. The ability to prove stable group behavior is especially important for applications such as locating military targets or land mines. In this paper, we demonstrate how phase plane analysis has been used to explain the behavior of a 16 cm³ autonomous line-tracking robot with four finite states. After which, the analysis is extended to include the design of a decentralized variable structure controller that guides multiple vehicles to a goal while avoiding each other.     

Model-based visual feedback control for a hand-eye coordinatedrobotic system

The integration of a single camera into a robotic system to control the relative position and orientation between the robot's end-effector and a moving part in real time is discussed. Only monocular vision techniques are considered because of current limitations in the speed of computer vision analysis. The approach uses geometric models of both the part and the camera, as well as the extracted image features, to generate the appropriate robot control signals for tracking. Part and camera models are also used during the teaching stage to predict important image features that appear during task completion     

Static grip selection for robot-based automated assembly systems

In this article we present an algorithmic approach to determine the suitable grasp of an object in an automated assembly environment. The algorithm is based on the available object surfaces and the initial and final task constraints and gripper characteristics. If the imposed task and gripper constraints do not allow a possible grasp, intermediate motions may need to be made to reorient the part. Once a set of possible grasps which statisfy task and gripper constraints are found, the stability of each grasp is analyzed using screw theory. An optimal grasp is one which minimizes the grasping forces over the possible set of grasps. Results utilizing our methodology are presented. Our method can be interfaced with CAD database such as a solid modelling system based on boundary representation for automatic selection of grasping configurations.     

Vision-based intelligent control for automated assembly

Development of an automated assembly system requires integration of different engineering modules and coordination of interactions between these modules. This paper presents some of the results of an effort in developing an assembly automation schene for an automated work cell. Integration of the control scheme with the vision module and an on-line trajectory planner is presented. Special characteristics of this automation scheme are dynamic integration of vision and feedback control, real-time operation, uncertainty compensation and error recovery. The hardware required for implementation of this scheme is described. Results of implementing this scheme on a PUMA robot performing a carburetor and gasket mating operation are presented.     

Design and evaluation of a decision support system in a water balance application

Visualization has become a vital tool for representing the results of scientific models in decision support applications. Both the raw data and the models from which these visualizations are derived usually have considerable uncertainty associated with them. Decision-makers are typically presented with results from these models with little or no insight as to the reliability of the information shown. For effective decisions to be made, a decision support system should allow collaborative participation from scientists and decision-makers, and it should display the locations, magnitudes, and sources of uncertainty in the results. This research work discusses a software application for visualizing the results of a water balance model and its associated uncertainty. The effectiveness of the application and its visual presentation methods were incrementally tested and improved through usability engineering principles.     

Visual servoing and CAD-driven microassembly

The authors describe current research and development on a robotic visual servoing system for assembly of LIGA (lithography galvonoforming abforming) parts. The workcell consists of an AMTI robot, precision stage, long working distance microscope, and LIGA fabricated tweezers for picking up the parts. Fourier optics methods are used to generate synthetic microscope images from CAD drawings. These synthetic images are used off-line to test image processing routines under varying magnifications and depths of field. They also provide reference image features which are used to visually servo the part to the desired position. Currently, we can visually servo a 100 micron outside diameter LIGA gear to a desired x,y reference position as determined from a synthetic image of the gear     

Interannual variations of the grassland boundaries bordering the eastern edges of the Gobi Desert in central Asia

The Mongolian Steppe that borders the northern and eastern edges of the Gobi Desert in central Asia is one of the world's largest grasslands, extending across the nation of Mongolia and the Inner Mongolian Autonomous Region (IMAR) of China. Recent findings show that this region has one of the strongest warming signals on Earth since the late 1970s. The objective of this study was to evaluate the relationships between climate and interannual variation of the grassland boundaries in Mongolia and IMAR between 1982 and 1990. The remote sensing data used in this study were the 15–day maximum Normalized Difference Vegetation Index (NDVI) composites derived from the Global Area Coverage of the Advanced Very High Resolution Radiometer (AVHRR). Monthly precipitation, mean monthly temperature, and monthly actual evapotranspiration (AE) were derived from meteorological station records acquired during the study period across the eastern Mongolian Steppe. The occurrence of onset of green–up, as determined with time-series NDVI data, was used to identify vegetated and non-vegetated areas. Great interannual variation of the Gobi boundary position was observed over the study period. This boundary variation was largely controlled by the climate before the growing season (the ‘preseason’ climate). Along the eastern edge of the Gobi desert in central IMAR, preseason AE was the major climatic factor affecting the annual shift of the Gobi boundary, while further north in Mongolia, preseason temperature was the driving climatic factor. Our findings suggest that the response of vegetation communities to climate changes varied as a function of land-use intensity within the ecosystem.     

Decentralized Fuzzy Control of Multiple Nonholonomic Vehicles

This work considers the problem of controlling multiple nonholonomic vehicles so that they converge to a scent source without colliding with each other. Since the control is to be implemented on a simple 8-bit microcontroller, fuzzy control rules are used to simplify a linear quadratic regulator control design. The inputs to the fuzzy controllers for each vehicle are the noisy direction to the source, the distance to the closest neighbor vehicle, and the direction to the closest vehicle. These directions are discretized into four values: forward, behind, left, and right; and the distance into three values: near, far, and gone. The values of the control at these discrete values are obtained based on the collision-avoidance repulsive forces and an attractive force towards the goal. A fuzzy inference system is used to obtain control values from a small number of discrete input values. Simulation results are provided which demonstrate that the fuzzy control law performs well compared to the exact controller. In fact, the fuzzy controller demonstrates improved robustness to noise.