We address the automatic detection of Ambush weapons such as rocket propelled grenades (RPGs) from range data which might be derived from multiple camera stereo with textured illumination or by other means. We describe our initial work in a new project involving the efficient acquisition of 3D scene data as well as discrete point invariant techniques to perform real time search for threats to a convoy. The shapes of the jump boundaries in the scene are exploited in this paper, rather than on-surface points, due to the large error typical of depth measurement at long range and the relatively high resolution obtainable in the transverse direction. We describe examples of the generation of a novel range-scaled chain code for detecting and matching jump boundaries.

SUMO, or Spacecraft for the Universal Modification of Orbits, is a risk reduction program for an advanced servicing spacecraft sponsored by the Defense Advanced Research Projects Agency and executed by the Naval Center for Space Technology at the Naval Research Laboratory in Washington, DC. The purpose of the program is to demonstrate the integration of machine vision, robotics, mechanisms, and autonomous control algorithms to accomplish autonomous rendezvous and grapple of a variety of interfaces traceable to future spacecraft servicing operations. The laboratory demonstration is being implemented in NRL's Proximity Operations Test Facility, which provides precise six degree of freedom motion control for both the servicer and customer spacecraft platforms. This paper will describe the conceptual design of the SUMO advanced servicing spacecraft, a concept for a near term low-cost flight demonstration, as well as plans and status for the laboratory demonstration. In addition, component requirements for the various spacecraft subsystems will be discussed.

Results are described of an ongoing project whose goal is to provide advanced Computer Vision for small low flying autonomous aircraft. The work consists of two parts; range-based vision for object recognition and pose estimation, and monocular vision for navigation and collision avoidance. A wide variety of range imaging methods were considered for the former, and it was found that a promising approach is multi-ocular stereo with a pseudo-random texture projected with a xenon flash. This provides high range resolution despite motion, and can be small and light. The resulting range images, taken at a few meters range, would support the use of Tripod Operators, an efficient and general method for recognizing and localizing surface shapes in 6 DOF. This would provide the ability to recognize immediately upon encounter many kinds of targets. The monocular navigation system is based on finding corresponding features in successive images, and deducing from these the relative pose of the aircraft. Two methods are under development, based on horizon registration and point correspondences, respectively. The first can serve as a preprocessor for the second. This approach aims to continuously and accurately estimate the net motion of the vehicle.

A new method is described for obtaining accurate range images at high speed in a low-cost instrument. A prototype has been built and tested, and a patent application submitted. The method resembles grid-coding in that a camera and a stripe projector are directed at a scene, but the projector is different. It consists of a thin light source (xenon tube and slit) on the axis of a turntable, and a binary mask conforming to a cylinder coaxial with this. The mask has alternate black and clear stripes parallel to the axis. It forms a DeBruijn sequence, i.e., a sequence in which all possible sub-sequences of given length n occur. No lens is used, deliberately smoothing the resulting illumination. In operation, the turntable rotates, and six consecutive images are taken at uniform intervals. A given pixel records six consecutive samples of a scene point. This six-vector, when normalized to unity to accommodate reflectance variations, is unique to the place in the sequence from which it came. Thus we can compute the position in 3-space of the surface point at which the pixel is looking. Observed accuracy is .1 millimeter at 30 centimeters range.

The subsumption architecture (SA) is a special case of behavior-based control for robotics. Behavioral modules are added as `layers', with each layer performing a complete behavior. Higher-level behaviors override lower level ones by taking control of their effectors or manipulating their internal states. The control layers are built of finite-state machines connected by links that act essentially like wires. A prototype airplane controller made with the architecture was developed. This controller flies a simulated aircraft from take-off to landing and was run on a C-based implementation of the subsumption architecture. It was noted that the SA as currently defined is not sufficiently modular, a clean interface between different behaviors would be desirable, and a more general relationship than strict hierarchy between high-level and low-level modules is required. None of these problems is insoluble within the behavior-based approach, but all must be solved if realistic problems are to be dealt with. Some candidate solutions are given