The tripod operator is a class of feature extraction operators for range images. It facilitates the recognition and/or localization of objects by extracting a few sparse point samples in a regimented way; n sampled surface points yield only n-3 scalar features containing all the surface shape information in these points and no other information. They have complete six degrees-of-freedom (DOF) isometry invariance. Isolated objects are recognized in noisy range images using a statistical treatment of a few isolated tripod operator placements. Experiments show fast, reliable recognition.>

The tripod operator, a class of feature extraction operators for range images which facilitate the recognition and localization of objects is described. It consists of three points in 3-space fixed at the vertices of an equilateral triangle and a procedure for making several scalar measurements in the coordinate frame of the triangle. The triangle is moved as a rigid body until the three vertices lie on the surface of some range image or modeled object. The resulting measurements are local shape features which are invariant under rigid motions. These features contain all the shape information in the surface points involved, and no other information. Tripod operators are applicable to all 3-D shapes. A cloud of points in feature space was generated for each object by random placement of the operator. Then new feature measurements were made by operator placements in a range image containing one of those objects. Using a simple nearest-neighbor approach, the authors determined which objects were rejected and which remained as recognition candidates. Experiments showed that tripod operators had excellent discriminating power.>

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.>