Showing papers by "Takeo Kanade published in 1983"

Control of a Direct-Drive Arm

Abstract: A direct-drive arm is a mechanical arm in which the shafts of articulated joints are directly coupled to the rotors of motors with high torque. Since the arm does not contain transmission mechanisms between the motors and their loads, the drive system has no backlash, small friction, and high mechanical stiffness, all of which are desirable for fast, accurate, and versatile robots. First, the prototype robot is described, and basic feedback compensation is discussed . This compensation significantly reduces the effect of interactions among multiple joints and nonlinear forces. The experiments showed the excellent performance of the direct-drive arm in terms of speed and accuracy.

Design of Direct-Drive Mechanical Arms'

Abstract: : This paper describes the design concept of a new robot based on the direct-drive method using rare-earth DC torque motors. Because these motors have high torque, light weight and compact size, we can construct robots with far better performance than those presently available. For example, we can eliminate all the transmission mechanism between the motors and their loads, such as reducers and chain belts, and construct a simple mechanism (direct-drive) where the arm links are directly coupled to the motor rotors. This elimination can lead to excellent performance: no backlash, low friction, low inertia, low compliance and high reliability, all of which are suited for high-speed high-precision robots. First we propose a basic configuration of direct-drive robots. Second a general procedure for designing direct-drive robots is shown, and the feasibility of direct drive for robot actuation is discussed in terms of weights and torques of joints. One of the difficulties in designing direct-drive robots is that motors to drive wrist joints are loads for motors to drive elbow joints and they are loads for motors at shoulders. To reduce this increasing series of loads is an essential issue for designing practical robots. We analyze the series of joint mass for a simplified kinematic model of the direct-drive robots, and show how the loads are reduced significantly by using rare-earth motors with light weight and high torque. We also discuss optimum kinematic structures with minimum arm weight. Finally, we describe the direct-drive robotic manipulator (CMU arm) developed at Carnegie-Mellon University, and verify the design theory. (Author)

Mapping Image Properties into Shape Constraints: Skewed Symmetry, Affine-Transformable Patterns, and the Shape-from-Texture Paradigm

Abstract: In this paper we demonstrate two new approaches to deriving three-dimensional surface orientation information (“shape‘) from two-dimensional image cues. The two approaches are the method of affine-transformable patterns and the shape-from-texture paradigm. They are introduced by a specific application common to both: the concept of skewed symmetry. Skewed symmetry is shown to constrain the relationship of observed distortions in a known object regularity to a small subset of possible underlying surface orientations. Besides this constraint, valuable in its own right, the two methods are shown to generate other surface constraints as well. Some applications are presented of skewed symmetry to line drawing analysis, to the use of gravity in shape understanding, and to global shape recovery.

Using shadows in finding surface orientations

Abstract: Given a line drawing from an image with shadow regions identified, the shapes of the shadows can be used to generate constraints on the orientations of the surfaces involved. This paper describes the theory which governs those constraints under orthography. A “Basic Shadow Problem” is first posed, in which there is a single light source, and a single surface casts a shadow on another (background) surface. There are six parameters to determine: the orientation (two parameters) for each surface, and the direction of the vector (two parameters) pointing at the light source. If some set of three of these are given in advance, the remaining three can then be determined geometrically. The solution method consists of identifying “illumination surfaces” consisting of illumination vectors, assigning Huffman-Clowes line labels to their edges, and applying the corresponding constraints in gradient space. The analysis is extended to shadows cast by polyhedra and curved surfaces. In both cases, the constraints provided by shadows can be analyzed in a manner analogous to the Basic shadow Problem. When the shadow falls upon a polyhedron or curved surface, similar techniques apply. The consequences of varying the position and number of light sources are also discussed. Finally, some methods are presented for combining shadow geometry with other gradient space techniques for 3D shape inference.

An Optical Proximity Sensor for Measuring Surface Position and Orientation for Robot Manipulation.

Abstract: : The authors developed a noncontact proximity sensor which can measure the distance and orientation of a surface in a range of four to five centimeters. The sensor is based on the scheme of active illumination and triangulation. It uses multiple infrared LEDs(light emitting diodes) as the light sources and a PIN-diode area sensor chip for detecting the spot positions. Six LEDs with optics for collimating the beam are mounted at the sensor head. The directions of the beams are aligned to form a cone of light converging at a distance of 4.5 cm from the sensor head. As each LED is sequentially pulsed, the sensor chip detects the position, in its field of view, of the spot projected by the LED light beam on the object surface. The 3-D location of the spot on the surface can be computed by triangulation. By doing this for six LEDs a set of six 3-D points is obtained. Then by fitting a plane to those points, the distance and orientation of a small portion of the object surface are calculated. Since there is no moving part and the spot position sensor chip is a analog sensor which outputs the position of the spot directly without scanning its field of view, fast operation of the proximity sensor can be realized. Currently the sensor can give approximately 1000 measurements of distance and orientation per second with precision of 0.07 mm for distance and 1.5 deg for surface orientation. This non-contact proximity sensor will be useful for such applications as tracing an object surface by a robot arm with specified distance and orientation relative to the surface. (Author)

Gradient space under orthography and perspective

Abstract: Mackworth's gradient space has proved to be a useful tool for image understanding. However, descriptions of its important properties have been somewhat scattered in the literature. The fundamental properties of the gradient space under orthography and perspective, and for curved surfaces, are developed and summarized. While largely a recounting of previously published results, there are a number of new observations, particularly concerning the gradient space and perspective projection. In addition, the definition and use of vector gradients as well as surface gradients provides concise notation for several results. The properties explored include the orthographic and perspective projections themselves; the definition of gradients; the gradient space consequences of vectors (edges) belonging to one or more surfaces, and of several vectors being contained on a single surface; and the relationships between vanishing points, vanishing lines, and the gradient space. The paper is intended as a study guide for learning about the gradient space, as well as a reference for researchers working with gradient space.

Geometrical aspects of interpreting images as a three-dimensional scene

Abstract: One of the fundamental aspects of vision is three-dimensional geometry referring to the relationship between the scene which is depicted and the images which are projections of that scene. This paper presents computational theories which deal with geometrical aspects of interpreting images as a three-dimensional (3D) scene. The presentation covers three levels of descriptions: micro-surface level, volumetric-object level, and scene level. The micro-surface level concerns the relationship between surface orientations of small surface patches and image properties. Theories are presented which provide computational constraints for recovering surface orientations from geometrical image properties, such as symmetry, texture, shadows, and perspective distortions. The volumetric-object level handles shape representations of primitive objects: the relationship between 3D shape of an object and its projections onto images must be understood. The generalized cylinder is a popular volumetric shape representation in vision. We will discuss its formal properties. Finally, the scene level aims at constructing and maintaining the 3D description of the whole scene. We will present the Incremental 3D Mosaic system under development at CMU, which incrementally constructs the total 3D scene description of the task area from aerial photographs.

The Theory of Straight Homogeneous Generalized Cylinders

Abstract: : In recent years, Binford's generalized cylinders have become an important tool for imagine understanding. However, research has been hampered by a lack of analytical results for these shapes. In this paper, a definition is presented for Straight Homogeneous Generalized Cylinders, those generalized cylinders, with a straight axis and with cross-sections which have constant shape but vary in size. This class of shapes, while still quite large, has properties which make considerable analysis possible. The results begin with deriving formulae for points and surface normals for these shapes. Theorems are presented concerning the conditions under which multiple descriptions can exist for a single solid shape. Then projections and contour generators are analyzed for some subclasses of shapes. The strongest results are obtained for solids of revolution (which the authors name Right Circular SHGCs), for which a closed-form method for analyzing image contours is presented. It is seen that a picture of the contours of a solid of revolution is ambiguous, with one degree of freedom related to the angle between the line of sight and the solid's axis. (Author)

The theory of straight homogeneous generalized cylinders and A taxonomy of generalized cylinders

Abstract: In recent years, Binford's generalized cyl inders have become a commonly used shape representation scheme in computer vision. However, research involving generalized cylinders has been hampered by a lack of analytical results at all levels, even including a lack of a precise definition of these shapes. In this paper, a definition is presented for Generalized Cylinders and for several subclasses. Straight Generalized Cylinders, with a linear axis, are important because the natural object-centered coordinates are not curved. The bulk of the paper is concerned with Straight Homogeneous Generalized Cylinders, in which the cross-sections have constant shape but vary in size. The results begin with deriving formulae for points and surface normals for these shapes. Theorems are presented concerning the conditions under which multiple descriptions can exist for a single solid shape. Then, projections, contour generators, shadow lines, and surface normals are analyzed for some subclasses of shapes. The strongest results are obtained for solids of revolution (which we name Right Circular SHGCs), for which several closed-form methods for analyzing images are presented. This research was sponsored by the Defense Advanced Research Projects Agency (DOD), ARPA Order No. 3597, monitored by the Air Force Avionics Laboratory Under Contract F33615-81 -K-1539. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Defense Advanced Research Projects Agency or the US Government. Table of

Three-wheeled adjustable vehicle

Abstract: A motor driven vehicle for traversing the interior of a pipe or conduit comprises a pair of arms pivoted to each other at one pair of ends, a drive wheel the axle of which may coincide with the pivot, a swiveling wheel carried at the other end of each arm and a spring positioned to pull the arms toward each other so that the dimension of the vehicle across a pipe is automatically maximized. The vehicle thus tends to position itself on the longest axis of any cross section of the pipe. The drive wheel may be constructed with rim segments which rotate about axes tangent to the means circumference of the rim.

Device for detecting physical position and direction of body

Abstract: An array of light sources transmit a series of light beams onto an object and the reflected light beams are focussed on a light responsive transducer. The output signals of the transducer are processed to determine the location and orientation of the object. The location and orientation information in turn is available to control the operation of a tool or manipulator relative to the object.

Representation and Control in Vision

Abstract: One of the central issues in vision is how to represent and use knowledge relevant to understanding the image. Partly because vision is so difficult, and partly because even the cheapest solutions can still be so useful, approaches to vision problems have had a tendency to be ad hoc and heuristic. Recently, however, new thrusts in computer vision are emerging, most notably in the Image Understanding community, that try to pursue more systematic and computational approaches. [1]

Appropriate lengths between phalanges of multijointed fingers for stable grasping

Abstract: An appropriate arrangement of finger joints is very important in designing multijointed fingers since the stability of grasping an object greatly depends on that arrangement. Multijointed fingers can grasp an object with many points of contact each of which is pressed against the object as if wrapping up that object. The amount of the wrapped up area and the form of the finger when an objected is grasped are therefore important factors for determining the stability of the grasping. We propose the wrap-up rate to be used for the evaluation of the stability of grasping by using these factors. We consider twenty eight models for the finger having three joints, and perform a simulation of their ability to grasp various shapes stably. Based on the simulation results, an appropriate arrangement of lengths between phalanges for a multijointed finger is presented.

Four-wheeled adjustable vehicle

Abstract: A motor driven vehicle for traversing the interior of a pipe or conduit accommodates itself to variations in the interior contour of the pipe and automatically positions itself on the longest axis of any cross section of the pipe. It comprises a pair of two-wheeled trucks each pivotally connected to an end of a stretcher member which urges the trucks away from each other against diametrically opposite paths of travel on the pipe wall. Each truck has a driving wheel and a swivelling wheel, the driving wheels being diagonally opposite each other. The driving wheel motors are servo-connected so as to keep the angles between stretcher and truck bolsters equal. The driving wheels are preferably constructed with rim segments which rotate about axes tangent to the mean circumference of the rim, thereby permitting movement sidewise of the wheel.