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Institute for Robotics and Intelligent Machines (IRIM)

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End date: 1999 × Start date: 1990 × Type: Text × search.filters.applied.f.resourcesubtype: Article ×

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Now showing 1 - 10 of 12
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    A generalized approach to real-time pattern recognition in sensed data
    (Georgia Institute of Technology, 1999-12) Howard, Ayanna M. ; Padgett, Curtis
    Many applications that focus on target detection in an image scene develop algorithms specific to the task at hand. These algorithms tend to be dependent on the type of input data used in the application and thus generally fail when transplanted to other detection spaces. We wish to address this data dependency issue and develop a novel technique which autonomously detects, in real time, all target objects embedded in an image scene irrespective of the imagery representation. We accomplish this task using a heirarchical approach in which we use an optimal set of linear filters to reduce the data dimensionality of an image scene and then spatially locate objects in the scene with a neural network classifier. We prove the generality of this approach by applying it to two distinctly separate applications. In the first application, we use our algorithm to detect a specified set of targets for an Automatic Target Recognition (ATR) task. The data for this application is retrieved from two-dimensional camera imagery. In the second task, we address the problem of sub-pixel target detection in a hyperspectral image scene. This data set is represented by hyperspectral pixel bands in which target objects occupy a portion of a hyperspectral pixel. A summarized description of our algorithm is given in the following section.
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    Modeling Mechanisms with Nonholonomic Joints Using the Boltzmann-Hamel Equations
    (Georgia Institute of Technology, 1997-02) Obergfell, Klaus ; Book, Wayne J.
    This article describes a new technique for deriving dynamic equations of motion for serial chain and tree topology mech anisms with common nonholonomic constraints. For each type of nonholonomic constraint, the Boltzmann-Hamel equations produce a concise set of dynamic equations. These equations are similar to Lagrange's equations and can be applied to mechanisms that incorporate that type of constraint. A small library of these equations can be used to efficiently analyze many different types of mechanisms. Nonholonomic constraints are usually included in a La grangian setting by adding Lagrange multipliers and then eliminating them from the final set of equations. The ap proach described in this article automatically produces a minimum set of equations of motion that do not include La grange multipliers.
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    A Time-Domain Inverse Dynamic Tracking Control of a Single-Link Flexible Manipulator
    (Georgia Institute of Technology, 1994-06) Kwon, Dong-Soo ; Book, Wayne J.
    A manipulator system with a large workspace volume and high payload capacity has greater link flexibility than do typical industrial robots and teleoperators. If link flexibility is significant, position control of the manipulator's end-effector exhibits nonminimum-phase, noncollocated, and flexible-structure system control problems. This paper addresses inverse dynamic trajectory planning issues of a single-link flexible manipulator. The inverse dynamic equation of a single-link flexible manipulator was solved in the time-domain. By dividing the inverse system equation into its causal part and anticausal part, the inverse dynamic method calculates the feed-forward torque and the trajectories of all state variables that do not excite structural vibrations for a given end-point trajectory. Through simulation and experiment with a single-link manipulator, the effectiveness of the inverse dynamic method in producing fast and vibration-free motion has been demonstrated.
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    Convolution Analysis of Milling Force Pulsation
    (Georgia Institute of Technology, 1994-02) Wang, J.-J. Junz ; Liang, Steven Y. ; Book, Wayne J.
    This paper presents the establishment of a closed form expression for the dynamic forces as explicit functions of cutting parameters and tool/workpiece geometry in milling processes. Based on the existing local cutting force model, the generation of total cutting forces is formulated as the angular domain convolution of three cutting process component functions, namely the elementary cutting function, the chip width density function, and the tooth sequence function. The elemental cutting force function is related to the chip formation process in an elemental cutting area and it is characterized by the chip thickness variation, and radial cutting configuration. The chip width density function defines the chip width per unit cutter rotation along a cutter flute within the range of axial depth of cut_ The tooth sequence function represents the spacing between flutes as well as their cutting sequence as the cutter rotates. The analysis of cutting forces is extended into the Fourier domain by taking the frequency multiplication of the transforms of the three component functions. Fourier series coefficients of the cutting forces are shown to be explicit algebraic functions of various tool parameters and cutting conditions. Numerical simulation results are presented in the frequency domain to illustrate the effects of various process parameters. A series of end milling experiments are performed and their results discussed to validate the analytical model.
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    Transfer functions of flexible beams and implication of flexibilty on controller performance
    (Georgia Institute of Technology, 1994) Cetinkunt, Sabri ; Book, Wayne J.
    Dynamic behavior of many mechanical motion systems having distributed flexibility are described by linear partial differential equations, i.e. flexible beams, satellite appendages, plates. Understanding the open loop transfer function (poles, zeros, d.c. gain) is a prerequisite for a successful controller design. The open loop pole-zero patterns of a flexible beam (using its infinite dimensional model) are studied as a function of actuator and sensor locations. The physics of the flexible beam dynamics is discussed in order to explain the physical source and the meaning of zeros, and its implications in terms, of the limitations imposed on the maximum closed loop bandwidth achievable. Although the actual system dynamics involve an infinite number of modes, finite dimensional models are needed for the design of a real time controller. The accuracy of finite dimensional models using different mode shapes are compared from a controller design point of view.
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    Structural Flexibility of Motion Systems in the Space Environment
    (Georgia Institute of Technology, 1993-10) Book, Wayne J.
    The state-of-the-art is summarized, focusing on interdisciplinary approaches and positions, and future directions in the design, analysis, and control of lightweight robotic and telerobotic motion systems for space application are discussed. The emphasis is on providing a logical connection between the special demands of space applications and the design of the motion system. Flexibility is presented as a natural consequence of these demands. A number of technologies are relevant to extending feasible performance into regions of the design space previously avoided due to the resulting flexibility of the structures and drives. Control technology is considered foremost, but passive damping, structural materials, structural design, operational strategy and sensor technology are closely related. Numerous references are presented for those wishing to employ these technologies.
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    Dynamics of Flexible Manipulator Arms: Alternative Derivation, Verification, and Characteristics for Control
    (Georgia Institute of Technology, 1993-09) Yuan, B. - S. ; Book, Wayne J. ; Huggins, J. D.
    This work seeks to provide an effective way for developing the dynamics of a multi-link flexible manipulator consisting of rotary joints connecting two links. Kinematics of both the rotary joint motion and the link deformation are described by 4 x 4 transformation matrices as proposed in previous works (Book, 1984). The link deflection is assumed small so that the link transformation can be composed of summations of assumed link shapes. To determine the appropriate choice of component mode shapes, two essential techniques employed here are experimental and finite element methods. The resulting equations of motion allow the complete non-linear model to be recursively derived from the Jacobian matrix and the mass properties via symbolic manipulation. Two prototype models of flexible manipulators are used to verify the dynamics with frequency and time responses. This paper contributes several new results: (1) the velocity terms (Coriolis and centrifugal forces) are related to variations in the mass matrix, (2) the skew symmetry of certain useful terms are shown, (3) the system is theoretically demonstrated to be stable with joint P.D. controllers in addition to an experimental approach, (4) practical and effective incorporation of actuator dynamics (hydraulic cylinder) and structural complexity (non-uniform cross section) is achieved through selection of mode shapes, (5) geometric constraints are incorporated through simplified coordinate transformations and (6) the results are verified on two physical cases.
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    Controlled Motion in an Elastic World
    (Georgia Institute of Technology, 1993-03) Book, Wayne J.
    The flexibility of the drives and structures of controlled motion systems are presented as an obstacle to be overcome in the design of high performance motion systems, particularly manipulator arms. The task and the measure of performance to be applied determine the technology appropriate to overcome this obstacle. Included in the technologies proposed are control algorithms (feedback and feedforward) , passive damping enhancement, operational strategies, and structural design. Modeling of the distributed, nonlinear system is difficult, and alternative approaches are discussed. The author presents personal perspectives on the history, status and future directions in this area.
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    Contact Control for Advanced Applications of Light Weight Arms
    (Georgia Institute of Technology, 1992) Book, Wayne J. ; Kwon, Dong-Soo
    Many applications of robotic and teleoperated manipulator arms require operation in contact and noncontact regimes. This paper deals with both regimes and the transition between them with special attention given to problems of flexibility in the links and drives. This is referred to as contact control. Inverse dynamics is used to plan the tip motion of the flexible link so that the free motion can stop very near the contact surface without collision due to overshoot. Contact mus occur at a very low speed since the high frequency impact forces are too sudden to be affected by any feedback generated torques applied to a joint at the other end of the link. The effects of approach velocity and surface properties are discussed. Force tracking is implemented by commands to the deflection states of the link and the contact force. This enable a natural transition between tip position and tip force control that is not possible when the arm is treated as rigid. The effects of feedback gain, force trajectory, and desired final force level are of particular interest and are studied. Experimental results are presented on a one-link arm and the system performance in the overall contact task is analyzed. Extension to multi-link cases with potential applications are discussed.
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    Experimental Investigations of the Effects of Cutting Angle on Chattering of a Flexible Manipulator
    (Georgia Institute of Technology, 1991-12) Lew, J. ; Huggins, J. ; Magee, D. ; Book, Wayne J.
    When a machine tool is mounted at the tip of a robotic manipulator, the manipulator becomes more flexible (the natural frequencies are lowered). Moreover, for a given flexible manipulator, its compliance will be different depending on feedback gains, configurations, and direction of interest. In this paper, the compliance of a manipulator is derived analytically, and magnitude is represented as a compliance ellipsoid. Then, using a two link flexible manipulator with an abrasive cut-off saw, the experimental investigation shows that the chattering varies with the saw cutting angle due to the different compliance. The main work is devoted to finding a desirable cutting angle which reduces the chattering.