Person:

Book, Wayne J.

Permanent Link

https://hdl.handle.net/1853/71109

Associated Organization(s)

Organizational Unit

George W. Woodruff School of Mechanical Engineering

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Now showing 1 - 10 of 15

Biodynamic Feedthrough Compensation and Experimental Results Using a Backhoe

(Georgia Institute of Technology, 2011-03) Heather C. Humphreys ; Book, Wayne J. ; Huggins, James D.

In some operator-controlled machines, motion of the controlled machine excites motion of the human operator, which is fed back into the control device, causing unwanted input and sometimes instability; this phenomenon is termed biodynamic feedthrough. In operation of backhoes and excavators, biodynamic feedthrough causes control performance degradation. This work utilizes a previously developed advanced backhoe user interface which uses coordinated position control with haptic feedback, using a SensAble Omni six degree-of-freedom haptic display device. Backhoe user interface designers and our own experiments indicate that biodynamic feedthrough produces undesirable oscillations in output with conventionally controlled backhoes and excavators, and it is even more of a problem with this advanced user interface. Results indicate that the coordinated control provides more intuitive operation, and the haptic feedback relays meaningful information back to the user. But the biodynamic feedthrough problem must be overcome in order for this improved interface to be applicable. For the purposes of reducing model complexity, the system is limited to a single degree of freedom, using fore-aft motion only. This paper investigates what types of controller-based methods of compensation for biodynamic feedthrough are most effective in backhoe operation, and how they can be implemented and tested with human operators.
Inertial Vibration Damping Control of a Flexible Base Manipulator

(Georgia Institute of Technology, 2002-11) George, Lynnane E. ; Book, Wayne J.

A rigid (micro) robot mounted serially to the tip of a long, flexible (macro) manipulator is often used to increase reach capability, but flexibility in the macromanipulator can interfere with positioning accuracy. A rigid manipulator attached to a flexible but un actuated base was used to study a scheme to achieve positioning of the micromanipulator combined with enhanced vibration damping of the base. Ineltial interaction forces and torques acting between the robot and its base were modeled and studied to determine how to use them to damp the vibration. One issue is that there are locations in the workspace where the rigid robot loses its ability to create interactions in one or more degrees of freedom. These "ineltial singularities" are functions of the rigid robot's joint variables. A performance index was developed to predict the ability of the rigid robot to damp vibrations and will help ensure the robot is operating in joint space configurations favorable for inertial damping. It is shown that when the performance index is used along with the appropriate choice of feedback gains, the inertia effects, or those directly due to accelerating the robot's links, have the greatest influence on the interactions. By commanding the robot link's accelerations propOitional to the base velocity, vibration energy will be removed from the system. This signal is then added to the rigid robot's position control signal. Simulations of a three-degree of freedom anthropomorphic rigid robot mounted on a flexible base were developed and show the effectiveness of the control scheme. In addition, results from two degree of freedom vibration damping are included.
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.
Modelling for Two-Time Scale Force/Position Control of Flexible Robots

(Georgia Institute of Technology, 1996-04) Rocco, Paolo ; Book, Wayne J.

Distributed flexibility of the links is a severe obstacle for the endpoint position control of lightweight manipulators. In order to accomplish with satisfactory performance certain tasks involving a controlled interaction of the tip of the robot with the worksurfaces, a combined control of the motion and the contact forces can provide some advantages, as it is now recognized for rigid robots. This paper presents a model of a flexible robot interacting with a rigid environment, together with a control scheme designed to achieve the simultaneous control of both the motion of the end effector and the forces at the contact. The time scale separation of the control actions, deriving from singular perturbation theory, is exploited in the design of the controller, which is made up by modular and easy-to-tune components. Simulation results obtained on a detailed nonlinear model of an existing 2 d.o.f. flexible arm are also given.
Integrated Modeling, Simulation, and Animation of Rigid Arms and Vehicles through Object-Oriented Programming

(Georgia Institute of Technology, 1994-02) Schmitt, Paul Richard ; Hogan, John E. ; Cameron, Jonathan M. ; Book, Wayne J.

This paper describes an object-oriented system, "MBSIM" (MultiBody SIMulator), that models, simulates, and animates the kinematics and dynamics of robotic arms and vehicles. This system creates a three dimensional graphical environment which can be used as a tool in robotic design and control.
Control and Control Theory for Flexible Robots

(Georgia Institute of Technology, 1993-04) Magee, David P. ; Book, Wayne J.

As the requirements for robot performance increase, the dynamics of the manipulator become more dominated by flexibility. These flexible effects generate model uncertainty which reduces the end-point positioning accuracy of the manipulator. Residual vibration or tip deflection due to uncertain payloads may contribute to the error in tip position. This paper addresses several control strategies currently used by researchers to account for flexibility in robots and their ability to perform tasks despite the flexibility.
A Singular Perturbation Approach to Control of Lightweight Flexible Manipulators

(Georgia Institute of Technology, 1988-08) Siciliano, Bruno ; Book, Wayne J.

The control of lightweight flexible manipulators moving along predefined paths is the focus of this work. The flexible manipulator dynamics is derived on the basis of a Lagrangian-assumed modes method. The full order flexible dynamic system does not allow the determination of a tracking control as for rigid manipulators, since there are not as many control inputs as output variables. This drawback is overcome by accomplishing a model order reduction, based on a singular perturbation strategy, where the perturbation parameter can be identified as the ratio of speeds of the slow versus the fast dynamics. A composite control is adopted. First a slow control is designed with the purpose to track the trajectory in the joint space as accurately as possible. A quasi steady-state trajectory is then determined for the fast variables, and a fast control is in charge of stabilizing them along that trajectory. The one link flexible arm prototype in the Flexible Automation Laboratory at Georgia Tech is chosen for developing a case study. Extensive simulation results are illustrated.
A Robust Scheme for Direct Adaptive Control of Flexible Arms

(Georgia Institute of Technology, 1987-11) Yuan, Bau-San ; Book, Wayne J.

In exchange for light weight in the design of arms, one must accept an increase in system flexibility and the associated difficulty in accurately controlling a flexible structure. Both rigid body motions and flexural vibrations are required to model the dynamic system. A robust feedback control which is constructed is based on the Lyapounv function for the analysis of uniform boundedness. The control signal is synthesized from estimated states. This is accomplished by separating the system into two parts: linear and nonlinear (uncertainty in the linear model). Performance of a one-link flexible arm resulting from this control algorithm is compared with that of purely linear feedback control.
Symbolic Modeling of Flexible Robotic Manipulators

(Georgia Institute of Technology, 1987-04) Book, Wayne J. ; Cetinkunt, Sabri

This paper presents a new systematic algorithm to symbolically derive the full nonlinear dynamic equations of motion of multi-link flexible manipulators. Lagrange's-assumed modes method is the basis of the new algorithm and adapted in a way suitable for symbolic manipulation by digital computers. The advantages of obtaining dynamic equations in symbolic form and of the presented algorithm are discussed. Application of the algorithm to a two-link flexible arm example via a commercially available symbolic manipulation program is presented. Simulation results are given and discussed.
Reconstruction and Robust Reduced-Order Observation of Flexible Variables

(Georgia Institute of Technology, 1986-12) Hastings, Gordon Greene ; Book, Wayne J.

Most models intended for real-time control of distributed parameter systems such as flexible manipulators rely on N-modal approximation schemes[l]. Measurements made on flexible systems yield time varying quantities which are linear combinations of the system states. This paper discusses reconstruction and estimation of flexible variables from multiple strain measurements for use in state feedback control of flexible manipulators. Reconstruction is proposed for obtaining flexible mode amplitudes from the measurements, and estimation for the modal velocities. Reduced order observers are briefly reviewed, and then application to flexible manipulators is discussed. Design of the observer for estimation of the velocities is discussed with regard to robust implementation. The performance of the observer is examined experimentally for several specifications of the error dynamics.