Organizational Unit:

Institute for Robotics and Intelligent Machines (IRIM)

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https://hdl.handle.net/1853/70657

Includes Organization(s)

Organizational Unit

Biorobotics and Human Modeling Lab

Organizational Unit

Humanoid Robotics Laboratory

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Now showing 1 - 9 of 9

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.
On the transfer function modeling of flexible structures with distributed damping

(Georgia Institute of Technology, 1986-12) Alberts, Thomas Edward ; Dickerson, Stephen L. ; Book, Wayne J.

The authors have suggested the use of distributed passive damping via constrained viscoelastic layer surface treatments, as a means of augmenting active controllers for flexible structures. This enhances system stability and provides justification for the use of low order dynamic models and controllers. In previous work a co located transfer. function based upon experimental measurements was employed in root locus analysis of a system with passive damping. Here we present a method of deriving co located and non-colocated transfer functions for flexible systems with distributed damping. The (sandwich) flexible structure is modeled as though it was constructed of an equivalent homogeneous material exhibiting linear viscoelastic behavior. Transfer functions are obtained through solution of a modified form of the Bernoulli-Euler equation which is derived using the standard constitutive relationship between stress and strain for viscoelastic materials in place of Hook's law. General observations are made with regard to open loop pole and zero locations for colocated and non-colocated transfer functions. The effect of joint damping is also considered.
Low cost automation with lighter, versatile machines

(Georgia Institute of Technology, 1986-11) Book, Wayne J.

This paper describes the opportunities for improving the cost/performance ratio for industrial robots and other industrial equipment through reduction in their weight. Also described are four approaches to taking advantage of these opportunities without encountering the adverse effects inherent in compliant structures. These approaches are 1) active joint control, 2) passive damping enhancement, 3) trajectory planning, and 4) operational strategies such as "bracing." It appears that using all four approaches in combination may be most effective.
The Bracing Strategy for Robot Operation

(Georgia Institute of Technology, 1984-06) Book, Wayne J. ; Sangveraphunsiri, Viboon ; Le, Sanh

A new strategy of robot operation, the bracing strategy, is presented. Under this strategy an arm is moved into position then rigidized by bracing against either the work piece or an auxiliary, static structure. Subsequent precision motion does not involve the entire arm, but only degrees of freedom at the end of the arm. The advantage of this strategy is that it allows high speed, precision motion with a light weight, flexible arm. Light arms require smaller actuators, less energy, may be faster, are safer, and are less expensive. Four means of clamping to the structure are considered: A simple normal force, mechanical clamping, vacuum attachment, and magnetic attachment. Each means has restrictions and advantages. Arm control with the bracing strategy requires four modes: gross motion control, rendezvous with the bracing structure, control of gross actuators after bracing and control of fine motion actuators distal to the bracing point.
Design studies on a robotic device for ultrasonic inspection

(Georgia Institute of Technology, 1981-09) Sangveraphunsiri, Viboon ; Book, Wayne J.

Design studies in progress on a special purpose robot are described. The robot is to be used for ultrasonic inspection of extruded and forged parts immersed in water in a large tank. The studies focus on establishing the best tradeoff between light weigh, with the associated fast movement time for large motion, and rigidity – as characterized by high structural natural frequency. High natural frequency allows high servo bandwidth and consequently faster response to small disturbances and greater dynamic accuracy.
Control of a Robotic Exercise Machine

(Georgia Institute of Technology, 1981-06) Book, Wayne J. ; Ruis, David A.

Exercise devices provide a means of resisting user applied forces for purposes of improving physical performance. The characteristics of the device include its path of motion and the functional relationship between applied force and ensuing motion. The characteristics of machines have in the past been limited to those achievable with mechanisms whose motions are resisted by passive prings, masses and frictional devices. A great increase in the number practically achievable characteristics is provided by the servo controlled exercise machines of the type discussed in this paper. The benefits, objectives and prototype configuration are briefly described followed by a discussion of the control algorithms used on a prototype machine and the performance obtained.