Precise tip positioning of a flexible manipulator using resonant control

A single-link flexible manipulator is fabricated to represent a typical flexible robotic arm. This flexible manipulator is modeled as a SIMO system with the motor-torque as the input and the hub angle and the tip position as the outputs. The two transfer functions are identified using a frequency-domain system identification method. A feedback loop around the hub angle response with a resonant controller is designed to damp the resonant modes. A high gain integral controller is also designed to achieve zero steady-state error in the tip position response. Experiments are performed to demonstrate the effectiveness of the proposed control scheme

Control of large space structures and associated precision-pointed payloads

Stability and robustness of a two-level control system for large space structures were investigated. In particular, the effects of actuator/sensor nonlinearities and dynamics on the closed-loop stability were studied and the problem of control-systems design for fine-pointing of several individually pointed payloads mounted on a large space platform was examined. A composite controller is proposed and is stable and robust

Precise tip positioning of a flexible manipulator using resonant control

A single-link flexible manipulator is fabricated to represent a typical flexible robotic arm. This flexible manipulator is modeled as an SIMO system with the motor torque as the input and the hub angle and the tip position as the outputs. The two transfer functions are identified using a frequency-domain system identification method, and the resonant modes are determined. A feedback loop around the hub angle response with a resonant controller is designed to damp the resonant modes. A high-gain integral controller is also implemented to achieve zero steady-state error in the tip position response. Experiments are performed to demonstrate the effectiveness of the proposed control scheme

Manipulation strategies for massive space payloads

The industrial and environmental applications for robots with a relatively large workspace has increased significantly in the last few years. To accommodate the demands, the manipulator is usually designed with long, lightweight links that are inherently flexible. Ongoing research at Georgia Tech into the behavior and design of these flexible links is discussed

Integral Resonant Control for vibration damping and precise tip-positioning of a single-link flexible manipulator

Peer reviewedPostprin

Modeling and Design Implications of Noncollocated Control in Flexible Systems,"

Introduction One of the most important problems in control system design for large flexible structures is simultaneously achieving high performance and robustness. Since there is a trade-off between robustness and model accuracy, accurate modeling of the structure is essential to successful control system design [1], Most existing control design methods for flexible system, such as the Independent Modal Space Control (IMSC) Noncollocated control systems, in contrast, lack these inherent stability characteristics. Here, inaccuracies resulting from model uncertainties and modal truncation present fundamental difficulties in both performance and stability. These limitations directly result from the fact that a noncollocated system is always nonminimum phase above some finite frequency. Nonminimum phase behavior is an inescapable result of the finite propagation speed of elastic deformation waves in the structure. Performance of nonminimum phase systems has inherent limitations; physical readability requirements on the compensator impose definite restrictions on achievable closed loop characteristic

Estimation and control of flexible space structures for autonomous on-orbit assembly

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.Includes bibliographical references (p. 135-139).The ability to autonomously assemble large structures in space is desirable for the construction of large orbiting solar arrays, interplanetary spacecraft, or space telescopes. One technique uses free-flying satellites to manipulate and connect elements of the structure. Since these elements are often flexible and lack embedded actuators and sensors, the assembly robot must use its own actuators and onboard measurements to suppress vibrations during transportation maneuvers. This thesis will examine the dynamic modeling of a free-flying robot attached to a flexible beam-like element, vision-based estimation of vibrational motion, and trajectory control for assembly of a space structure.by Jacob G. Katz.S.M

Normal forms for underactuated mechanical systems with symmetry

We introduce cascade normal forms for underactuated mechanical systems that are convenient for control design. These normal forms include three classes of cascade systems, namely, nonlinear systems in strict feedback form, feedforward form, and nontriangular quadratic form (to be defined). In each case, the transformation to cascade systems is provided in closed-form. We apply our results to the Acrobot, the rotating pendulum, and the cart-pole system