Flexible manipulator control experiments and analysis

Modeling and control design for flexible manipulators, both from an experimental and analytical viewpoint, are described. From the application perspective, an ongoing effort within the laboratory environment at the Ohio State University, where experimentation on a single link flexible arm is underway is described. Several unique features of this study are described here. First, the manipulator arm is slewed by a direct drive dc motor and has a rigid counterbalance appendage. Current experimentation is from two viewpoints: (1) rigid body slewing and vibration control via actuation with the hub motor, and (2) vibration suppression through the use of structure-mounted proof-mass actuation at the tip. Such an application to manipulator control is of interest particularly in design of space-based telerobotic control systems, but has received little attention to date. From an analytical viewpoint, parameter estimation techniques within the closed-loop for self-tuning adaptive control approaches are discussed. Also introduced is a control approach based on output feedback and frequency weighting to counteract effects of spillover in reduced-order model design. A model of the flexible manipulator based on experimental measurements is evaluated for such estimation and control approaches

A dual scheme for compression and restoration of sequentially transmitted images over Wireless Sensor Networks

A dual scheme for the compression and restoration of sequentially transmitted images over Wireless Sensor Networks (WSNs) is presented. These networks are characterized by low transmission rates, extended packet losses and limited power resources, factors that degrade the overall system performance. Especially in the cases of transmitting multimedia content, a considerable number of data packets are dropped, with a corresponding direct effect on the received image quality. For dealing with this loss of valuable information, various retransmission schemes have been proposed that act as quality of service modules. However, this approach increases energy consumption and inserts considerable time delays, due to the rise of the traffic load in the network. This article proposes a novel dual transmission scheme, targeting mainly the area of Multimedia WSNs (WMSN), that aims to decrease the overall traffic load introduced by the retransmission schemes, by performing image restoration for lost data packets, at the receiver side. The proposed novel dual scheme is based on: (a) the quad tree decomposition algorithm that is adopted for compressing the image data before transmission over the WSN, and (b) the fast image inpainting algorithm for restoring the effect of the missing data packets. The overall proposed scheme has been applied in multiple experimental studies that prove its efficacy. © 2012 Elsevier B.V. All rights reserved