Wireless sensors capable of sensing, processing, and wireless communication have been adopted for monitoring purposes in a variety of contexts, many of which feature challenging radio propagation characteristics. Fast rotating structures are commonly found in mechanical, transportation and energy systems, and the challenges of using wireless sensors on such structures have not been adequately addressed. For wireless sensors on rotating structures, it has been found there is an eminent dependency of packet error rates on rotation speeds, bursty bit errors, periodic variation in received signal strengths, and dominance of multipath effects. Previously, a reliable data transmission approach was developed to recover transmission errors, and it was found that transmission errors have mostly occurred in certain high-error regions. The objective of this study is to utilize the transmission approach to infer the transmission error pattern of such regions. The paper presents a sliding window algorithm for estimating the error region width, and a transmission simulator for studying dependencies among error burst statistics, error region distribution and widths, and accuracy of the rotation speeds. It is concluded that i) the number, width, and distribution of error regions can be inferred from normalized error burst distance distributions, ii) the error burst distance distributions depend sensitively on accuracy of the rotation speed, and iii) the error in speed can be inferred from the error burst distance distributions. The conclusions directly guide future work on transmission error modeling, on-line error pattern inference, and error-avoidant transmission methods for radios on rotating structures.
Holding the work piece for machining, forming, assembly, or inspection operations is a universally encountered problem in the manufacturing world. The apparatus used to accomplish this is a fixture. Using efficient fixtures is a good way of improving the throughputs of the processes by reducing the part setup time, which can be defined as locating the part in the desired position in a safe way to allow machining. Identification of design requirements, fixture analysis and fixture synthesis can be named as the phases of computer aided fixture design. Typical fixture design systems focus on one of these phases, as the knowledge representation requirements differ for each stage. This paper discusses these phases with respect to the general manufacturing scheme and identifies the issues on integration in order to have a successful variant approach to the fixture selection problem. A system architecture is discussed that is based upon the new graph-based integrated fixture representation. This system architecture should facilitate the rapid exploration of existing fixtures and fixture assemblies to find suitable matches for new part manufacture.
Conference Committee Involvement (1)
Intelligent Systems in Design and Manufacturing V
25 October 2004 | Philadelphia, Pennsylvania, United States