Coupled Extensional-Torsional Vibration Frequency of Hoisting Rope in Tower-Type Friction Drive Hoist System
In order to avoid resonance, and to enhance safety of hoisting system and monitoring reliability, an impact mechanical model of mine hoisting rope for friction drive hoist system was built. According to Hamilton principle and considering the effect of oriented pulley and hoisting rope string, coupled extensional-torsional and extensional only mathematical models of hoisting rope were deduced. Mode shape and transcendental equation of angular frequency were obtained based on the hypothesis that the wave of vibration propagated with sine shape. With numerical calculation, results show that the frequency considering the effect of oriented pulley and hoisting rope string was slightly lower comparing with the frequency ignoring the effect at the bottom of shaft, but much different at the mouth; and there is significant difference between coupled frequency and extensional vibration only. Thereby, to make the design and monitoring of mine hoisting much more reliably, it is suggested that the extensional-torsional coupled vibration of hoisting rope, oriented pulley and hoisting rope string should be considered.
Notice of RetractionCoupled vibration of hoist rope with complicated operating condition
In order to provide help for designing hoist control system to avoid resonance and enhance the safety in mine or elevator hoist system, coupled vibration behavior of hoist rope was investigated with complicated boundary such as the hoist rope restricted by guide pulleys. According to Hamilton principle, the mathematical model of extensional-torsional coupled considering arbitrary concentrated-mass of guide pulleys and torsional displacement boundary condition was built. Basing on the property of step function, the mode function of hoist rope was obtained and the method of numerical solution for displacement was proposed. At last, the analytical expressions of extensional and torsional displacements were obtained by supposing that the extensional and torsional damping coefficients were same. And the coupled displacement was obtained as an application example while a cargo merged into a conveyance.
New approach to vision-based BGA package inspection
Ball grid array (BGA) techniques have developed very fast due to the advantages of more I/O ports, small size, and so on. In this paper, a vision-based algorithm for BGA package inspection is proposed to accurately estimate center and diameters of solder-balls of BGA packages, so that defects of BGA packages, such as missing or extra balls, oversize or undersize balls, over-height or under-height balls, and pitch can be detected for ensuring the quality of BGA packages.