Propagation characteristics of hoist ropes for mobile-crane PLC

摘要

In recent years, mobile cranes have been larger, and enhancements of various safety devices and assist functions have also been demanded. In this paper, a hoist-rope channel of mobile crane has been explored as a new area for PLC application to achieve a high-speed communication between boom-tip and hook. The channel is a loop circuit formed by a rope and two sheaves, and its simple channel model based on the transmission line theory has been proposed. Although the primary line constant R of the rope has to be derived from the channel impedance measurements from 1M to 50MHz, other constants L and C are given from the well-known formulas, which need only information on the diameter d and distance D of the rope. It has been confirmed that the transfer function calculated from this channel model agreed with the measured values well, where the signal was injected and received through ferrite transformers for a contactless coupling. The throughput of 70Mbps using the transformers was achieved for a truck-mounted crane. It has been also proposed to use the kHz band in combination with the MHz band to deliver the electrical power from the boom-tip to the hook, because the channel impedance of the kHz band is lower. According to our scenario, the signal attenuation at the kHz band was less than that at the MHz band about 16 dB at the maximum.