Patent CA-1281104-C (CA)
Title: Guide wire communications system and method
Inventor: SHERMAN LEIGH E
IPC: G05D1/02
Filed: 1985-12-20
Granted: 1991-03-05
Abstract: ABSTRACT OF DISCLOURE        In a guidance system for guiding a plurality of unmanned vehicles along a traffic lay out comprising a plurality of guide wires, a guide wire communications system is disclosed which is provided with a plurality of data communications circuits which can be linked together in a logical tree structure to form an extensive network. The communications circuits are connected to a vehicle traffic control computer which is provided with means for composing a coded vehicle instruction for assigning tasks to said unmanned vehicles. Various parts of the system, including for example, segments along guide wires, are designated as resources. The computer uniquely allocates those resources to each vehicle which are necessary for the performance of the tasks assigned to that vehicle. The vehicle traffic control computer further includes polling means which enables it to poll the status of each vehicle at varying time intervals and to receive a response from said vehicle when the computer next polls the vehicle. The guide wire communications system can communicate coded instructions to the vehicles either individually or as a group.      The guide wire communications system further comprises a network connecting the computer and the communications circuits which is provided with means for preventing reception of data transmissions from more than one vehicle at a time.      The communications circuits comprise data transmitters provided with means for generating a communications wave with low frequency and low power but high data transmission rate. The data transmitters further include means for encoding and decoding digital data using at least two data transmission frequencies. Said means comprise a circuit for digitally constructing a string of single cycles of cosine wave forms of selected frequencies. The communications circuits are provided with receivers for detecting cosine wave segments, tranforming such segments into sine wave segments and recovering digital data at a rate substantially equal to the lowest data transmission frequency employed. The data communications circuits also include means for selecting low impedence or high impedence characterisitics for a guide wire depending on the function of the guide wire as a data receiving , antenna, a data transmitting antenna or a tracking-signal carrier, permitting low power signals to be used.      The guidewire communications system further includes a communications circuit on each of a plurality of vehilces which comprises a low frequency, high gain transmit antenna composed of a substantially figure-eight pattern of conductors mounted on the bottom of the vehicle; a transmitter and a reciever substantially as described above, memory for storing a plurality of instructions for serial execution by the vehicle essentially independantly; and means for determining estimated completion time of assigned tasks to permit minimum polling of each vehicle by the vehicle traffic control computer at varying time intervals.