Section 8.Theory of Operation

Functional Operation

When the Guidance Card takes over issuing steer commands, the truck is in an Aligning Mode. While in Aligning Mode, the TM ignores the steering request from the CM and all the wire guidance icon LEDs blink. The truck is now auto steering and no longer responds to operator steer tiller inputs. The Guidance Card also monitors the DC voltages from the Filter Card representing the AC voltages being picked up by the outer coils (Guidance Coils) on both the tractor end and the load end sensors as the truck begins to align over the wire. When the voltages that the truck detects from the load end and tractor end guidance coils begin to balance out and match the Learned Offset values for those coils, the Guidance Card switch from Aligning Mode to Locked on Wire or Guided Mode. At that time, all of the wire guidance icon LEDs illuminate solid and full travel speed is allowed in either direction.

The Guidance Card constantly monitors the voltages from each of the four guidance coils via the Filter Card. It compares the voltage from each coil to the value for each coil that was obtained through the Learn procedure. By comparing the actual values for all four guidance coils with the learned values stored in the memory, the Guidance Card can issue the appropriate steering commands to the TM to keep the truck centered over the guide wire. Also, using these values, the Guidance Card calculates the HA and the DFW and issues the appropriate Slow or Stop commands to the TM when DFW or HA values set in Configure Mode are exceeded. See Table3-1 on page3-15

End-of-Aisle Control

The End-of-Aisle system consists of truck mounted components and magnets embedded in the floor inside of the aisle. The truck mounted hardware consis ts of four magnet sensors mounted between the baselegs under the operator's platform. They are connected directly to the TM. When the system is activated, the TM monitors the inputs from the sensors. When entering the aisle and both sensors cross a magnet in less than 24 in. (610mm), the TM recognizes this as In-AisleState. This information is stored in Non Volatile Memory (NVM). NVM cannot be changed by a