Model 9600/9700 Swing-Reach ® Lift Truck
Section 8. Theory of Operation Functional Operation
counterclockwise rotation to the Steer Power Amplifier (SA). The SA drives the Steer Motor to obtain the movement requested from the tiller. The TM monitors steer current, the Steer Motor Encoder, Steer Home Prox, and Neutral Pulse to determine that the steering system is operating correctly. When the deadman is pressed, the TM energizes the STR contactor, providing B+ to the SA to power the Steer Motor.
Guidance Overview When the truck is in the wire guided mode, steering functions the same way as when in manual steering mode with one exception. Steering requests do not come from the CM when in wire guided mode as they do in manual steering. In the wire guided mode, steering requests originate in the GM rather than from steering encoder. To switch from manual steering to the wire guided mode, several events must occur. First, the CM must detect the Auto/Manual switch (S4) is open (Auto position). Next, the CM must advise the TM that S4 is open. When the TM is advised that S4 is in the Auto position and aligning, it transfers steering control from the Steering Encoder to the GM. The GM calculates the position of the truck relative to the wire and advises the TM what direction and how far to steer the drive unit. During wire guided operation, the GM constantly updates the TM with corrections since the trucks position relative to the guide wire constantly changes. If the truck exceeds the deviation values for Distance from Wire (DFW - how far the truck is from the wire) or Heading Angle (HA - angle of the truck to the wire) that are set in Configure, the GM informs the TM to slow or stop the truck, depending on the magnitude of the deviation. Functional Description During normal manual steering operation, the CM is in constant communication with the TM, updating the TM with the status of the components connected to it such as switches, the control handle, and the Steering Encoder. Likewise, the GM is constantly attempting to
Publication: 1089040, Issued: 08 Apr 2016
calculate the position of the truck relative to the guide wire. The TM is constantly being updated as to the position of the drive unit relative to home position as well as travel speed and direction that it in turn communicates to the GM. When the CM detects that S4 is opened (Auto position), it advises the TM that S4 is open. The TM determines that the truck is ready for wire guided operation and informs the GM. The GM then tells the TM to put the truck into Seeking Mode and try to acquire the wire. Travel speed is limited to 1 mph (1.6 km/h) in the forks-first direction and limited to the Acquire speed set in Configure Mode for tractorfirst travel. If the Sense Creep Speed (SensCreep) option is enabled in the Configure Mode menu, truck speed is limited to 1 mph (1.6 km/h) whenever S4 is detected closed (Manual position) and the GM reports that a guide wire is detected. During Seeking Mode, an audible tone is generated and the green LED triangles of the wire guidance icon blink. Steering at this time is still in manual control because the truck has not acquired the wire. The operator must steer the truck toward the guide wire location to help the truck acquire the wire. As either the tractor or load end center pair of sensor coils (Near Wire coils) approach the guide wire, they begin to detect the magnetic field around the guide wire. If the Near Wire coils do not detect this magnetic field for any reason, the truck does not acquire the wire, even if the outer coils (Guidance coils) detect the magnetic field. The magnetic field around the guide wire causes an AC voltage to be induced into the sensor coils that is sent to the Filter Card (GM) for conditioning. The Filter Card removes any noise that is picked up by the antenna coils and also converts this AC voltage into a DC voltage to be used by the Guidance Card. As either the tractor end or the load end Near Wire coils get closer to the wire, the value of the DC voltage to the Guidance Card increases. When the Near Wire coils get close enough (to the wire), and the voltage is high enough, the Guidance Card tells the TM to release full control of issuing the steering commands to the Guidance Card.
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