Path Finder Alignment Procedure I

MANUAL MODE VERIFICATION

Place the system in the Manual Mode and check for the following indications:

  • The Red indicator light should be on
  • The truck should have power steering
  • There should be no indication of binding, dragging or lag in the steering assembly. The steered wheel should turn smoothly from lock to lock.

PRIMARY ALIGNMENT

The primary alignment procedure is preformed in the automatic mode.

NOTE

Steered wheel guidance, (alignment steps 1 thru 6), must Be completed prior to attempting load wheel guidance. If the system is not guiding correctly in the steered wheel direction, it will not guide correctly in the load wheel direction.

STEP 1: POSITION THE TRUCK

Center the steered wheel sensors over the guidepath with the steered wheel pointing straight ahead.

STEP 2: VERIFY STEERED WHEEL SENSOR POSITION AND CONDITION

Visually check the position of the steered wheel sensors. The sensors should be equally distant from the guidepath side to side and at equal height from the floor. Optimum sensor height from the floor is 3 ¾ to 4 ¼ inches (93.8 mm to 106.3mm)

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Refer to illustration 4.3-62. If the sensors are not in position as shown, due to damage to the sensor mount or other cause, correct the problem before continuing. The truck can not be aligned if the sensors are not correctly positioned.

STEP 3: BALANCE THE STEERED WHEEL SENSOR INPUTS

  • Set the digital voltmeter to measure a 200mVac signal
  • Measure the voltage between TP-1 and Ground on the Sensor Amplifier Board.
  • Adjust Potentiometer R-3 so that the voltage level at TP-1 is 135mVac plus or minus .5mVac. This setting is for 6.25Khz systems.

NOTE

135mVac is the optimum setting. Permissible tolerance is from 125 to 150mVac. All four sensors must have the same input for correct guidance. For example: if TP-1 is set at 140mVac, TP-2,3, and 4, must be set at 140mVac

STEP 4: ADJUST DETECTOR ZERO,R-41

  • Set the digital voltmeter to measure a 200mVdc signal
  • Connect the digital voltmeter between TP-3 and
  • Analog ground, (TP-4) on the Servo Amplifier PC Board. Enter the automatic mode and wait for time out. Time out will occur 30 to 50 seconds after going to automatic if the truck is not moving. (Time out has occurred if the meter indication at TP-3 is stable.) The meter indication should be 0 volts DC plus or minus 1 millivolt. If the meter indication is not 0 volts, adjust R-41 for a 0 volt reading a TP-3. This adjustment is very sensitive and requires only a small change in the potentiometer position.

STEP 5: ADJUST THE POSITION POTENTIOMETER

Place the truck over the guidepath, turn the steering wheel to the straight ahead position, and switch to the automatic mode. Adjust Fine Centering potentiometer R-125, to the 12:00 position.

STEP 6: STEERED WHEEL GUIDANCE OPERATION

This procedure requires two people, an observer and a truck driver. Tape a tie wrap, soda straw, or a similar item to the center of the Sensor mounting, or at a midway point between the sensor bracket mounting bolts, as shown in illustration 4.3-66. This will allow closer observation of system performance.

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NOTE

Vehicles equipped with the castering load wheels must travel one truck length after a change in direction to start steering smoothly. Allow the casters to swivel before starting your observation.

  • Place the system in the Automatic mode and acquire the wire.
  • Drive the truck in the steered wheel direction and observe the steering. The truck should remain over the guidepath, weaving back and forth across the guidepath ¼ inch (6.3mm) left and right. Careful observation is required to determine whether or not further adjustments need to be made. If the truck does not weave equal distance right and left of the wire the position pot may be adjusted incorrectly. Check to see if the pot is set correctly. The pot is correctly aligned when the output of the potentiometer is at its lowest value with the steered wheel pointing straight ahead. If the truck weaves back and forth across the guidepath in excess of ¼ inch (6.3mm) left and ¼ inch (6.3mm) right, verify that the truck steering components are not slack, excessively worn, or otherwise out of adjustment. If, after adjusting the steering components, the truck still weaves in excess of ¼ inch (6.3mm) left and right, perform the adjustments described for Position Potentiometer Feedback Adjustments, R-53,

Loop Gain Adjustment, R-38. Perform the procedure described for adjusting Fine Centering Adjustment, R-125. Once the truck is guiding within specifications in the steered wheel direction of travel, continue with the Load Wheel Direction Alignment.

STEP 7: VERIFY LOAD WHEEL SENSOR POSITION AND CONDITION

  • Visually check the position of the load wheel sensors. The sensors should be equally distant from the guidepath side to side and at a equal height from the floor. Optimum sensor height from the floor is 3 ¾ to 4 ¼ inches (93.8 to 106.3mm)
  • If necessary, center the load wheel sensors over the guidepath by either positioning the truck, or moving the sensors in their adjustable bracket. Note the original bracket location and return it to the original position after balancing the sensor inputs.
  • (Refer to illustration 4.3-67). If the sensors are not positioned as shown due to damage to the sensor mount or other cause, correct the problem before continuing. The truck cannot be aligned if the sensors are not correctly positioned.

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STEP 8: BALANCE THE LOAD WHEEL SENSOR INPUTS

  • Set digital voltmeter to measure 200mVac signal.
  • Measure the voltage between TP-3 and ground on the Sensor Amp Board. (see illustration 4.3-63)
  • Adjust potentiometer R-66 so that the voltage level at TP-3 is 135mVac plus or minus .5mVac
  • Measure the voltage between TP-4 and ground on the Sensor Amp PC Board.
  • Adjust potentiometer R-68 so that the voltage level at TP-4 is 135mVac plus or minus .5mVac
  • If the sensor mounting bracket was moved to center the sensors over the guidepath, return it to its original position.

NOTE

135mVac is the optimum setting. Permissable tolerance is from 125 to 150mVac. All four sensors must have the same input for correct guidance. For example: if TP-1 is set at 140mVac, TP-2, 3 and 4 must be set at 140mVac.

STEP 9: LOAD WHEEL DIRECTION STEERING VERIFICATION

Observations for load wheel steering are made by observing the tie-wrap taped to the steered wheel mounting bracket as the greatest deviation will occur at that point. The tie-wrap may deviate more than ¼ inch (6mm) left and right when traveling in the load wheel direction because the truck pivots at a point between the load wheels. The longer the truck wheel-base, the more the acceptable deviation at the steered wheel sensor. A truck may have an acceptable deviation at the steered wheel or ½ inch (12mm) plus or minus 1/8th inch (3mm) per foot (300mm) of separation between the load wheels and the steered wheel. On a truck with a 8 foot (2400mm) wheel base, the acceptable deviation at the steered wheel end of the truck is ½ inch (12mm) plus or minus 1/8th inch (3mm) times 8 feet (2400mm) or 1 ½ inches (37mm). The tie-wrap may deviate ¾ inch (19mm) left and right of the guidepath cut in the floor.

  • Acquire the wire in the steered wheel direction of travel and coast to a stop. Start the truck off in the load wheel direction and observe the immediate truck reaction. Allow for the caster effect to take place before starting your observation. If the truck leaves the wire immediately, in either direction, it is an indication that there is a mechanical offset causing the truck to steer off the wire. Perform the following:
  • Check to insure that you returned the sensor bracket back to its original position after performing the load wheel sensor balance adjustment.
  • Check to insure that the load wheels are turning freely. A tire that is dragging will appear to be cleaner than the tire on the opposite side.
  • If all indications are correct:
    Move the sensor bracket in the direction that the truck left the guidepath. It is of primary importance that the load wheel sensors be parallel to the steered wheel sensors along the rolling axis of the truck. The truck should not move immediately left or right as the direction of travel is changed. Recheck the guidance at all speeds before proceeding. If unable to correct the tendency to leave the guidepath by moving the rear sensor bracket, it may be necessary to electrically offset the sensors. Electrically offset the sensors requires changing the settings of R-66 and R-68 electrically in opposite directions. For example: turn R-66 so that the meter reading at TP-3 on the Sensor Amp Board increases by 5 millivolts AC, and turn R-68 so that the meter reading at TP-4 decreases by 5 millivolts, or the other way around, depending on which direction the truck must move. The truck will move away from the sensor with the highest input. Always offset the sensors electrically by equal amounts in order to maintain a balance while traveling down the guidepath. If the truck weaves excessively in the load wheel direction of travel it may indicate any one of the following problems. Rule out each of these problems in order to eliminate the cause of the weaving.
  • Excessive slack in the truck steering.
  • Incorrect setting of R-43, Angle Sensitivity Adjustment
  • Incorrect setting of R-53, Position Potentiometer Feedback Adjustment
  • Incorrect setting of R-38, Loop Gain Adjustment
  • Rear Sensor Bracket is offset
  • Masked sensors, caused by not elevating the forks 6 to12 inches
  • Dragging brakes on one side

If the truck weaves quickly from side to side, perform the procedure described under the Angle Sensitivity Adjustment, R-43. If the truck guides normally at slow speeds, but starts weaving and leaves the wire at high speeds in the load wheel direction, it is an indication that there is insufficient position potentiometer feedback, or excessive steering system play. Turn R-53, the Position Potentiometer Feedback Potentiometer, 1 hour counterclockwise and observe the results.