Encoder calibration

Encoder calibration

HOIST/DRAG LIMIT CALIBRATION

An encoder attached to the end of the hoist and drag drum shafts continually monitors the drum position during operation. As the bucket nears the preset limits, reference is gradually removed until the drum rotation is stopped. To prevent tight-lining or pulling the bucket into the boom, the sum of the hoist and drag ropes payed out is monitored. If this sum reaches a preset length, the hoist or drag functions will be slowed, then stopped.

The limits must be recalibrated after changing the ropes, or anytime maintenance is performed that alters the encoder versus drum rotation. Recalibration is required on the function, hoist or drag, being serviced.

There are two calibration points on each rope. The first is with 1.5 dead wraps on the drum. The second is with the ropes at 16,5 ft. (5 M) from either the point sheaves or the fairlead. Rope length is calculated from the calibration points, and the active rope length is used to determine limit status.

There are three limits at each end of travel. Slowdown limit is the first. When this point is passed, the reference is starting to be limited linearly toward the stop limit. Stop limit is the second. At this point the reference is reduced to zero. The last limit is the final limit. When this is reached, the brakes are set and the drive is turned off. The first two limits can be exited by reversing the joystick to the opposite direction. The final limit needs to be exited with the limit bypass switch.

Limits are set using the Hoist/Drag Limit Calibrate screen. A password is required to access this screen. On this screen, limits are defeated and maximum speed is reduced.

Rope installation should be done using the Rope Reeving Screen. A password is required to access this screen. On this screen, limits are defeated and maximum speed is reduced.

HOIST LIMIT

Hoist Calibration new rope

1. Select Rope Reeving Screen.

2. Position the drum with minimum 1.5 dead wraps on drum.

3. Set hoist and drag brakes, turn excitation off.

4. Select Hoist/Drag Limit Calibrate screen. Press and hold the “Hoist Encoder Calibrate 1” button for three seconds. A position accepted light should turn on.

5. Tie a flag on the hoist rope 16.5 ft. (5 M) from the socket at the dump blocks. Use the Rope Reeving Screen to hoist the bucket until the flag touches the boom point sheave.

6. Set hoist and drag brakes, turn excitation off.

7. Select Hoist/Drag Limit Calibrate screen. Press and hold the “Hoist Encoder Calibrate 2” button for three seconds. A position accepted light should turn on. The active rope should show 16.5 ft. (5 M) and the total rope length will be visible. All of the limits will be set. If changes to individual limits are desired, they can be manually entered. The limit entries are checked for valid values before they are accepted.

Hoist Calibration shortened rope

1. Set hoist and drag brakes, turn excitation off.

2. Tie a flag on the hoist rope 16.5 ft. (5 M) from the socket at the dump blocks. Use the Rope Reeving Screen to hoist the bucket until the flag touches the boom point sheave.

3. Set hoist and drag brakes, turn excitation off.

4. Select Hoist/Drag Limit Calibrate screen. Press and hold the “Hoist Encoder Calibrate 2” button for three seconds. A position accepted light should turn on. The active rope should show 16.5 ft. (5 M) and the total rope length will be visible.

5. All of the limits will be set. If changes to individual limits are desired they can be manually entered. The limit entries are checked for valid values before they are accepted.

After completing the above steps, the upper and lower limits are set and the machine can be returned to service. The limits should be checked for proper operation.

DRAG LIMIT

Drag Calibration new rope

1. Select Rope Reeving Screen.

2. Position the drum with minimum 1.5 dead wraps on drum.

3. Set hoist and drag brakes, turn excitation off.

4. Select Hoist/Drag Limit Calibrate screen. Press and hold the “Drag Encoder Calibrate 1” button for three seconds. A position accepted light should turn on.

5. Tie a flag on the Drag rope 16.5 ft. (5 M) from the socket at the dump blocks. Use the Rope Reeving Screen to Drag the bucket until the flag touches the fairlead.

6. Set hoist and drag brakes, turn excitation off.

7. Select Hoist/Drag Limit Calibrate screen. Press and hold the “Drag Encoder Calibrate 2” button for three seconds. A position accepted light should turn on. The active rope should show 16.5 ft. (5 M) and the total rope length will be visible.

8. All of the limits will be set. If changes to individual limits are desired they can be manually entered. The limit entries are checked for valid values before they are accepted.

Drag Calibration shortened rope

1. Set hoist and drag brakes, turn excitation off.

2. Tie a flag on the Drag rope 16.5 ft. (5 M) from the drag rope socket. Use the Rope Reeving Screen to drag in the bucket until the flag touches fairlead.

3. Set hoist and drag brakes, turn excitation off.

4. Select Hoist/Drag Limit Calibrate screen. Press and hold the “Drag Encoder Calibrate 2” button for three seconds. A position accepted light should turn on. The active rope should show 16.5 ft. (5 M), and the total rope length will be visible.

5. All of the limits will be set. If changes to individual limits are desired, they can be manually entered. The limit entries are checked for valid values before they are accepted.

After completing the above steps, the drag in and payout limits are set, and the machine can be returned to service. The limits should be checked for proper operation.

HOIST AND DRAG ENCODER CALIBRATION

The hoist and drag limits are used to prevent the bucket rigging from contacting the dragline components.

Encoders on the Hoist and Drag Drums provide position and rotation information about the drums for calibration and operation of the limits. The hoist and drag encoders need to be calibrated prior to setting the limits. The encoders have 4096 counts per revolution. Encoders must count up in the lowering or payout direction.

• The Hoist Limits provide a slowdown, stop and final limit prior to the Bucket Hoist Rope Sockets contacting the Boom Point Sheave.

• The Lower Limits provide a slowdown, stop and final limit prior to the hoist rope coming off of the drum.

• The Drag Limits provide a slowdown, stop and final limit prior to the Bucket Drag Rope Sockets contacting the Fairlead.

• The Payout Limits provide a slowdown, stop and final limit prior to the drag rope coming off of the drum.

When limits are active, the drive reference ramps are made quicker.

Slowdown Limit starts the linear reduction of the drum speed reference toward the Stop Limit. At the Stop Limit, the speed reference is set to zero to electrically stop the motion. The reduction to speed reference is a clamp, thus, if the operator has reduced the speed command below the clamp there will be no further reduction in reference. The slow down and stop limits can be exited by moving the Hoist or Drag Joystick in the opposite direction. If the rope length reaches the Final Limit, the brakes are set and the drive is turned off.

The final limit can be exited from with the rope limit bypass mode. The rope limit bypass mode is entered by pressing and holding the bypass button in the cab. The rope bypass light will flash. The motion can be started by control start once the motion control on light is on and the bypass mode is latched. The rope bypass light will be on. The motion brakes can then be released and the motion moved out of the final limit. If the motion is moved in the wrong direction, the rope limit bypass mode will be exited and motion will shut down. Speed is limited to 15% in bypass mode. When the motion is outside the stop limit, then the bypass mode will be exited. Normal limit functions will be active.

Limits are set from the Hoist/Drag Limit Calibration screen, which is password protected.

The encoder calibration needs to be enabled. Once encoder calibration is enabled, hoist and drag motions will be in a reduced reference (15% maximum speed) mode. The hoist encoder needs to be set to increase count in the lower direction. The drag encoder needs to be set to increase count in the payout direction. The motion travel limits will be disabled. Drive start and stop operation is standard.

The first calibration point relates to the Lower and Payout Limits that prevent the rope, on the Hoist and Drag Drums, from unwinding less than 1.5 dead wraps on the drum. The second calibration point relates to the hoist and drag limits. The calibration point is with the rope sockets at 16.5 ft. (5M) from the Boom Point Sheave or the Fairlead. If the second calibration value is greater than the first calibration value, the encoder direction value is generated. The PLC calculates the rope length between the calibration points including the 16.5 ft. (5 M) offset. The limits are set to default values relative to the rope length. The total rope length is displayed on the Limit calibrate screen as well as the active rope length. The active rope length is the rope that is between the rope sockets and either the point sheave or fairlead. The active rope length will be 16.5 ft. (5 M) after calibration 2 is pressed. The individual limits can be altered using data entry on the Limit Calibrate Screen. All data entry values are checked for valid information.

The limits require calibration after changing or reattaching the ropes, or anytime maintenance is performed on the drums, which alter the encoders with respect to drum rotation. Calibration is required only on the system being serviced either hoist or drag. When a rope is shortened, only calibration 2 is required.

Displays of length are selectable between meters and feet.