Emerson EZMotion - If on Sensor Options

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36 EZMotion User/Programming Guide

www.controltechniques.com Revision: A8

6.2.3 Home to Sensor then Marker

The Home to Sensor then Marker profile is a combination of the two home types described above. Because in many applications the

load will be more than one revolution away from the desired home position, a Home to Marker cannot be used because the marker

activates once every revolution of the motor. Therefore, an external sensor is mounted on the machine to determine the home

position. EZMotion allows the user to home first to the external sensor, followed by a home to the next marker pulse. The Home to

Sensor then Marker combines the accuracy of homing to the encoder marker with the flexibility of homing to an external sensor.

The Home to Sensor then Marker routine begins by accelerating up to the Home Velocity. The motor then continues at the Home

Velocity until the external sensor activates. After the sensor activates, the motor continues at the Home Velocity until the next rising

edge of the encoder marker is detected. Once the encoder marker activates, the motor either begins to decelerate immediately, or

continues for a specified offset distance before stopping. Figures 40 and 41 show examples of the Home to Sensor then Marker

profile, with calculated offset and specified offset respectively.

Figure 40: Home to Sensor then Marker Profile (Calculated Offset)

Figure 41: Home to Sensor then Marker Profile Specified Offset)

6.2.4 If On Sensor Options

In a Home to Sensor, or Home to Sensor then Marker profile special conditions must be created to handle the situation when the

External Sensor is already active when Home is initiated. Different users want the system to act differently in this condition, so

EZMotion has pre-programmed solutions for this condition. The two options are explained below.

Back Off Before Homing

If the Home Sensor is active when home is initiated, one option is to move the motor in the direction opposite from the programmed

direction until the home sensor deactivates, and then again in the positive direction until the home sensor activates. Figure 42 shows

the Home to Sensor profile when the Home Sensor is active when the home is initiated and Back Off Before Homing is selected.

Velocity

Home Accel

Home Velocity

Home Decel

Time

Home Initiate

Encoder Marker

External Sensor

External Sensor Activates wait

for next Encoder Marker